SUBSTITUTE CHEMICAL PROGRAM
  INITIAL SCIENTIFIC
 AND MINIECONOMIC
          REVIEW OF
       CARBOFURAN
                JULY 1976
       U.S. ENVIRONMENTAL PROTECTION AGENCY
           OFFICE OF PESTICIDE PROGRAMS
         CRITERIA AND EVALUATION DIVISION
             WASHINGTON, D.C. 20460


                EPA 540/1-76-009

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      This report has been compiled  by the Criteria  and  Evaluation
      Division,  Office of Pesticide  Programs,  EPA, in  conjunction
      with other sources listed  in the Preface.   Mention of  trade
      names or commercial products does not constitute endorsement
      or recommendation for use.
For sale by National Technical Information Service, 5285 Port Royal Road,
                       Springfield, Virginia  22161

   Limited copies are available from EPA Forms and Publications Center,
          M-D-41, Research Triangle Park, North Carolina  27711

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          SUBSTITUTE CHEMICAL PROGRAM



                   INITIAL SCIENTIFIC

                                  AND

                  MINIECONOMIC REVIEW

                                   OF

                           CARBOFURAN
                           JULY  1976
U.S. ENVIRONMENTAL PROTECTION AGENCY
        OFFICE OF PESTICIDE PROGRAMS
    CRITERIA AND EVALUATION DIVISION
             WASHINGTON, D.C.  20460
                    EPA-540/1-76-009

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                                    PREFACE


     The Alternative (Substitute)  Chemicals Program was initiated under Public
Law 93-135 of October 24, 1973,  to "provide research on,  and testing of, substi-
tute chemicals."  The legislative  intent is to avoid the  use of substitute chem-
icals that would be even more deleterious to man and his  environment than a pes-
ticide that is cancelled or suspended for causing "unreasonable adverse effects
to man or his environment."  The major objective of the program is to determine
whether potential substitute chemicals are suitable replacements for cancelled
or suspended pesticides or for pesticides that are under  litigation or are can-
didates for Rebuttable Presumption Against Registration (RPAR).

     The review of the substitute  chemical considers its  chemistry, toxicology,
and pharmacology as well as its use patterns, efficacy, and environmental fate
and movement.  EPA realizes that,  even though a compound  is registered, it still
may not be a practical substitute  for certain uses of a problem pesticide.  There-
fore, the utilitarian value of the "substitute" must be established by reviewing
its biological and economic data.

     The reviews of substitute chemicals are carried out in two phases.  Phase I
Initial Scientific Review evaluates the "safety and efficacy" of the substitute
chemical based on data readily accessible at the present time.   The Phase II
Integrated Use Analysis examines the effects of possible regulatory action
against a hazardous pesticide for  each of its major and critical uses.  The
examination considers the suitable substitutes in conjunction with alternative
agricultural management practices.  Current and projected environmental, health,
and economic impacts are also evaluated.

     This report contains the Phase I Initial Scientific Review of carbofuran.
Carbofuran was identified as a registered substitute chemical for certain prob-
lematic uses of chlordane, heptachlor and aldrin which have been cancelled by
EPA.  The report covers all uses of carbofuran and is intended to be adaptable
to future needs.  Should carbofuran be identified as a substitute for a problem
pesticide other than those mentioned above, the review can be updated and made
readily available for use.  The data searches ended in June, 1975.  The report
summarizes rather than interprets  scientific data reviewed during the course
of the studies.  Data from different sources is not correlated, nor are opin-
ions presented on contradictory findings.

     A team of EPA scientists in the Criteria and Evaluation Division of  the
Office of Pesticide Programs coordinated the review; the team  leader provided
guidance and direction and technically reviewed information retrieved during
the course of the study.  The following EPA scientists comprised  the review
team:  E. Neil Pelletier, Ph.D. (Team Leader); Padma Datta, Ph.D., and Hudson
Boyd (Chemistry); Roger Gardner (Pharmacology and Toxicology); Willard  Cummings
and Richard Stevens (Fate and Significance in the Environment);  Ralph Wright
(Registered Uses); and Gary Ballard and Harry Gaede, Ph.D.  (Economics).
                                      iii

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     Data research, abstracting, and collection were performed primarily by Mid-
west Research Institute  (MRI), Kansas City, Missouri (EPA Contract #68-01-2448)
under the direction of Thomas L. Ferguson.  The following MRI scientists were
principal contributors to the report:  Alfred F. Meiners, Ph.D.; James V. Dilley,
Ph.D.; Frank E. Wells, Ph.D.; William J. Spangler, Ph.D.; David F. Hahlen; and
Thomas L. Ferguson.  Other MRI project team members who contributed to the devel-
opment of this review were John R. Hodgson, Ph.D.; Edward W. Lawless, Ph.D.;
Daniel G. Puzak, and Kathryn Lawrence.  Rosmarie von Rumker, Ph.D., and Freda
Horay, both of RvR Consultants, were also contributors.

     The scientific staffs of EPA's Environmental Research Laboratories reviewed
draft copies of the report.  Comments and supplemental material provided by the
following laboratories were greatly appreciated and have been incorporated into
this report:  Gulf Breeze Environmental Research Laboratory, Gulf Breeze,
Florida, and the National Ecological Research Laboratory, Corvallis, Oregon.
FMC Corporation, which manufactures carbofuran, and the Chemagro Division of
Mobay Chemical Corporation, which markets carbofuran under a license from FMC,
both reviewed the draft  of this report and made certain comments and additions.
                                          iv

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                            GENERAL CONTENTS

                                                                  Page

List of Figures	    vi


List of Tables	vii


Part   I.      Summary	     1


Part  II.      Initial Scientific Review	    15

      Subpart A.   Chemistry 	    15
      Subpart B.   Pharmacology and Toxicology 	    51
      Subpart C.   Fate and Significance in the Environment. ...    96
      Subpart D.   Production and Use	   142


Part III.      Minieconomic Review	   162

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                                 FIGURES

No.                                                                       Page

1    Manufacturing Process for Carbofuran 	      3

2    Preparation of Carbofuran from £-Nitrophenol 	     16

3    Production Schematic for Carbofuran	     17

4    Degradation Curves for Carbofuran in Sultan Silt Loam at
       4 pH Levels	     40

5    Oxidation and Hydrolysis Routes of Carbofuran	     44

6    Scheme for Producing Parental and Progeny Stock for a 3-
       Generation Study (Rats)	     67

7    Proposed Products of Carbofuran Oxidation and Hydrolysis 	     77

8    Materials Flow Diagram for Carbofuran  (1972) 	    148
                                         vi

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                                 TABLES
 1   Method Requirements for Specific Samples ..........  22

 2   Other Analytical Methods for Carbofuran Residues ......  25

 3   Residues of Carbofuran on Sugarcane ............  28

 4   Maximum Total Residues (ppm of Carbofuran, Including 3-
       hydroxycarbofuran) Found on Field Corn Silage and
       Stover ..........................  29

 5   Residues of Carbofuran in Alfalfa  (ppm Al/acre) ......  30

 6   Residues of Carbofuran on Peanuts  .............  32

 7   Residues in Milk of 3 Metabolites  of Carbofuran Fed at
       200 ppm Total Metabolites ................  35

 8   Residues in Tissue of 3 Metabolites of Carbofuran  at End
       of 28-Day Feeding Period .................  36

 9   U.  S. Tolerances for Carbofuran  ..............  37

10   Summary of Acute Toxicity Data for Rats  ..........   54

11   Acute Oral Toxicity of Carbofuran  Metabolites  .......   55

12   Summary of Acute Toxicity Data for Animals Other  than
       Rats ...........................   56

13   Changes in Plasma Cholinesterase Activity in Dogs After
       Dosing with Carbofuran ..................   57

14   Changes in Erythrocyte Cholinesterase  Activity in Dogs
       Dosed with Carbofuran  ..................   57

15    Survival Indices for a 3-Generation  Study on Rats (30 ppm
       Carbofuran)  .......................   69

16    Summary of Tumor Incidence  During  an 18-Month Carcinogenic
        Study with Swiss  White Mice ...............    71

17   Metabolites of  Carbofuran  .................   78

18    Ratios of  Carbofuran Metabolite Residues in 6 Major
        Crops  ..........................   81
                                       vii

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                            TABLES  (Continued)

No.                                                               Page

19     Degradation of Labeled Carbofuran by Rat Liver 15,000
         G  Solubles	    86

20     Toxicity of Technical Carbofuran and Its Formulations
         to Fish	    99

21     Acute Toxicity of Carbofuran to Birds  	   102

22     Subacute Toxicity of Carbofuran to  Birds	   105

23     Effect  of  Furadan 10G on Oxygen Uptake in Field Soil. .  .   Ill

24     Radioactive Carbofuran Equivalents  Recovered as Carbo-
         furan, Soil-Bound Residue, and Expired C02 from
         Irradiated and Nonirradiated Soils Treated with
         14c-Carbonyl-Labeled Insecticide  at  20 ug/cm3 	   120

25    Carbofuran  Residues in Soil Samples  (mg/m^)	   124

26    Runoff-Producing Rainfalls and Carbofuran Losses in
        Runoff Water from Carbofuran-Treated  Watersheds	   133

27    Currently Registered Uses of Carbofuran	   149

28    Use of Carbofuran in the U. S. by Crops, 1971	   155

29    Use of Carbofuran in the U. S. by Regions, 1971	   156

30    Use of Carbofuran in California by Major Crops and Other
        Uses,  1970-1974	   157

31    Use of Carbofuran in California in 1972, 1973 and 1974
        by  Crops  and Other Uses, Applications, Quantities, and
        Acres Treated	   158

32    Estimated Uses of Carbofuran in the  U.  S. by Regions
        in  1971,  1972 and 1974	   159

33    Summary of  Carbofuran Tests on Alfalfa  	   175

34    Summary of  Carbofuran Tests on Corn	   176

35    Summary of  Carbofuran Tests on Peanuts  	   177

36    Summary of  Carbofuran Tests on Potatoes	   178
                                      viii

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                            TABLES (Continued)




No.                                                               Page




37    Summary of Carbofuran Tests on Rice	179




38    Summary of Carbofuran Tests on Sugarcane 	 179




39    Summary of Carbofuran Tests on Tobacco 	 180




40    Summary of Carbofuran Tests on Peppers 	 180
                                        ix

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                             PART I.  SUMMARY




                                 CONTENTS




                                                                  Page




Production and Use	    2






Toxicity and Physiological Effects	    2






Food Tolerances and Acceptable Intake 	    7






Environmental Effects 	    8






Efficacy and Cost Effectiveness	   12

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      This section contains a summary of the "Initial Scientific and  Minieconomic
 Review" conducted on carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl  methyl-
 carbamate).   The section summarizes rather than interprets data reviewed.


 Production and Use

      Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate)  is  a
 broad-spectrum insecticide-nematicide,  especially effective against  corn  root-
 worms.   Carbofuran is manufactured by FMC Corporation (owner of the  manufactur-
 ing and use patents) at Middleport, New York,  and is also marketed under  license
 by the  Chemagro Division of Mobay Chemical Corporation.

      Carbofuran is a white crystalline  solid that undergoes alkaline hydrolysis
 (cleavage at the carbamate linkage), oxidation and photodecomposition.  Carbo-
 furan is readily metabolized by plants, animals,  insects, and soil microorgan-
 isms.   Oxidation and photodecomposition appear to be minor environmental  degra-
 dation  routes.  (See Figure 1.)

      Carbofuran is available in 4 granular formulations  (2, 3, 5,  and 10%)
 and a 4 Ib/gal flowable formulation.  The only formulations available for domestic
 use are those made by the manufacturer; carbofuran is not available  in the
 United  States as a technical active ingredient.

      Carbofuran production in 1972 was  estimated  at 6 million Ib active ingredi-
 ent (AI),  approximately 1 million Ib of which  were exported.  Estimated 1974
 domestic  usage was slightly over 7.0 million Ib.   Approximately 6.8  of the 7.0
 million pounds  were used on corn (6.3 million  Ib  in the  corn belt, lake and
 northern  plains states;  500,000 Ib in the remaining corn-growing states).


 Toxicity  and Physiological Effects


 Acute Toxicity - In tests with various  animal  species, chickens appeared  to
 possess the  greatest resistance to carbofuran  (LD5Q = 25.0 to 38.9 mg/kg) and
 mice, the least resistance (LDso = 2 mg/kg).  Dogs were  intermediate (U>50 =
 1.5.85 mg/kg).   Sex differences were not apparent.

     In tests with rats  the acute toxicity of  carbofuran was found to be  as
 follows:

   Route of
administration     Formulation        Measurement              Value

Oral                Technical        LDso           1-65 mg/kg (newborn)
                    (98.8%)                        3.36 mg/kg (weanling)
                                                   6.4 to 14.1 mg/kg  (adult)

Intraperitoneal     Technical        LD5Q           1.37 mg/kg
                     (98.8%)

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            NO,
       o-nltrophenol   methallyl
                       chloride
                                  base (-HCl
CH3
                                               o-methallyloxy-
                                               nitrobenzene (I)
                                                                   rearrangement
                                                                       heat
                                                                   175-190'C
                                                                                       HO,
                                                                               *     0,
                                                                                          -OH
                          2-nitro-6-raethallylphenol (II)
                                                                                    NO,
                                                                                         OH

                                                                                        -CH=C(CH3)2

                                                                                2-nltro-6-isobutenylphenol (III)
II and  III
           cycllzatlon
           acid catalyst
           (FcCl- preferred)
            150-190*C
                                          CH,
                             2,3-dihydro-2,2-dimethyl-
                               7-nitrobenzofuran  (IV)
                                                            hydrogenation
                                                            catalyst
                                                                                7-amino-2,3-dihydro-
                                                                                  2,i -Jiinethylbenzofuran (V)
                   dlatotization,
                   room temperature
                                                     CH,
                                                            SO,
                                         7-dlazonium-2,3-dihydro-
                                           2,2-dimethybenzofuran
                                           +  Na2SOA + H20
                                                                   H20, heat
                                                                          catalyst
                                                                                                  CH,
                                                                                       2,3-dihydro-2,2-diraethyl-
                                                                                         7-benzofuranol (VI)
VI + CH3NCO

     methyl
     isocyanate
                           OCON1ICH
                        carbofuran
                          Figure  1.   Manufacturing  Process  for Carbofuran

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      The acute dermal LD5Q for rabbits of technical carbofuran in an organic
 solvent (Dowanol DPM) was 14.7 mg/kg; however, the acute dermal LD,-n of the
 technical carbofuran in water was greater than 10.2 g/kg.  A 10% granular for-
 mulation (10G) had an LD5Q of 10.2 g/kg.  Furadan® 4 flowable had a dermal LDso
 value of 6.8 g/kg.

      In  studies  on the  effects of carbofuran metabolites  on  rats,  3-hydroxy-
 carbofuran was found  to be highly toxic;  2,3-dihydro-7-hydroxy-2,2-dimethyl-3-
 oxobenzofuran and 3-ketocarbofuran moderately toxic;  and  2,3-dihydro-2,2-
 dimethyl-7-hydroxybenzofuran  and  2,2-dimethyl-3,7-dihydroxy-2,3-dihydrobenzo-
 furan, slightly  toxic.

      In  tests with 1- to 2-week-old calves,  a single  dose of carbofuran at 1 mg/kg
 resulted in  death; the  same dose  in older animals  resulted only in salivation,
 tearing, hyperactivity  and diarrhea.

      Sheep exhibited  increased salivation,  stomach cramps, and  frequent micturi-
 tion at  carbofuran doses higher than  2.5 mg/kg.  At 10  mg/kg dosing,  death
 occurred, even though the animals were treated with atropine sulfate.


 Subacute Toxicity - The  subacute  effects  of  carbofuran  were  evaluated in tests
 using rats,  rabbits, guinea pigs,  chickens,  and dairy cows.

      Rats fed 0.1 to  1,600 ppm carbofuran for 90 days did not  exhibit abnormal
 changes  when compared to controls;  comparisons were made  of  gross  pathology,
 histopathology,  hematology, and urine constituents.   Although  no deaths were
 recorded, animals that  received diets containing carbofuran  at  1,600  ppm
 exhibited slight  to moderate,  generalized tremors.

      Other rats were  fed at dietary levels  up to 3,000  ppm for  90  days without
 significant  observable  differences between  test groups  and controls.  Comparisons
 were made of hematology,  urine constituents,  blood chemistry,  gross pathology,
 and  histopathology.

     As  part of a 16-week study,  rats were  dosed after  13 weeks with  carbofuran
 at levels of 0, 0.1, 0.3,  1.0,  and 3.0 mg/kg/day.   A  slight  reduction in
 cholinesterase values at the  highest  dose occurred.

     A study in which female  rats were given 3 mg/kg/day  for 3  weeks  showed  that
 the  time of  testing for  cholinesterase activity after dosing is important.
 Samples  taken from 0 to  60 min after  administration of  carbofuran  showed greatest
 cholinesterase inhibition a short time after treatment.

     At  5 mg/kg/day, cholinesterase activity in dogs  treated for 92 days was not
radically reduced  (the dogs exhibited frequent coughing and  gagging).  Daily
exposure to  carbofuran resulted in  some adaptation  to the pesticide.  The  depres-
sion of  cholinesterase activity after a single dose given to rats  previously
exposed  to carbofuran for  14  to 28  days was  not as  great  as  that which occurred
in rats  that  had  not been  previously  exposed.

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     Rabbits fed a diet  containing 700 ppm carbofuran for 14 days showed a
slight decrease in body  weight.   No other effects were noted.

     Three metabolites of  carbofuran (3-hydroxycarbofuran phenol, 3-ketocarbo-
furan phenol, and carbofuran phenol)  were fed to chickens for 28 days without
any apparent adverse changes in  appearance,  behavior, food consumption, or egg
production.  These same  metabolites were  also fed to dairy cows in combinations
Up to 200 ppm (66.7 ppm  dietary  for each  metabolite) for 28 days.  No abnormal
effects were observed in any test animal.


Chronic Toxicity - Two-yr  chronic studies were conducted with rats and dogs.
Rats were given carbofuran at dietary levels of 1, 10, and 100 ppm.  Both males
and females in the 100 ppm test  group exhibited a weight depression, but the
lowered rate of gain was statistically significant in males only (P < 0.05).
In all other measurements, no differences were observed between the untreated
controls and treated animals. Comparisons were made by hematological tests,
tests for urinary constituents,  blood chemistry tests, and gross pathology and
histopathology.

     An additional study was performed at dietary levels of 25 and 50 ppm.  The
only differences noted between treated and control rats was a reduction in food
consumption by males at  the 50 ppm level  for the first 9 months of the test.
All other comparisons (mortality, behavioral reactions, gross pathology, and
histopathology) did not  demonstrate any differences between the untreated con-
trols and the animals fed  the 50-ppm diet.

     In a 2-yr chronic study with dogs, no abnormal behavioral reactions were
observed in animals fed  1, 2, 10, 20, and 50 ppm carbofuran diets.  At 100 ppm,
slight coughing and gagging reactions were observed.  At 200 and 400 ppm,
coughing and gagging were  observed daily.  Muscular tremors and weakness in the
hinquarters were also seen in dogs fed 200 ppm.  Death occurred in some animals
at 400 ppm.


Effects on Reproduction  -  A 3-generation  reproduction study with rats fed a 1,
10, and 100 ppm showed a low 5-day survival index for pups and a greater
incidence of stillbirths in the  100 ppm test group.  In another test conducted
at 50 ppm, results for Fo  parents and F^a and FH, progeny paralleled the 100 ppm
study.  The 5-day survival indexes for the progeny from the treated animals
were lower than those of the controls; weanling body weights were also lower
in treated than in untreated animals.

     A 3-generation study  at 20  and 30 ppm carbofuran suggested  that the 30 ppm
treatment level (a) affected the mating of parental animals, and  (b) had an
effect on the 5-day survival index of progeny from treated parents.

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      Three metabolites of  carbofuran fed  to .rats at  10 and  50  ppm apparently
 did not have any effect on the ability of the  animals  to  mate,  conceive,  or
 to carry their young.

      A reproduction study  with dogs  indicated  that dietary  levels of  carbo-
 furan at 20 and 50 ppm for 20 months had  no adverse  effects on parental animals
 with respect to mortality, estrus  cycles, mating, parturition  or  lactation.
 Treatment of parents did not  affect  progeny with respect  to litter size,
 survival indices,  or ability  to nurse.  When pregnant  bitches  were fed carbo-
 furan at 20 ppm during the last half of gestation, no  effects  were observed
 in the pups or the mother.  All pups appeared  normal and  maintained normal
 growth patterns.


 Carcinogenicity -  The  incidence of tumors in rats fed  dietary  levels  of 10 ppm
 carbofuran for 2 yr was no different than in untreated controls.   Similar
 results were observed  in a study at  50 ppm.

      Mice were fed carbofuran at 30  and 100 ppm for  18 months  in  a study  to
 determine whether  or not carbofuran  was carcinogenic by oral routes.  The
 percent of mice bearing tumors at  the end of the study (10.5%)  was the same
 for the controls and for the  animals treated at 100  ppm.  In a positive
 control group (treated with urethane)  76% of the animals  had tumors.


 Mutagenesis - One  study with  mice  indicated that a dose of  0.5 mg/kg  carbofuran
 did not induce a dominant  lethal mutation in mice.
 Teratology - Female rabbits were administered carbofuran in gelatin capsules
 (0.1 and 0.5 mg/kg/day)  beginning on the sixth day of gestation and continuing
 through the eighteenth day.  On the twenty-ninth day of gestation the does were
 sacrificed and the litters recovered by caesarian section.   Examination of 120
 fetuses failed to reveal any abnormalities that could be attributed to exposure
 to carbofuran.   It appeared,  however,  that resorption was twice as high in the
 carbofuran test groups as in the controls.


 Potentiation -  Twelve  pesticides  were  included  in a study to determine whether
 or not  combination with  carbofuran  resulted  in  potentiation.   No potentiation
 as determined by  acute oral toxicity was  observed.


 Signs and Symptoms - Depending  on dose,  signs and symptoms  reported for carbo-
 furan intoxication were  similar in  most  animals.   These included fibrillary
action, salivation, ataxia, exophthalmos,  hyperpnea,  tonoclonic convulsions,
labored breathing, affected limbs  (weakness,  paralysis),  depression,  prostration,
and death.

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Antidotes - Studies with rats, dogs, rabbits, cattle, and sheep indicated that
treatment of affected animals with atropine sulfate could reverse the toxic
effects of carbofuran if treatment was started early enough.  A 50 mg/kg dose
was effective in rats and dogs.  A 10 mg dose of atropine sulfate protected
rabbits from lethal effects of carbofuran at 5.3 mg/kg.  The results of one
study with rats, however, indicated that 2-pyridine aldoxime methochloride
(2-PAM) was not antidotal.


Eye Irritation - Instillation of 5 mg of technical carbofuran into the conjunc-
tival sac of the eyes of New Zealand white rabbits resulted in miosis for a
period of 2 hr.  Thereafter, the condition cleared.


Skin Irritation - Intracutaneous injection of technical carbofuran into the skin
of male guinea pigs every other day for 20 days (0.05 ml initial injection and
all others 0.10 ml) did  not elicit  a  sensitizing  reaction.


Neurotoxicity - White leghorn hens dosed with technical carbofuran at concentra-
tion equivalent to the reported LD5Q  (38.9 mg/kg) exhibited salivation and
general weakness, but not leg and wing weakness.  Surviving birds were given a
second dose at day 21 with similar results.  No physical signs of neurotoxicity
were observed.


Metabolism - The main pathway of oxidative metabolism of carbofuran in animals
(and in plants and insects) appears to consist of hydroxylation at the benzylic
carbon to yield 3-hydroxycarbofuran (2,3-dihydro-2,2-dimethyl-3-hydroxybenzo-
furanyl-7-methylcarbamate).  The hydroxylated product is further oxidized  to give
3-ketocarbofuran (2,3-dihydro-2,2-dimethyl-3-ketobenzofuranyl-7-N-methylcarba-
mate).  Hydrolysis and conjugation  then result.   Carbofuran can also be hydro-
lyzeJ to carbofuran phenol  (2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran).   In
addition, hydrolysis can occur following oxidation to 3-hydroxycarbofuran  (or
3-ketocarbofuran).  The  3-keto compound is hydrolyzed at a much faster rate  than
carbofuran.

     The available data  also  indicates that  hydrolysis  is generally preceded by
oxidative metabolism.  The hydroxylated metabolites  can be  conjugated  as gluco-
sides in plants, or glucuronides in  animals.  Carbofuran metabolites are  stored
in plants but are not reported to accumulate or persist in  animal  tissues  or milk.


Food Tolerances and Acceptable Intake

     Carbofuran has not  been  reported as a  significant  residue in  any class  of
food, nor is it detected by the Food  and Drug Administration  analytical system
routinely used  to monitor pesticide residues in food.

     Tolerances have been established for  "carbofuran"  (evaluated as carbofuran
plus its 4 major metabolites,  and total  carbamates)  for 24  food and feed

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commodities.  These tolerances range from 0.05 ppm (including a maximum 0.02 ppm
carbamates) in meat, fat, and meat by-products to 40 ppm (including a maximum 20
ppm carbamate) in alfalfa hay.  See page 37

     An acceptable daily intake (ADI) has not yet been proposed for carbofuran.


Environmental Effects


Fish - Ten  species of  fish were used in laboratory testing of the toxicity of
carbofuran.  From all  tests, the 96 hr LC5Q ranged from 0.08 to 1.18 ppm.  The
toxicity of carbofuran varied considerably depending upon the species of fish
and the physical conditions associated with the tests.  For example, the LC5Q
(24 hr) of  carbofuran  to brown trout was 0.355 mg/1  (ppm) in city water, but
was found to be 0.842  ppm in reconstituted standard water.

     The bluegill appeared to be the most sensitive species and the fathead
minnow the  most resistant.  Intoxicated fish were at first hyperactive, but
this stage  was followed by lethargy, body paralysis, scoliosis, loss of equili-
brium, opercular paralysis, and death.

     When 3% granular  carbofuran was applied to rice fields at the rate of
0.5 Ib Al/acre, some casualties fo mosquitofish (Gambusia affinis) occurred
1 hr after  treatment.  Heavy mortality of mosquitofish, large-scale menhaden
(Brevoortia patronus), Atlantic croaker (Micropogon undulatus) and European
carp (Cyprinus carpio) was found 24 and 48 hr after treatment.  The rice seed
used to plant the fields had been treated with another insecticide.  If, and
to what extent, the seed treatment may have influenced the fish mortalities is
unknown.


Lower Aquatic Animals  - Carbofuran was of intermediate toxicity (compared to
several other commonly-used insecticides) to lower aquatic animals in one test,
highly toxic in another test.  The LC5Q for white river-crawfish and bullfrog
tadpoles was 500 and 2,700 ppb, respectively.  The LC5Q for Daphnia magna was
20 ppb.  The 24- and 48-hr £059  values for pink shrimp exposed to technical
carbofuran  were 0.0068 and 0.0046 ppm, respectively.  Technical carbofuran did
not appear  to affect the eastern oyster in exposures up to 96 hr at 1.0 ppm.

     In a field study, carbofuran granules (0.5 Ib Al/acre) resulted in heavy
mortality of cricket frogs, crayfish, earthworms, and nontarget aquatic insects
between 1 and 45 hr after treatment.


Wildlife -  Data on carbofuran''s toxicity to wildlife demonstrates that the oral
1050 to 8 species of adult birds for technical grade carbofuran ranged from
0.238 mg/kg for the fulvous tree duck (Dendrocygna bicolor) to 8.0 mg/kg for
the bobwhite quail (Colinus virginianus).  Dermal toxicity was 100 mg/kg in
tests with  2 species (house sparrow, Passer domesticus, and quelea, Quelea quelea.

     Oral LD50 for Furadan 10G ranged from 0.71 mg/kg for mallard ducks  (Anas
platyrhynchos; to 100 mg/kg for bobwhite quail.

-------
     Subacute toxicity studies indicated that the mallard duck was the most
sensitive of the birds studied (oral LDso = 0.397 mg/kg)  and that the bobwhite
quail was the most resistant (oral LDso =8.0 mg/kg)  to technical grade carbo-
furan.  Toxicity symptoms among the surviving bird species lasted from 5 to 7
days and occurred as soon as 5 min after treatment.

     Carbofuran fed to quail for 6 weeks was not highly toxic at levels of 200
ppm or less, but was highly toxic at 400 ppm.  Feed  efficiency decreased at
dietary levels above 200 ppm.

     Although sex differences were not observed with single acute doses, the
males appeared to be more susceptible than females to extended, subacute
dosing.

     The fertility of females and the hatchability of eggs were greatly
reduced at levels of 200 ppm and above.  However, no abnormal embryos or
hatchlings were observed.

     In one field study on the effects of carbofuran on wildlife, an application
of 3% granular carbofuran to rice fields at a rate of 0.5 Ib Al/acre resulted in
bird death or illness at 17 and 24 hr after treatment, with anywhere from 1 to 8
carbofuran granules in their stomachs.  In 5 other field studies, no mortality
or significant adverse effects on mallard ducks, bobwhite quail, and ring-neck
pheasant resulted from exposure to various carbofuran formulations.


Beneficial Insects - Carbofuran was highly toxic to honeybees (Apis mellifera)
by direct contact.  The LD5Q was 0.16 yg/bee.  No label warnings occur on
granular carbofuran formulations since granulars apparently offer little or no
hazard to bees.
Lower Terrestrial Flora - When applied at rates of 1 and 5 yg/g soil, carbofuran
did not drastically reduce the fungal population.  However, the higher rate did
depress fungal populations at 1, 2, and 4 weeks, but at 8 and 12 weeks there was
no significant difference between carbofuran-treated plots and untreated controls.

     Carbofuran applied at 5 yg/g soil significantly decreased bacterial popula-
tions during the first week.  However, bacterial populations soon recovered to
previous levels or levels above controls.

     The above studies also showed that carbofuran had no effect on ammonifica-
tion or nitrification of ammonium from soil organic nitrogen.  However, oxidation
of elemental sulfur was significantly depressed.

     Measurement of soil microbial respiration showed that oxygen consumption
increased as carbofuran concentration increased.  The authors concluded that
soil microorganisms are able to tolerate carbofuran.

-------
      Carbofuran applied at 100 ppm and 10 ppm AI had little effect on soil
 respiration.   Oxygen uptake in carbofuran-treated soil was slightly higher
 than the untreated control.  Possible degradation of the formulation was
 indicated.

      Other studies showed that carbofuran had no effect on nitrification  at
 application rates of 5, 50, and 500 ppm.   In addition, growth of  the rhizobia
 bacteria Rhizobium meliloti and Rhizobium japonicum was not affected.'  However,
 there was some growth inhibition of Rhizobium leguminosarum and Rhizobium tri-
 folii.

      Legume seedling growth was studied at the 5, 50, and 500 ppm application
 rates using sweet clover and alfalfa.  At the field application rate (5 ppm),
 carbofuran did not affect seedling growth.  However, at 500 ppm,  growth was
 drastically reduced.

      The effects of carbofuran on microflora under field conditions were
 studied using field plots designed to approximate actual pesticide applica-
 tion and timing in the growing of shade leaf tobacco.  Carbofuran depressed
 relative numbers of fungi, bacteria,  actinomycetes, and algae,  although not  at
 a statistically significant level.  Nitrification depression was  also not
 statistically significant.

      Carbofuran had no harmful effect on the Rhizobium species  peanut  (Arachis
 hypogaea)  symbiosis when applied at normal field rates.

      A study  to determine the influence of carbofuran on the growth rate  of  2
 soil-borne  fungi was conducted in vitro.   The growth of Fusarium  oxysporium  f.
 lycopersici was slightly inhibited when grown on nutrient media containing 5 ppm
 carbofuran.   The dry weight of Penicillium digitatum increased  slightly.

      The effects of 1,000 ppm AI carbofuran on microbial populations was  studied.
 Twenty-four hr after application the  average number of bacteria and fungi per
 gram of soil  did not differ significantly between the treated.and untreated
 samples.

      When carbofuran (0.47g AI/100 ml)  was added to commercial  formulations  of
 Bacillus thuringiensis,  the survival  of the bacteria on inert surfaces was not
 affected.
Lower Terrestrial Fauna  - The  effect  of  10%  granular carbofuran  applications  on
earthworms  (Lumbricus  terrestris) was studied.   Surface level  dead  and  dying
earthworm   counts were made  6  days  after application.   Earthworms in  the  immedi-
ate area of 2.0 and 4.0  Ib Al/acre  carbofuran banded applications were  killed in
large numbers.  The LDso for earthworms  was  1.3  mg/kg.   When carbofuran was
mixed with  soil, the LCso over a 5-day test  period was  12.2 ppm.  Studies using
14d-labeled carbofuran indicated that earthworms metabolize carbofuran  initially
in a manner similar to other animals  and plants.  However, the study  suggested
that toxicity to worms was caused by  factors other than cholinesterase  inhibi-
tion.
                                        10

-------
     The reactions of the manure worm (Eisenia foetida)  were compared to those
of earthworms (Lumbricus terrestris).   Carbofuran appeared to repel E,  foetida
while seeming to immobilize I,,  terrestris.   Carbofuran uptake in a 6-hr period
was similar for both species.   However, excretion of this material in 48 hr was
95% and 10%, respectively.


Bioaccumulation and Biomagnification  - Bioaccumulation and biomagnification
studies were performed using a  terrestrial-aquatic model ecosystem with a 7-
element food chain.  The terrestrial  phase  of the system was treated with l^C-
labeled carbofuran at a rate equivalent to  1 Ib Al/acre and allowed to run 33
days.  At the end of the experiment,  none of the organisms contained carbofuran,
although several carbofuran metabolites were isolated from a freshwater plant,
Elodea canadensis (maximum concentration 0.035 ppm) .

     Carbofuran was highly biodegradable, with low residual activity in the
ecosystem.  Detoxification occurred by hydroxylation of the carbofuran mole-
cules.  The authors concluded that carbofuran does not present ecological
problems related to food chain  accumulation or biomagnification.


Fate in Soil - The fate of carbofuran in soil was studied by incorporating 10%
granules applied at 1.85 ppm (recommended rate) into soils.  Soil concentration
of carbofuran after 8 weeks was 20% of the original.  Biological activity in
sandy loam soil disappeared within 16 weeks.  In muck soils, biological activity
persisted for 24.weeks.

     Degradation in soils of pH 7.8 was rapid; a tenfold difference in half-life
was noted between soils of pH 4.3 and 7.8.   Rapid chemical hydrolysis is the
primary route of carbofuran degradation in alkaline soils.  In acid and neutral
soils, both chemical and microbial degradation mechanisms predominate, but over-
all degradation rates are slower.

     Field investigations showed that carbofuran reached maximum insecticidal
toxicity 3 to 5 days after application.  Toxicity degradation in the 2 soils
tested (pH 5.2 and 6.4) was approximately equal.

     Time periods required for  carbofuran toxicity  to reach soil surfaces when
incorporated into the soil at depths of 1/2, 3/4 and 1  in were  1,  2 to 3, and
3 to 4 weeks, respectively.

     Three soil types were treated with 2.0 and 9.0 ppm -^C-labeled carbofuran.
Dissipation was more rapid in sandy loam soil than  in muck  soil with half-life
ranging from 20 to 40 days.

     Studies of carbofuran dissipation showed no correlation between climate
and dissipation rate.  However, dissipation was greater after broadcast  appli-
cation than after band or in-furrow application.   In addition,  studies  showed
no indication of soil residue increase with  carbofuran  applications in successive
years.   '
                                        11

-------
 Fate in Water  -  Little data was  available on the fate or effects  of  carbofuran
 in water.   Maximum  carbofuran  residues  in water from rice fields  treated with
 0.5 Ib Al/acre were as follows:   0.7  ppm 8 hr after  a postflood application
 and 0.05 to 0.1  ppm 7 days after a  preflood application.


 Fate in Air and  Nontarget Plants -  Limited data was  found on the  fate or the
 effects of  carbofuran residues in the air, or on effects of  residues in non-
 target plants.


 Transport - In a test simulating application of carbofuran granules  to flooded
 rice fields, carbofuran  residues in quantities toxic to leafhoppers  (test
 animal) moved  laterally  22.5 cm  in  48 hr.

      Transport studies showed  that  carbofuran leaches more slowly in soils
 which are high in clay or organic matter.   If soils  are of the same  clay content,
 movement is further in soils with lower exchange capacities.

      In a lysimeter study, carbofuran residues after 1 yr were negligible in the
 top 1.5 ft  of  2  heavy soils (high organic  matter) but were distributed equally
 throughout  the top  3 ft  of the sandy  loam  soil.   Field studies showed that
 carbofuran  residues generally  remain  in the upper 6  in of treated soils.  Below
 6  in depths, concentrations were less than 0.1 to 0.2 ppm in most instances.

      Runoff studies showed that  major losses of carbofuran occurred  only with
 early rainfall events.   In an  extensive 2-yr study,  carbofuran losses
 represented only 0.5 to  2.0% of  the total  applied.   Most of  the carbofuran  which
 was lost was found  in the water,  not  the sediment.
Efficacy and Cost Effectiveness

     Carbofuran is recommended for control of armyworms, corn borers, corn root-
worms , wireworms, nematodes, flea beetles, thrips, leaf hoppers, aphids,
Colorado potato beetles, rice water weevils, tobacco budworms, hornworms,
mosquito larvae, potato tuberworms, and lygus bugs on crops, and several pests
attacking trees.  Crops which are affected by these pests include alfalfa,
bananas, field corn, peanuts, peppers, potatoes, rice, sugarcane, and tobacco.

     The efficacy and cost effectiveness of carbofuran in pest control are
summarized below.
                                       12

-------
Alfalfa - The alfalfa weevil was  controlled  for  28  days  when 0.5  Ib/acre of
carbofuran was applied  to  the  crop.  Carbofuran  at  1.0 Ib/acre gave effective
control of the Egyptian alfalfa weevil when  applied 80 days  prior to cutting.
Control of lygus bugs was  achieved for up  to 33  days, but  control of aphids
was effective for a shorter period and additional applications were needed.


Corn - Control of corn  rootworms, the European and  southwestern corn borers,
and the armyworms in field corn was obtained at  rates of 1.0 Ib of carbofuran
per acre or less, except for the  Illinois  region where rates of 2.0 to 3.0 Ib/
acre were needed to control corn  borers.   Yields were generally increased with
improved control.

     In the tests reviewed, control of nematodes in carbofuran-treated field
corn was slightly better than  in  untreated checks,  but yields were significantly
increased.  Control of  wireworms  in the  tests reported was poor.

     The use of carbofuran on  field corn resulted in yield changes ranging from
a loss of 6.6 bu/acre to a gain of 49.4  bu/acre, as compared to untreated test
plots.  Economic benefits  from these yield changes  ranged  from a loss of $35.40/
acre to a gain of $90.20/acre  from the use of carbofuran.

Peanuts - Carbofuran is effective as a nematicide for  control of root-knot,
sting, and stunt nematodes in  peanuts.   Thrips were also controlled.  Control
of ring nematodes, however, was reported as  poor.   Yield increases were found
to be directly related  to  control of the root-knot  nematode; little relation
was found between thrips control  and yield.

     Most test plots produced  significant  yield  increases  of peanuts when
treated with carbofuran.  Compared to untreated  plots,  yield changes varied
from a loss of 412 Ib/acre to  a gain of  2,258 Ib/acre.   Economic benefits
ranged from a loss of $70.70/acre to a gain  of  $293.00/acre.


Potatoes - Carbofuran was  found to be effective  against potato infestation
caused by the Colorado  potato  beetle, wireworms, flea  beetles, and aphids.
Control was effective for  several weeks, with 1  application at rates vary-
ing from 0.5 to 8.0 Ib/acre.   Yields increased  significantly in all but one
test.  Compared to untreated plots, yields varied  from a loss of 21 cwt/acre
to a gain of 213 cwt/acre. Economic benefits ranged from a loss of $83.50/
acre to a gain of $625.00/acre.


Rice ~ Carbofuran was found to be effective  in  controlling the rice water weevil
for up to 6 weeks.  Applications  made as preplant  or up to 5 weeks after flood
were effective.  Control of mosquito larvae  was  reported as excellent with
carbofuran.  Rice yields generally increased with  the  use of carbofuran.   Com-
pared to untreated test plots, yields ranged from a loss of 214 Ib/acre to  a
gain of 1,302 Ib/acre.   Economic  benefits  ranged from a loss of $24.60/acre to
a gain of $106.50/acre.
                                       13

-------
Tobacco - Carbofuran is used for control of wireworms and the hornworm in
tobacco.  It is also reported to be effective in control of the tobacco budworm
and tobacco flea beetle.  Control of the hornworm was achieved for 7 weeks
after 1 application.  Better control of the budworm was achieved at 4.0 to 6.0
Ib/acre than at lower rates.  Control of the flea beetles was greatest with a
pretransplant application followed by a posttransplant application.  Tobacco
yield changes ranged from 152 to 161 Ib/acre compared to untreated plots.
Economic benefits varied from $102.00 to $110.00/acre.
Peppers - Carbofuran is recommended for control of  the green peach aphid and
European corn borer in peppers.  Two applications were successful in control-
ling the borer.  Yields increased in all  tests reviewed, and some were signi-
ficantly better than untreated test plots.  Yield changes varied from a gain
of 22 cwt to 82 cwt/acre, compared to untreated test plots.  Economic benefits
range from $269.00 to $l,035.00/acre.


Sugarcane - Carbofuran is considered effective for  controlling the sugarcane
borer and wireworms.  It also is used in  control of nematodes, and it signifi-
cantly increases sugarcane yields.  Economic benefits, based on one test, were
$410.00/acre.
                                        14

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                  PART II.  INITIAL SCIENTIFIC REVIEW

                          SUBPART A.  CHEMISTRY

                                 CONTENTS

                                                                   Page

Synthesis and Production Technology	16


Physical Properties. 	  19


Analytical Methods 	  21

   Multi-Residue Methods 	  21
   Residue Analysis	21
   Formulation Analysis	24
   Other Residue Methods	24


Occurrence of Residues in Food'and Feed Commodities	27


Acceptable Daily Intake	34


Tolerances ..... 	  34


Composition and Formulation	38


Chemical Properties	38

   Hydrolysis	39
   Hydroxylation  (oxidation)  	  '*3
   Photodecomposition	43


References	45
                                       15

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     This section contains a detailed review of  available data on carbofuran's
chemistry and presence in foods.   Eight subject  areas have been examined:
Synthesis and Production Technology;  Physical Properties of Carbofuran;
Analytical Methods;  Composition and Formulation;  Chemical Properties,
Degradation Reactions and Decomposition Processes;  Occurrence of Residues
in Food  and Feed Commodities; Acceptable Daily Intake; and Tolerances.   The
section  summarizes  rather than interprets data reviewed.
Synthesis and Production Technology

      Carbofuran  (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate)  is
manufactured by  the  Agricultural  (formerly Niagara)  Chemical Division  of the
FMC Corporation.   FMC's manufacturing plant for  carbofuran is located  at
Middleport, New  York,  but an important intermediate of carbofuran  (2,3-dihydro-
2,2-dimethyl-7-benzofuranol) is produced at Baltimore.

      The process used  for manufacturing carbofuran (FMC, 1975), is described in
patents  by Borivoj  (1967) and Thorpe (1974).  The reactions for this process
are shown in Figure  2.   A schematic diagram of this  process is shown in
Figure 3.
          C1CH CCH
          C1CH2CCH3
          chloride
                             CHj
                                   t«Cf.ng««nt
                                   175-190*C
LCH,C-CH,
                                                          (II)
    ,011

    -CH-C(CHj)2

2-nlcro-6-tiobuti«iul (III)
                       nurob«
        (ftCL ?r«;«rr«d)
        :5C-i?o'c
                                 H2. hydrogttution

                                   catalyit
                   7-Gicrobanzofuran (IV)
                                                S!'2 . .CH,
                                                2.2-dlMthylb«iuofur»a (V)
  + H.SO. + 3USO,  or b.Io
                             ^ •>• HjO
                                   SO,
                                        H,0, hHC
                                        —	
                                    4   CuS04
                                                  2,3-dlhyd»-2,2-dlB4Chyl-
                                                   7-baasofurftaol (VZ)
 VI + OijNCO
            Figure  2.   Preparation  of Carbofuran from o-Nitrophenol

 Source:   FMC (1975).
                                           16

-------
        Methallyl Chloride
o-Nitrophenol
        Aqueous  Base
Ferric Chloride
         Sodium Nitrite
        Mineral  Acid
Cupric Sulfate
         Steam
                                   Etherification
                                        Unit
                                     Separation
                                                • Aqueous Waste
                                        1
                                   Rearrangement
                                        and
                                  Cyclization Unit
                                         1
Hydrogen
Catalyst

Hydrogenation
Unit
t
Filter



                                        I
                                    Diazotization
                                        and
                                   Hydrolysis Unit
                                        1
                                  Steam Distillation
                                         1
Methyl Isocyanate
Methylene Chloride
i
Solvent


Rec
Carbofuran Unit
ycle

I
I
                                     Carbofuran



Figure 3.   Production  Schematic  for Carbofuran

Source:   FMC  (1975).
                                                         Catalyst
                                                         Recycle
                                                •Aqueous Waste
                                 17

-------
        An  alternate manufacturing process  for carbofuran is described by
    Scharpf  (1969). The  reactions  for  this process are as follows:
      OH     CH2   RefluxinS
             II     (Acetone)
      + C1CH2CCH3
                   Base,
                   KI Cat.
Catechol   Methallyl
           chloride
                               Methallyloxyphenol
2,3-Dihydro-
  2,2-dimethyl-
  7-benzofurano1
               CH3  + CH3NCO
                    Methyl
                  Isocyanate
                                   Ether
                                                  OCONHCH3
                               Triethylamine
                                                                             (2)
                                                       CH-i
                                               Carbofuran
        In the laboratory preparation described in the Scharpf patent, the
   yield in the step from catechol to methallyloxyphenol was 44%. The yield
   for Reaction (2) was 73%. The overall yield could not be calculated
   from the data given.
        Several other patents issued to FMC describe processes for the manu-
   facture of the intermediate 2,3-dihydro-2,2,-dimethyl-7-benzof.uranol.
   These processes are described below. Orwoll (1967) describes a process
   beginning with £-bromophenol as shown in Equations (3),  (4a) ,  and  (4b) .
                                Re fluxing, several
                                   solvents at
                                 different times
                                Vacuum distillation
-Bromophenol
                    Methallyl
                    chloride
                                                               CH3
                                                                     (3)
                                            2,3-Dihydro-2,2-dimethy1
                                              7-bromobenzofuran (I)
                                        18

-------
  + HOCH2CH2OH
    Ethylene
    glycol
+   NaOH   +  Cu(N03)2'3H20
   Sodium        Copper
  hydroxide      nitrate
  + NaOH   +   CU20
   Sodium    Cuprous
 "hydroxide    oxide
                                                    2,3-Dihydro-
                                                      2,2-dimethyl-
                                                      7-benzofuranol
                                                                      (4a)
                                                                      (4b)
     Before the patent  to  Scharpf  (1969) was issued, Borivoj  (1967) reported
that catechol is an expensive  starting material compared to a-nitrophenol.
Furthermore, the overall yield from o-nitrophenol was reported to be high,
about 50% based upon £-nitrophenol, even though the process involved many
steps.  (See Figure 2.)

Physical Properties

     Chemical name;  2,3-dihydro-2,2-diraethyl-7-benzofuranyl methylcarba-
                        mate

     Common name:  Carbofuran

     Other names;  Furadan®, XIA. 10242, Em 27164
     Pesticide class;  Insecticide, acaricide, nematicide; carbaraate
     Empirical formula;
Structural formula:
                                Pi "
                               >-C-N-CH3
                                        CH-i
     Molecular weight;  221.3
     Elemental analysis;  C, 65.2%; H, 6.8%; N, 6.3%; 0, 21.7%
                                   19

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     Physical state;   White,  crystalline solid

     Odor;  Odorless  (Martin, 1971)
            Slightly  phenolic (FMC,  1971b)

     Density;  1.180  at 20/20°C

     Melting point;  Pure,  153 to 154°C
                     Technical, 150  to 152°C
                     Degrades at temperatures in excess of 130°C (FMC,
                       1971b)

     Vapor pressure;   2 x 10"  mm Hg at 33°C
                      1.1 x 10"4 mm  Hg at 50°C

     Solubility;   7. weight/weight, 25° C (Cook, 1973)

                    Acetone                       15
                    Acetonitrile                  14
                    Benzene                        4
                    Cyclohexanone                  9
                    Dimethyl  formamide            27
                    Dimethyl  sulfoxide            25
                    Ethanol                        4
                    Kerosene                      < 1
                    N-Methyl-2-pyrrolidone        30
                    Methyl chloride                12
                    Petroleum ether               < 1
                    Xylene                       < 1
                    Water                          0.07 (700 ppra)

Carbofuran is essentially insoluble  in conventional formulation solvents
employed in agriculture (FMC, 1971b).

     Flammability;  Not flammable--will support combustion if ignited.

     Explosive hazard;  Nonhazardous at normal temperatures

     Corrosive action:  Noncorrosive
                                    20

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Analytical Methods

     This subsection reviews analytical methods  for  carbofuran.   The  review
describes multi-residue methods,  residue analysis  principles,  and formulation
analysis principles.  Information on the sensitivity and  selectivity  of  the
methods is also presented.


Multi-Residue Methods - Carbofuran cannot be detected by  the multi-residue
methods described in the Pesticide Analytical Manual (PAM,  Vol.  I,  1971);  it
is not obtained in the eluate from the extraction  and cleanup  procedures.

     A procedure has recently been developed by  Holden (1973)  that  can be  used
for several methylcarbamate pesticides in plant  materials.  The  procedure  calls
for extraction of the crop  material with acetonitrile, then partitioning the
extract with petroleum ether.  The extract is purified by means  of  a  coagula-
tion procedure using phosphoric acid-ammonium chloride solution.   The mixture
is filtered through celite  and the filtrate is extracted  with  methylene
chloride.  Phenolic impurities are eliminated by partitioning  the methylene
chloride extract with 0.1 N potassium hydroxide.  The residue, after  evapora-
tion of the methylene chloride, is treated with  l-fluoro-2,4-dinitrobenzene
to form an ether derivative.  Conversion in this step is  essentially  complete.
Determination is then made  by electron capture gas chromatography.  Residues
may be determined as low as 0.05 ppm, with recoveries between  90 and  110%.
This procedure, however, will not detect phenolic metabolites  or plant metabo-
lic conjugates such as the  3-hydroxycarbofuran glycosides.
Residue Analysis Principles - There is one basic method for carbofuran residue
analysis.  It employs microcoulometric gas chromatography with a nitrogen
detection system.  The most important studies all use this basic method,
although there are changes in extraction and cleanup procedures for specific
food products.  The method was first published by Cook et al. (1969).  The
method is also described in PAM (Vol. II, 1967) and in Residue Reviews (Cassil
et al., 1969).  Cook (1973) has summarized previous reports for carbofuran in
40 products, including various plant materials, animal materials, milk, water,
and soil (Table 1).  The details of the extraction methods are described below.
The following diagram shows the steps in this method (McCarthy, 1970).
     Acid hydrolysis of  sample
                 I
   Methylene chloride extraction
                 J
           Concentration
                 I
   Acetonitrile/hexane partition
   Methylene chloride  extraction
           Concentration  >
                 J
  Silica gel/nuchar-attaclay cleanup
                 I
     Hexane/ethyl acetate elution
                 *
            Conccntrat ion
Nitrogen analysis by microcoulometric
          gas chromatography
                                                        Calculation
                                         21

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                                   Table 1.  Method Requirements for Specific Sample!
Column cleanup

Simple
Alfalfa
Alfalfa, hay
Apple*
Beans, green
Beans, lima
Carrots
Corn, cobs
Corn, grain
Corn, husks
Com, silage
Corn, stover
Eggs
Lettuce
Milk
Peaches
Peanut, hay
Peanut, hull a
Peanut, vines
Peanuts
Pears
Peppers, green
Potatoes
Pumpkins
Rice, grain
Rice, hulls
Rice, green stjrav
Rice, dry strav
Soil
Sugar beets, foliage
Sugar beets, pulp
Sugar beets, roots
Sugar cane
Sugar cane Juice
Tissue, glztards
Tissue, kidney
Tissue, liver
Tissue, muscle
Tobacco, dry
Tobacco, green
Tomatoes
Water
Sample
•lie (g)
25
5
50
50
50
100
50
70
50
50
50
100
SO
100
50
100
20
20
40
50
100
100
50
20
20
40
10
50
50
20
50
40
40
100
100
100
100
10
50
50
100
Nuchar-actaclay (g):
Partition
No
No
No
Yet
Yes
No
No
Yea
Yes
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
No
Yes
No
Yes
Yes
Yes
No
Yes
No
No
No
No
No
No
No
Yes
Yes
Yes
No
No
No
No

7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
7:
5:
5:
S:
5:
7:
7:
5:
7:
3:
3:
3:
3:
7
7:
7:
7:
5:
5:
7
7:
7:
7:
7:
7:
5:
5:
packing (g)
10 silicic acid
10 silicic acid
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
5 silica gel
10 silicic acid
5 silica gel
5 silica gel
10 Florlill*-'
10 Florlslli/
10 Florlslli/
10 Florlslli'
5 silica gel
5 silica gel
10 Florlsll
5 silica gel
15 Florlsllf
15 FlorisllV
15 Florlstl^'
15 FlorlsllV
10 aluminum oxlde£'
10 aluminum oxide*-'
10 aluminum oxlde^'
10 PlorlsllS-'
10 Florlsll*y

5 silica gel
5 silica gel
5 silica gel
10 silicic acid
10 silicic acid
10 Florisll
10 Florlsll
ml Ethyl acetate/
hexane (v/v)
125-70/30
125-70/30
100-70/30
100-70/30
100-70/30
300-70/30
100-70/30
100-70/30
150-60/20
150-80/20
100-70/30
150-70/30
125-70/30
150-70/30
100-70/30
100-80/20
100-80/20
100-80/20
100-80/20
100-70/30
200-70/30
150-70/30
100-70
230-100/0
230-100/0
230-100/0
230-100/0
150-80/20
125-100/02.'
125-100/0
125-100/0
100-60/40
100-60/40
150-80/20
150-70/80
150-70/80
150-70/80
125-70/80
125-70/80
100-80/20
110-80/20
Method
sensitivity (pptn)
0.20 ,
0.20
0.10
0.10
0.10
0.05
0.10
0.10
0.10
0.10
0.10
0.05
0.20
0.025
0.10
0.5
0.1
0.5
0.1
0.1
0.05
0.05
0.10
0.20
0.20
0.20
0.20
0.10
0.10
0.10
0.10
0.10
0.10
0.05
0.05
0.05
0.05
0.20
0.20
0.05
0.01

    Concentrate  the  dried ncthylene chlmlde extract (1 ,fiOO ml)  In a Ki:dcrn,n-D.inl»h
     oncent r
-------
     Cook (1973)  described extraction methods  for  plant  materials as follows:

        Place the appropriate amount of chopped  and blended  crop in a
        1,000-ml  round-bottomed  flask containing a magnetic  stirring
        bar.   Add 600 ml of 0.25 N hydrochloric  acid.  Connect the round-
        bottomed  flask  to a Liebig condenser using a  50/50 to 24/40 $
        neck adapter.   Reflux the crop-acid mixture for  1  hr using a
        heating mantle.  Swirl the flask  contents  by  hand  during the
        initial heating period and then continuously  stir  the mixture
        with a magnetic stirring bar.  Fortify check  crop  samples prior
        to the addition of acid.

        After 1 hr of refluxing, remove the round-bottomed flask from the
        heating mantle  and filter the hot sample through glass wool into
        a 1,000-ml Erlenmeyer flask.  Wash the reflux flask  and glass wool
        with an additional 300 ml of hot  0.25  N  hydrochloric acid.  Cool
        the filtrate for 1 hr at -10°C and transfer into a 2,000-ml
        separatory funnel.  Add  approximately  250  mg  of  sodium lauryl
        sulfate to the  filtrate  and mix.   Extract  the aqueous phase 3
        times with 600  ml of distilled methylene chloride.  Combine the
        methylene chloride extracts and dry over anhydrous sodium sulfate.

A modification of this  procedure which is suitable for residues in small fruits
is reported in Williams and Brown (1973).

     Cook (1973)  described extraction methods  for  milk as  follows:

        Pour 100  ml (100 g) of milk into  a blender.   Add 500 ml of dis-
        tilled acetone  and blend for 3.0  min.  Fortify check milk samples
        prior to  the addition of acetone. Filter  the sample in a 1,000-ml
        round-bottom flask.  Add 100 ml of 0.375 N hydrochloric acid and
        2 or 3 glass beads.  Connect a. Snyder  column  to  the flask.  Place
        the sample mixture in the steam bath and evaporate all the acetone,
        leaving  the sample in the aqueous solution.   Reflux the aqueous
        solution  for 15 min.  Remove the  round-bottom flask from the steam
        bath and  rinse  the bubble column  with  0.375 N hydrochloric acid.
        Place the aqueous solution in a  freezer  (-10°C).  Allow the sample
        to cool until ice just begins to  form  (about  1.5 hr) .  Remove the
        sample from the freezer  and filter quickly through glass wool into
        a 1,000-ml separatory funnel to  remove any oils  or waxes which have
        solidified during cooling.  Rinse the  round-bottom flask and glass
        wool with about 50 ml of 0.375 N hydrochloric acid.   Extract the
        aqueous phase 3 times with 200 ml of distilled methylene chloride.
        Combine  the methylene chloride extracts  and dry  over anhydrous
        sodium sulfate.

   Cook (1973) described extraction methods  for  animal material as follows:

        Place the appropriate amount of  subsampled diced  tissue or eggs
        (shells  removed) into a  blender.   Add  300  ml of acetone and
        blend for 3.0 min.  Filter  the blended mixture through  a  Buchner
                                        23

-------
         funnel, using No. 5 filter paper.  Retain the filtrate.  Return
         the filter paper and the tissue residue to the blender.  Add
         300 ml of acetone and blend again for 30 min.  Filter the blended
         mixture through a Buchner funnel using No. 5 filter paper.  Com-
         bine the first and second filtrates.

         Allow the combined filtrates to stand in a 1,000-ml separatory
         funnel for 0.75 hr.   Drain off any oils that settle to the bottom.
         (Note:  Beef tissue and egg filtrate "oil" will settle out at
         room temperature.  Chicken tissue filtrate may require cooling to
         settle out the "oil.")

         Place the acetone filtrate from above into a 1,000-ml round-bottom
         flask (24/40 S neck) with a few glass beads.  Connect a Snyder
         column to the flask and concentrate the acetone to approximately
         50% of its initial volume on a steam bath.  Remove the flask from
         the steam bath and add  150 ml of 0.25 N hydrochloric acid.  Replace
         the sample mixture in the steam bath and evaporate all the acetone.
         Reflux the aqueous solution for an additional 0.25 hr to insure
         complete conversion of  the conjugated residues to the aglycone form.
         Remove the round-bottom flask from the steam bath.  Rinse the bubble
         column with 0.25 N hydrochloric acid.  Place the aqueous solution
         in a freezer (-10°C) for 1.5 hr to allow the remaining fats and oils
         to solidify.  Remove the sample from the freezer and quickly filter
         through a small bed  of  glass wool into a 500-ml separatory funnel.
         Rinse the flask and  glass wool with 50 ml of 0.25 N hydrochloric
         acid.   Extract the filtrate 3 times with 100-ml portions of methylene
         chloride.   Combine the  methylene chloride extract and dry over an-
         hydrous sodium sulfate.

      Cook  (1973)  described extraction methods for water as follows:

         Place the appropriate amount of subsampled water into a 250-ml
         separatory funnel.   Extract 3 times with 100-ml portions of methylene
         chloride.   Combine the  methylene chloride extracts, dry over sodium
         sulfate,  and filter.  Wash the sodium sulfate and filter paper with
         methylene chloride.


 Formulation Analysis - "Dhe recommended method for analysis qf carbofuran formu-
 lations  is by gas chromatography,  using an internal standard, comparing the peak
 area  of  the unknown sample to the peak area of the standard (Cook, 1973).  Other
 analytical methods  for identification and/or reference are infrared spectrometry
 (Chen and  Benson,  1966);  nuclear magnetic resource spectrometry, (Keith and Alford,
 1970), and spectrometry (Vickers et al.,  1973).


Other Residue Methods  - Table 2  lists  other analytical methods and sensitivities.
                                         24

-------
           Table  2.  Other Analytical Methods for Carbofuran Residues
      Type  of method
Sensitivity
     Source
 Spectrophotofluorometry
0.5 ppm
 Gas  liquid chromatography         0.04 ppm
   Alkaline hydrolysis to phenol,
   steam distillation and derivi-
   tization as thiophosphoryl
   ether followed by fluoro
   photometric detection in
   phosphorous mode.
 Infrared analysis
50 yg
Electron-capture gas chroma-      0.01-0.10 ppm
   tography of trichloroacetates
   after hydrolysis of carbofuran
   residues to phenols
Electron-capture gas liquid
  chromatography of trichloro-
  acetates of carbamates after
  removal of phenolic metabolites
0.01 ppm
Electron-capture gas chroma-      0.1 ppm
  tography of dinitrophenyl ethers

High-speed liquid chromatography  2-10 ng/injection

Electron-capture gas chromatography    -
Thin-layer chromatography-
  spectrophotofluorometry
Thin-layer chromatography-
  enzyme inhibition-
Thin-layer chromatography

Phosphorescence
ppb range
ng range
 Bowman and Beroza
 (1967b)

 Bowman and Beroza
 (1967a)
 Broderick et al.
 (1966)

 Butler and McDonough
 (1968)
 Butler and McDonough
 (1971)
 Caro et al. (1973b)


 Frei et al. (1974)

 Holden et al. (1969)

 Lawrence and Frei
 (1972b), Lawrence and
 Frei (1972a), Lawrence
 et al. (1972)

 Mendoza (1972),
 Mendoza and Shields
 (1970), Mendoza and
 Shields (1971)

CWinterlin et al.  (1968)

 Moye and Winefordner
 (1965)
                                         25

-------
       Table 2.   Other Analytical Methods for Carbofuran Residues  (Continued)
      Type of method
Sensitivity
    Source
 Gas chromatography of N-perfluoro-
   acyl derivatives

 Electron-capture gas chromato-
   graphy of various ether
   derivatives

 Transesterification with methanol
   via reaction gas chromatography
   to form methyl N-methylcarbamate
   with alkali flame detection

 Spectrometry (laser excited Ramen
   and fluorescence spectra)

 Gas chromatography (Review article)
   0.05 ppm
                       Seiber (1972)
                       Seiber et al.  (1972)
Van Middlelem et al.
(1971)
                       Vickers et al.  (1973)
                       Williams (1970)
      In addition to carbofuran itself,  2 types of metabolites  are detected  by
 the  method  of  Cook (1973).   These are 3-hydroxycarbofuran and  various  conjugated
 forms of 3-hydroxycarbofuran including glycosides (plant metabolic conjugates)
 and  glucuronides (conjugated products of animal metabolism).

      The water-soluble conjugated forms are converted into the 3-hydroxycarbo-
 furan (aglycone)  form before extraction.  The equation for this acid hydrolysis
 reaction is as follows (Cook,  1973):

                                                      0
                                                      II
                                                     OCNHCH3
                     0-Glucoside
         3-Hydroxyglucoside
               3-Hydroxycarbofuran
     It should be noted  that  some  of  the methods  listed  in Table 2  are not
applicable to the conjugated  forms because  organic  solvent extraction techniques
were used that did not remove the  water-soluble conjugated form.  These were  the
methods of Bowman and Beroza  (1967a)  and Butler and McDonough  (1968).
                                         26

-------
     In addition, Ruhr and Casida (1967)  and Metcalf (1968)  indicate that
certain glycosidic conjugates are difficult to cleave to corresponding
aglycone.

     More  recently an analytical method has been developed to detect the
phenolic metabolites of carbofuran.   These metabolites are carbofuran phenol,
3-ketocarbofuran-7-phenol, and 3-hydroxycarbofuran-7-phenol.   The method con-
sists of hydrolyzing possible conjugates,  deriving the 3-hydroxy moiety to the
ethoxy or  rv-propoxy ether and then deriving the phenol to the 2,4-dinitrophenyl
ether.  Analysis is by GC, using a nitrogen-specific detector (FMC^1971a).
Its application to potato tubers, milk, eggs, and cattle and  poultry tissue
are reported by Jackson (1973a and 1973b)  and Shuttleworth (1973).

     It should be noted that all current  tolerances include  consideration of
both phenolic metabolites (and conjugates) as well as oxidation products still
containing the carbamate functional grouping  (see p. 34).


Occurrence of Residues in Food and Feed Commodities

     Methods for detecting residues in crops are described in the subsection on
Analytical Methods  (see p. 21).  Residue tests for various crops are described
below,
Sugarcane - Carbofuran was applied to sugarcane grown in 7 locations in Florida
and Louisiana.  Twenty-seven test plots treated with 3 and 4 applications  of
carbofuran 3G  (total of 3 to 4 Ib Al/acre) were sampled at post-harvest intervals
ranging from 0 to 55 days.  There were only 3 instances in which the total resi-
dues from the 4 Ib Al/acre rate measured 0.1 ppm or greater.   In one test,  at
0 days from last application to harvest, 0.23 ppm residues were found.  In a
second test, 18 days after the harvest, residues ranged from 0.1 to 0.2 ppm.
In a third test, also 18 days after the harvest, 0.37 ppm residues were found.

     Carbofuran 10G applied at rates to 32 Ib Al/acre, with post-harvest  inter-
vals ranging from 212 to 427 days, resulted in no detectable residues.

     Applications of carbofuran 75 WP produced variable results, as shown, with
other applications in the following table  (FMC, 1969a).
                                         27

-------
              Table 3.   Residues of Carbofuran on  Sugarcane^

Active

ingredient per Number

Formulation
10G
10G
10G
10G
75 WPl/
75 WP
75 WP

75 WP
75 WP
75 WP
75 WP
75 WP
75 WP
75 WP
' 75 WP
75 WP
75 WP
75 WP
3G
3G
3G
3G

3G
3G
3G
3G
3G
application
(Ib/acre)
8
8
8
8
0
0.6
0;6

0.6
0.6
0.6
0.6
1.2
1.2
1.2
1.2
1.2
1.2
1.2
0
0.9
0.9
0.9

0.9
0.9
0.9
0.45
0.45
of

Days from last
application to
applications harvest
1
1
2
2
0
4
4

4
4
4
4
4
4
4
4
4
4
4
0
4
4
4

4
4
4
3
3
356.
356
212
212

2
2

17
17
33
33
2
2
17
17
17
33
33

0
0
18

18
41
41
55
55

Total
residue—
(ppro)
ND
ND
ND
ND
ND
1.03
0.5 to
0.6
< 0.1
< 0.1
< 0.1
< 0.1
0.83
0.48
0.11
0.11
< 0.1
< 0.1
ND
ND
0.23
< 0.1
0.1 to
0.20
0.37
ND
< 0.1
ND
ND


a/ Data from


seven locations in states
l>/ Total residue equals
~~ lytical
method used
a nitrogen detector
c/ ND = None
detectable.
d/ Formulation currently
carbofuran plus
of Florida and Louisiana.
3-hydroxy carbofuran.
The ana-
was microcoulometric gas chromatography with
, corrected for

not available.
recovery.





Source:  FMC (1969a).
                                    28

-------
Corn Fields  -  Table 4 summarizes data for carbofuran tests on  field  corn  grown
in 4 states.
  75
  76
  92
  98
 101
 111
 133
 133
 136
              Table 4.  Maximum Total Residues  (ppm of Carbofuran
                       Including 3-hydroxycarbofuran) Found on
                       Field Corn Silage and Stover
Al/acre
Days
lapsed Location
1 Ib
rate
2 Ib
rate
4 Ib
rate
8 Ib
rate
Arkansas
Arkansas
New York
Iowa
Nebraska
New York
Arkansas
Iowa
Nebraska
3.0 (0.8)-/ 5.1 (3.9)
1.0
4.6 (1.9)
2.4
0.5
1.3
3.1
0.8
0.1
0.4
                                       7.3
                                       2.8
a/  Values in parentheses  are  from  the banded  treatment  (7-in band/40-in row).
    All others are in-furrow,  10G formulation.

Note:  Carbofuran was found  to be nondetectable in corn  grain at rates to 8 Ib/
       acre harvested from 111 to 133 days  after application.  The maximum
       recommended application rate is 3  Ib Al/acre.

Source:  FMC (1971a).


Alfalfa - Dissipation studies  (FMC, 1968) were conducted on alfalfa grown in
9 states with carbofuran applied at levels  ranging from 0.25 to 2.0 Ib Al/acre.
Total carbamate residues were  determined  on green alfalfa by a nitrogen specific
microcoulometric gas  chromatograph  method sensitive to 0.2 ppm carbofuran and
0.2 ppm of the metabolite  3-hydroxycarbofuran.  Only carbofuran, 3-hydroxy-
carbofuran, and 3-hydrocarbofuran glucoside were found.   The glucoside was hydro-
lized quantitatively  and reported as 3-hydroxycarbofuran.  All results were
adjusted for 80% moisture  in the alfalfa.
                                        29

-------
     Wide variations were  found  in  residue  dissipation due to the combined
effect of various factors  including climatic  conditions, metabolism in the
plant, rate of growth, density,  and uniformity  of  the stand.  Maximum total
carbamate residues  in ppm  were as follows:
                 Table  5.  Residues  of  Carbofuran in Alfalfa
                                 (ppm Al/acre)
                    0.25
0.50
1.0
2.0
0
7
14
21
28
15.5
0.9
0.5
—
0.5
32.4
20.6
3.8
1.4
1.0
114.0
48.5
6.6
7.4
4.1
145.5
87.0
11.4
8.2
"• —
Source:  FMC  (1968).
     In some  of  the  studies,  samples  of alfalfa hay were taken  to  compare residue
values with those  in the  green alfalfa of the same time interval.  Water deter-
mination  gave an average  of  16% in the hay.   A drying method, reducing  the mois-
ture from 80% to 15%, would  give a factor of 4.25; this theoretical  factor was
verified  by tests  on the  green and dried samples of the same interval cuttings.
Studies from  9 states with carbofuran applied at 1.0 Ib Al/acre showed  total
residues  ranging from 1.4 to 14.5 ppm at zero day and 4.1 to 0.1 ppm Al/acre 28
days posttreatment.

     A study  was made on  the persistence of carbofuran and 3-hydroxycarbofuran
on alfalfa in Massachusetts.   When carbofuran was applied to first-cutting  al-
falfa at  the  rate  of 0.5  Ib  Al/acre,  no detectable residue of carbofuran was
found in  the  green plant  21  days posttreatment; 3-hydroxycarbofuran amounted
to 0.55 ppm.   At 1.0 Ib Al/acre, the  carbofuran residue was below the  sensiti-
vity of the method and  the metabolite was measured at 1.26 ppm 21 days  posttreat-
ment.  Stubble sprays of  carbofuran at 0.5 and 1.0 Ib Al/acre resulted  in no
detectable residues  of  carbofuran and a maximum of 1.5 ppm of the metabolite  on
the dry hay  (Shaw  et al., 1969).

     Studies  of  Fahey (1970)  on green and dehydrated alfalfa grown in  South
Dakota and treated with carbofuran at 0.5 and 1.0 Ib Al/acre showed no  measur-
able residues of carbofuran  in samples collected 14 and 21 days after  treatment.
The loss  of carbofuran  attributed to  dehydration averaged 67% for plots treated
with 1.0  and  0.5 Ib  Al/acre  and sampled the same day.
                                                               •

Rice - Test data was obtained from rice grown in California, Louisiana, and
Texas (FMC 1969b) .   When  carbofuran was applied as a 2 G formulation at rates
from 0.5  to 2.0  Ib Al/acre,  green straw rice harvested from 25  to 148  days
after application  contained  less than 0.3 ppm carbofuran residues.
                                       30

-------
     Whole grain rice grown on soil treated with carbofuran 2G at rates of
0.5 to 2.0 Ib Al/acre and harvested from 110 to 168 days after application
likewise contained less than 0.3 ppm carbofuran residues, with the majority
of samples containing less than 0.2 ppm.  Similar results were obtained when
carbofuran 3G was applied at 0.5 to 1.0 Ib Al/acre, with a post-harvest
interval of only 51 days.  Hulls, polishings, broken grains, and polished
grain from rice harvested 87 to 92 days after applications of carbofuran 3G
at 0.5 to 1.0 Ib/acre contained less than 0.3 ppm residues.

     Total residues equaled carbofuran plus 3-hydroxycarbofuran.  The analyti-
cal method used was microcoulometric gas chromatograph (MCGC), with a nitrogen
detector corrected for recovery.  It should be noted that, even on samples ta-
ken from rice receiving no treatment, residues were reported as <0.2 ppm.

Peanuts - Table 6 lists the data obtained from tests of carbofuran on peanuts
(FMC,1970).  The data listed includes portions of plant, type of application,
amount of active ingredient applied per acre, days lapsed, and total residue
of carbofuran plus 3-hydroxycarbofuran.  The maximum residue in the nut por-
tion was less than 0.1 ppm.  The maximum residue in the hulls was 0.8 ppm.
The maximum residues in the vines by type of application were:  banded at
planting, 1.5 ppm; in-furrow at planting, 20 ppm; banded at pegging, 9 ppm;
and in-furrow at planting plus banded at pegging, 37 ppm.
                   •
General - A study (Shuttleworth, 1974) was conducted to determine whether or not
a buildup of residues of carbofuran and its metabolite 3-hydroxycarbofuran would
occur in raw agricultural commodities (corn, potatoes, peanuts, and tobacco)
grown on plots treated 4 consecutive years with carbofuran at registered or
proposed rates and use patterns.  Plots were located in the south, midwest, and
east.   Samples were analyzed by a nitrogen specific microcoulometric gas
chromatograph.  Depending upon the crop, method sensitivities ranged from 0.075
ppm to 0.20 total carbamates.  Recoveries exceeded 70% for both carbofuran and
the metabolite.

     Potato tubers grown in New York and receiving 5 foliar applications of
carbofuran 4F at 1.0 Ib Al/acre yielded no carbamate residues approaching the
sensitivity of the method.

     Corn grown in Nebraska and New York on soils treated with carbofuran 10G
(in-furrow and banded) at 3.0 Ib Al/acre contained no detectable residues in
either grain or stalk samples from either location.

     Peanuts grown in Arkansas on soil  treated with 1.0 and  2.0 Ib Al/acre
(as carbofuran 10G) in-furrow and at pegging, respectively,  showed trace
residues (0.025 ppm)  of carbofuran and  20.10 ppm of 3-hydroxycarbofuran.

     Tobacco samples from Arkansas plots treated with 6.0  Ib Al/acre carbofuran
10G broadcast yielded total carbamate residues of 0.13 ppm.  Previous  samples
yielded up to 15.0 ppm after 3 yr of consecutive treatments.  High variability
from plot to plot was indicated because re-analyses verified prior results.
                                         31

-------
Table 6.  Residues  of  Carbofuran on Peanuts.3./
Portion
of
plant
Nuts
Hulls
Vines
Nuts

Hulls

Vines

Nuts

Hulls

Vines

Nuts

Hulls

Vines


Nuts

Hulls
Vines

Nuts

Hulls
Vines

Active
Type of ingredient
application (Ib/acre)
14-in band 2
on 42-in row
at planting
18-in band 4
on 36-in row
at planting



In-furrow at 1
planting




. In-furrow at 1
planting
1

1

i
In-furrow at 3
planting

t

12-in band 2
on 36-in row
at pegging


Total
Days residue?-/
lapsed (ppm)
166 ND^
< 0.20
NA*/
139 ND
< 0.10
0.26
0.33
1.33
1.47
153 ND
ND
0.81
0.59
15.6
11.9
123 ND
ND
123 0.36
0.32
123 4.1
20.3

123 < 0.10
ND
0.69
37.2
38.8
92 ND
ND
NA
9.09
8.54
                         32

-------
                             Table 6.  (Continued)
  Portion
     of
   plant
.  Type of
application
  Active
ingredient
 (Ib/acre)
 Days
lapsed
 Total
residue^/
 (ppm)
    Nuts

    Hulls

    Vines
12-in  band
on 36-in  row
at pegging
                 79
           < 0.10
             ND
             0.62
             0.67
           < 1.43,
             1.63
                                                     > 0.93
     Nuts

     Hulls
     Vines
Dual-in-furrow
at plant plus
banded at pegging
  1 and 2
  74
< 0.10
< 0.10
  0.71
 36.6
 34.5
   a/  Data from five locations in Florida, Georgia, Mississippi,  North
         Carolina,  and Virginia.
   b_/  Total residue equals carbofuran plus 3-hydroxycarbofuran.   The
         analytical, method used was microcoulometric gns chromatogrnphy
         with a nitrogen detector, corrected for recovery.
   £/  ND =• None detectable.
   d/  NA — Not available or not analyzed.

   Source:   FMC  (1970).
     It was  concluded that carbamate residues above existing or proposed  toler-
ances would  not  occur from annual treatments with carbofuran at registered  or
proposed rates.


     Meat and Milk  - Reno (1973b) fed 3 phenolic metabolites of carbofuran  to
cows at a dietary level of 200 ppm.  The 3 metabolites were carbofuran phenol,
3-keto-7-phenol-carbofuran and 3-hydroxy-carbofuran phenol.  Equal  quantities
of each metabolite  were fed and  the dietary levels were  20, 60, and 200 ppm
total metabolites.
                                        33

-------
      The results of the milk residue study are shown in Table 7.   Table 7 shows
 the results of the 200 ppm study.  The results for the average level (of the 4
 cows) and the maximum level are given for 2 of the metabolites.   The third
 metabolite, 3-hydroxy-7-phenol carbofuran, was not detectable (Shuttleworth,
 X if / J / •

      The results of tissue analyses from this study are shown in Table 8.  The
 tissue was taken by sacrificing 2 of the test animals at the end of the 28-day
 feeding period.

      Reno (1973a) conducted a similar feeding test with chickens.  Test animals
 were fed 2, 6, and 20 ppm total metabolites (one-third each metabolite).  Egg
 and tissue (liver, fat, and breast) samples from the 20 ppm study were analyzed
 by the FMC Corporation using a gas chromatograph equipped with a nitrogen
 specific Coulson conductivity detection system (Shuttleworth, 1973).  No
 phenolic residues were detected at or above 0.05 ppm (method sensitivity).

      Other residue data related to carbofuran and its metabolites in milk and
 tissue samples from domestic ruminants is discussed in the subsection on toler-
 ances .
 Acceptable Daily Intake

      The acceptable daily intake (ADI) is defined as the daily intake which,
 during an entire lifetime, appears to be without appreciable risk on the basis
 of all known facts at the time of evaluation (Lu, 1973).  It is expressed in
 milligrams of the chemical per kilogram of body weight (mg/kg).

      The ADI for pesticides is established jointly by the Food and Agricultural
 Organization (FAO) Committee on Pesticides in Agriculture and the World Health
 Organization (WHO) Expert Committee on Pesticide Residues.  However, an ADI for
 carbofuran has not yet been established.
 Tolerances

     The  tolerances  for  carbofuran  apply  to  the  total  of  carbofuran plus  the
 following  4 metabolites:   3-hydroxycarbofuran  (2,3,-dihydro-2,2-dimethyl-3-
 hydroxy-7-benzofuranyl-N-methylcarbamate), structure II,  p.  38;  carbofuran
 phenol  (2,3-dihydro-2,2-dimethyl-7-benzofuranol),  structure  VII, p. 38; 3-
 hydroxycarbofuran phenol  (2,3-dihydro-2,2-dimethyl-3,7-benzofurandiol), struc-
 ture IX, p. 38; and  3-ketocarbofuran phenol  (2,3-dihydro-2,2-dimethyl-3-oxo-7-
 benzofuranol), structure VIII, p. 38.

     Official pesticide  tolerances  are published in the Code of  Federal
 Regulations, Title 40, and updated  in the Federal  Register.  A summary of
 current tolerances for carbofuran is presented in  Table 9.   A distinction is
made between residues containing a  carbamate function  (cholinesterase-inhibiting
 compounds) and those without this function.  Tolerances are  based upon the as-
 sumption that complete hydrolysis of all conjugates has taken place prior to
analysis.
                                         34

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       Table 7.   Residues in Milk of 3 Metabolites  of Carbofuran
                   Fed  at 200 ppm Total Metabolites?/
                                      Residue
                       Carbofuran phenol
3-Keto-7-phenol
   carbofuran
Days lapsed
Pretest (0)
2
4
7
14
18
21
25
28
Recovery day 1
Average£/
ND!/
0.044
0.043
0.025
0.030
0.049
0.052
0.046
0.034
ND
Maximum
ND
0.057
0.069
0.034
0.047
0.060
0.065
0.057
0.046
ND
Average
ND
0.44
0.36
0.37
0.41
0.58
0.49
0.55
0.46
ND
Maximum
ND
0.49
0.55
0.48
0.59
0.77
0.70
0.71
0.54
ND

a,/  Total metabolites,  200  ppm:
      66.7 ppm carbofuran phenol,
      66.7 ppm 3-keto-7-pnenol-carbofuran, and
      66.7 ppm 3-hydroxy-7-phenol-carbofuran
b/  No 3-hydroxycarbofuran  phenol was  detected  at  a  method  sensitivity
      of 0.050 ppm.  The analytical method  used was  microcoulometric
      g.is chromatography with a nitrogen  detector, corrected  for  in-
      strument efficiency and average  recovery.
cl  Average of 4 cows.
d/  ND = None detectable.
Source:  Shuttleworth (1973).
                                     35

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        Table 8.  Residues  in Tissues of 3 Metabolites  ot
                   Carbofuran  at End  of 28-day  Feeding Period
 Tissue and
Feeding level
Residue,  ppro—
                 Carbofuran  phenol
3-Keto-7-phenol
   Carbofuran
3-Hydroxy-7-phenol
    carbofuran
Muscle
200
200
Liver
200
200
Fat
200
200
Kidney
20
20
60
60
200
200

ND£/
ND

ND
ND

ND
ND

ND
ND
ND
ND
0.15
0.32

ND
ND

ND
ND

ND
ND

ND
ND
ND
ND
0.27
0.34

ND
ND

ND
ND

ND
ND

ND
ND
< 0.10
ND
0.32
0.40

a/  Feeding level of 200 pptn:
      66.7 ppm carbofuran phenol,
      66.7 ppm 3-keto-7-phenol-carbo£uran,
      66.7 ppm 3-hydroxy-7-phanol-carbofuran.
    Feeding level of 60 ppm:
      20 ppm of each of the above.
    Feeding level of 20 pptn:
      6.7 ppm of rach of the above.
b/  Method sensitivity:  muscle,  livov,  and  fat, 0.05 ppm; kidney,  0.10
      ppm.  Analytical method:  micrccoulomctric gas chromntography with
      a nitrogen detector,  corrected  for instrument efficiency and  aver-
      age recovery.
£/  ND ™ None detrctable.

Source:  Shuttleworth (1973).
                                   36

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                  Table 9.   U.S.  Tolerances  for Carbofuran
ppm                                          Crop

10                  Alfalfa (fresh)  (limited to 5 ppm carbamates)
40                  Alfalfa hay (limited to 20 ppm carbamates)
 0.1                Bananas
 0.05               Cattle (meat,  fat,  meat by-products)  limited to 0.02
                       ppm carbamates
 0.1                Coffee beans
25                  Corn fodder and  forage (limited to 5  ppm carbamates)
 0.2                Corn grain including popcorn (limited to 0.1 ppm carba-
                       mates)
 0.05               Goats (meat, fat, meat by-products)  limited to 0.02
                       ppm carbamates
 0.05               Hogs (meat, fat,  meat by-products) limited  to 0.02 ppm
                       carbamates
 0.05               Horses (meat,  fat,  meat by-products)  limited to 0.02
                      ppm carbamates
 0.1                Milk (limited  to  0.02 ppm carbamates)
 0.2                Peanuts (limited  to 0.1 ppm carbamates)
 5                  Peanut hulls (limited to 1 ppm carbamates)
 1                  Peppers (limited  to 0.2 ppm carbamates)
 2                  Potatoes (limited to 1.0 ppm carbamates)
 0.2                Rice
 1                  Rice straw (limited to 0.2 ppm carbamates)
 0.05               Sheep (meat, fat, meat by-products)  limited to 0.02
                       ppm carbamates
 3                  Sorghum fodder and forage (limited to 0.5 ppm carbamates)
 0.1                Sorghum grain
 0.5                Strawberries (limited to 0.2 ppm carbamates)
 0.1                Sugar beets
 2                  Sugar beet tops  (limited to 1 ppm carbamates)
 0.1                Sugarcane
Source:  Code of Federal Regulations, Title 40, Chapter 1, Part 180, Subpart
         C, Section 180.254, July 1975, as amended in Federal Register 41(2):
         763.  January 5, 1976.
                                      37

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Composition  and  Formulation
     According  to the manufacturer  (FMC, 1972a),  technical carbofuran is 98.8% pure.
The other  1.2%,  classified as an inert ingredient,  is 2,3-dihydro-2,2-dimethyl-
7-benzofuranol,  an unreacted raw material  from the  final processing step (see the
Synthesis  and Production Technology section).

     Carbofuran  is available in 2 principal  formulations from the manufacturer,
These are  granules, 10, 5, 3, and 2%  (designated  10G, 5G, 3G, and 2G), and 4 lb/
gal flowable formulation.  Two wettable powder formulations (50 and 75%) have been
used for crop residue studies, but are not currently available.

Chemical Properties

     Most  of the available information on  the  chemical degradation of carbofuran
was obtained by  researchers concerned with the metabolism of carbofuran and its
degradation in  animals and plants.  Carbofuran undergoes 3 types of chemical
degradation:  hydrolysis, oxidation,  and photodecomposition.  The structures and
common  names of  carbofuran and its principal degradation products are given below.

           0
           n
          OCNHCH3
                     CH3
           Carbofuran

              I
3-Hydroxycarbofuran

     II
 3-K.etocarbofiiran

      III
          OCN1!CH2OH
    N-Methyl hydroxycarbofuran   3-keto-N-methyl
                            hydroxycarbofuran
           IV
                                  V
                                               OH
                    3-Keto-6-hydroxy-
                      ccrbofurun
                         VI
                  CH3
      Carbofuran-7-phenol
            VII
 3-ketocarbofuran-
    phenol

   VIII
                                                              CH,
3-hydroxy-7-phenol
   carbofuran

        IX
                                         38

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 Hydrolysis - Cook (1973)  states that carbofuran is stable in neutral or
 slightly acid solutions,  but will hydrolyze under basic or strongly acid
 conditions.  Cleavage occurs at the carbamate linkage.

      Metcalf et al.  (1968)  studied the hydrolysis rate of carbofuran and
 several of its metabolites  in alkaline solution at 37.5°C.  The various
 carbamates were added at  0.1% weight/volume in methanol to phosphate buf-
 fer at pH 9.5, and the hydrolysis constants were determined by the rate
 of formation of the phenolic hydrolysis products which were measured by
 ultraviolet spectrophotometry.  The results are shown below.

                                        Khyd, min ~!            Tl/2. min

 Carbofuran                               0.0104                    66.9
 3-Hydroxycarbofuran                      0.0263                    26.4
 3-Ketocarbofuran                         1.715                      0.404
 N-Methylhydroxycarbofuran                0.130                      5.33
 3-Keto-N-methylhydroxycarbofuran       > 7.0                        0.1

      Getzin (1973) studied  the degradation of carbofuran in soil.  Figure
 4 shows his results at 4  pH levels in Sultan silt loam,  Getzin also studied
 carbofuran hydrolysis in  alkaline (unstated pH) aqueous solution and obtained
 a half life of 8 days at  25°C.  The hydrolysis occurred at the carbamate link-
 age yielding carbofuran-7-phenol as one product.   (Getzin did not report other
 hydrolysis products, nor  did he describe his experimental method.)  Getzin con-
 cludes that, in alkaline  soils, the primary route of degradation is chemical
 hydrolysis, while in acid or neutral soils slow microbial and chemical degra-
 dation occurs.

      Caro et al. (I973a)  primarily studied dissipation of carbofuran in the
 soil.   They determined the  half-life of carbofuran in solution (unspecified
 concentration) at pH 6.35 and 5.20.  The half-life at pH 6.35 was 140 days and
 at pH 5.20, 1,600 days.   The results in soil are discussed in the Fate and Sig-
 nificance in the Environment Section of this report.

     Caro et al. (1973a) also estimated the effect of temperature on hydrolysis
by utilizing the Arrhenius equation:


                                 k = Ae-E*/RT
                                        39

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     lOOn
       0
8
                                                 PH4.3
         16             24
WEEKS AFTER TREATMENT
32
          Figure 4.  Degradation Gurves for Carbofuran in
                     Sultan Silt Loam at 4 pH  Levels
Source:  Getzin, L.W. (1973).  Persistence and degradation of carbofuran
         in soil. F.nviron. Entomol. 2(3) :461-467.   Reprinted by permis-
         sion of Entomological Society of America.
                                       40

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      Studies were  done on the hydrolysis of technical carbofuran, 2 carbofuran
 formulations,  and  3-hydroxycarbofuran, a major metabolite of carbofuran.  In the
 first test, the pH levels were 4, 7, and 9.2; only one analysis was taken after
 24  hr.  The samples were saturated solutions, buffered in water at 25°C.  The
 results showed little or no hydrolysis at pH 4 and 7, and complete hydrolysis at
 PH  9.2  (McDonald,  1972).

      McDonald  then conducted a further test at pH 9.2, which included  intermediate
 measurements.  The results are as follows:

                           Timed  interval  and  rate  of hydrolysis (%)
      Product              0 hr        3 hr       5.5 hr         24 hr

Technical carbofuran        0          39.1       64.4         100
Furadan® 75 WP              0          78.4       79.1         100
Furadan®10 G               0          20.2       62.4          96.6
3-Hydroxycarbofuran         0          67.2       87.6         100

     McDonald indicated that the incomplete hydrolysis of the granules was  "associated
with water release characteristics or solubility of  this  formulated  product in water."

     McDonald then studied several pH levels between 7 and 9.2,  using  the same
buffering procedure, but only with technical carbofuran.   The results  are as
follows:

                                        Percent hydrolysis in
                                            24 hr at ?.5°C

             7.0                                 0
             7.6                                 4.6
             8.0                                18.2
             8.6                                31.0
             9.2                               100
                                       41

-------
     These values may be plotted on a log percent versus time graph and the half-
life read from the 50% point  (FMC,1972b).  A different line (with only the ini-
tial and final points) is drawn from each pH value.  This method for determining
half-life is valid if an assumption of first-order kenetics is correct.  This
assumption is discussed below.  Using this method, the above report gave the
following half-lives at 25°C:  pH  8.6, 1.9 days; pH  8.0, 3.6 days; pH 7.6,
16.1 days.

     The following chemical reaction occurs in hydrolysis under slightly alkaline
conditions (pH 5-10).
     C-N-CHc
     8 A
                      CH3
                                                                H
                                   methylcarbamic
                                   acid
    [CH3NHCOOH]
        CH3NH2 + C02

        methylamine
     In a strongly alkaline solution such as 20% NaOH, and at temperatures above
100°C, the reaction as given by McDonald (1972), would be of second order with
respect to carbofuran.
       ,u,
     0-C-N-C%
    o
CH3
CH3 +
Base

                             CH3NCNCH3

                                 0
                               2,2-Dimethyl-7-
                                 hydroxy-2,3-
                                 dihydrobenzofuran
                           1,3-Dime thylurea
                                         42

-------
     The rates of hydrolysis under various pH and temperature conditions have
been determined.  These findings are summarized below (Cook and Robinson, 1972).


pH                      Temperature (°C)                        Results

5                              28                    No hydrolysis in 28 days

7                              28                    Stable for 3 days, 48,4%
                                                     remaining at 21 days,
                                                     erratic step pattern
9
                               28                    19.9% remaining after 1 day
9                              26                    Half-life of 12 hr (0.46
                                                     days) (60% remaining after
                                                     7 hr)

9                               5                    Half-life of 1.5 days (53.8%
                                                     remaining after 1 day (0.7%
                                                     after 7 days)

Hydroxylation (oxidation) - Metcalf et al. (1968) studied the oxidation of car-
bofuran in plants, insects, mice, and in a model system.  Results are depicted
graphically in Figure 5.  Major metabolic pathways were:  (1) hydroxylation at
carbon position number 3, (2) further oxidation to corresponding 3-ketocarbofuran
compounds and (3) hydrolysis of carbamate moieties to the corresponding phenols.


Photodecomposition - Metcalf et al. (1968) studied the effects of fluorescent
light and sunlight on residues of crystalline carbofuran in Petri dishes.  3-
hydroxycarbofuran was detected by thin-layer chromatography (TLC) after 2 days
in outdoor sunlight, and also on TLC plates exposed to fluorescent light at 70°F
for 1 week.   After 2% weeks, 3 other unidentified compounds were detected in the
samples irradiated in sunlight.  The authors speculated that one was carbofuran
phenol because it did not inhibit cholinesterase.  However, none of these compounds
were analytically identical.  The authors also noted that the 3-ketocarbofuran
did not appear.
                                        43

-------
Carbofuran
  phenol
                            Carbofuran
                               10]
                                            (?)
3-Ke to-6- hydroxycarbofuran

   (unconfirmed)
                               3-Hydroxycarbofuran
                                                                       Hydrolysis
3-Hydroxycarbofuran-7-phenol
                                                                      (0)
                                                                     	>
                                                                      Hydrolysis
                                                     3-Ketocarbofuran
   3-Ketocarbofuran-7-phenol
                    Figure  5.    Oxidation  and Hydrolysis  Routes  of Carbofuran
Note:   Heavy lines indicate major pathways.


Source:  Based on data  in Metcalf et  al.  (1968).

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                                     45

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                                   46

-------
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                                  47

-------
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   '1968).

 Metcalf,  R.  L.,  T. R. Fukuto, C. Collins,  K.  Borck, S. A. El-Aziz, R.  Mumoz,
   and C.  C.  Cassil,  "Metabolism of  2,2,-Dimethyl-2,3-dihydrobenzofuranyl-7-
   N-Methylcarbamate (Furadan) in Plants, Insects and Mammals,"  J. Agr.  Food
   Chem.,  16(2):300-311  (1968).

 Moye,  H.  A.,  and J.  D.  Winefordner, "Phosphorimetric Study of Some Common
   Pesticides," J. Agr.  Food Chem.,  13(6):516-518 (1965).

 Orwoll, E. F.  (to FMC Corporation), U.S. Patent No. 3,356,690 (December 5,
   1967).

 PAM,  Pesticide Analytical Manual, Vol.  1.  Methods Which Detect  Multiple Resi-
   dues, Food  and Drug Administration, U.S.  Department of Health, Education
   and  Welfare (1971).

 PAM, Pesticide Analytical Manual, Vol.  II,  Methods For Individual Pesticide
   Residues, Food and Drug Administration,  U.S.  Department of Health, Education,
   and  Welfare (1967).

 Reno,  R. E., "Chicken Feeding Study, Three  Phenolic Metabolites of Carbofuran,"
   FMC  Corporation, Middleport,  N.Y.  (unpublished,  August 2,  1973a).

 Reno,  R. E., "Cow Feeding Study,  Three  Phenolic Metabolites  of  Carbofuran,"
   FMC  Corporation, Middleport,  N.Y.  (unpublished,  August 2,  1973b).

 Scharpf, W. G. (to FMC  Corporation), U.S.  Patent No.  3,474,171  (October 21,
   1969).

 Seiber, J. N., "N-Perfluoroacyl Derivatives for Methylcarbamate Analysis  by
  Gas Chromatography,"  J.  Agr.  Food Chem.,  20(2):443-446 (1972).

Seiber, J. N., D.  G. Crosby,  H.  Fouda,  and  C.  J.  Soderquist,  "Ether  Deriva-
  tives for the Determination  of Phenols and Phenol-Generating  Pesticides by
  Electron Capture Gas  Chromatography,"  J.  Chromatogr.,  73:89-97 (1972).
                                     48

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Shaw, F.  R.,  D.  Miller,  M.  C.  Miller,  and C.  P.  S.  Yadava,  "Persistence of
  Carbofuran and of 3-Hydroxycarbofuran on Alfalfa,"  J.  Econ.  Entomol.,
  62(4):953-954  (1969).

Shuttleworth, J. M.,  "Carbofuran Environmental Impact Study:   Harvest Inter-
  val," Report No.  M-3525,  FMC Corporation, Middleport,  N.Y.  (unpublished,
  1974).

Thorpe, D.  F., (to FMC Corporation),  U.S. Patent No.  3,816,474 (June 11,  1974).

Van Middlelim, C. H., H. A. Moye, and M. J. Hanes,  "Carbofuran.and 3-Hydroxy-
  carbofuran Determination in Lettuce by Alkali-Flame Gas Chromatography,"
  J. Agr. Food Chem., 19(3):459-461 (1971).

Vickers, R. S.,  P. W. Chan, and R. E. Johnsen, "Laser Excited Raman and
  Fluorescence Spectra of Some Important Pesticides," Spectrsc.  Lett., 6(2):
  131-137 (1973).

Williams, I. H., "Carbamate Insecticide Residues in Plant Material:  Determi-
  nation by Gas Chromatography," Residue Rev., 38:1-20  (1970).

Williams, I. H., and M. J. Brown, "Determination of Carbofuran and 3-Hydroxycar-
  bofuran Residues in Small Fruits," J. Agr.  Food Chem., 21(3):399-401 (1973).

Winterlin, W., G. Walker, and H. Frank,  "Detection of Cholinesterase-Inhibiting
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  Chem.. 16(5):808-812  (1968).
                                      49

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                    PART II.  INITIAL SCIENTIFIC REVIEW

                  SUBPART B.  PHARMACOLOGY AND TOXICOLOGY

                                 CONTENTS

                                                                            Page

Acute, Subacute, and Chronic Toxicity 	   53

  Acute Oral Toxicity—Rats	   53
  Acute Oral Toxicity—Dogs	   55
  Acute Dermal Toxicity—Rabbits  	   57
  Acute Oral Toxicity—Mice	   5g
  Acute Oral Toxicity—Chickens	   53
  Acute Oral and Topical Toxicity—Cattle	   58
  Acute Oral Toxicity—Sheep	   59
  Subacute Oral Toxicity—Rats	   59
  Subacute Oral Toxicity—Dogs	   62
  Subacute Oral Toxicity—Rabbits 	   62
  Subacute Oral Toxicity—Chickens	   62
  Subacute Oral Toxicity—Cattle	   63
  Chronic Oral Toxicity—Rats	   64
  Chronic Oral Toxicity—Dogs	   65

Reproduction Studies	   66

  Effects on Reproduction—Rats 	   66
  Metabolite Study—Rats	   68
  Effects on Reproduction—Dogs 	   68

Oncogenic Effects 	   70

  Oncogenic Effects—Mice  	   70
  Oncogenic Effects—Rats  	   70

Mutagenic Effects 	   71

Teratogenic Effects 	   72

Other Toxicity Tests	72

  Eye Irritation—Rabbits	72
  Skin Sensitivity—Guinea Pigs	73
  Neurotoxicity-Chickens	73
  Potentiation Studies	73

Symptoraology and Pathology	73

  Signs of Toxicity	73
  Symptoms of Toxicity	74
                                         51

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                           CONTENTS (Continued)


                                                                 Page

Treatment of Intoxication 	  74

Accidential Exposures 	  75

Metabolism	76
                                                                   I
  Insect Metabolism	76
  Plant Metabolism	81
  Metabolism in Mammals 	  85

Cholinesterase Inhibition 	  88

References	89
                                   52

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     This section Is concerned with Information on  the acute,  subacute,  and
chronic toxiclty of carbofuran In laboratory  and domestic  animals  (mice,  rats,
dogs, rabbits,  cattle,  sheep,  and chickens).   A review is  given  of  the charac-
teristic symptoms and pathology of carbofuran poisoning  in mammals,  in addition
to possible antidotes.   Studies are discussed concerning the effects  of  carbo-
furan on the reproductive cycles of rats and  dogs.   Oncogenic  effects are also
considered plus a review of mutagenic,  teratogenic  and potentiation studies.
The section summarizes rather  than interprets data  reviewed.


Acute, Subacute, and Chronic Toxicity

Acute Oral Toxiclty - Rats - A number of acute oral toxlcity  tests  have  indi-
cated that the oral W$Q for technical  carbofuran  in the adult rat  ranges from
6.4 rag/kg to 14.1 mg/kg (see Table 10).  The  oral  toxicity of  a  formulation is
proportional to the amount of  active ingredient present.   For  example,  the
oral LD5Q for the formulation  10G (10%  granular) was reported  to be  131.2
mg/kg (Schoenig, 1968h).   The  intraperitoneal LD5Q  of technical  grade carbo-
furan was reported as 1.37 mg/kg (Kohn  et al., 1967b).

     The acute oral toxiclty of different formulations varies with the  formu-
lation, but there does not appear to be a sex difference in  response.  Dif-
ferences in the sensitivity of the newborn, the weanling,  and the  adult  rat
to technical carbofuran are summarized  in Table 10.

     The acute oral toxlcity of carbofuran metabolites was also evaluated.
Five metabolites were studied  in tests on young  albino  rats  (Sprague-Dawley
strain).  Selected dosages were given to groups  of 4 rats  each  (2  males and
2 females) by intubation, followed by a 14 day observation period.  The
results of the tests are summarized in Table 11.

     The effect of acute doses of carhofuran on  cholinesterase activity was
studied in Charles River strain rats.  Groups of  25 rats were intubated at
dose levels of 0.2, 0.5, 1.0,  3.0, and 10.0 mg/kg.  After administration of
the pesticide, blood samples were withdrawn from the orbital sinuses of the
animals.  Brain cholinesterase was determined in groups  of 5 animals at 1, 2,
4, 6, and  24 hr.   The  results  for  the  various dose levels were  as  follows:
At 0.2 mg/kg there was no effect on plasma,  red blood cell (RBC) or  brain cho-
linesterase at  1,  2, 4, 6, or  24 hr.   At 0.5 mg/kg,  the only effect  seen was a
36% depression  of  brain cholinsesterase at 6 hr.    There was no  effect on  brain
or blood cholinesterase at other  intervals.  At 1.0  mg/kg, a 497. depression  of
brain cholinesterase was noted at  6 hr, but  no depression at  1,2, 4, or  24  hr.
Plasma cholinesterase was depressed at  1,  2, 4,  and  6 hr, but returned  to normal
at 24 hr.  No effect on RBC cholinesterase was observed.  At  3.0 mg/kg,  there
was a depression of plasma and brain cholinesterase  up  to 6 hr  which reLurned  to
normal at  24 hr.   No effect on RBC  activity  was noted at  1, 2,  4,  6, or  24 hr.
At 10.0 mg/kg,  there was a significant  mean  depression  of brain cholinester.jse
levels at  1, 2, 4,  and 6 or 24 hr.  Marginal  effects on RBC activity were ob-
served at  2, 4, and  24 hr  (Kretchmer, 1972).
                                      53

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                                Table 10.   Summary of Acute Toxicity Data for Rats
        Animal
Formulation
                Administration
                               Toxicity
                                   Reference
    Rat§/
    Rat£/
    Rat (
    Rat (F)*/
    Rat (M)*/
    Rat (newborn)—
    Rat (weanling)—'
    Rat§7
    Rat*/
    Rat*/
    Rat£/
    Rat£/
    Rat£/
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
10 G
Tech.
Tech.
Tech.
Tech.
Tech.
(PG)*
(PG) _
(PG, CO)**
(CO)
(CO)
(CO)
(CO)
(CO)
(CO)

(PG)
(PG)
(PG)
(PG)
(PG)
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Oral
Intraperitoneal
Intraperitoneal
Intraperitoneal
in
LD50 =7.1 mg/kg (+ 0.7)
II>5o = 6.4 mg/kg
LD50 =14.1 mg/kg (8.91-22.4)
LD50 =11.9 mg/kg (+ 2.5)
LD50 = 11.34 mg/kg (+ 1.15)
LD50 = 11.34 mg/kg C 2.16)
LD5Q =8.2 mg/kg
LD50 =1.65 mg/kg (± 0.24)
LD50 = 3.36 mg/kg (1 0.64)
LD50 = 131.2 mg/kg (± 13.3)
LDj  =5.3 mg/kg (-)
IJ>99 = 9.5 mg/kg (-)
LD50 = 1.37 mg/kg (± 0.17 mg)
W±  =1.05 mg/kg
LD99 =1.80 mg/kg
Palazzolo (1963a)
Palazzolo (1963a)
Powers (1964)
Kohn et al.  (1967a)
Schoenig (1967f)
Schoenig (1967f)
Schoenig (1966)
Schoenig (1967f)
Schoenig (1967f)
Schoenig (1968b)
Palazzolo (1963a)
Palazzolo (1963a)
Kohn et al.  (1967b)
Kohn et al.  (1967b)
Kohn et al.  (1967b)
     * PG = Propylene  glycol  carrier.
    ** CO = Corn oil carrier.

    a/ Sprague-Dawley  strain.
    b_/ Unspecified  strain.
    c_/ Slmonson Laboratory  strain.

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          Table 11.  Acute Oral Toxicity of Carbofuran Metabolites


	Metabolite  	LDsn	Reference

2,3-Dihydro-2,2-dijnethyl-7-      2.2 1 0.5 g/kgi/         (Schoenig, 1967b)
  hydroxybenzofuran              1.8 "t 0.4 g/kgb/
                                 1.8 ± 0.3 g/kg£/

2,3-Dihydro-7-hydroxy-2,2-       295.1 ± 29.96 mg/kgd/    (Schoenig, 1967c)
  dimethy1-3-oxobenzofuran

2,2-Dimethyl-3,7-dihydroxy-      1,350 1 158.4 mg/kgl/    (Schoenig, 1967d)
  2,3-dihydrobenzofuran

3-Hydroxycarbofuran              17.9 t 4.3 mg/kg®/       (Schoenig, 1967e)

3-Ketocarbofur^n                 69.0 ± 14.7 mg/kgl/      (Schoenig, 1967e)
a/ Undiluted.
b/ 25% (w/v) corn oil solution.
c/ 75% (w/v) propylene glycol solution.
d/ 5% (w/v) corn oil suspension.
e/ 0.1% (w/v) suspension in corn oil.
fj 1% (w/v) suspension in corn oil.


Acute Oral Toxicity - Dogs - The results of oral toxicity tests indicated that
dogs were somewhat more resistant than rats to the action of carbofuran.  The
U>50 for dogs is reported to be 18.85 mg/kg.  However, acute inhalation tests
indicated that the dog was equally susceptible by the respiratory route (see
Table 12).

     During an acute toxicity study with beagle dogs, the inhibition of blood
cholinesterase by technical carbofuran was also investigated.  The reduction
of cholinesterase activity for plasma and erythrocytes with time and dose is
shown in Tables 13 and 14   (Baran, 1967a).  The lowest level of cholinesterase
activity appeared following the first hr of administration.  Signs of recovery
were observed at 24 hr (Baran, 1967a).
                                        55

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                      Table  12.   Summary  of  Acute  Toxicity Data  for Animals  Other  Than  Rats
ON
Animal
Dog*/
Dog*/
Rabbit^/
Rabbit^/
Rabbi tb/
Chicken^/
Chicken!/
Mouse
Formulation
Tech. (GC)*
Tech.
Tech.
Tech.
10 G
Furadan® 4
(flowable,
Tech.
Tech.
Tech.
Administration
Oral
Oral
Oral
Dermal
Dermal
Dermal
paste)
Oral
Oral
Oral

LD50 =
LDgg =
LD50 =
' LD50 -
LD50 =
LD50 =
Lp50 =
Toxicity
18.85 mg/kg (+ 1.02)
16.46 mg/kg (-)
21.55 mg/kg (-)
14.7 mg/kg
10.2 g/kg
6.8 g/kg (+ 0.8)
25.0 mg/kg (12.5-50)
38.9 mg/kg (-)
2 mg/kg
Reference
Baran (1967a)
Baran (1967a)
Baran (1967a)
Palazzolo (1963a)
Schoenig (1967a)
Schoenig (1968a)
Palazzolo (1966)
Jackson (1967)
Fahmy et al. (1970)
    *   GC  = Gelatin capsule.

    a/  Beagle.
    b/  New Zealand albino strain.
    cf  English strain.
    d_/  White leghorn strain.

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               Table 13.  Changes in Plasma Cholinesterace Activity
                            in Dogs After Dosing With Carbofuran
Cholinesterase activity?.'


1
2
3
4

Dog
(male)
(female)
(male)
(female)
Dose
(mg/kg)
15.38
15.38
23.07
23.07
Time after dose (hr)
0
0.499
0.471
0.516
0.470
1/2
0.455
0.372
0.291
0.297
1
0.364
0.333
0.184
0.300
2
0.510
0.305
-b/
0.401
24
0.444
0.446
-
0.398
a/ Acetic acid (um/min/ml) of plasma.
b_/ Dog died.
Source:  Baran (1967a).
             Table 14.
Changes in Erythrocyte Cholinesterase Activity
    in Dogs Dosed With Carbofuran

Cholineeterase activity3.'


1
2
3
4

Dog
(male)
(female)
(male)
(female)
Dose
(rag/kg)
15.38
15.38
23.07
23.07
Time after dose (hr)
0
0.328
0.336
0.273
0.361
1/2
0.259
0.312
0.263
0.132
1
0.243
0.277
0.171
0.311
2
0.274
0.243
_b/
0.294
24
0.315
0.296
—
0.321
 a/ Acetic acid Qam/min/ml)  erythrocytes.
b7 Dog died.
Source:  Baran (1967a).

Acute Dermal Toxicity - Rabbits - Furadan (4 Ib/gal) was applied as an aqueous
slurry to the shaved skin of rabbits.  Animals were wrapped and a plastic
collar was used to prevent migration of the test material during the 24 hr
exposure.  All animals that died, as well as survivors, were necropsied
(Schoenig, 1967a).

     Animals that received doses of 4.6, 6.8, and 10.2 g/kg showed hypoactiv-
ity and muscular weakness 1 to 6 hr posttreatment.  Reactions continued 1 to 2
days in survivors.  Salivation, tremors, fibrillary action and miosis were
noted at 6.8 and 10.2 g/kg, 1 to 6 hr after treatment and continued 6 to 18
hr.
                                        57

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      Skin reactions were characterized by pale, red, definable erythema in all
 dose groups at termination of the 24 hr contact period.  At 7 and 14 days fol-
 lowing treatment, only dryness and desquamation of skin were noted at the appli-
 cation site.  No significant pathological alterations were noted in any animal
 at necropsy.  The acute dermal LD50 was calculated to be 6.8 g/kg (i 0.8)
 (Schoenig, 1968b).

      The acute dermal LD5Q of technical carbofuran in an organic solvent (Dowa-
 nol DPM) for rabbits was determined to be 14.7 mg/kg; however, the acute dermal
 LD50 of the technical carbofuran in water was greater than 10.2 g/kg (FMC, 1963
 and 1969).


 Acute Oral Toxicity - Mice - The acute oral W$Q for technical carbofuran admini-
 stered to Swiss mice was determined to be 2 mg/kg body weight (Fahmy et al.,
 1970).


 Acute Oral Toxicity - Chickens - The acute oral toxicity for chickens was report-
 ed to range from LD5Q 25.0 to 11)50 38.9 mg/kg.  This data indicates that chickens
 possess more resistance to carbofuran than any other animal for which data is
 available (Palazzolo, 1966 and Jackson, 1967).  The LD5Qfs reported for domestic
 chicken also indicate that this bird is more resistant to the acute toxic effects
 of carbofuran than  wild birds (see section on Effects on Wildlife).


 Acute Oral and Topical Toxicity - Cattle - In a metabolism study, administration
 of a single 0.52 mg/kg dose of carbofuran to 1 cow resulted in marked nervous-
 ness of the animal  for about 3 hr, but no other signs of poisoning appeared.
 Another dose of 1.0 mg/kg caused salivation, tearing, hyperactivity, and diar-
 rhea within 50 min  after dosing.  The signs of toxicity were most severe after
 2  hr but subsided to an apparent normal condition in 4 hr (Ivie and Dorough,
 1968).

      In another study,  a 635 kg Holstein cow was given a single 5 g (7.9 mg/kg)
 oral dose of carbofuran.  The animal exhibited extreme signs of distress within
 30 min.   The signs  of poisoning were very rapid breathing and muscular twitching
 followed by convulsions.  One hr after administration of carbofuran, the animal
 was  treated with atropine sulfate, and recovery appeared complete within 12 hr
 (Miles  et al.,  1971).

      The effects of oral dosage and topical application of carbofuran to 1- to
 2-week-old  calves and older cattle was studied.  The compound was administered
 orally  as a 75%  wettable powder or as 96.7% technical grade carbofuran, in
 gelatin  capsules, 1 hr  after feeding.

      Intoxication in the 1- to 2-week-old calves resulted from oral doses of
 0.25  mg/kg  or greater.   At  1 mg/kg,  1 animal died even though it was treated
with  atropine sulfate.   Necropsy findings (1 mg/kg)  were congestion of the lungs
 and  reddening of  the visceral mucosa.   In older cattle, the highest oral dose
 of carbofuran  (1.0  mg/kg)  resulted in only mild signs of toxicosis which did
not necessitate  administration of atropine sulfate.


                                       58

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     For topical application,  4 liters  of  an 0.01,  0.05,  or  0.19%  spray  were admin-
istered.  Animals receiving topical  applications  greater  than  0.05%  carbofuran
(4 liters of emulsion)  showed  mild signs of toxicity.   Signs of  toxicity occurred
within 1 hr after treatment.   Animals treated topically with 0.1%  emulsion
required atropine sulfate treatment  to  prevent death.

     Two yr-old heifers receiving 0.05% topical applications showed  signs of
toxicity but did not require atropine sulfate treatment.   At 0.1%, yearlings
exhibited increased salivation, muscular tremors and prostration.  Washing
away the residual and atropine sulfate treatment was required  to save the
animals.  Animals showing indication of toxicosis generally had  depressed
blood cholinesterase levels (Palmer and Schlinke, 1973).


Acute Oral Toxicity - Sheep - Carbofuran was administered orally to  yearling
crossbred sheep as single 1.0, 5.0, 10.0,  and 25.0 mg/kg  doses in gelatin
capsules.  Doses higher than 2.5 mg/kg body weight resulted in severe toxicosis
requiring atropine treatment to save the animals.  One animal receiving a
10.0 mg/kg dose died within 2 hr in spite of atropine treatment.  The severity
of toxicosis was generally indicated by reduced blood cholinesterase levels.
The animal that died after treatment with 10 mg/kg carbofuran exhibited pulmo-
nary edema and congestion of internal organs  (Palmer and  Schlinke, 1973).


Subacute Oral Toxicity - Rats - The subacute toxicity of  technical carbofuran
for Sprague-Dawley rats was determined over a period of 90 days (Kohn, 1965).
The test groups established and the feeding schedule for each group  are  shown
below.  Ten males and 10 females were used for each test  group and for the
controls.  Diets were fed ad libitum:


                     Carbofuran (ppm) fed for indicated days
                                        0-21   22-35    36-49   50-90

Controls                                 -                -       -

Test group
         I                              0.1    0.4      1.6       1.6
        II                              0.4    1.6      6.4       6.4
       III                              2.0    8.0      32.0      32.0
        IV                              10.0    40.0     160.0     160.0
         V                              25.0   100.0     400.0    1,600.0
     After  90 days  all  animals were  sacrificed.   Standard gross and microscopic
pathological examinations were conducted on several organs including the liver,
kidney,  spleen,  gonads,  heart, and brain.


                                       59

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      Some effects on growth were noted in both males and females.  Lowered
 weight gains were recorded for both sexes in Treatment Groups IV and V.   It
 was suggested that reduced palatability in the higher treatment groups may
 have contributed to the reduced weight gains (192 g weight gain for controls,
 171 g for Group IV females and 133 g for Group V females).  There were no dif-
 ferences between controls and treated animals in hematology, urinalysis,
 behavioral effects, gross pathology, microscopic pathology, and in selected
 organ weights.  No deaths were recorded throughout the study (Kohn, 1965).

      In another test, groups of Charles River albino rats (15 males and 15
 females per group) were fed carbofuran for 90 days at dose rates of 0, 300,
 1,000, and 3,000 ppm.  During the feeding period, weight gains were determined
 at weekly intervals and food consumption was carefully monitored for 5 animals
 of each sex per test group.  Mortality and abnormal reactions were recorded
 daily.  Blood and urine samples were collected from 10 rats of both sexes for
 the control and 3,000 ppm test groups after 45 and 84 days of feeding.  Hema-
 tology, blood chemistry, and urinalysis were monitored.

      All animals were sacrificed at the end of 90 days of feeding and each was
 subjected to necropsy.  Weights of livers, kidneys, spleens, gonads, hearts,
 and brains, were recorded.  Microscopic examination was carried out on tissues
 from 10 rats of each sex for the control and the 3,000-ppm test group.

      An examination of the results of all tests indicated no significant  dif-
 ference between the control and the test group for any parameter compared
 (Reyna,  1972).  Charles River strain albino rats were dosed at 0.1, 0.3,  1.0,
 and 3.0 mg/kg/day for 16 weeks (propylene glycol solutions, intubated) and the
 effect of treatment on cholinesterase activity was then determined after  1, 3,
 6,  and 13 weeks.  After 13 weeks, treatment was reported to have caused little
 reduction of cholinesterase activity at the highest concentration (3.0 mg/kg)
 used.

      Some of the 13-week values obtained in this study are shown below:
                              Cholinesterase activity3/
                                     Plasma	Erythrocyte	Brain
Controls

Test

- Male
Female
- Male
Female
0.263
0.390
0.275
0.492
0.513
0.383
0.530
0.491
4.277
4.826
5.196
5.080
a./ Acetic acid  (um/min/ml) of plasma  or  erythrocytes  and  um/min/g  for  brain.

Source:  Wolf (1966a).
                                        60

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     The effect of time of sampling on cholinesterase activity was shown by
Wolf in a subacute study using  female  Charles  River rats.   After dosing at
3.0 mg/kg/day for 3 weeks (technical carbofuran),  blood samples were drawn at
intervals from 0 time (after  dosing) to 60  min.  The following results suggest
that a depression of cholinesterase acitivity  is observed  if sampling is done
a short time following dosing:
               Effect  of  time  of  sampling  on  cholinesterase activity
Time of sampling:
after dosing
0
15 min
30 min
45 min
60 min
Cholinesterase
Erythrocyte
0.482
0.396
0.361
0.370
0.329
activity—/
Plasma
0.323
0.251
0.245
0.205
0.1522
a./ Acetic acid Qim/min/ml)

Source:  Wolf (1966a).
     A 28-day cholinesterase study was performed using female Charles River
rats (Plank, 1972).   A group of 40 rats was administered daily doses of 1.0
mg/kg carbofuran in corn oil by gavage.  A control group of 10 animals was
given daily doses of corn oil by gavage.  At 14 and 28 days, 5 test animals
were sacrificed 1, 2, 6, and 24 hr following carbofuran administration.  Five
control animals were also sacrificed at 14 and 28 days.  Plasma, RBC and brain
cholinesterase activity were determined for each animal sacrificed.

     In the 14- to 28-day test,  only slight depression (less than 15%) of
plasma or RBC cholinesterase was observed 1 to 6 hr after dosing.  However,
because a single 1 mg/kg dose resulted in 30% depression in 1 to 6 hr in other
animals, the investigator concluded that daily exposure resulted in some adapta-
tion during the 14-  or 28-day exposure periods.

     Brain cholinesterase was significantly depressed after 2 and 6 hr at  the
14- and 28-day exposure periods.   The cholinesterase level returned to normal
within 24 hr.  The results suggest there is no adaptive mechanism for brain
cholinesterase depression by carbofuran (Plank, 1972).

     Ninety-day subacute tests for oral toxicity were conducted  using 3-
hydroxycarbofuran at dietary levels of 10, 30, and 100 ppm  (Plank, 1969) and
2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran at 300, 1,000, and  3,000 ppm
(Reyna, 1972).  Charles~River strain rats were used as test animals.
                                        61

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     At 100 ppm 3-hydroxycarbofuran,  no differences in behavior, mortality,
hematologic, biochemical or urologic  tests were observed between the treated
animals and the controls.  Data from  gross pathological examinations indicated
that differences due to treatment could not be identified.

     Differences between untreated rats and those fed 2,3-dihydro-2,2-dimethyl-
7-hydroxybenzofuran at 3,000 ppm were not observed for body weight, food con-
sumption, mortality, behavioral reactions, hematological tests, blood chemistry,
urine constituents, or gross pathology.  Erythrocyte cholinesterase activity
of treated animals  (3,000 ppm, 90 days) was not inhibited as a result of feeding
the metabolite.


Subacute Oral Toxicity - Dogs - In an effort to establish a maximum dose level
that would have no effect on plasma or erythrocyte cholinesterase, a study was
conducted for 92 days by treating beagle dogs with technical carbofuran.  Both
male and female pure-bred beagles were used; 3 males and 3 females at each of
5 dose levels.  When cholinesterase activity was determined 20 hr after dosing,
no significant differences were reported between controls and animals treated
at the highest concentration, 5 mg/kg/day.  Although differences in cholines-
terase activity were not noted, the dogs treated at 5 mg/kg/day exhibited
frequent coughing and gagging, occasional salivation, muscular tremors and
emesis (Baran, 1966).

Subacute Oral Toxicity - Rabbits - A study was conducted  to assess possible
hazards to rabbits  feeding on alfalfa  treated with carbofuran.  The dietary
levels were 70, 210, and 700 ppm.  Seventy ppm was considered  the average  0
day deposition on 8-in alfalfa when applied at the rate of 1.0  Ib/acre.  These
3 levels were fed to groups  (3 males and 3 females per group)  of albino rabbits
for 14 days.

     No deaths or untoward behavioral  reactions were noted.  Slight adverse
effects on body weights were noted among animals in all groups; however, 5 of
6 animals in the 700 ppm group lost weight while only 1 or 2 animals in other
groups lost weight.  The weight losses may have been due  at least in part  to a
slight reduction in food intake (Mastri, 1967).


Subacute Oral Toxicity - Chickens - The effects of 3 phenolic metabolites  of
carbofuran were studied in chickens (Hybrid laying hens).  Groups of 10 birds
each were fed 3 levels of mixtures of  the metabolites  3-hydroxycarbofuran
phenol, 3-ketocarbofuran phenol, and carbofuran phenol as indicated below:
                                        62

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Group
No. of animals
Dietary level—
  carbofuran
    (ppm)
Dietary level-
  metabolites
     (ppm)
1
2
3
4
10
10
10
10
0
20
60
200
0
6.67
20
66.7
Source:  Reno (1973b).
     The diets were fed for 28 days to determine the levels  of metabolites
which would occur in eggs and body tissue and to determine the rate  at  which
the metabolites clear the system upon withdrawal from the diet.

     After the 28-day feeding period, 5 birds from each of the 4  groups were
sacrificed.  Following a 15-day recovery period, the remaining birds were
sacrificed.

     Appearance, behavior, body weights, food consumption, and  egg production
were observed throughout the feeding and recovery periods.  At  necropsy,
liver, gizzard, skin, fat, heart, muscle, and kidney were taken  for analysis
of residues.

     There were no significant differences observed in appearance, behavior,
food consumption, and egg production between the control group and the test
groups.  No gross pathological alterations or tissue changes were observed at
the time of sacrifice.  No results were reported for the analysis of tissues
and eggs (Reno, 1973b).
Subacute Oral Toxicity - Cattle - The effects of 3 metabolites of carbofuran
were also studied in the lactating Holstein dairy cow, using groups of 10
animals each.  They were fed the same levels and dosages of phenolic metabo-
lite mixtures as reported  in the chronic study on chickens  (Reno, 1973b).

     The diets were fed to the cows for 28 days to determine the levels  of
metabolites which would occur in milk and tissues and to determine the rate
at which the metabolites clear the system upon withdrawal from the diet.

     After being fed the metabolite for 28 days, 2 animals  from each of  the
4 groups were sacrificed.  Following a 15-day recovery period on the basal
diet without metabolites,  the remaining animals were sacrificed.
                                        63

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      Body weights and food consumption were recorded for each animal through-
 out the test period and milk samples were taken for residue analysis.  At
 sacrifice, gross necropsies were performed and samples of muscle,  fat, liver,
 and kidneys were taken for residue analysis.

      Except for 2 injuries and a minor respiratory infection, no untoward
 effects were observed in the animals during the test.  All but 2 of the cattle
 receiving metabolites showed an unexpected decrease in body weight during
 feeding.  However, these animals began to gain weight during the recovery
 period.  No gross tissue changes were observed in any of the animals sacrificed
 (Reno,  1973a).


 Chronic Oral Toxicity - Rats - Long-term chronic toxicity tests (2 yr) with
 Charles River albino rats treated at dietary levels of 1, 10, and  100 ppm did
 not result in any mortality in the treated groups that could be attributed to
 carbofuran consumption (50% of the animals died).

      Both males and females in the 10 ppm test group exhibited a weight depres-
 sion, but this lowered gain was confirmed statistically (P<:0.05)  only in males.
                         •
      Throughout the study no behavioral abnormalities were observed to have
 resulted from treatment.

      Blood studies were conducted at the end of the treatment period  (2 yr) ,
 but no  difference between controls and the highest treatment level could be
 detected for values of hemoglobin concentrations, hematocrits, erythrocyte
 counts,  leucocyte counts and differentials.

      Blood chemistry tests were done for blood urea nitrogen (BUN), serum alka-
 line phosphatase activity (SAP), and serum glutamic pyruvic transaminase  (SGPT).
 Differences could not be detected between the controls and treated animals.

      Gross pathological examinations were conducted at 12 months and at 2 yr.
 The only abnormality noted was the spleen weight in males treated  at 100 ppm for
 1 yr (5  males and 5 females from the controls and the 100-ppm group were exam-
 ined) .   The difference between the control values and the 100-ppm  group, how-
 ever, was not found to be statistically significant.  The author reported that
 the finding may be important because of the observed weight loss which occurred
 in  these males.

      All animals that survived for 2 yr were sacrificed and gross  and micro-
 scopic pathological examinations were conducted.

     No  differences  in gross pathology could be detected between the controls
and  the  treated  rats.   Histopathological examination confirmed the absence of
differences between  treated  groups and controls.
                                        64

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     Absolute organ weights of liver,  kidney,  spleen,  gonads,  heart,  and brain
and organ-to-body or organ-to-brain weight  ratios  did  not  reveal  any  consistent
differences between the control animals and those  fed  carbofuran  (Wolf,  1967b).

     In another 2 yr chronic study, dietary levels of  technical carbofuran of
25 and 50 ppm were fed to Charles River albino rats (Plank,  1968).  Seventy
animals (35 males and 35 females) were included in each test group.   A total
of 77% of the animals died during the  test, but since  mortality was randomly
scattered throughout controls and treatment, the deaths were not  considered to
have been related to treatment.

     A reduction in food consumption was noted only in males at the  50-ppm
level during the first 9 months of the study.   Females fed 50 ppm,  and both
males and females fed 25 ppm, consumed feed at intakes comparable to  untreated
controls.

     At the dietary level of 50 ppm, males  gained  less than controls  for the
first 12 months; thereafter, the gain  was similar.

     No differences were noted in gross pathology  between untreated controls
and carbofuran-fed animals (Plank, 1968).

     Wolf reported no significant difference between control and  test groups
with regard to weight gain, food consumption or behavioral effects.   Gross
pathological examination and examination of tissues collected at  necropsy re-
vealed no significant differences between the control and test groups at the
end of the 2-yr feeding study  (Wolf, 1968).


Chronic Oral Toxicity - Dogs - Pure-bred beagle dogs were fed carbofuran for
2 yr according to the schedule shown below.

                                     Dietary level
Test grou£
I

II
f
III

IV

V


(ppm)
1
2
10
20
50
100
100
200
100
200
400
Days fed
1-267
268-737
1-267
268-737
1-142
143-730
1-267
268-737
1-14
15-267
268-737
                                        65

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      At the end of the 2-yr period, comparisons of treated and  control  groups
 were made for food consumption, hematology, blood chemistry,  liver  function,
 urine analyses, organ weights, and pathology (gross and microscopic).   No  sig-
 nificant differences were observed between treated and control  groups.

      Abnormal behavioral reactions were not observed in dogs  at 1,  2, 10,  20,
 and  50  ppm.   At 100  ppm (Groups IV and  V),  minimal  coughing and  gagging
 were observed.   At 200 to  400  ppm  (Groups  IV and  V), dogs  showed a slight
 coughing and  gagging.   Slight  salivation,  emesis, muscular tremors and weakness
 in the  hindquarters  were observed  in  dogs  of Group  IV  (200 ppm)  at 500  to
 737  days,  and in dogs  of Group V (200 to 400 ppm) at days  15  to  737.
 Fatalities occurred  in the Test Group V animals at  400  ppm (Baran, 1967b and
 1967c).
 Reproduction Studies


 Effects on Reproduction - Rats -  A 3-generation reproductive study was  con-
 ducted with weanling rats (Charles River - Sprague-Dawley derived)  which were
 fed diets containing 1, 10,  or 100 ppm technical carbofuran (Kennedy,  1967b).
 Each of the 3 test groups and the control group consisted of  8 males and 16
 females which were parents for the first generation of the study.   Parental
 stock and progeny were produced by following the scheme outlined  in Figure 6.
 Animals from each generation were maintained on their respective  test  diets
 until sacrifice.

      Eight males  and 16 females from the second litters of each group  were
 randomly selected at weaning for use as parental animals for  the  succeeding
 generation.  Mating was conducted when the animals were 100 days  old.  At 100
 ppm,  a weight depression was noted in the males (10 to 18% below  untreated
 controls).   All deaths that  occurred were reported to be due  to respiratory
 infection and not to treatment with carbofuran.

      Mating and  fertility indices of the 100 ppm test animals were  similar  to
 those of untreated controls.  In all 3 generations most of the 100  ppm females
 delivering apparently normal pups lost their entire litters prior to weaning
 at  21 days.

      A greater incidence of  stillbirths was observed for all  3 generations  in
 the 100 ppm test  group than  in the controls or in any of the  other  treatment
 groups (Kennedy,  1967b).

      A 1-generation  reproductive study was conducted with Charles River  rats
at  dietary  levels of  0 and 50 ppm carbofuran (Kennedy,  1967a).  The weanling
body  weights  in the F^a and  F^ test groups were lower than the corresponding
control  groups.   The  5~day survival indices for the treated F^a and F^  groups
were  also lower (44.7  for F^a and 30.4 for Flb) than the same indices  for the
controls  (96.6 for Fla and 76.8 for F^) .   These results appear to  parallel the
above  studies performed at 100 ppm by Kennedy (1967a).
                                        66

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   c
   o
   •r4
   4J
4J  Id
tO  »4
iH  0)

   C
           o
           •H
           4J
        •o  rt
        C  M
        CM  
-------
      A second-generation study on albino  Charles  River  rats used  2 groups of
 24 animals each (8 males and 16 females).   One group  was  given  30 ppm carbo-
 furan in the diet while the other group was maintained  on a diet  containing
 no carbofuran.

      No significant differences in body weights and no  untoward behavioral re-
 actions were noted in the F]_ parental  animals.  No gross  pathological altera-
 tions or histopathological differences were observed  in test or control F,
 animals.

      Mating indices and incidences of  pregnancy and parturition were signifi-
 cantly lower in the test than in the control groups.  The first litter lacta-
 tion index was  also lower for the test group.   The number of pups born and
 the number of pups viable at various periods of lactation were  lower in both
 litters (F2a or ?2b)  for the test groups  as compared  to controls.  In the
 first litters only the 5-day survival  index was lower for the test groups;
 however, all survival indices were lower  for second litters of  the test group.

      The only significant differences  in  weights  of weanlings were observed in
 second litter females which had lower  average body weights than the controls
 (Arnold, 1968a).

      Feeding carbofuran at 30 ppm generally appeared  to have affected the
 mating of parental animals and to have had  a subsequent effect  on the progeny.
 The survival indices  for all 3 generations  are shown  in Table 16  (Arnold,
 1968b).
Metabolite  Study  - The  compound  3-ketocarbofuran phenol,  a metabolite of carbo-
furan, was  fed  to Charles River  albino  rats  at  dietary  levels of 10 and 50 ppm.
The animals were  mated  when  they were 100  days  old  (79  days on test).  After
32 weeks, when  the F^  litters were weaned,  the FQ  parents were  sacrificed and
subjected to gross pathological  examinations.

     The results  of this study indicated that the metabolite had no effect on
the ability of  the animals to mate or on the females' ability to conceive and
carry the young.  There were no  differences  between the treated and the con-
trols in (a) the  number of pups  delivered;  (b)  the  number of stillborn;  (c)
viable pups at birth; (d) number of pups weaned; (e) survival of pups; (f)
weanling body weights;  (g) physical reactions;  or (h) physical appearances of
pups.

     Histopathological  examinations indicated that  there were no differences
between untreated controls and treated  animals  (Arnold, 1969).


Effects on Reproduction - Dogs - A reproduction study was carried out with
dogs fed dietary  levels of '20 and 50 ppm carbofuran for 20 months.  One male
and 4 females were used per  group.  One control and 2 test groups of 6-month-
old virgin females were fed  ad_ libitum  for the  duration of the study.  The
                                        68

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              Table  15.   Survival Indices  for a 3-Generation Study
                            on Rats  (30 ppm Carbofuran)

Controls : F^a
Fib
F2a
F2b
F3a
F3b
30 ppm test: Fia
Fib
F2a
F2b
F3a
F3b
Live birth
index*/
93.5
98.9
92.5
100.0
79.3
92.4
90.5
94.7
90.6
85.7
85.0
84.6
24-Hr survival
indexb/
97.9
98.3
92.6
97.5
82.6
84.5
90.3
96.0
88.5
66.7
100.0
100.0
5-Day survival
index£/
95.1
79.1
89.0
82.5
73.0
47.4
82.1
80.7
70.1
55.6
94.1
36.4
a/ Live birth index:   viable pups  x 100
                      total pups
b_/ 24-Hr survival index:   pups viable on lactation day 1 x IQO.
                                    viable pups
c/ 5-Day survival index:   pups viable on lactation day 5 x IQO.
~~                                viable pups born

Source:  Adapted from Arnold (1967, 1968a, 1968b).
study was terminated after litters  of  3  or  4  females  per group were 4 weeks
old.  At 1 week, X-rays were taken  of  each  pup  to determine any adverse effects
on skeletal development.  At 4  weeks,  1  male  and  1 female from each litter were
sacrificed and subjected to complete pathological examination.

     The results showed no adverse  effects  on parental animals with respect to
mortality, general reactions, body  weight,  food consumption, estrus cycles,
mating performance, parturition and lactation.  No adverse effects were ob-
served in the progeny of control or test animals  with respect to litter size,
survival indices,-general reactions, body weights, ability to nurse, or skele-
tal abnormalities and gross pathological findings (Stephens, 1970).

     Three pregnant female beagle dogs were fed carbofuran in the diet at 20
ppm during the last half of the gestation period  and  continuing through lac-
tation.  Initially, the dietary level  was 5 ppm but it was increased every 5
days by 5 ppm until 20 ppm was  reached.
                                      69

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      The females did  not  exhibit  any physical  signs  of  intoxication  during  the
 test period.   All the pups  born of  these  test  animals appeared  normal  and main-
 tained normal growth  patterns  (Carlson, 1968).


 Oncogenic Effects
 Oncogenic Effects - Mice  -  The  carcinogenicity  of  technical carbofuran to
 Charles River,  random-bred  mice was  considered  in  a study by Reyna (1973).
 The mice were divided into  4  groups  of  100 animals (50 males and 50 females).
 One group was held as untreated controls  and  2  of  the remaining 3 groups were
 given carbofuran in the diet  at 30 and  100 ppm.  The last group was a positive
 control and was given urethane  at 600 ppm.  The mice were fed on their respec-
 tive diets for  18 months.

      Each animal was examined weekly for  signs  of  tumor formation and complete
 gross pathological examinations were conducted  on  all postmortem animals and
 on all animals  surviving  the  treatment.

      Tumors were observed in  test animals,  but  they were not different in
 number nor in their latent  periods from those observed in untreated animals.
 Treatment with  urethane resulted in  an  increase in tumor incidence.  A summary
 of tumor incidence is given in  Table 16  (Reyna,  1973).


 Oncogenic Effects - Rats -  Rats fed  100 ppm dietary carbofuran in a chronic
 toxicity study  were evaluated after  2 yr  for  incidence of tumors.  The results
 indicated that  the incidence  of tumors  in treated  animals was not related  to
 treatment with  carbofuran.

                        Dietary dose         Tumor incidence
 	(ppm)	(%}	

                                0                      24.2
                                1                      12.5
                              10                      15.6
                              100                       8.8

 Source:   Wolf (1967a  and 1967b).


 The  tumors  found were primarily chromophobe adenomas of the pituitary and  mam-
 mary adenofibromas  (Wolf 1967a  and 1967b).

     Treated survivors fed up to 50 ppm carbofuran for 2 yr had the same inci-
dence of tumors  as untreated controls (Plank, 1968).
                                        70

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               Table 16.   Summary of Tumor Incidence During an 18-Month
                           Carcinogenic Study With  Swiss White Mice
         Groups

Number submitted for
  histopathologic ex-
  amination3.'

Number with  tumors

 Percent  of total examined
  with tumors
      Type of  tumor

 Alveologenic adenoma
 Alveologenic carcinoma
 Hemangioma
 Squamous cell  carcinoma
 Lympho s ar coma
 Reticulum cell sarcoma

 Total number of tumors
Control

  57



   6

  10.5
    4
    0
    0
    0
    2
    0
Positive
control

  25
  19
   76.0
                                                          Carbofuran
30 ppm

 31
 16.1
              Number  of  tumors
   16
    1
    6
    2
    0
    0
   •^••^M

   25
   4
   0
   1
   0
   0
   0
100 ppm

  39



   8

  20.5
   7
   0
   2
   0
   3
   0
  Mtf^V

   12
 a/   The number of animals  submitted  for  histopathologic examination included all
     animals  sacrificed  at  the conclusion of  the  investigation and any post-mortem
     animal or animals sacrificed  in  extremis with signs of possible tumor forma-
     tion.  All other animals were examined grossly and found to be free of tumors
     or tumor-like growth.

 Source:  Reyna (1973).


 Mutagenic  Effects

      Mutagenesis studies have been carried out using Charles River strain albino
 mice as test animals.  A dominant lethal mutation study was conducted with tech-
 nical grade  carbofuran  by Arnold  (1971). An untreated control,  a positive con-
 trol, methyl methanesulfonate and 2  levels of treatment with carbofuran  (0.25
 and 0.5 mg/kg) were utilized in the  test. Twelve males were included  in each
 treatment group including the controls.   Each male was mated to  3 females per
 week for 6 weeks.  The  females were  sacrificed 1 week after removal  from  the
 breeding cage and were  examined for  implantation sites,  resorption  sites, and
 embryos.
                                         71

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      Data for the first 2 weeks of the positive control group  indicated that
 a dominant lethal mutation had occurred.  The data from the control and carbo-
 furan treatment groups revealed that no dominant lethal mutation was present
 in these animals (Arnold, 1971).


 Teratogenic Effects

      Teratogenesis studies were conducted using New Zealand albino rabbits.
 A total of 40 female rabbits were observed for 60 days before  testing.  Four
 groups of 10 females each were placed on test according to  the following
 protocol:


Group
Control
Positive control
Test Group I
Test Group II


Test material
None3./
Thalidomide
Carbofuran
Carbofuran
Dose level
(mg/kg of body weight)
per day

75.0
o.ib/
0.5
Number of
females per
group
10
10
10
10
a/ Control  group  females received a sham dose (empty gelatin capsule).
b/ Technical  grade  carbofuran
Source:  Jackson  (1968).

     Treatments were  given  on day 6 through day 18  of the  gestation period.
On gestation  day  29,  all females  were sacrificed and the litters recovered
by caesarian  section.  After  24 hr of observation for viability, the fetuses
were sacrificed and examined  by dissection.   Particular attention was given
to the skeletal tissue and  the differences  in size,  shape, and position of
major organs  and  blood vessels.   A positive thalidomide control group was
included to indicate  teratogenic  sensitivity of the rabbit strain used.

     Examination  of 120  fetuses  from females treated with  carbofuran revealed
no gross abnormalities.   Internal structural formation was normal and skeletal
development was well  defined. The young were present in normal numbers, were
well formed,  and  showed  good  survival during the first 24  hr after Caesarian
delivery.   However, the  incidence of resorption was twice  as high in both
carbofuran  test groups as in  the  control group (Jackson, 1968).
Other Toxicity Tests

Eye Irritation -  Rabbits  -  Palazzolo (1963c)  conducted a study  on  eye  irrita-
tion using New Zealand white  rabbits.   Technical carbofuran (5  rag) was  instil-
led into the conjunctival sac of  the right eyes of 2 rabbits; the  left  eyes
were used as controls.  Examinations were then made at intervals up  to  7  days.
                                       72

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     After 10 mln,  both rabbits  exhibited  miosis which persisted  for  2  hr.
Thereafter, the condition cleared.   Only minimal irritation was reported  in
this test (Palazzolo,  1963).


Skin Sensitivity - Guinea Pigs - Technical carbofuran injected intracutaneous-
ly into the skin of male guinea  pigs did not  elicit  a sensitizing reaction.
Injections were given every other day for  20  days.   The  first injection was
0.05 ml and all others were 0.10 ml each.   The  challenge dose was given 2
weeks following the 10th injection (Schoenig, 1967g).


Neurotoxicity - Chickens - When treated with  a  concentration of technical
carbofuran equal to the LD5Q concentration of 38.9 mg/kg,  white Leghorn hens
dosed with technical carbofuran exhibited  salivation and general  weakness,
but not leg and wing weakness at a concentration equivalent to the LD5Q (38.9
mg/kg).  In surviving birds,  the weakness  subsided in 24 hr.  Surviving birds
were given another acute dose at 21 days with similar results.  No physical
signs of delayed neurotoxicity (demyelination)  were  observed and, therefore,
microscopic examinations were not performed (Jackson, 1967).


Potentiation Studies - Sprague-Dawley rats were the  test animals  used in  po-
tentiation studies.  Schoenig (1966) determined the  LD5Q of  carbofuran and
other pesticides (12 compounds), and then  determined the LD5Q of  equitoxic
mixtures of carbofuran and each of the other compounds.   The  results were
compared to theoretical LD5Q values derived from assumption  of  strictly addi-
tive toxicity.  Potentiation of the acute  oral  toxicity of carbofuran by any
of the other test materials was not observed.  For example,  the  theoretical
LD5Q of an equitoxic mixture of carbofuran and  ethion was 104.1  while the
observed LD5Q was 180.  The theoretical LDso of a mixture of carbofuran and
Sevin was 129.1 and the observed LD5Q was  111.0.   The ratio  of  theoretical
to observed LD5Q was 0.58 for ethion and carbofuran, and 1.16 for Sevin and
carbofuran (Schoenig, 1966).


Symptomology and Pathology


Signs of Toxicity - Signs of intoxication that developed in rats  after an  acute
dose of carbofuran were reported by various investigators as follows:  fibril-
lary action, salivation, ataxia, lacrimation, exophthalmos, hyperpnea, cyanosis,
hemorrhagic conjunctivitis, tonoclonic convulsions, diuresis, labored  breathing,
sprawling of the limbs, and depression.   The dosage resulted in  the  deaths of
some animals.   (Palazzolo, 1965; Powers,  1964; and Palazzolo, 1963c).

     The signs  observed in the  dog were similar to  those  seen in the rat.   The
predominant reactions  reported  for a  single  acute dose  of carbofuran were trem-
ors  (lasting 4  to 6 hr) emesis  and moderate  to severe convulsions.   The  dose
resulted in the deaths of  some  animals (Baran, 1967a).

     Signs of  subacute  intoxication are coughing, gagging, salivation, muscu-
lar  tremors, and emesis  (Baran,  1966).

                                      73

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      The most frequently observed signs  of  acute  intoxication with carbofuran
 in sheep and cattle were reported by  Palmer and Schlinke  (1973) to be in-
 creased salivation, lolling tongue movements,  stiff uncoordinated gait,
 dyspnea, muscular tremors,  ataxia, and prostration.  Acute intoxication might
 also prove to be fatal.

      Signs reported for acute intoxication  in  chickens  include  salivation,
 general weakness, and a specific extreme leg and  wing weakness  (Jackson, 1967).


 Symptoms of Toxicity - In humans the  symptoms  of  carbofuran  intoxication are
 assumed to be those produced by other cholinesterase inhibitors:  headache,
 nervousness, blurred vision, general  weakness, nausea and cramps, diarrhea,
 sweating, tearing, excessive respiratory tract secretion, cyanosis, convul-
 sions,  coma, loss of reflexes,  loss of sphincter  control, and cardiac arrest.
 Carbofuran intoxication can also cause death (Hayes, 1963).


 Treatment of Intoxication

      Sprague-Dawley rats with a body  weight of 150 g  were administered tech-
 nical carbofuran orally at concentrations of 3.5  and 5.3  mg/kg.  Within 30
 seconds after dosing with the insecticide,  atropine sulfate  (1.5% solution)
 was given intraperitoneally.

      Animals which were not given atropine  exhibited salivation, lacrimation,
 miosis,  and generalized tremors.   Those  treated with atropine exhibited only
 generalized tremors.  At a dosa of 3.5 mg/kg carbofuran,  25% of the rats died;
 animals treated  at 3.5 mg/kg carbofuran  plus 50 mg/kg atropine  had a mortal-
 ity of  8.3%.   Rats dosed at 5.3 mg/kg of carbofuran followed by treatment with
 atropine sulfate at 100 mg/kg had a mortality  of  6.2%,  while the test animals
 at  5.3  mg/kg carbofuran exhibited mortality equal to 69%  (Palazzolo, 1963a).

      Sprague-Dawley albino  rats weighing 175 g were administered technical
 carbofuran at  5.3 mg/kg.  Thirty seconds after treatment, 2-pyridine aldozime methn-
 chloride (2-PAM  Cl) was given to 2 groups of carbofuran-treated animals at
 100 or  150 mg/kg.   Eighty percent of  the carbofuran controls and 60% of both
 groups  given 2-PAM Cl treatment died.  These results appeared to indicate that
 2-PAM Cl cannot  be recommended  as treatment for carbofuran intoxication.  In
 addition,  the  animals which received  only 2-PAM Cl exhibited reactions of
 dyspnea,  exophthalmos,  excitation, and mild generalized tremors 5 to 30 min
 following  dosing.   These  symptoms persisted for about 1-1/2  hr  (Palazzolo,
 1964a).

     Treatment of  dogs with atropine  sulfate was  also found  to  reduce reactions
due  to treatment with technical carbofuran  (5.3 mg/kg).   Two dogs were treated
with atropine  sulfate (50 mg) when symptoms of intoxication  appeared.  Severe
reactions  occurred  for 3  hr in  the absence  of  an  atropine treatment.  Dogs
treated with 50 mg  atropine sulfate responded  immediately (Palazzolo, 1963d).
                                      74

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     New Zealand strain albino rabbits were  given a single dose of technical
carbofuran by gavage and,  as soon as  signs of  intoxication appeared, half of
the test animals were given an injection  containing 10 mg of atropine  sulfate.
The atropine-treated animals responded immediately.  Symptoms of intoxication
persisted in the nontreated animals for 5 hr.   Seventy-five percent of the
non-atropine-treated rabbits died, but none  of the atropine-treated animals
succumbed (Palazzolo, 1964b).

     Calves, 1 to 2 weeks  old, were treated  orally, with  technical carbofuran
at doses from 0.25 mg to 5 mg/kg.

     When signs of toxicosis appeared, animals which had received doses of 1
and 5 mg/kg carbofuran were treated with  atropine sulfate peritoneally at a
dosage of 0.5 mg/kg body weight.   The animal administered 1 mg/kg carbofuran
died even though treated with atropine sulfate; the animal dosed with  carbo-
furan at 5 mg/kg and treated with atropine sulfate survived.  The authors
did not comment on the results (Palmer and Schlinke, 1973).

     Sheep were administered carbofuran at 5 and 10 mg/kg body weight.  When
signs of toxicosis were observed, 3 animals  treated at  5 mg/kg and  1 animal
treated at 10 mg/kg were treated intravenously with atropine  sulfate at a  dose
of 0.5 mg/kg body weight.   The animals that  received 5  mg/kg  carbofuran sur-
vived; the animal given 10 mg/kg carbofuran  died even though  treated with
atropine sulfate (Palmer and Schlinke, 1973).

     For treatment of organophosphorus pesticide poisoning  in man,  Hayes
(1963) recommends a dosage of 1 to 2 mg  atropine sulfate at  the  appearance
of symptoms.  In cases where excessive  secretions  occur, the  individual should
be given atropine sulfate every hour up  to 50  mg a day.

     The recommendation made in the Merck Manual (1966)  for organic phosphate
poisoning is 1 to 4 mg of atropine intramuscularly or  intravenously,  followed
by 1 to 2 mg every 20 min up to a total  of 10 to 20 mg/day.


Accidental Exposures

     Accidental exposures to carbofuran are recorded by the EPA Pesticide
Episode Review System  (PERS).  Computerized PERS data for the period  1972
through January 1974 showed carbofuran to be  the twenty-sixth most frequently
cited compound in the  review  system.  More recently, a  review was conducted
of the PERS data for the period  January  1967  to April 1975 (EPA, 1975).  This
review indicated that  a total of  55  episodes  had been reported, including
those involving humans, animals,  plants, and  contaminated areas.  However, in
most cases, carbofuran was  not conclusively established as the cause  of the
episode.  There was  substantial  evidence to link the pesticide to the episodic
effect for only 3 of the 26 episodes involving accidental human exposure.
The available data was too  limited to establish any relationship between the
episodes and any specific method of  application or use  of carbofuran.
                                      75

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      The geographical distribution of the 55 episodes, according to EPA
 Region, is as follows:

                  EPA region          No. of episodes

                       1                     0
                       2                     1
                       3                     1
                       4                     6
                       5                     4
                       6                     6
                       7                     7
                       8                    13
                       9                    14
                      10                     3

 Metabolism

      The main pathway of oxidative metabolism of carbofuran in plants,
 insects,  and animals appears to consist of hydroxylation at the benzylic
 carbon  to yield  3-hydroxycarbofuran (see Table 19 and Figure 7)«  The hy-
 droxylated product  is further oxidized to give 3-ketocarbofuran.  Hydroly-
 sis  and conjugation then occur. The 3-keto compound is hydrolyzed at a
 much faster rate than the parent carbofuran although hydrolysis and con-
 jugation  can also occur at other stages of metabolism. Carbofuran can be
 converted (hydrolyzed) to 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran
 (carbofuran phenol) or hydroylsis can follow oxidation to 3-hydroxycar-
 bofuran .

      The  available  data  appears to  indicate  that hydrolysis is preceded
 by oxidative metabolism  (Schlagbauer  and  Schlagbauer,  1972; Metcalf, 1968;
 Casida  and  Lykken,  1969;  O'Brien,  1967; and  Ryan, 1971).

      Numerous studies  describing  the  specific steps in the metabolic path-
 ways of carbofuran  in  plants and  animals  are cited in Table 17.  The pro-
 ducts of  oxidation  and hydrolysis of  carbofuran in rats, cows, and in
 plants, as  proposed  by Knaak  (1971),  are  shown in Figure 7.
Insect Metabolism - Microsomal preparations of housefly tissues were used by
Metcalf et al. (1968) to study the effects of mixed function oxidases on
carbofuran.  The results of this study suggested that carbofuran is hydroxy-
lated at 4 sites:  the 3-position of the furan ring, the 6-position of the
aryl ring, the N-methyl group and the 2-methyl groups.  The authors stated,
however, that formation of substantial amounts of metabolites hydroxylated
at the N-methyl or 2-methyl groups does not appear likely.
                                      76

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                         In alfalfa
      V
                                  0-Cluco«e
                                                     Hydroxylation


                                                      OCNHCH3
In rats and eovs
      0
                                                                                  Hydrolysis
                                                                                 OH
                            Hydrolysis
N
cose 0-Gl
' • OSO I!
j
ucose 0-CL /
f \
OS03H
icid 0-GL A
f ^
OS03H
cid 0-GL i
*
1C id
Source:  Knaak,  G.  B.   1971.  Biological  and  nonbiological modifications of carbamates.
           Bull.  World Health Ore. 44:121-131.   Reprinted, by permission of the World
           Health'Organization.
                         Figure 7 .  Proposed Products of Carbofur.an Oxidation and Hydrolysis

-------
                                                                         Table  17.   Metabolites of Carbofurun
Name of compound usually
found In the  literature

Carbofuran (I)
                                                       Formula
                  3-tfydroxycarbofuran (II)
Probable, metabolic
reaction resulting
   In formation

Pesticldal compound
  could also be
  secondarily re-
  leased from (XII)
                                                                           Aromatic hydroxylatlon
                                                                             of (1) (Oxldatlve)
00
                  3-Ketocarbofuran (III)
                                                          Oxidation of  (II)
 Plants and animals
 in which metabolite
    has been found

KaramulB, blrda,  fish
Insects, plants, soil
                              Rat
                              Chicken
                              Cattle

                              Mouse
                              Cotton
                              Alfalfa
                              Corn

                              Beans
                              Tobacco
                              tine
                              Insects

                              Earthworms
                              Soil

                              Rat
                              Cattle
                              Mouse
                              Cotton
                              Alfalfa
                              Corn

                              Beans
                              Tobacco
                              Insects

                              Soil
          References

Sc'nlagbauer  and  Schlux'u.iucr (1972)
Catilda and Lykken (19.',9); u'Brlon (1967)
  Rynn (1971); Knnak (1971); Fnkuto (1972);
  Menzic  (1969);  WustntT et al. (1974);
  Menn (1972); Kiihr (1970)

Lucier (1972); Dorough (1968b)
Hicks et  al.  (1970)
Ivie and  Dorough  (196U); Knaak ct al. (1970b);
  Miles et al. (1971)
Metcalf (1968)
Hetcalf et al. (1968)
Knaak et  al.  (1970a)
Turner and Caro  (1973);  Caro et al.  (1973);
  Metcalf ct  al.  (1968)
Dorough (19*<8a)
Ashuortli  and  Sheets (1972)
Prcc and  Saunders (1974)
Black et  al.  (1973); Shrivastava et  •»!.  (1971);
  Metcalf (1968); Sangha (1971)
Stenersen ct  al.  (1973)
Cr.ro et al.  (1973)

Dorough (1968b);  Lucior  et al. (1972)
Ivie and  Dorough  (1968)
Metcalf et al. (1968)
Metcalf et al. (1968)
Knaak et  al.  (1970b)
Caro et al.  (1973); Turner and Caro  (1973);
  Metcalf ct  al.  (1968)
Dorough (1968a)
Ashworth  and  Sheets (1972)
Shrivastava  et al.  (1971):
  Sangha  (1971);  Metcalf U968)
Caro rt al.  (1973)

-------
                                                                Table  17.   (Continued)
X»M of conpound  usually
found jr. the literature

Carbofuran phenol (IV)
                                      formula
                                  OH
Probable metabolic
reaction resulting
   in formation

Hydrolysis of (I)
plants -nd ar.irr.al3
in vhic!1' T^cabolite
   nas bean  found

       < o-*\

       Cattle
       Mouse
       Cotton
       Alfalfa
      . Eeans
       Tobacco
       Injects
       Pine
     Rc-forences

Metcalf «t al.  (1968)
Dorouih (1968b):  Lucier et  al.  (1972)
Knaak'cc al.  (1970b);  Ivit  a^  Dorough (1968)
Metcalf et al.  (1968)
Metcalf et al.  (1968)
Knaak et al.  U970a)
Dorouf.h (1968&)
Ashworth and  Sheets  (1972)
Metcalf et al.  (1968)
Pree and SaunUe'rs (1974)
3-Hydroxycarbofuran
  phtnol (V)
                                                           Hydrolyai. of (11)
                                                                                          r-.1C3
                                                                                          Chicken
                                                                                          '.attle
                                                                                          Alfslfa
                                                                                    Beans «ind tobacco
                                                                                          Insects
                                                                                          Earthworms
                                                                                          Cotton
                                                                                          ?ine
                                                L-.-er et al. (1972)
                                                Kicks et al. (1970)
                                                Ivle and Dorougb (1968); Knaak et al.  (1970b)
                                                Knaak et al. (1970a)
                                                Ashwo-th and Sheets (1972); Dorough  (1968a)
                                                hetctlf et al. (1968)
                                                Stcnersen et al. (1973)
                                                Metcalf et »l. (1968)
                                                Pree and Saunders (1974)
3-Katocarbofurcn phanol
  (VI)
                                                           ^rdrolyala of (III)
                                                             01 oxidation of
                               -,a-              Dorough (1968o): Lucier et al. (1972)
                               Chicken          Hicks et al. (1970)
                               Cattle        •  Ivie .and Dorough (1968); Knaak et al.  (1970b)
                               Souse            Metcali et al.  (1968)
                               .Mfalfa          Kr.jak et al. 'li'70a)
                               Lorn             Metcalf et ai.  U9r-3)
                               Eeanc            Dorough (1963a)
                               Tobacco          Ashworth *nd Sheets  (1972)
                               fine             Pree and Saunders  (1974)
                               Insects          Metcalf et al.  (1968)
                               Cotton           Metcalf et al.  (1968)
Carbofuraa phenol con-
  jugate (VII)
                                  0-conjugat*
                                                           Conjugation of (IV)
                                                                                           Cattle
                                                                                           Mouse
                                                                                           Cotton
                                                                                           .'Ifilfa
                                                                                           Tonacco
                                                                                           insects
                                                Dorouih  (196Kb)
                                                Knaak et t.1.  (1970b)
                                                Ketcalf et al.  (1-J68)
                                                Metcalf et -1.  (1968)
                                                Knaak et ai.  Ui"0a)
                                                Ashworth and  ^eeta  (1972); Ketcali et al. (1968)
                                                Metcalf at jl.  (1968)

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                                                                             Table 17.   (Continued)
00
O

Nane of compound usually
found in the literature Formula
3- Hydroxycarbofuran 0-conjuga:c
conjugate (VIH) I £j.
f/'~V|x ^fC.r|
IVvJ 	 1^ 3
OH
3-Kctocarbofuran con-
jugate (IX) 0-conjugace
Jl o ^c"3
(QLJ;:^
3-Hydroxy-N-nethylol- 0
carbofuran (X) ixNILIUOII
1 * -xCHi
ff)T' "Y^-CH
x~x"— — ^ 3
\x^ OH

N-ttathylolcarbofuran 0
(xi) OC'NHCHJOH
JL n CHi
oT Yc«3
3-Oxy-carbofuran con- 0
jugate (Xll) OCNHCHj
Prob.ible metabolic
reaction rosultinK
In formation
Conjugation uf (V)




Conjugation of (VI)



Aliphatic hydroxyla-
tion of (II) or
aromatic hydroxy-
lation of (XI)
(oxidatlvc)


Aliphatic hydroxy-
latlon of (1)
(oxidatlva)

Conjugation of (11)
can be metabolized
Plants and aniruls
in which metabolite
has been found
Cattle
Muu jt.'
Alfalfa
Corn
Tobacco
Cattle
Mouse
Alfalfa
Corn
Rat
Chicken
House
Beana
Insects
Cattle
Cotton
Chicken
Mouse
Pine
InaectB
Rat


References
Knaak et al. (1970b)
Metcalf et al. (1968); Black et
Knaak et al. (1970a)
Metcalf et al. (1968)
Aahworth and Sheets (1972)
Knaak et al. (1970b)
Metcalf et al. (1968); Black et
Knaak et al. (1970a)
Metcalf et al. (1968)
Dorough (I968b); Lucier et al.
Hicks et al. (1970)
Black et al. (1973)
Dorough (1968a)
Dorough U°68a) (1968b)
Ivle and Drough (1968)
Metcalf et al. (1968)
Hicks et al. (1970)
Metcalf et al. (1968)
Free and Saundera (1974)
Dorough (1968b); Metcalf et al.
Dorough (1968b)




al. (1973)




al. (1973)


(1972)








(1968)

                                                                            to (HI)
                                                            -eonjugate

-------
 Plant  Metabolism -  The  following studies summarize available information on
 the metabolism of carbofuran in specific crops.  The ratios of major carbo-
 furan  metabolites in  6  crops are given in Table 18.

     Isolated  cotton  leaves were allowed to imbibe labeled carbofuran and
 then,  at  intervals  up to  12 days, representative samples were homogenized,
 extracted,  and chromatographed.  Total recovery of radioactivity ranged from
 80 to  94% in the leaf homogenates (Metcalf et al., 1968).

     Two-dimensional  thin layer chromatography (TLC) of leaf extracts re-
 sulted in detection of  the following metabolites:  carbofuran phenol, 3-
 hydroxycarbofuran,  3-hydroxycarbofuran phenol, 3-ketocarbofuran, 3-keto-
 carbofuran phenol,  and  conjugates of the phenolic and alcoholic metabolites.
 In this study  conjugates  of N-methylolcarbofuran were not detected.

     Exposure  of the  conjugates to  fi-glucosidase enzymes  (emulsion)  resulted
 in liberation  of the  aglycones (3-hydroxycarbofuran phenol, 3-ketocarbofuran
 phenol) showing that  these plant conjugates were glucosides  (Metcalf et al.,
 1968).  Only a small  quantity  of the 3-hydroxycarbofuran  conjugate  could be
 released by either  enzymates or acid digestion.

     The  metabolites  formed by the  intact cotton plant were demonstrated to
 be similar to  those formed in  isolated leaves.  However,  the rate of meta-
 bolism in the  intact  plant was more rapid than in isolated leaves (Metcalf
 et al., 1968).

     The  metabolism of  carbofuran was studied in isolated corn leaves and
 in corn seedlings.  The isolated leaves were allowed to imbibe the  insecticide,
 but the seedlings-were  grown from seeds treated topically.
                   Table 18.  Ratios of Carbofuran Metabolite
                                Residues in 6 Major Crops
        Plant
  Major metabolite
Phenol/carbamate
     ratio
Potato
Corn (foliage)
Alfalfa
Sugar beet  (foliage)
Tomato (vine)
Bean plant  (bean)
Carbofuran phenol
Phenols
3-Hydroxycarbofuran
3-Ketocarbofuran phenol
3-Hydroxycarbofuran
3-Hydroxycarbofuran
      8/1
      3/1
      1/1
      1/1
      1/2
      1/16
 Source:   FMC  Corporation (1971).
                                      81

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      The rate of metabolism in isolated corn leaves was  slower than the rate
 in isolated cotton leaves,  but the conjugate metabolites appeared to be the
 same for the 2 plants.

      TLC revealed the presence of 3-hydroxycarbofuran and  3-ketocarbofuran
 phenol in the leaves together with the phenolic  conjugates.  The roots were
 found to contain large proportions of carbofuran phenol  and  lesser amounts
 of 3-hydroxycarbofuran and  3-ketocarbofuran (Metcalf et  al., 1968).

      The metabolism of carbofuran in corn plants was also  studied by Turner
 and Caro (1973).  The investigators reported that over 90% of the carbofuran
 was converted to 3-hydroxycarbofuran and 3-ketocarbofuran  by the time the
 plants reached silage stage.   Most of the residue in leaves  (92 to 93%) was
 3-hydroxycarbofuran.  The author also reported that, in  the  corn stalks, the
 principal metabolic process was hydrolysis to 3-hydroxycarbofuran with no
 accompanying oxidation.

      Metabolites of carbofuran were isolated from roots  and  tops of tobacco
 plants by Ashworth and Sheets (1972) in studies  on root  and  foliar uptake of
 the insecticide.

      Neither carbofuran nor its unconjugated metabolites were found to accumu-
 late in the roots of the tobacco plants.   In addition, only  trace amounts of
 glycosidic aglycones (3-hydroxycarbofuran) were  detected after acid hydrolysis
 of the methanol-soluble root  extracts.

      Analyses from root-uptake studies of the tops of tobacco plants, however,
 showed that the  expected metabolites were present— carbofuran phenol, 3-
 ketocarbofuran phenol,  3-ketocarbofuran,  3-hydroxycarbofuran, and several un-
 identified compounds.

      Some differences were  noted by these investigators  when the results of
 analyses from root-uptake studies were compared  to foliar-uptake studies.
 Carbofuran was not  found in plant parts other than the treated leaves.  The
 hydrolysis product,  carbofuran phenol,  was the major unconjugated metabolite.

      In the root-uptake  studies,  the oxidation product 3-hydroxycarbofuran
 was most  abundant.   From studies with topically  applied  material the investi-
 gators  also  concluded that  most  of  the  carbofuran does not penetrate plant
 cuticle and  is therefore not  subjected  to metabolic processes in the plant.

     The  half-life  of carbofuran absorbed through the root system and in the
 leaves  of  tobacco plants was  approximately 4  days.  Carbofuran and the oxi-
dation  products,  3-hydroxycarbofuran and  3-ketocarbofuran, were hydrolyzed
 to their  corresponding phenols.   The hydroxy  compounds were  eventually con-
jugated as glycosides.

     Bean plants  (Dorough,  1968a) and animals (Borough,  1968b) were reported
to produce the same metabolic  products  of carbofuran.  The metabolite present
in highest concentration was  3-hydroxycarbofuran.  This  material was found
                                      82

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as the free carbamate, but its concentration never equaled its  concentration
as a water-soluble conjugate.   The compounds 3-ketocarbofuran and 3-hydroxy-
N-methylolcarbofuran, both free and conjugated,  were also detected in the
plants.  In a test using ^C ring-labeled carbofuran,  the hydrolytic products
carbofuran phenol, 3-hydroxycarbofuran phenol,  and 3-ketocarbofuran phenol
were isolated.

     Of the hydrolytic products, only carbofuran phenol was found in the
free form, but always at a concentration below  the soluble conjugated form.

     pie metabolism in the potato of radio-labeled carbofuran (^C ring-labeled
and -"C carboxyl-labeled) was also investigated.  Carbofuran was applied to
the soil around 60-day-old field plants and to  the soil around  greenhouse
plants.  The greenhouse potatoes were harvested 7 days later and the field
potatoes 60 days later.

     Using greenhouse plants, the following glycosides were found after 7 days:
carbofuran phenol (45% of metabolites); 3-ketocarbofuran phenol (6.8%); 3-hydroxy-
carbofuran phenol (4.2%); and 3-hydroxycarbofuran (26.2%).  Carbofuran and
3-hydroxycarbofuran were also found at respective levels of 9.2 and 6.4%.

     Using field-grown plants, the following glycosides were found after 60
days:  carbofuran phenol (71.5% of metabolites); 3-ketocarbofuran phenol
(8.6%); 3-hydroxycarbofuran phenol (3.8%); and 3-hydroxycarbofuran  (11.5%).

     Extraction, hydrolysis and chromatographic studies indicated that carbo-
furan was absorbed by the potato roots and was transferred to the tubers
prior to hydrolysis and conjugation.  The   C carboxyl label remained in the
tubers and became a part of the natural product  (Knaak, 1970b) .

     The residue content and metabolism of carbofuran was also  investigated
in field-grown tomato plants.  One-week-old plants were treated with the
equivalent of 2.2 Ib/acre of radio-labeled   C-carbofuran and sampled  for
analysis at 11 days  (immature) and 50 days  (mature) after treatment.

     Total l^C residues  in mature and immature  (tomato) vines were  1.15  and
1.58 ppm  (ring-l^C)  and  0.33  and  1.0 ppm  (carbonyl-^C) at  the  respective
intervals.  Total -"-^C-residues  in mature  and immature  fruit  were  0.08  and
0.07 ppm  (ring-l^C)  and  0.04  and  0.18 ppm (carbonyl-l^C).  Mature and  immature
roots exhibited a total  ^C-content of  15.98 and 9.44  ppm (ring-14C)  and 26.42
and  7.60 ppm  (carbonyl-  ^C).

     Carbofuran was  metabolized in  the  plant by oxidation to form 3-hydroxy-
carbofuran (33.0% in mature vine  and  35.7%  in  immature vine).   More carbofuran
was  found in  the  immature  (28.3%)  than  in the mature  (2.6%)  vine.  The major
phenolic component was  3-ketocarbofuran phenol  (19.9% mature and 12.1% immature).
                                      83

-------
      In mature root the major metabolite was 3-hydroxycarbofuran  (52.2%); in
 immature root, the carbofuran was the major component  (46.4%).

      In tomato fruit, the ^C levels of activity were  too  low to  permit an
 accurate evaluation of possible metabolites (Hunger, 1972).

      Twelve 35-day-old sugar beet plants were placed within  barriers  and, at
 65 days, 4 plants were administered 18.0 mg/plant l^C  ring-labeled  carbofuran
 and 4 were administered 18.0 rag/plant carbonyl l^C-carbofuran.  Four  untreated
 plants were selected as controls.  One-half of the treated and  the  control
 plants were harvested at 30 days and the remainder at  72 days.

      Carbofuran was readily absorbed into the sugar beet roots  and  was trans-
 located to foliage.  The major carbamate metabolite identified  was  3-hydroxy-
 carbofuran while the predominant phenol was 3-ketocarbofuran phenol (Robinson,
 1972).

      Carbofuran was applied to the soil of potted alfalfa  plants  (9 mg/pot
 of l^C ring-labeled carbofuran), and after a 30-day growth period,  the plants
 were harvested and analyzed for carbofuran metabolites.

      The major metabolites identified (Knaak et al., 1970b)  were  the  glyco-
 sides of 3-hydroxycarbofuran (37.3%), 3-hydroxycarbofuran  phenol  (18.5%), and
 3-ketocarbofuran phenol (20%).  Total residue uptake expressed  as carbofuran
 amounted to 76 ppm.

      The roots of Mugho pine shrubs (30 to 45 cm in height)  were  exposed  for
 24 days to a solution of l^C carbomyl or -^C ring-labeled  carbofuran.  The
 needles were collected at various dates and were analyzed  for metabolites
 along with the buds,  roots,  trunk,  and current wood growth of the shrubs.
 (Free and Saunders, 1974).

      An unidentified  metabolite and 3-hydroxycarbofuran were the  only organo-
 soluble metabolites detected in the plant fraction from trees treated with
 carbonyl-l^c carbofuran.   Accumulation of metabolites  was  greatest  in the
 needles.

      In the  trees treated with -^C  ring-labeled carbofuran,  carbofuran phenol
 was  the main organo-soluble  in each sample,  although 3-hydroxycarbofuran  and
 3-ketocarbofuran  phenol were also found.   Two unidentified metabolites were
 also  present.

      The  separation of  carbofuran and its free metabolites from their con-
jugated  forms  indicated that most of the metabolites were  in the  conjugated
 form,  although  all  compounds were also present in the  free form.  Treatment
with /J-glucosidase  or /J-glucuronidase converted all of the identified metabo-
lites  from the  conjugated  form to the free form.
                                     84

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Metabolism in Mammals

     Male Swiss white mice were  given  radio-labeled  carbofuran (^H-labeled,
1.68 mc/mmole), and  over  the  following 24-hr  period,  urine was collected
and analyzed for metabolites.  Two mice treated  orally  with 2  rag/kg of the
3R-labeled carbofuran eliminated 37  and 67% of the administered radioactivity
in the 24-hr period.

     The major metabolite, 3-hydroxycarbofuran,  was  detected in the urine
by an ether extraction  procedure.  Smaller amounts of 3-ketocarbofuran and
carbofuran phenol were  also identified.  The  major conjugate and aqueous
portion was of 3-ketocarbofuran  phenol.

     The metabolism  of  carbofuran in mice was shown  to  be similar to that
in plants and insects;  however,  more of the carbofuran  dose was metabolized
by mice to the water-soluble  3-hydroxycarbofuran than was true for plants
or insects (Metcalf  et  al., 1968).   In plants, 3-hydroxycarbofuran; in
mice nearly 45% of the  radio-label recovered  in  metabolites was present in
3-hydroxycarbofuran.

     Carbofuran metabolites formed by  the soluble fraction of rat liver homo-
genates were identified by Dorough  (1968b) as 3-hydroxy-N-methylolcarbofuran,
N-methylolcarbofuran, 3-hydroxycarbofuran, 3-hydroxycarbofuran phenol, 3-
ketqcarbofuran phenol and carbofuran phenol.   Three  unidentified compounds
and other water-soluble complexes were also found.   The metabolites formed
and their relative concentrations are  shown in Table 19.

     The 3-hydroxy-N-methylolcarbofuran, when incubated singly with liver
15,000 g solubles, was  largely converted to water-soluble materials (con-
jugates) .  Both N-methylolcarbofuran and 3-hydroxycarbofuran were reported
to have been metabolized  (a)  to  an unidentified  fraction (2.2 and 0.6%,
respectively), (b) to 3-hydroxy-N-methylolcarbofuran (6.9 and 8.9%),  (c)
to 3-hydroxycarbofuran  phenol (4.1  and 3.9%,  respectively), and  (d) to water
soluble materials (23.9 and 23.4%,  respectively).

     Carbofuran phenol  was metabolized by  the rat liver enzymes  system primarily
to conjugated, water-soluble  compounds.

     The in vivo metabolism in rats  was studied  by housing  treated animals
in metabolic cages and  collecting and  analyzing  urine and feces  separately.
Analysis of the organo-extractable metabolites in urine indicated  that
jin vivo metabolism was  similar to in vitro metabolism with  liver homogenates.
Two metabolites, 3-ketocarbofuran phenol and  an  unknown, were not  detected
in the unconjugated  form  in  the rat  urine, but they were present as water-
soluble conjugates.   Four additional metabolites were also  produced from the
water-soluble conjugates  by means of acid  hydrolysis:  3-hydroxy-N-methylol-
carbofuran, 3-hydroxycarbofuran, 3-hydroxycarbofuran phenol,  and carbofuran
phenol.

     Radioactivity in the water fraction from 14C-ring-labeled  carbofuran
incubation was about 3  times  greater when  microsomes from control  rats  were
                                      85

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used than when microsomes from methylmercury hydroxide-treated rats were
used.

     Rats treated with methylmercury hydroxide excreted carbofuran-1^-C
equivalents more rapidly than controls.

     The metabolites obtained from the treated animals were identified as
3-hydroxycarbofuran, carbofuran phenol,  3-hydroxycarbofuran phenol, 3-
ketocarbofuran, 3-hydroxy-N-methylolcarbofuran, and N-methylolcarbofuran.
  Table 19.   Degradation of  Labeled  Carbofuran by Rat Liver 15,000  C Solubles
                                         %  of  radioactivity added
                                Carbonyl-labeled          Ring-labeled
                                	14jC	              14C

 Unknown I                            0.07                     0.10
 Unknown II                           0.011                    0.09
 Unknown III                          0.05                     0.03
 3-OH-N-Methylolcarbofuran            1.76                     2.07
 N-Methylolcarbofuran                 6.40                     7.05
 3-OH-Carbofuran                     21.09                    20.13
 3-OH-Carbofuran  phenol               0.00                     0.02
 3-ketocarbofuran phenol              0.00                     0.02
 Carbofuran phenol                    0.00                     3.82
 Water  solubles                       5.89                     7.01
 Carbofuran                          60.29                    58.50
Source:  Adapted from Dorough  (1968b).
     Prior treatment of rats with either methylmercury hydroxide or chlor-
ine affected the rate at which microsomal  fractions  from the rat's liver
would metabolize carbofuran.  However, the  treatment  did  not  alter the type
of metabolite which resulted (Lucier et al.,  1972).
                                       86

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     The excretion of carbofuran metabolites in cows'  milk was studied  by  Dorough
and Ivie (1968).   Two percent of an oral dose (gelatin capsule of -^C-carbonyl-
labeled carbofuran, 2.7 mg) was eliminated in milk,  but only 0.16% of a ^C-ring
labeled dose was detected.  The investigators noted  a  distinctly different distri-
bution of the radioactivity from that found with other carbamates.  Significant
quantities of labeled residues could not be extracted  from milk, and most  of  the
residues extractable by organic solvents could not be  extracted from lipid materials
This suggested that some of the radioactivity in milk  from cows fed 1^C-carbonyl
labeled carbofuran was not in metabolites, but in naturally occurring chemicals
that had incorporated the -^C atom from the treatment.

      Another study by Ivie and Dorough (1968)  included only ^C-labeled carbo-
 furan,  but  also  l^C-labeled sodium bicarbonate.   Results  from these tests  supported
 the earlier idea that the greater 14c-carbonyl-labeled residue resulted from in-
 corporation of 14C02 into body chemicals normally found in milk.   The  authors
 calculated  that  only 0.31% of the radioactive  dose  of l^C-carbonyl-labeled carbo-
 furan was eliminated in the milk as extractable  metabolites.   With the extract-
 able metabolites from milk, traces of parent carbofuran were present along with
 3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxy-N-methylolcarbofuran,  3-hydroxy-
 carbofuran phenol, 3-ketocarbofuran phenol,  and  one unidentified metabolite.
 The 3 metabolites (3-hydroxycarbofuran, 3-ketocarbofuran  phenol,  and carbofuran
 phenol) were the products in highest concentration  (70 to 80%).

     The metabolism of  carbofuran residues in  alfalfa fed  to  cows was  studied
by  Knaak et  al.  (1970b).   The carbofuran residues present  in  the  alfalfa were
identified  as  carbofuran  and  the  glycosides  of 3-hydroxycarbofuran, carbofuran
phenol, 3-hydroxycarbofuran phenol,  and 3-ketocarbofuran  phenol.   Since these
materials were all present in the alfalfa at the time of  feeding,  metabolic
pathways could not be defined.  These residues were metabolized and excreted
as  sulfates  of 3-ketocarbofuran phenol,  carbofuran  phenol,  and 3-hydroxycarbofuran
phenol.

     The  overall process  was  reported to include hydrolysis of the glycosides
and the carbomates,  oxidation of  the phenols,  and conjugation of the resulting
compounds with sulfuric or glucuronic acid.

      Cows were also treated with -^C-carbonyl-labeled carbofuran by Miles et al.
 (1971)  and  the milk from these animals was  analyzed for metabolites.

     When  cows were administered carbofuran, either by gelatin capsule or by
 feeding in  silage, the only metabolite reported in  the milk was 3-hydroxy-
 carbofuran.   Its concentration ranged from nondetectable  to 0.26 ppm  in the
milk from 8 cows, averaging 0.13 ppm (Miles et al., 1971).  An average of 0.05%
 of  the administered dose was excreted in the milk as  3-hydroxycarbofuran.  Ivie
 and Dorough (1968) reported that carbofuran and at  least  6 metabolites were
 detected  in milk from carbofuran-treated cows.

     Metabolites excreted in the fecal material of  laying hens given  ^C-carbonyl-
 labeled carbofuran and ^C-ring-labeled carbofuran were detected by Hicks et al.
 (1970).   The authors found that rapid hydrolytic degradation occured.   After 6 hr
 54% of the  dose  had been hydrolyzed; by 24 hr, 72% had been hydrolyzed.  Five
 unidentified metabolites were detected along with 3-hydroxycarbofuran, N-methylol-


                                          87

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 carbofuran,  3-hydroxy-N-methylolcarbofuran,  3-ketocarbofuran,  and  carbofuran phenol.
 The  predominant  metabolite was 3-hydroxycarbofuran phenol.

      The  concentration of carbofuran metabolites in eggs was  low.  Maximum radio-
 active  residue in eggs from hens treated with l^C-ring-labeled carbofuran was
 0.13 ppm.

      Samples of  liver, kidney, gizzard,  heart, breast,  thigh,  leg, skin, brain,
 fat,  and  blood were collected and were analyzed for radioactive residues.  All
 tissues at both  6 and 24 hr contained -^C-carbofuran equivalents;  none were
 detected  after this time in hens treated with ^C-ring-labeled carbofuran.  However,
 some residues were detected in tissues from  hens treated with l^C-carbonyl-labeled
 carbofuran after 3 days.  There was no proof, however,  that the radioactivity de-
 tected  was actually present as label in carbofuran or carbofuran metabolites.

      Free and conjugated forms of 3-hydroxy-N-methylolcarbofuran and N-methylol-
 carbofuran were  found in the liver.  Analyses of gizzard tissue revealed the
 presence  of  carbofuran,  3-hydroxycarbofuran, 3-hydroxy-N-methylolcarbofuran and
 an unidentified  metabolite.

       Metabolism in  soil  -  In a study on persistence of carbofuran in soil,
 Caro et al.   (1973) found  that after application of carbofuran to  the soil,
 partial conversion of the pesticides to the oxidation  product, 3-ketocarbo-
 furan, occurred.  However,  only traces  of the product,  3-hydroxycarbofuran,
 were found  in soil samples.   In corn grown  on the treated soil, over 90% of
 the parent  carbofuran was detected as 3-hydroxycarbofuran in  the  stalks.


 Cholinesterase Inhibition


       A comparative study using  carbofuran,  3-hydroxycarbofuran and 3-ketocar-
 bofuran as  inhibitors of cholinesterase indicated that  in rats all compounds
 were generally ineffective  inhibitors at a  concentration of 1 x 10~3 jug/ml
 (Lazanas, 1967).  However,  in dogs,  both carbofuran and 3-hydroxycarbofuran
 caused  greater than 50% inhibition at 1 x 10~3 jjg/mg, while 3-ketocarbofuran
 only resulted in 26.9% inhibition.

       The concentration of inhibitor  (ng/ml)  resulting  in 50% inhibition of
 erythrocyte  cholinesterase in dogs was  1  x  10~5  for  carbofuran and between
 1 x  10~4  and 1 x 10~4 and 1 x 10~5  for  3-hydroxycarbofuran.  The results of
 these tests  are  summarized as follows :

                                                     % Inhibition of
                            concentration  of           erythrocyte
                            inhibitor                 cholinesterase
 Inhibitor                     (|ig/ml)	        Dog          Rat

Carbofuran                    1 x 10~3               65.5         22.2

3-Hydroxycarbofuran           1 x 10~3              67.2         21.7

3-Ketocarbofuran              1 x 10~3              26.9         21.7

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   FMC Corporation, Middleport,  N.Y.  (unpublished,  1966a).

 Wolf,  C.,  "The Effects  of NIA  10242  on Cholinesterase  Activity in the Albino
   Rat  - Addendum Report," FMC Corporation,  Middleport, N.Y.  (unpublished,  1966b),

 Wolf,  C.,  "Two-Year Chronic  Oral  Toxicity of NIA 10242 - Albino  Rats,"  FMC
   Corporation, Middleport, N.Y. (unpublished,  1967a).

 Wolf,  C., "Two-Year Chronic  Oral  Toxicity of NIA 10242 - Albino  Rats,"  FMC
   Corporation, Middleport, N.Y. (unpublished,  1967b).

Wolf,  C., "Two-Year Chronic Oral  Toxicity of NIA 10242, 25  and 50 ppm - Albino
   Rats," FMC Corporation,  Middleport, N.Y.  (unpublished, 1968).

Wustner, D. A., M. A. Fahmy, and T. R. Fukuto, "New Aspects  of Organophosphorus
  Pesticides.   V. Oxidative Rearrangement of Organophosphorus  Thioate Esters,"
  Residue Rev.. 53:56-65 (1974).
                                       94

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                    PART II.   INITIAL SCIENTIFIC REVIEW


                     SUBPART  C.   FATE AND SIGNIFICANCE


                                 CONTENT

                                                                    Page

Effects on Aquatic Species 	   98

  Fish	'.  .  .  .   98
  Lower Aquatic Organisms	100


Effects on Wildlife	102

  Laboratory Studies 	   102
  Field Studies	104
  Field Investigations	106


Effects on Beneficial Insects	  .   107

  Bees	107
  Field Reports on Bee Toxicity	108
  Beneficial Parasites and Predators  	   109


Interactions with Lower Terrestial Organisms  	   110

  Flora	110
  Fauna	114


Residues  in Soil	117

  Laboratory and Greenhouse  Studies	117
  Field and Combined Field/Laboratory Studies	121


Residues  in Water	127


Phytotoxicity	127


Bioaccumulation  and Biomagnification 	   128
                                      96

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                            CONTENTS (Continued)


                                                                       Page

Environmental Transport Mechanisms 	   130

  Lateral Movement	130
  Leaching Studies 	   131
  Runoff Studies 	   132
References
                                                                        136
                                      97

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      This section contains  data on the environmental effects of carbofuran,
 including its effects on  aquatic species, wildlife, and beneficial insects.
 The interactions of carbofuran with lower terrestrial organisms and  its  resi-
 dues in soil and water are  also discussed.  The section summarizes rather  than
 interprets the data reviewed.
 Effects on Aquatic Species
 Fish -

      Laboratory Studies - The  toxicity of technical carbofuran to  fish  reported
 in different tests  (see Table  20)  appeared to vary depending upon  the species
 of fish tested and  on  the conditions prevailing at the time of testing.

      Longnose killifish (Fundulus  similis) were not affected by doses of  tech-
 nical carbofuran up to 0.1 ppm,  but  sheepshead minnow (Cyprinodon  variegatus)
 were irritated by 0.1 ppm carbofuran.   However, the killifish were irritated
 when exposed to Furadan 3G at  10 Ib/acre for 48 hr; 10% mortality  occurred with-
 in 24 hr when exposed to Furadan 3G  at 20 Ib/acre.  The fish recovered when
 placed in clean water  (Lowe, 1970).

      A study by Schoenig (1967)  indicated that rainbow trout, channel catfish,
 and  bluegill were of about equal sensitivity to technical carbofuran and  that
 the  96 hr TLm ranged from 0.21 to  0.28 ppm for these 3 species (Table 20).

      The 24 hr LC5Q of technical carbofuran to channel catfish was reported to
 be 2.03 ppm by Carter and Graves (1973)  under static conditions of testing, a
 value 10 times higher than that  reported by Schoenig (1967) for channel catfish
 also  tested under static conditions.

      In a test conducted by Carter (1971)  on channel catfish, it was also re-
 ported that the amount of carbofuran  required to effect a 50% reduction in
 cholinesterase activity was 0.19 ppm.   Treated fish showed the following  sequen-
 tial  signs  of toxicity:  hypoactivity ,  lethargy, body paralysis, scoliosis,
 loss  of equilibrium, opercular and mouth paralysis followed by death.

      The  signs and symptoms of toxicity  that appeared in 3 species of fish during
tests  to  determine the TI^ of a  formulation (Furadar£)lOG) were reported  by
Schoenig  (1967)  as follows:

           Rainbow trout;  96 hr TLn, -4.0 ppm
            Signs at:  1 ppm        No signs observed.
                     1.8 ppm      Hypoactivity.
                     3.2 ppm      Hypoactivity, increased respiration, and
                                   intermittent loss of equilibrium.
                     5.6 ppm      Hypoactivity, intermittent loss of equili-
                                   brium, convulsions, gasping mouth, dis-
                                   tended operculum, increased respiration.

           Channel catfish; 96 hr TL,,, - 4.1 ppm

            Signs at:  1 ppm        No signs noted.
                                        98

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                          1.8 ppm     Hypoactivity, increased respiration, inter-
                                       mittent loss of equilibrium.
                          3.2, 5.6,   Hypoactivity, increased respiration, intermit-
                            and 10.OS/  tent loss of equilibrium, flaccidity (inter-
                            ppm         mittent), convulsions, gasping mouth, disten-
                                       ded operculum.
              Bluegill;  96  hr TL,,, - 2.3
                                       ppm
               Signs at:   1.0 ppm
                          X • 0 PptD
                          3.2 and
                           5.6 ppio
    No signs noted.
    Hypoactivity, Increased  respiration,  intermit-
      tent  loss of equilibrium, intermittent flac-
      cidity, intermittent convulsions
    Same as 1.8.
         £/  At this level, all fish were dead within 3 hr.
      Field Studies - The U.S.  Department of  the  Interior's Denver Wildlife Re-
search Center (Flickinger, 1975)  studied the  effects  of carbofuran on fish and
other nontarget organisms in several areas  in Texas  where  it was used  to con-
trol larvae of the rice water weevil,  Lissorhoptrus  oryzophilus.

      When carbofuran  (as 3%  granules)  was applied to rice  fields at the  rate of
0.5  Ib Al/acre, some mortality of mosquito  fish  (Gambusia  affinis)  occurred  1
hr after  treatment.   Heavy mortality of mosquito fish, large-scale  menhaden  (Bre-
voortia patronus), Atlantic  croaker  (Micropogon  undulatus), and European carp
(Cyprinus carpio)  was  found  24 and 48  hr after treatment.

      In the rice  fields where these observations were made, rice seeds were  trea-
ted  with  another  insecticide.   It is not known if and to what  extent the insecti-
cide in seed  treatment may have  contributed  to the  fish mortalities observed.

                  Table 20.  Toxiclty of Technical Carbofuran and Its Formulations  to Fish
                 Pllh
                 ec let
Formulae Ion
  tested
 Toxiclty
calculation
                                                             Toxtcity meaaurcd
                                                                               Reference*
     Channel c«t[Uh (Ict«luru« punctual)     T«ch.
     Channel catfllh (Ictnlurus punctatua)     Tech.
     Yellow perch (Perca flaveiceni)
      City water                      Tech.
     Yellow perch (Perca flavescens)
      City water                      Tech.
     Blueglll (Ixsponili aacrochlrm)          Tech.
     Mosquito fish (Cambuata aftlnlt)         Tech.
     Fathead minnow (Ptnephalei prone las)
      City water                      Tech.
     Fathead rtlnnow (Ptnephalea pronelai)
      City water                      Tech.
           24
           24

           24

           96
           96
           96

           24

           96
  LCM
  "=50

  "=50

  LC50
  LC5o
  "=50

  1*50

  "=50
2.03 pp.. (-)
2,030 ug/i  (-)

ISO Mg/i (126-179)

147 MS/1 (115-187)
80 ug/i (-)
300 Mg/Z (-)
Carter (1971)
Carter and Craves (1973)

Mluck (1972)

Mauck (1972)
Carter and Craves (1973)
Carter and Craves (1973)
1,320 ug/i (991-1,760)  Mauck (1972)

1,180 pg/i (814-1,710)  Hauck (1972)
                                                99

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           Table 20.  Toxlcity of Technical Carbofuran and Ita Formulations to Flah (Continued)
                           Formulation
                             tested
 Toxlcity
calculation
                                                         Toxleltv meaauro.d  References
SCeelhead trout (Salno nalrdnerl)
Standard water
Steelhcad trout (Si Imp talrdneri)
Standard water
Brown trout (Salno trutta)
City water
Standard water
Brown trout (Salno trutta)
City water
Lake trout (Salvollnua namaycuah)
Lake trout (Salve I tnua naipavcuehl
Coho lllmon (Oncorhynchua klautch)
Standard water
Coho falmon (Oncorhynchui kllutch)
Standard water
Rainbow trout (Salno gilrdntrl)
Channel catflah (Ictalurua punctatua)
Blutglll (Ltponle macrochlrua)

Rainbow trout (Salno galrdnerl)
Chennel catfleh (Ictalurue ounctatua)
Blueglll (Lepomla imacrochlrua)


Tech.

Tech.

Tech.
Tech.

Tech.
Tech.
Tech.
Tech.

Tech.

Tech.
10 C
10 C
10 C
Tech.
Tech.
Tech.

24

96

24
24

96
Oft
yo
24
96

24

96
96
96
96
96
96
96

1*50

UCjO

"50
IC50

"=50
LC.
"•50
LCjo
LCSO

"=50

"50
TL,,
§

1,020 ug/I (635-1,640)

600 pg/i (436-826)

355 ug/* (242-521)
842 pg/1 (705-1,010)

280 pg/i (205-383)
560 pg/A (475-660)
164 pg/t (119-226)
164 ug/t .(U9-226)

530 wg/t (432-650)

524 tig/Z (-)
«.0 ppca (2.5-6.1)
4.1 pp. (2.4-7.0)
2.3 pp. (1.7-2.9)
0.28 ppei (0.23-0. JS)
0.21 ppa (0.16-0.28)
0.24 ppm (0.18-0.34)

Hauck (1972)

Hauck (1972)

Hauck (1972)
Hauck (1972)

Hauck (1972)
Hauck (1972)
Hauck (1972)
Hauck (1972)

Hauck (1972)

Hauck (1972)
Schoenlg (1967)
Schoenlg (1967)
Schoenlg (1967)
Schoenlg (1967)
Schoenlg (1967)
Schoenlg (1967)
      Extensive search of  the  literature and contacts with several laboratories
 known to be engaged in  fish  toxicity studies with pesticides failed to produce
 additional reports on the effects,  if any, of carbofuran on fish under field
 conditions.

      Commercial labels  of carbofuran 10% granules carry the following warning
 regarding fish toxicity:

          This product is  toxic  to birds, fish, shrimp, crab and other
          wildlife.  Birds and other wildlife in treated areas may be
          killed.  Keep  out of lakes, streams, ponds, tidal marshes
          and estuaries.   Cover  or incorporate granules which are
          spilled during loading and which are exposed on the soil sur-
          face in turn areas.  Do not apply where runoff is likely to
          occur.   Do not contaminate water by cleaning of equipment
          or disposal of wastes.

      A similar warning  is included  in the labeling of the carbofuran 4 Ib Al/gal
 flowable formulations.

      Typical labels of carbofuran 2, 3 and 5% granules state:  "This product is
 toxic to fish and wildlife; keep out of lakes, streams, or ponds.  Keep  irri-
 gation water out of lakes, streams, and ponds for at least 7 days."

Lower Aquatic Organisms -

      Laboratory  Studies -  Carter and Graves (1973) studied the acute toxicity
of several  commonly-used  insecticides (including carbofuran) to several  species

                                        100

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 of fish, to the white  river-crawfish,  and to bullfrog tadpoles.   The crawfish
 were seined from roadside  ditches  near the Louisiana State University and
 placed into large aluminum pans with a capacity of 2.5 1.   The bullfrog tad-
 poles were obtained by seining ponds of the Louisiana State University Fisher
 ies Unit on the Ben Hur Plantation and tested in aquaria lined with polyethy-
 lene bags.  Statis bioassay tests  were carried out in tap  water (PH 7.0, hard
 ness of 2 to 5 ppm) that was aged  and  aerated for at least 2 days.   The bio-
 assay procedures, conditions, and  results were as follows:

           Procedure, condition           Whlte rlver_               Bullfrog
           and re3ult9 _           crawfish                  tadpole

           Mean weight of test animals, g       0.7                     34
           Number of animals per container      3                      in'
           Replications per dose             5                      2
           Exposure time, hr               95                      96
           Test container volume, liters        05                     20
           Water temperature, C              26                      23-26
           Dissolved oxygen, ppm             9_U                    g,9
           LC50,  ppb                     500                   2700
         ™S °f the ®ther insecticides  included  in these studies ranged from
 2  to  50,000 ppb for the crawfish, and  from 270  to 185,000  ppb for the bullfrog
 tadpole.   The crawfish was more sensitive  to  all insecticides tested than the
 bullfrog tadpole.  In comparison to the  other insecticides, carbofuran ranged
 intermediate in toxicity to both test  animals.

      In model ecosystem studies (reported  in  greater detail in the section on
 Bioaccumulation and Biomagnification) , Sangha (1972) and Yu et al. (1974) found
 that  carbofuran was highly toxic to the  lower aquatic organisms with which the
 test  tanks were stocked, including fresh water  clams (Corbicula manilensis) .
 fresh water crabs (Uca minax) , frogs (species not identified) , snails (Physa
 species) ,  and water fleas (Daphnia magna) .  Most of these  organisms were killed
 shortly after sorghum plants growing on  the terrestrial part of the system were
 treated with carbofuran at a rate equivalent  to 1 lb Al/acre.  Fresh aquatic
 organisms  were reintroduced into the test  tanks every 5 to 7 days.  Those
 stocked 20 days after the application  of carbofuran survived.  The authors did
not report the concentration of carbofuran  in the water during this period.
Sangha  (1972)  stated that the LC50 of  carbofuran to Daphnia was found to be
20 ppb.                                               — * -

      Technical carbofuran did not appear to affect  the eastern oyster (Crasso-
s^trea virginica)  in 24-, 48-, and 96-hr  tests of up to 1.0 ppm carbofuran.
However, technical carbofuran and Furadan  3G  were highly toxic to pink shrimp
 (Penaeus duorarum) .   The 24-, and 48-hr  EC50  values for the shrimp exposed to
technical  carbofuran were 0.0068 and 0.0046 ppm, respectively.  Furadan 3G at
15 Ib/acre caused 70% paralysis or mortality  of the shrimp within 24 hr (Lowe
1970).

      Field Studies - In the previously mentioned field studies on the effects
of the  use of  carbofuran 3% granules on  rice  (Flickinger, 1975) , there was heavy
                                      101

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mortality  of  cricket frogs,  crayfish,  earthworms,  and  nontarget  aquatic  insects
which  occurred  generally between 1  and 45 hr  after treatment.  No details re-
garding the degree  of mortality  or  the nontarget  species  involved are given  in
the unpublished progress reports available at this time.
Effects on Wildlife
Laboratory  Studies  - The oral 11)50 of carbofuran  ranged from 0.238 mg/kg to
5.04 mg/kg  in  8 species  of  adult birds.   The  fulvous  tree  duck  was most  sensi-
tive and  the bobwhite quail was  most  resistent (see summary of  toxicity  in
Table  21).   Dermal  toxicity was  studied with  2 species  (Quelea  quelea and Pas-
ser domesticus)  and in both cases was reported to be  100 mg/kg  (Schafer  et al.j
1973).

      The  age of mallard  ducks was shown to affect their response to  carbofuran
although  the difference  in  the LD^g between the most  sensitive  age group and
the most  resistant  age group was only about twofold (Hudson et  al.,1972).  The
greatest  susceptibility  to  carbofuran appeared to occur at hatching  or shortly
thereafter  and  decreased to the  minimum value around  1  week of  age.   The sus-
ceptibility then appeared to increase to  30 days  of age and began again  to ap-
proach  maximum  susceptibility at 6 months of  age.

                          Table 21.  Acute Toxicity of Carbofuran to Birds
        Speclea

 King-neck phcassnt  (3 months)
   (Pha» tanus colchlcus)

 Mil I lad duck (3-6 months)
   (Anas platyrhynchos)
 Mallard duck
   (Anaa platyrhynochos)
   36-hr old
   7-days old
   30-days old
   6-aontha old

 Fulvoun trre duck (3-6 months)
   (Dcndrocynna blcolor)

 lobwhtce quail
   (Collnua vlrelnlanus)
 Japaneae quail (H) (2 weeks)
   (Commit inpinlci)
 Japanese quail (F) (2 weeks)
   (Coturnlx laponlca)
 Qua lea (Quelea quelea)
 Houac sparrow
   (Paster domc*ttcus)
 Red-wing blackbird
   (Aaelalus phoenlceus)
 Quelea (Quelra ouelca)
 House sparrow
  (Passer domettlcu»)
                          Fornulatlon
                           teated
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.
Tech.


Tech.


Tech.

Tech.

Tech.

Tech.

Tech.

Tech.

Tech.
            Toxicity
           calculation
                                                    Toxlctty meaaured
LDjO (oral)  4.15 mg/kg (2.38-7.22)
                                                                         Kaierencea
                                         Tucker and Crabtree (1970)
           LD50 (oral)   0.397 mg/kg (0.315-0.5r.O)  Tucker and Crabtree (1970)
U>i0 (oral)  0.370 mg/kg (0.283-0.484)   Hudson et al. (1972)
LD50 (oral)  0.620 mi;/kg (0.530-0.744)   Hudson et al. (1972)
LDjo (oral)  0.510 mg/kg (0.410-0.635)   Hudson et al. (1972)
    (oral)  0.415 mg/kg (0.333-0.516)   Hudson et al. (1972)
                               Tucker and Crabtree (1970)


                               Tucker and Crabtree (1970)


                               Sherman and Ross (1969)

                               Sherman and Ross (1969)

                               Schafer et al. (1973)

                               Schafer et al. (1973)

                               Sctufcr et al. (1973)

                               Schaiar at al. (1973)

                               Schafer at al. (1973)
L0jO (oral)   0.238 ng/kg


LDso (oral)   5.04 mg/kg (3.64-6.99)


LDj0 (oral)   1.9 «g/kg (1.7-2.1)

LDjo (oral)   1.7 ng/kg (1.3-1.9)

LOjo (oral)   0.42 ng/kg (-)

LDio (oral)   1.3 ng/kg (-)

I.DJQ (oral)   0.42 me/kg (-)

LD50 (dermal)  100 ng/kg (-)

LOjo (dermal)  100 Kg/kg (-)
                                             102

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     The sequential signs of poisoning for Japanese  quail  administered  techni-
cal carbofuran were lethargy, ataxla,  quivering,  and death.  When  death did not
occur, lethargy usually lasted 24 hr (Sherman and Ross, 1969).

     Similar signs and symptoms of acute  poisoning were reported for  mallards,
pheasants, and bobwhite quail by Tucker and Crabtree (1970).   The  authors ob-
served the following signs to be associated with  acute  toxicity:   ataxia, wings
crossed high over back, nutation, diarrhea, phonation,  salivation,  lacrimation,
immobility with wings spread, dyspnea, miosis,  terminal wingbeat convulsions or
opisthotonos.  Symptoms in survivors persisted up to 7  days.   Mortalities oc-
curred as soon as 5 min after treatment.

     Subacute toxicity of carbofuran to Japanese  quail  was studied by Sherman
and Ross (1969).  Rations containing 50,  100, 200, 400  and 800 ppm carbofuran
were fed ad libitum to groups of quail (20/group) for 6 weeks.  The feed con-
sumption, weight gain, and mortality were recorded over the entire feeding
period.  The results indicated that carbofuran was not  toxic at dietary levels
of 200 ppm or less, but was highly toxic  when fed at 400 ppm or more for the
6-week feeding period.  Feed efficiency was affected significantly at levels
greater than 200 ppm.

     Although there appeared to be no sex difference in susceptibility to a
single oral dose, the male appeared more  susceptible to continued  subacute
doses.  At the highest level fed (800 ppm) some females survived  to the third
week while all males died during the first week.   At 400 ppm all males died by
the fourth week while one-third of the females survived the entire 6-week feed-
ing period.  During the feeding experiment, eggs were collected from females
over a 17-day period after reaching the egg-producing age.  The results  indi-
cate that fertility and hatchability were greatly depressed at levels of 200
ppm and higher.  No abnormal embryos were observed among the fertile eggs fail-
ing to hatch, and there were no abnormalities observed  among the  newly hatched
quail.

     Hudson  (1972) studied subacute toxicity of technical  carbofuran adminis-
tered orally by gelatin capsules to ring-necked pheasants.  A group of 3 cocks
and 3 hens,  20 or 25 weeks old, were exposed daily for 30 days to 2.10 and
4.20 mg/kg/day.  No mortality occurred at  the lower rate.   At 4.20 mg/kg/day,
1 male died  after 8 doses, and 1 female died after 3 doses.  Weight loss of
41 g was observed at  2.10 mg/kg/day and 75 g at 4.20 mg/kg/day during  the  first
week of treatment.  The birds began to gain weight by  the second week.   By  the
end of the 30-day period, weight gains in  the pheasants were similar to  the
controls.

      Signs which  appeared most  severe during the first several days  of treat-
ment  included  ataxia,  hyperexcitability,  tremors, jerkiness,  tenseness,  ata-
raxia, high  carriage,  hypoactivity,  running and  falling and chronic  convulsions,
Brain acetylcholinesterase  in the  dead birds was inhibited 47.6%;  survivors of
both  levels  showed  little  or no inhibition.

      Symptoms  of  carbofuran  toxicity  to bobwhite quail, ring-necked  pheasants,
Japanese quail and mallard ducks exposed  to technical  carbofuran  and Furadan
                                      103

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 10G (Gough and Shellenberger,1972) were mild lethargy, hypoactivity, regurgita-
 tion, and lacrimation; at higher levels terminal wing-beat convulsions and par-
 tial paralysis were observed prior to death.  Following necropsy, mild to moder-
 ate hemorrhagic areas in the lung, stomach, esophagus, and crop were observed
 in those birds found dead as a result of treatment.  Surviving birds generally
 appeared normal 3 to 4 days following treatment.  The results of other studies
 on subacute toxicity are summarized in Table 22.  The mallard duck appeared to
 be more susceptible to the toxic action of carbofuran than either pheasant or
 Japanese quail.


 Field Studies - The U.S. Department of Interior's Denver Wildlife Research Cen-
 ter (Flickinger,1975) studied  the effects of applications of carbofuran to rice
 fields on a number of wildlife species, including birds.  Observations were made
 in 3 Texas study areas in 1970 and 1973 after applications of carbofuran 3% gran-
 ules to rice fields at the rate of 0.5 Al/acre.   Species of birds found dead or
 sick at 17 and 24 hr after treatment were western sandpiper (Ereunetes mauri),
 pectoral sandpiper (Erolia melanotos), and red-winged blackbird (Agelaius phoe-
 niceus).   The western sandpiper was found to be  the species most susceptible to
 carbofuran.   All dead sandpipers contained from  1 to 8 carbofuran granules in
 their stomachs.  Mortality of  all birds thus was believed to be largely the re-
 sult of consumption of the carbofuran-treated granules,  although it was pointed
 out that  in the study area,  rice seeds were treated with another insecticide.

      A field test was conducted by Harris and Applewhite (1969) to assess the
 hazard of carbofuran to mallard ducks when applied as Furadan 3G under condi-
 tions  representing pre-flood rice application.   Twelve pairs of adult mallards
 (a pair consisting of one  drake and one hen)  were used for each formulation.
 Furadan 2G was applied at  the  rate of 25 Ib/acre,  16 hr before water was allowed
 to enter  the field,  and Furadan 3G at 20 Ib/acre.   Daily feedings consisted of
 8  oz of cracked corn scattered  in the water.   After 14 days of observation no
 mortality or adverse affects were seen in any of the mallard ducks.

     Furadan 10G  was tested  under field conditions simulating normal applica-
 tion procedure to a  prepared seed bed.   Its  effect upon  adult bobwhite quail
 at rates  of  20, 60 and  200 Ib/acre  was  studied.   After the 5-week experimental
 period, no marked adverse effects  on  body  weight of males and females were ob-
 served  other than fluctuations  in weekly average body weights.   Two  males died
 at the  60 Ib/acre  level  and 2 males at  the  200 Ib/acre level.   Intestinal enter-
 itis was  thought  to  be  the cause  of these  4  deaths.   One-half of the surviving
 males and females  were necropsied and evidence of  an intetstinal enteritis was
 observed in  several  birds of all  treatment  levels.   It was  not  established
 that Furadan  10G was  the.cause of the intestinal enteritis  (Shellenberger,
 1971).

     In a field study with 14 pairs of  12-week-old ring-necked  pheasants  ex-
posed to Furadan 75 WP at a rate of 1.3  Ib/acre  (1.0  Al/acre)  for 14 days,
Stephens (1969) observed no mortality or adverse effects  in  any of the test
groups.

     In another field- study,  Zorb (1971) found similar results  with  Furadan
75  WP.   Sprays of 1.0 Ib/acre were applied directly on pheasants,  food or


                                       104

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                            Table 22.  Subacute Toxicity of Carbofuran to Birds
Species
Formulation
tested
Ring-neck pheasant        10G
(Phasianus colchicus)     Tech.
                          Tech.
Days
exposure

   7
   5
   5
Toxicity
calculation

    LC5Q
    LC50
                               LC
                                                        50
         Toxicity
         measured  (ppm)
         expressed  m
         (95% confidence limits)

         9,600   (775-13,598)
           438   (356-529)
           573   (492-666)
                            References

                            Jackson (1968)
                            Hill (1974)
                            Stickel (1975)
Mallard duck
(Anas platyrhynchos)
   10G
   Tech.
   Tech.
   7
   5
   5
    LC50
    LC5Q
    LC5Q
         2,100  (1,455-3,034)
           190  (156-230)
           190  (156-230)
                            Jackson (1968)
                            Hill (1974)
                            Stickel (1975)
Bobwhite quail
   10G
               LC
                                                        50
                10,250
                                     Jackson (1968)
Japanese quail
(Coturnix japonica)
   Tech.
   Tech.
   Tech.
   5
   5
   LC
   LC
                                          6  (weeks)    LC
50
50
50
  438  (356-529)
  437  (356-529)
200-400
Hill (1974)
Stickel (1975)
Sherman & Ross (1969)

-------
 vegetation, and combinations of these 3 treatments.   Pheasants that  died had
 high infestations of internal parasites.   It was not established  whether the
 Furadan or the parasite killed the birds.   There were no apparent effects on
 reproduction in the treated birds that had received  an application 8 months be-
 fore and during egg laying.  The author concluded that Furadan 75 WP causes no
 ill effects on pheasants.

      Carbofuran at 0.2 Ib  Al/acre was applied to a 5 acre pond in the  Kern
 National Wildlife Refuge in California to  simulate control of  mosquito larvae.
 Birds on or around the pond included sandpiper,  killdeer, blackbirds,  meadow-
 larks,  horned larks and lark sparrows.  On an adjacent pond of the refuge
 there were pintail, teal,  sandpipers, dowitchers and yellow legs. There was
 no evidence of dead or affected wildlife (Hagen,1971).

 Field Investigations - The U.S. Environmental Protection Agency's Pesticide
 Episode Review System (PERS) contains 3 reports  of carbofuran  episodes involv-
 ing birds during the period January 1967 to April 1975 (EPA, 1975).

      In 1972,  a "bird kill" (not further defined) in Wisconsin was ascribed
 to carbofuran.   However, the report on this episode  states that no evidence
 exists  to link carbofuran  to the bird kill.   A survey of 60 fields revealed
 only 1  owl with (unspecified)  pesticide residues.

      In 1972 in California, 19 geese were  found  ill,  and 15 of them  died in an
 alfalfa field  24 hr after  application of carbofuran  (formulation  and rate not
 given).   The episode report states,  however,  that insufficient evidence exists
 to link carbofuran to this incident.

      On March  15,  1974,  in California,  2,450 widgeon ducks,  2  Canadian geese,
 and  1 mallard  duck died  in an  alfalfa field  located  near a reservoir.   The
 alfalfa had  been treated with  carbofuran (4  Ib Al/gal flowable formulation) to
 control  the  Egyptian alfalfa weevil (Hypera  brunneipennis).  Laboratory analy-
 sis  revealed that  the deaths were not caused by  a disease,  and carbofuran was
 present  in the  crops of  the sample birds.  Local  officials felt that the pre-
 sence of  large  numbers of  birds was due to an unusual delay in migration.  It
was  concluded  that,  in this case,  substantial evidence existed linking carbo-
 furan to  the bird  kill.

     The  label  of  Furadarf^4 flowable,  a liquid  formulation containing 4 Ib of
carbofuran Al/gal,  carries  the following warning  regarding bird toxicity:
"This product is toxic to  fish,  birds and  other wildlife.   Birds  feeding on
treated areas may  be killed."

     The label  for  carbofuran  10%  granular bears  the  following statement regard-
ing bird toxicify:

          This product is  toxic  to birds,  fish, shrimp,  crab and  other
          wildlife.   Birds  and  other  wildlife in  treated areas may be
          killed.  Keep out  of  lakes, streams, ponds,  tidal marshes  and
          estuaries.  Cover  or  incorporate granules which are  spilled
          during loading and which are  exposed on the  soil  surface in
          turned areas.

                                      106

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     Labels for carbofuran 2,  3,  and  5%  granular formulations state:   "This
product is toxic to fish and wildlife .... Birds  feeding on treated areas
may be killed."


Effects on Beneficial Insects


Bees - Bailey and Swift (1968)  and  Anderson  et  al.  (1971), based on  laboratory
and field data, classified carbofuran as "highly toxic"  to honeybees.  The  term
"highly toxic" was defined as  including  severe  losses which "may be  expected  if
the pesticide is used when bees are present  at  treatment time or within  a day
thereafter."

     These bee toxicity ratings are based on laboratory  studies by Atkins et
al. (1973), as well as on more than 120  large-scale  field tests on crops in
bloom and highly attractive to honeybees (Anderson  et al.,1971).  Most tests
were run on alfalfa, and a few were made on  ladino  clover, cotton, sweet corn,
and in peach and citrus orchards.  The test  insecticides were applied  by air-
plane or by power ground sprayers.  The  publication by Anderson et al. (1971)
does not include experimental  details pertaining specifically to the testing  of
carbofuran in this program.

     Atkins et al. (1973) summarized  the results of toxicity  tests  in  which a
large number of pesticides and other  agricultural chemicals were studied with
regard to their effects on the honeybee (Apis mellifera). In a laboratory
procedure which primarily measures a  chemical's contact  effect, pesticides
were applied in dust form to groups of 25 bees  per  test  dose,  3 replicates  per
each of 3 colonies, for a total of 9  replicates per test dose.  This procedure
permits determination of an U^Q value for each pesticide in micrograms  of
chemical per bee.  Honeybees (worker  bees of uniform age obtained  from the  same
colony before treatment) were exposed to carbofuran for  48 hr  at  80°F (26.7°C)
and 65% relative humidity.  Under these conditions, the  LI>50  of  carbofuran was
0.15 jig/bee, placing it into Group I, ''highly toxic to honeybees."

     In their test procedures, Atkins et al. (1973) also determined the slope
of the dosage-mortality curve for each pesticide tested, and  recorded it as  a
"slope value" in terms of probit units,   Pesticides with a slope value of 4
probits or higher can often be made safer to honeybees by lowering the dosage
only slightly.  Conversely, by increasing the dosage only slightly,  the pesti-
cide can become highly hazardous to bees.  Carbofuran rated a slope value of
4.31, indicative of a moderately steep dosage-mortality curve.

     Atkins et al.  (1970) studied the effects of a carbofuran application at
the rate of 1.0 Ib Al/acre  on seed alfalfa on the Santiaga Ranch in Kern County,
California, in 1968.  Carbofuran was applied as a spray  in 10 gal of  water per
acre by airplane to a non-replicated 16-acre plot in a  field in good  bloom
which contained 2 to 3 well-established  colonies of bees per acre.  The treat-
ment was made directly over the  unprotected  test bee colonies.  Effects of the
treatment were determined  from records  of honeybee kill  at the hive and in
field cages, colony strength and behavior,  and field bee blossom visitation
rates.  Observations were made for several  days before,  the day of, and for  4


                                      107

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to  5 days after  treatment.  Dead bee  records at the colonies were obtained by
daily  counts  of  bees  collected  in  traps  placed on 6 colonies per treatment.
Cages  of bees were  placed  in  the fields  at  fly-over time to measure the initial
contact effect.   Other  cages  of bees  were placed in the treated areas at inter-
vals after  treatment  to study residual fumigation.  Average summer weather con-
ditions prevailed during the  test  period.

     Field  bee visitation  returned to normal after a drastic reduction for 5
days following carbofuran  application.   There was no significant kill in trapped
colonies placed  in  the  carbofuran-treated field, 4, 7, or 10 days after treat-
ment.  The  carbofuran treatment killed 100% of the caged bees exposed during
treatment,  but there  were  no  fumigation  effects at 1 to 2 hr post-treatment.
The authors concluded that bee  colonies  can be safely placed in carbofuran-
treated fields 4 days after treatment,


Field  Reports on Bee  Toxicity - The U.S. Environmental Protection Agency's
Pesticide Episode Review System contains several reports of injury to bees at-
tributed to carbofuran  during the  period January 1967 to April 1975 (EPA,1975).

     On June  12,  1972,  all honeybees  in  36  hives were destroyed in Utah after
the application  of  carbofuran to a nearby alfalfa field,  No further information
was given regarding application details, or how the bees were exposed.  The
episode report states that insufficient  evidence existed to link carbofuran to
this bee kill.

     On March 27, 1973,  a  bee kill (not  further defined) occurred in California,
apparently  caused by  bees  carrying contaminated pollen back to the hives where
a progressive kill  occurred.  No details are given regarding the crop or type
of  carbofuran application  involved, and  carbofuran was not verified as the
causative agent.

     On June  1,  1973, in Wyoming,  192 honeybee colonies were "moderately dam-
aged"  (no further details  given) after carbofuran had been applied to a nearby
field  to control  alfalfa weevils.   Formulation, method, and rate of application
were not given.   Seven  apiaries were  involved.  The episode report states that
insufficient  evidence existed to link carbofuran to the bee damage.

     Three  additional episodes  involving damage to bee colonies in Wyoming in
June of 1973  have been  reported.   In  1 case, 89 honeybee colonies from 2 api-
aries were  moderately damaged.  In another  case, 63 honeybee colonies were
damaged severely, and 11 colonies  were damaged moderately; 3 apiaries were in-
volved.  In the  third case, 33  bee colonies from 1 apiary were moderately dam-
aged.  In all 3  instances,  carbofuran was applied to nearby fields for the
control of  alfalfa  weevils.   No details  regarding the carbofuran applications
or  the manner of  exposure  of  the bees were  given.  Carbofuran was not verified
as  the causative  agent  in  any of these episodes.

     On August 12,  1974, in Montana,  25  beehives were "affected" when bees had
to pass through a corn  field  recently treated with carbofuran (treatment details
not given)   in order to  reach  an alfalfa  field.  There were 300 to 400  dead bees
                                     108

-------
found lying around each hive.   The episode report  stated  that  circumstantial
evidence existed linking carbofuran to the incident.

     The commercial label for  Furadarr^ 4 flowable  (containing  4  Ib  of  carbo-
furan Al/gal) includes the warning:  "Do not move  bees  into  alfalfa fields
within 7 days of application."

     No bee toxicity statements are found in the labeling of carbofuran gran-
ular formulations.
Beneficial Parasites and Predators - Croft  and  Meyer  (1973)  studied  the  toxicity
of carbofuran to 3 different strains of the phytoseiid mite,  Amblyseius  falla-
cis, a common predator of spider mites in commercial  fruit  orchards  in central
and eastern United States and Canada.   Carbofuran 75% wettable  powder  was  tested
against an organophosphate-resistant strain from Hartford,  Michigan, a strain
selected with carbaryl for 9 yr, and a strain selected with carbofuran for 4
yr.  The LC^Q'S of carbofuran as determined by  a laboratory leaf-dip technique
were 0.002 Ib for the first strain and 0.006 Ib for the latter  2.  This  data
indicates that there was no appreciable development of resistance  of the predator
to carbofuran.

     Elsey (1973) investigated the effects  of carbofuran and several other in-
secticides on the spined stilt bug, Jalysus spinosus, a foliage-inhabiting
predator of insect eggs and aphids on tobacco.   Carbofuran 10%  granules  were
applied at the rate of 6 Ib Al/acre as a broadcast treatment before tobacco
was transplanted.  Treated and untreated plots  were randomized  and replicated
3 times.  The density of stilt bug adults in the carbofuran-treated  plots was
slightly lower than in the check plots throughout the season, though the dif-
ferences were seldom statistically significant  at the 5% level  by Duncan's
multiple range test.  The populations of stilt  bug nymphs were much lower, and
nymphs were seldom found in the plots treated with carbofuran.   Since  some
stilt bug adults and eggs remained in the carbofuran-treated plots throughout
the season, the investigators attributed the lack of  nymphs to the poisoning
and death of eggs or newly-hatched nymphs which fed on treated plant tissue or
came in contact with carbofuran residues brought to the leaf surface by tri-
chome exudates.  Other predators were present but not abundant in the plots,
and there were no statistical differences between treated and untreated plots.

     On 4 different dates in August, each of the test plots was infested with
30 eggs of the tobacco budworm, Heliothis virescens,  from a laboratory culture
by gluing 3 eggs per plant to the underside of leaves on 10 plants in the  center
2 rows of each plot.  The plants were checked after 48 hr for  indications  of
insect predation, and for missing and normal eggs.  Egg losses caused by pre-
dators with chewing mouthparts were not  included,  In this test,  the  predation
of budworm eggs in the carbofuran-treated plots was significantly lower than
in the check plots (at the 5% level by Duncan's multiple range test)  on 3  of  the
4 test dates.
                                     109

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 Interactions with Lower Terrestrial Organisms

 Flora - The effects of carbofuran and 3 other nematicides on microorganisms in
 soil were studied by Tu (1972)  in experiments conducted with Delhi loamy sand,
 a typical agricultural soil in  southwestern Ontario.   The soil contained 0.81%
 organic matter and 0.03% nitrogen,  and had a moisture-holding capacity of 27%,
 and pH of 8.2.  Carbofuran was  added to the soil at the rates of 1 and 5 ug/g of
 soil.  Reagent grade peptone and elemental sulfur powder were added to the soil
 samples at 1,000 ug of nitrogen or sulfur per g to measure ammonification and sul-
 fur oxidation, respectively.  Oxidation of ammonium from soil organic nigrogen was
 studied by nitrification.   The  experimental mixtures  and controls were held in 0.5
 pint milk bottles closed with polyethylene film.  Soil moisture was maintained at
 60% of capacity.   The treatments,  in duplicate, were  incubated 1 week in the lab-
 oratory at 28°C for ammonification,  1 and 2 weeks for nitrification, and 4 weeks
 for sulfur oxidation.   Changes  in  population of soil  microorganisms were deter-
 mined after 1, 2,  4,  8,  and 12  weeks.

      Plate count data indicated that neither carbofuran nor any of the other 3
 nematicides affected fungal population drastically.   Five ug/g of carbofuran
 slightly depressed fungal population 1,  2,  and 4 weeks into the experiment.  At
 8 and 12 weeks,  there were no significant differences in the fungal counts be-
 tween carbofuran treatments and untreated controls.   The higher rate of carbo-
 furan significantly decreased bacterial populations during the first week of in-
 cubation,  but they subsequently recovered to levels at or above those found in the
 controls.   Plate counts  in the  controls showed a decrease in fungal and bacterial
 populations during the 12-week  incubation period.   The carbofuran treatments gene-
 rally had  no significant effects on  ammonification or nitrification of ammonium
 from soil  organic nitrogen.   Oxidation of elemental sulfur was depressed signifi-
 cantly by  both carbofuran treatments.

      Tu (1972)  also measured  the soil microbial respiration using the Warburg
 technique.   Oxygen consumption  from  decomposition of  native organic matter was
 greater in the carbofuran  treated soils  than in the controls.   Oxygen consumption
 increased  as carbofuran  concentrations were increased in soils with and without
 supplemented glucose-carbon.  The author concluded that indigenous soil microor-
 ganisms can tolerate  carbofuran  and  the  other  nematicides tested.

      In further experiments with the  same soil  and with carbofuran at the same
 rates  (1 and 5 ppm), Tu  (1973) added  temperature as another variable.   Treated
 soil  samples  were  incubated at 5 and  28°C.   Fungal and bacterial populations
 were  counted  2, 14,  28,  and 56 days  after incubation,  soil respiration with and
 without glucose was measured, and effects of the treatments on ammonification
 and nitrification were determined.  Carbofuran  again  did not  significantly affect
 bacterial or  fungal counts, ammonification,  nitrification,  mineralization of soil
 organic sulfur, or oxidation of mineral  sulfur.   The  carbofuran treatments did
 not significantly decrease oxygen consumption  from the decomposition of indig-
 enous soil organic matter at either temperature.   However,  there was a marked
 respiration increase in soils without  supplemental glucose-C  at 30°C with the 5
ppm carbofuran concentration.  The author ascribed this  to readjustments of mi-
croflora and ascendancy of certain groups and species  following the  depression
of competitors and antagonists,  resulting in increased microbial activity.
                                     110

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     Harnish and Wendler  (1972)  investigated the  effects of carbofuran on  oxygen
uptake by microorganisms  in  the  soil.  Topsoil treated  with Furadan 10G at a
rate of  100 ppm and 10 ppm AI was added to flasks (100  g of soil per flask).
Sufficient  water was introduced  to bring the samples  to 60% of their moisture-
holding  capacity.  Using  a Gilson Differential Respirometer and standard mano-
metric techniques, oxygen uptake was observed for an  incubation period of  85 hr.

     The data in Table 23 indicates that Furadan  10G  at 100 and 10 ppm AI  had no
noticeable  influence on soil respiration.  Oxygen uptake in both Furadan treat-
ments was slightly higher than  the untreated check.   The authors suggest this
could indicate "slight degradation of carbofuran  or one of the components  in the
formulation."
               Table 23.  Effect of FURADAN 10G on Oxygen Uptake in Field Soil




                          Oxygen Uptake (ul) at Specified Incubation Period^.'
          Substrate8/       1 Hr      2^5 Hr      4.5 Hr       60 Hr      85 Hr

          FURADAN 100 ppm    66        36.4       45,2         43.4       44.2

          FURADAN 10 ppm      3.0       32.8       34,0         30.8       32.4

          GLUCOSE 200 ppm    30.2      108.4       152.6        172.2      229.8

          FURADAN 100 ppm

          GLUCOSE 200 ppm    37.8      104.0       139.6        161.6      198.4

          FURADAN 10 ppm
GLUCOSE 200 ppm
Untreated
31.2
0.0
92.2
22.2
127.0
24.0
138.6
11.2
186.6
20.5

          —  FURADAN applied as 102 Granules, rate expressed in ppm active ingredient
             carbofuran.
          >_/ Incubated  at 25°C; 5 g soil.

          Source:  Harnish, W. N., S. J. Wendler, FMC Corporation, iti Studies of the
                 impact of carbofuran on the environment, 1972.

      When glucose was added to  the  untreated soil,  respiration was  stimulated,
 indicating metabolism of the substrate by soil microorganisms.  The addition of
 Furadan 10G to  the soil containing  glucose had little effect on soil respiration.

      Lin et al.  (1972) studied  the  effects of carbofuran and several other in-
 secticides on soil nitrification,  growth of legume seedlings, and  growth of 4
 species of rhizobia bacteria.   Tests were carried out in a Bearden loam soil
 without previous  record of  insecticide application.  Carbofuran was added at
 rates of 5, 50, and 500 ppm.  Moisture-holding  capacity was  adjusted to 60%,
 and the treatments were incubated in 250 ml flasks capped with plastic film
 at 30°C.
                                         Ill

-------
     Carbofuran had no effect on nitrification at any of the tested concentra-
tions.  Tested by the disc-inhibition method on a yeast-mannitol agar, carbo-
furan at 2 and 20 pi/disc had no effects on the growth of Rhi zobium meliloti or
R. japonic urn, but there was some inhibiting effect on R. legujninosarum and R..
trifolii.

     The effect of carbofuran on the growth of legume seedlings was tested by
growing sweet clover and alfalfa in disposable plastic pouches in 25 ml of nu-
trient solution to which carbofuran was added at 5, 50, and 500 ppm AI.  After
germination of the seeds, 1 ml of 1:5 (w/v) Nitragin AB, a preparation of nodu-
1.-iting bacteria, was distributed evenly over the seeds as an inoculum.  Untreat-
ed control seeds were grown with and without Inoculum.  The plants were allowed
co grow for 30 days under artificial light on a 12 hr on, 12 hr off photoperiod.
The average dry weight of all plants was determined at the end of the 30-day
period.  The results in the carbofuran series, expressed as average dry weights
ol  plants in milligrams, were as follows:

            Carbofuran
            concentration              Alfalfa                  Sweetclover

            5 ppm                       11.8                     9.2

            SO ppm                       6.1                     5.6

            500 ppm                      2.6                     2.2

            0 inoculated                 12.6                     7.9

            0 noninoculated               6.0                     5.6

      This  data  indicates that,  at  the  field  use rate (5 ppm),  carbofuran did not
significantly affect  the growth of  the  seedlings,  while at 500 ppm, plant growth
rates  were well  below  those  of  both controls.   Fifty ppm applications of carbo-
furan  resulted  in growth rates  closely  comparable  to the noninoculated controls.

      Hubbell  et  al.  (1973) studied  the  effects of  carbofuran and several other
pesticides on the relative numbers  of microbes and on nitrification in soil.
The pesticides,  alone  and  in combinations, had been applied to field plots at
times  and  rates  of  application  approximating agronomic practices in the growing
of shadeleaf  tobacco  in the  area of Quincy,  Florida.   The field plots were laid
out on a Norfolk loamy fine  sand prepared  and fertilized for the growing of
tobacco.  Carbofuran was  applied at the rate of 10 Ib of Al/acre (11.2 kg/ha).
Numbers of microorganisms and nitrification  were monitored at  2-week intervals
for 16 weeks  following application.

     The carbofuran treatments  somewhat  depressed  the relative numbers of fungi,
bacteria, actinomycetes  and  algae,  although  none of these effects were statisti-
cally significant at the 5%  level.   The  rate of nitrification as determined by
nitrate nitrogen appeared to be reduced  by about 25% during the first 8 weeks
in the carbofuran-treated plots, but the reduction was not statistically signi-
ficant at the 5% level.   In  all treatments,  there  was a drastic reduction in
nitrate nitrogen after 8 weeks.  This reduction followed a heavy rainfall and
was apparently due  to  leaching  of  the nitrate.  There were no significant differ-
ences between treatments  during the remainder of the experimental period.

                                      112

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      Kulkarni  et  al.  (1974)  studied  the  effects  of  carbofuran and 3 other insec-
 ticides,  applied  to  soil  at  their  recommended  rates, on the symbiosis of Rhizo-
 biurc  species with "groundnuts"  (for  example, peanuts), Arachis hypogaea.  Carbo-
 furan (type of formulation not  given)  at the rate of 16 kg/ha (14.2 Ib/acre) was
 applied  to red loamy soil of pH 6.8  in pots.   (It is not clear whether the appli-
 cation rate is given in terms of active  ingredient  or formulated product.)  Pea-
 nut seeds inoculated with a  5-day-old  culture  of Rhizobium species were sown in
 plots maintained  under greenhouse  conditions.  Eight weeks after planting, some
 plants were removed  carefully,  and the number  and fresh weight of root nodules
 were  determined.   The leghaemoglobin concentration  of freshly excised nodules
 was determined.   At  harvest  time,  pot  yield and  dry matter weight of plants were
 recorded, and  the nitrogen content of  the plants was determined.

      The  carbofuran  treatment had  no significant effect on nodule numbers, but
 increased the  fresh  nodule weight  in terms of  milligrams per plant, and the
 average weight per nodule.   Carbofuran had no  significant effect on the leghae-
 moglobin  content  in  the nodules, nor on  the yield of peanut pods per plant, the
 dry matter weight, or the nitrogen content of  the plant.  The authors concluded
 that  carbofuran,  used at  normal field  rates, has no harmful effect on symbiotic
 nitrogen-fixing bacteria  and peanut  growth.


      Harnish and  Wendler  (1972)  conducted a study to determine the influence of
 carbofuran on  the growth  rate of 2 soil-borne  fungi, Fusarium oxysporum f. ly_-
 coperisici qnd Pencillium digitatum.   Carbofuran (5 ppm) was added to 25 ml of
 liquid broth medium  in a  sterile flask.   The flasks were inoculated with a 4 mm
 block of  agar  plus mycelium  and incubated on a gyratory shaker at room tempera-
 ture.  The mycelium  and spores  were  harvested  daily, washed, dried in a desic-
 cator for 48 hr,  and  then weighed.


      The  JP._ digitatum grown  in  the carbofuran-treated medium produced a maximum
 amount of growth  (208 mg) on the third day, whereas the untreated  control  reached
 a maximum (178 mg) on the second day.  Conversely,  F. oxysporum  f. Ivcopersici
 grown in  the medium  containing  5 ppm carbofuran  weighed 160 mg compared to  209
 mg in the untreated  control.  The  authors concluded that  carbofuran  slightly  in-
 hibits the growth of F. oxysporum  f. lycopersici and slightly increased the dry
 weight of P^ digitatum.

      In another test, Harnish and  Wendler (1972) studied  the effects of carbo-
 furan on  microbial populations  using a dilution  plate technique.   Soil was
 treated with 1,000 ppm AI carbofuran and then  incubated at room  temperature for
 24 hr.  The number of fungi  on  potato  dextrose agar and the number of bacteria
 in nutrient agar  were reported  as  follows:

 Soil  Treatment                         Average  Number of Microbes/g soil x  104
                                           Bacterial?             Fungi*?/

Carbofuran 1,000  ppm                        114                  14
Untreated check                             H5                  13

 a/ Isolated on nutrient agar
 b/ On potato dextrose agar  (PDA)


                                   113

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 Counts per gram of treated soil did not differ  significantly from the untreated
 check.

      Chen et al. (1974) conducted a laboratory  test  to determine the effects of
 several organophosphate and carbamate  insecticides on 2 commercial preparations
 of  Bacillus thuringiensis.  Carbofuran (75% wettable powder) was added to a
 thoroughly mixed suspension of B^ thuringiensis  at a concentration of 0.47 g
 AI/100 ml.  The test surface, a sterile membrane filter of cellulose acetate,
 was inoculated with 0.2 ml of the test solution  and  allowed to incubate.  Spore
 numbers on the filters were determined at 0,  2,  and  4 weeks.  Three replicates
 were used for each time interval.

      Their results indicated that the  addition  of carbofuran to the commercial
 formulations of B. thuringiensis did not affect  the  survival of the bacteria on
 inert surfaces.  Several of the insecticides  tested, however, adversely affected
 the survival of B. thuringiensis.


 Fauna - Thompson and Gore (1972)  investigated the effects of carbofuran and a
 number of other insecticides on springtails, Folsomia Candida,  soil-inhabiting
 insects of the order Collembola that contribute  to the breakdown of  organic
 matter.   To determine the direct  contact toxicity of technical-grade carbofuran
 (95 to 99% purity),  it was applied in a volume to volume ratio of 19:1 acetone:
 olive oil solvent mixture in a Potter spray tower.  The spray was applied for
 15  sec and 15 more sec were allowed for the droplets to settle.   Because temper-
 ature can greatly affect the toxicity of insecticides,  tests were run at 2 dif-
 ferent pre treatment and post treatment temperatures, 13 and 24°C.   The contact
 toxicity of carbofuran to _F.  Candida was as follows:

 Pre-treatment and post-               Average corrected % mortality caused by
 treatment temperature (°C)             indicated  % carbofuran solution	
                                        0.001       0.01       0.1       1.0

          13                             0          45        100       100

          24                             0          30         95       100

      In further tests, Thompson and Gore (1972)  determined the toxicity to
 springtails of carbofuran applied to a Plainfield sand that contained 6.5% wa-
 ter,  0.7% organic matter and, in the mineral fraction,  93.5% sand, 4.9% silt,
 and  1.7% clay.   Carbofuran was applied to the soil in 9 different concentra-
 tions  in chromatographically distilled n-pentane at  21 - 2°C.  Five g aliquots
 of  treated soil were kept at 2 different pretreatment temperatures for at least
 2 hr  before 10 springtails per vial were placed  on the treated soil.  The test
vials  were kept in darkness for 24 hr before dead insects were counted.  The
 following results were obtained with carbofuran  in this test series:

       Test             Average corrected % mortality caused by indicated carbo-
       temperature ("C)    furan concentration in soil (ppm dry weight soil)

           13

           24

                                      114
0.005
5
0
0.01
5
0
0.05
5
20
0.1
35
95
0.5
100
100
1.0-50
100
100

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     This data shows that the direct  contact  toxicity  of  carbofuran  to  F.  candi-
da was not significantly affected by  temperature.  The carbofuran  soil  treatments
were more toxic to the test insects at  the higher  temperature.

     Kring (1969) studied the effects of carbofuran  on the  earthworm (Lumbricus
terrestris).  Carbofuran and the other  materials were  applied  in the form  of  10%
granules in a band 20 cm wide over the  row and  raked in lightly.   Shade tobacco
was planted in the rows the day following the treatment.  Dead and dying earth-
worms on the surface were observed and  counted  in  the  fields 6 days  after  the
treatment.  Only earthworms on the surface of the  soil in the  planted row  were
counted.  Each plot consisted of a single row 6 m  long, and the different  treat-
ments were randomized and replicated  4  times.  The following numbers of dead
earthworms were found in the carbofuran treatments:

     Carbofuran rate
     kg/hectare = Ib/acre                                Number of
     (active ingredient)                                 dead earthworms

     0                0                                         0.25

     0.56             0.5                                       8

     1.12             1.0                                      12

     2.24             2.0                                      20

     4.48             4.0                                      20

     Observations indicated that all  earthworms in the immediate area of the
carbofuran treatments at 2.0 and 4.0 Ib/acre were killed.  Blow flies  (Lucilia
species) attracted to the decaying earthworms were killed in large numbers in
the plots treated with carbofuran.

     Thompson  (1971) and Thompson and Sans (1974)  studied the effects  of carbo-
furan and other insecticides on  the numbers and biomass of earthworms  (Lumbri-
cidae) in pasture.  The experiment was set up in a trefoil pasture  that had  not
been treated with herbicides or  insecticides for at least 5 yr.  Carbofuran
(from a wettable powder formulation)  was applied at the rate  of 4.48 kg of Al/ha
(4.0 Ib/acre)  in a Latin square  design to plots 10 ft square.  Each treatment
was replicated 10 times, and there were untreated strips 6 ft wide  between plots
and around the experimental area.  Three weeks after  treatment, the arithmetic
mean of the number of earthworms found in 20 2 ft square wooden quadrats was 3.1
in the carbofuran-treated soil,  compared  to  17.9  in the untreated control, a
reduction of 82.7%.  In the carbofuran plots,  the number of worms found in 20
quadrats ranged from 0 to 7, compared  to  9 to  32  in the untreated control.   The
difference between the mean number of worms  per quadrat between the carbofuran
treatment and  the untreated control was  significant at p >0.01.   When earthworm
counts were taken again 52 weeks after  treatment, there were  no statistically
significant differences  (p = 0.05) between numbers  of earthworms  in the carbo-
furan-treated  and untreated plots.
                                    115

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      The biomass of earthworms in the carbofuran-treated plots (in grams of
 fresh weight of the worms from 20 quadrats) 3 weeks after treatment was 160.3,
 compared to 404.6 in the untreated control, a reduction of 60.4%.   The differ-
 ence between the carbofuran-treated plots and the untreated control was signifi-
 cant at p >0.01.  There were no statistically significant differences in the
 mean earthworm biomass per quadrat between the carbofuran-treated  and the un-
 treated plots 52 weeks after treatment.

      Chemical analysis of the earthworms obtained 3 weeks after treatment from
 the carbofuran-treated plots revealed no residues of carbofuran or its metabo-
 lites above the limits of detection of the analytical method.   Samples were
 analyzed by gas chromatography, but the limits of detection for carbofuran were
 not given.

      Stenersen et al. (1973 and 1974) studied the toxicity and mechanism of  ac-
 tion of carbofuran in the earthworm (Lumbricus terrestris), and its metabolism
 by this species.  Earthworms were obtained from a-live bait dealer who had
 collected them largely from London, Ontario area golf courses, which would in-
 dicate that the worms had been exposed to many herbicides and  insecticides.   All
 worms used  for experiments were sexually mature (showed well-developed clitella)
 and weighed between 3 and 5g.  Worms were injected with dosages of carbofuran
 between 1.0 and 5.0 ug (0.5 to 1.55 mg/kg), and the LD^Q was determined to be
 1.3 mg/kg.   When carbofuran was mixed in the soil (sterilized  moistened loam;
 organic content approximately 20%, water content 10%, peat moss added at 1.5
 by volume), the LC^Q over a 5-day period was 12.2 ppm.

      In in  vitro cholinesterase studies of the inhibition of earthworm cholin-
 esterase, the carbofuran concentration producing 50% enzyme inhibition was
 found to be 10~6-31 (0.5 ppm).   Two organophosphates, tested under the same
 conditions, depressed earthworm cholinesterase more severely,  while a methyl
 carbamate insecticide inhibited it less than carbofuran.  Cholinesterase recov-
 ery in the  live carbofuran-treated worms occurred more rapidly than in those
 treated with other chemicals tested.   Characteristic signs of  carbofuran poi-
 soning were rigidity,  immobility,  sores and segmental swellings; only rigidity
 and immobility were observed after treatment with the organophosphorus insecti-
 cides.

      In tests with ring-labeled l^C carbofuran,  it was determined  that earth-
 worms excreted carbofuran mainly as the unchanged parent compound, its hydroxy-
 lated analog (3-hydroxycarbofuran),  and at least 2 unidentified products.  The
 earthworms  reabsorbed excreted  insecticide and its metabolites from a sand
 medium.   Earthworms excreted less  than 10% of the total amount of  carbofuran
 taken up originally.   Comparing these observations with carbofuran metabolism
 studies  on  other organisms by  other authors,  Stenersen et al.  (1973)  concluded
 that  the earthworm would  appear to metabolize carbofuran initially in a similar
 fashion  to  both  plants and other  animals.   They  further suggested  that the toxi-
 city  of  carbofuran to  earthworms may be caused by factors other than cholines-
 terase  inhibition.

      Oilman and  Vardanis  (1974)  performed  additional studies on the toxicity
 and metabolism of  carbofuran in the  common dew worm (L. terrestris),  and a
manure worm. (Eisenia  foetida),  after  seemingly conflicting reports on the


                                    116

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effects of carbofuran on earthworms had been released by the manufacturer (FMC
Corporation).  Oilman and Vardanis discovered that the apparent discrepancy was
not valid; FMC had used as its test animal a species that is not strictly an
earthworm, i.e., E. foetida, a worm that inhabits animal dung and manure and
feeds on organic debris without ever surfacing.  By injection, carbofuran was
about 6 times more toxic to L,^ terrestris than to E_._ foetida.  When applied to
the soil, carbofuran was twice as toxic to L^ terrestris as to E^. foetida.

     When placed in soil treated with carbofuran at 4 ppm, coiling was always
observed in both species.  Eighty percent of the _L^ terrestris were found coiled
at the soil surface within 24 hr while E_^ foetida showed some coiling, but re-
mained buried in treated soils.  In experiments designed to study the ability of
the 2 species to detect carbofuran-treated soils, it was observed that carbo-
furan appeared to repel E^_ foetida but not L^ terrestris.  The authors pointed
out that L. terrestris, which comprises a large percent of the detritus feeder
biomass in Ontario, seems to be immobilized by carbofuran, as demonstrated by a
marked inability to leave treated soils, leaving affected earthworms susceptible
to predation and dehydration.

     In uptake and excretion tests, the total amount of carbofuran taken up by
both worms after 6 hr was similar when compared on the basis of micrograms per
gram of worm.  However, E. foetida excreted 95% of this material in 48 hr com-
pared to only 10% excreted by L^ terrestris.  Approximately half of the material
excreted by E. foetida was unchanged insecticide.  Of the carbofuran metabolized
by the worms in a 48-hr period, E. foetida retained only 5% as metabolites, where-
as L. terrestris retained 87%.

     The authors pointed out that this comparative study emphasizes that  great
care must be taken in selecting truly representative species for the  evaluation
of the ecological effects of chemicals.


Residues in Soil
Laboratory and Greenhouse Studies - Onsager and  Rusk (1969)  studied the residual
toxicity of carbofuran and other insecticides  to the sugar beet wireworm (Limo-
nius californicus)  in a  laboratory experiment.   Carbofuran 10% granules were
applied at an initial concentration of  1.85 ppm, the field application rate sug-
gested by the manufacturer.  The insecticide was thoroughly  incorporated into the
soil ("Sagemoor  sandy loam soil").  The treated  soils were buried outdoors in
specially prepared  steel casings in such a manner that the level of soil inside
the casing was flush with the  level of  the soil  outside.   The soils were kept
moist by adding  water to each  casing  twice each  week.  Soil  samples were taken
immediately after mixing and at 2, 4, and 6 weeks thereafter.  All samples were
subjected to bioassay with field-collected, sugar beet wireworms.  The results
observed in the  carbofuran treatments were as  follows:
                 Weeks after
                 treatment            Percent mortality after indicated days of expoBure

                   0
                   2
                   4
                   6

                                     117
6-8
SO
40
34
36
13-15
56
71
38
83
20-22
74
75

91
27-29
100
83

95
>41

85



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      Chemical analysis of the carbofuran-treated soil showed that under the  con-
 ditions of this test, carbofuran had an initial half-life of 36 days.   About 20%
 of the initial concentration of carbofuran was still present in the soil 8 weeks
 after application.

      Harris (1969b) employed a laboratory bioassay procedure to assess  the per-
 sistence of biological activity of carbofuran and other insecticides in soils.
 Two soil types were used:  Beverly fine sandy loam (pH 7.2,  1.5% organic matter,
 76.6% sand, 21.1% clay), and a muck soil (pH 6.5; 64.6% organic matter;  and  35.4%
 mineral content consisting of 14.5% sand, 38.8% silt, 46.7%  clay).   When treated
 with insecticide, the sandy loam contained 12.3 and the muck 164.0% water.

      First-instar nymphs of the common field cricket, Acheta (Gryllus)  pennsylva-
 i-icus, were used as test insects.   The LD5Q of carbofuran to this insect was
 2.34 ppm in the sandy loam, 74.2 ppm in the muck soil.   Equally large differ-
 ences in toxicity between the 2 types of soil occurred  for the  other 9  insecti-
 < ides investigated in the same manner.  Soil persistence tests  were run by ap-
 plying carbofuran and the other insecticides to the 2 soils  at  levels of 4 times
 the LD50.   Samples were bioassayed at 0, 1, 2, 4, 7, 12, 16, 24, 36, and 48
 veeks after treatment.  In the sandy loam soil, the biological  activity of car-
 bofuran disappeared within 16 weeks, placing it into the "moderately residual"
 troup ranging in between "highly residual" and "slightly residual"  insecticides.
 In the muck soil, the biological activity of carbofuran persisted for about  24
 weeks.

      Campbell et al.  (1971) studied the influence of organic matter content  of
 toils on the efficacy of carbofuran and of several other insecticides on the
 wireworm,  Melanotus communis, in the laboratory, following up on reports from
 ' he field  about difficulties in controlling this insect.  Carbofuran and the
 ether insecticides were applied to Bladen silt loam soil (9.0%  organic  matter),
 organic loam soil (7.4% organic matter), and loamy fine sand (3.5%  organic mat-
 ter) .   Late-instar wireworm larvae collected from these soils in problem fields
 were placed in their  respective native soils which had  previously been  treated
 with the test insecticides, including carbofuran from a 10%  granular formulation
 at  the rate of 1 and  2 Ib Al/acre.   Wireworm control of some of the other insec-
 ticides tested decreased with an increase in the organic matter content  of the
 test  soils,  but carbofuran produced very low or no mortality of wireworms in any
 of  the soils  for reasons which the authors apparently did not investigate.

      The persistence  of the biological activity of carbofuran and 6 other in-
 secticides  in  soil was studied by  Thompson (1973), using Folsomia Candida, a
 soil-inhabiting  species of Collembola,  as test insect.   Equitoxic dosage rates
 of  the  test  insecticides were thoroughly incorporated into Plainfield sand con-
 taining  6.5% water.   The mineral fraction consisted of  93.5% sand,  4.9%  silt,
 1.7%  clay,  and  there  was 0.7% organic matter.   For each insecticide, the appli-
 cation  rate was  the lowest concentration that  would cause 100%  mortality of  F.
 i andida  in  the  soil in 24  hr,  that  is,  0.5  ppm in the case of carbofuran.  Two
 parallel sets  of  the  experiment  were run at 2  different temperatures, 13 and
 24 - 1°C.  Soil  samples were  bioassayed  1,  2,  4,  8,  12,  and  16  weeks after
 treatment of the  soils.   Carbofuran killed  100% of the  test  insects at both
 temperatures throughout  the  entire  test  period.   The author  concluded that the
concentration of carbofuran  employed was too high,  probably  twice the LDgg,  and

                                     118

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that carbofuran did not degrade to less than the LDgg under the conditions  of
the experiment.   Based on comparative data, the author classified carbofuran
as "moderately persistent."

     Getzin (1973) studied the persistence and degradation of ^C-carbofuran  in
4 different soil types under laboratory conditions.  The physical and  chemical
properties of the 4 soils used were as follows:
Soil

Ritzville silt
  loam
Sultan silt
  loam
Chehalis clay
  loam
Organic
  (muck)
Organic
matter (%)
   1.0

   3.0

   7.2

  40.0
7.8

6.0

6.2

5.9
Cation
exchange
capacity
(meq/100 g)
    17.8

    13.4

    32.8

    49.1
                              Moisture
                    Bulk      equivalent
                    density   (% of dry     Clay
                    (g/cm3)   wt)	    (%)
1.2         20         19

1.2         20         17

1.0         34         36

0.6         79
     To determine the extent,  if  any, of microbial degradation,  portions of these
soils were radiation-sterilized.   Initially,  the  irradiated  soils were sterile,
but they became contaminated with airborne  spores during  insecticide application
and subsequent handling procedures.  ^-^C-carbonyl carbofuran was applied to ir-
radiated and nonirradiated  samples of the 4 soils at  the  rate of 20 >ig/cm3 and
moisture levels were adjusted.  Replicated  samples of  each soil  were put into
wide-mouth pint jars that were then  equipped  with C02  traps  and  kept in a con-
stant-temperature room.  Water was added periodically to  maintain the moisture
content within 5% of the original level.  The NaOH in the C02 traps was replaced
at 2- to 4-week intervals,  and the absorbed C02 was precipitated and assayed for
14C02.  Duplicate 20-cm3 soil  samples were  removed for analysis  at the desired
intervals.  Table 24 presents  the results of  this test in the 4  different soils
at 0, 4, 8, 16 32, and 54 weeks after treatment.  The parent compound, expired
C02, and nonextractable residues  in  the soil  accounted for most  of the radio-
activity.  Water-soluble degradation products amounted to less than 1% of the
extractable radioactivity  in all  soils throughout the experiment and are not in-
cluded in Table 24.  The data  showed that the persistence of carbofuran varied
considerably between soils; the approximate times required  for 50% loss of carbo-
furan were about 4 weeks in the Ritzville silt loam,  8 weeks in the Chehalis
clay loam, and more than 54 weeks in both the Sultan  silt loam and the organic
soil.  Sterilization had no effect on the degradation rate of carbofuran in the
Ritzville silt loam, and only  a slight effect in the  Sultan and organic soils,
but significant effect in  the  Chehalis clay loam. Most of the -^C from the de-
graded carbonyl-labeled carbofuran was expired as -
     In a second test, Ritzville silt loam and Chehalis clay loam were treated
with !*C ring-labeled carbofuran at 5 ug/cm3.  The initial half-life of ring-
labeled carbofuran in the 2 soils corresponded closely to the degradation rates
for carbonyl-labeled carbofuran observed with these soils in the previous test.
The breakdown of ring-labeled carbofuran resulted in the accumulation of
                                   119

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nonextractable soil-bound radioactivity and a gradual evolution of    CC^.   Only
small quantities of carbofuran  phenol,  an expected  degradation product  of  the
insecticide,  were recovered  from treated soils.

     When  ^c-carbofuran phenol was added to Ritzville silt loam  and  Chehalis
clay loam  at  the rate of 5 ug/cm3,  the compound was bound to the  soils  very rap-
idly.  Nonextractable radioactivity amounted to 21  and 24% in the 2 soils  imme-
diately  after treatment, reaching a maximum of 70 to 80% of the applied rate 2
weeks after treatment.  About 25% of the ^C added  as carbofuran  phenol was ex-
pired as ^002 within the 32-week experimental period.  The soil-bound  radioac-
tivity and extractable radioactivity decreased gradually at the same  time.

     The persistence of carbofuran in relation to soil pH was determined in
Sultan silt loam adjusted to 4  different pH levels  and treated with carbonyl-
!4c-carbofuran at the rate of 4 mg/400cm3 of soil (10 ug/cm3) .  Aliquot samples
were removed  at intervals and assayed.   Carbofuran was rapidly degraded at pH
7.8; there was a tenfold difference in the time required for 50%  breakdown be-
tween the  soils at pH 4.3 and 7.8.   This data indicates that the  short  residual
life of  carbofuran in the Ritzville silt loam  (Table 24) was at least in part
the result of alkaline degradation.
                Table 24.  Radioactive Carbofuran Equivalents Recovered as Carbofuran,
                 Soil-Bound Residue, and Expired C(>2 from Irradiated and Honlrradlated
                 Soils Treated with ^C-Carbonyl-Labeled Insecticide at 20 ug/cn3
Weeks
after
treatment
M( Equivalents/cm3
Nonirradlated soil
Carbofuran
Soil-bound
of soil


Irradiated soil
CO? Carbofuran
Soil-bound
Ritzville silt loam
0
4
8
16
32
54

0
4
8
16
32
54

0
4
8
16
32
54
18.7
10.0
5.5
2.4
0.9
0.4

19.3
13.5
9.2
5.5
3.6
2.5

19.0
17.9
16.0
12.8
12.1
11.1
0.1
0.8
0.9
0.7
1.3
0.9
Chehalis
0
0
0.1
0.4
0.3
0.2
Sultan
0
0
0.1
0.3
0.3
0.2
0
7.1
10.2
13.9
15.6
15.8
clay loam
0
7.3
9.8
11.9
14.4
15.7
silt loam
0
1.2
2.2
3.8
5.9
7.9
18.2
10.8
6.0
2.2
0.9
0.4

19.2
18.4
17.6
15.5
14.0
11.1

18.8
.19.4
17.5
17.3
16.7
12.3
0.2
1.8
3.1
3.4
3.6
3.2

0
0
0.2
0.3
0.7
1.1

0
0
0.1
0.1
0.3
0.5
CO;

0
3.3
5.3
6.8
10.6
11.0

0
0.5
0.8
2.1
5.2
9.4

0
0.3
0.6
1.4
3.7
7.1
Organic soil
0
4
8
16
32
54
22.0 •
19.7
19.5
18.1
16.3
15.3
0
0
0.1
0.2
0.3
0.4
0
1.0
1.5
2.5
3.9
5.4
20.9
20.2
20.1
19.5
17.8
17.3
0
0
0.1
0.2
0.3
0.2
0
0.2
0.3
0.8
2.1
3.4
             Source:  Getzin (1973).  Reprinted from Environmental Entomology by permission
                    of the publisher.
                                        120

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     Getzin  (1973) concluded  that  rapid chemical hydrolysis is the primary route
of degradation of carbofuran  in  alkaline soils.   A slower breakdown occurs in
acid and neutral soils, and is caused  by both chemical and microbial degradation
mechanisms.

     Stanovick (1968) studied the  degradation of carbofuran in 3 soil types
(sandy loam, silt loam, and muck)  treated with ^C-ring- and carbonyl-labeled
carbofuran at 2.0 and 9.0 ppm.   Moisture content was maintained at 75% of field
capacity in  the sandy and silt loam soils, and 85% of field capacity in the muck
soil.  The soils were kept in wide-mouthed gallon jars at room temperature for
174 days.  Fifty g samples were  analyzed at various time intervals during the
study period.  The soil was exhaustively extracted with methanol, and the radio-
activity in  the extract was determined by liquid scintillation.  Samples from the
last time interval were  (a) acid-hydrolyzed and extracted with methylene chloride,
and (b) combusted by the Parr Bomb procedure.

     The initial half-life of carbofuran under these conditions was 20 to 40
days.  Carbofuran degraded fastest in  the sandy loam and slowest in the muck
soil; it dissipated 3.0 half-lives in  the sandy loam, 2.3 half-lives in the silt
loam, and 1.4 half-lives in the  muck soil over the 174-day period.

     Carbofuran was the only  compound  detected in the methanol and methylene
chloride extracts by thin-layer  and gas chromatography procedures.  At the 174-
day interval, the presence of 2,3-dihydro-7-hydroxy-2,2-dimethylbenzofuran resi-
dues was indicated in the Parr Bomb analysis, but this compound was not extract-
able from the soils by either methanol or acid hydrolysis.  Acid hydrolysis,
followed by  methylene chloride extraction, was found to be the most efficient
method for extraction of aged carbofuran residues.


Field and Combined Field/Laboratory Studies - Read  (1969)  studied  the  persistence
of carbofuran and several  other  insecticides in acid mineral  soils  in  the labo-
ratory and in microplots in  the  field by a bioassay  technique, using first-instar
larvae of the cabbage maggot, Hylemya brassjlcae.   Soils  used  in  the field inves-
tigations were Kildare  sandy soil (pH 5.2) and Charlottetown  fine  sandy  loam (pH
6.4).  The Kildare soil  was  also used in  the greenhouse  study.   The tests were
set up to simulate field conditions (banding 3/4  in  deep in ridges)  as closely
as possible.  Carbofuran was applied as a 10% granular formulation.

     The activity of  carbofuran in the  field microplots,  measured by percent
mortality of H.  brassicae  larvae, was as  follows:


                  Daye after         Carbofuran concentration placed
                  carbofuran         	in the BO 11 (ppm)	
                  application         3.     10      20      50
                                     Kildare sandy soil
                     2             64     98     100     100
                     5             85     96     100     100
                    30             89    100     100     100
                    45             78     98     100     100
                    60             73     97      99     100
                    90             68     97      99     100
                   120             49     63      94     100
                   150              0      3      10      22

                                      121

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98
98
90
97
88
91
0

100
99
96
99
93
90
0

100
99.9
99
100
100
100
8
4
100
100
100
100
100
100
32
12
                     Daya after         Carbofuran concentration placed
                     carbofuran         	In the soil (ppm)	
                     application        1     10      20     50
                                     Charlottetovm fine sandy loam
                       2
                       5
                       30
                       45
                       60
                       90
                      120
                      150

      Carbofuran, like most of  the  other insecticides  studied, was more  toxic  to
 the larvae 3 to 5 days after application than  within  the  first  24 to  48 hr.   Re-
 duction in toxicity occurred somewhat more slowly  in  the  greenhouse than  in the
 field.  There was no marked difference  in the  rate of loss  in toxicity  in the
 sandy or fine sandy loam soils, indicating that the texture  of  the 2  mineral
 soils was not an important factor  in toxicity  degradation.

      Read (1971a and 1971b) reported further observations on the activation,
 deactivation, bioactivity and  persistence of carbofuran and  several other insec-
 ticides in 2 other published articles.   In the first  of these (Readj1971a), field
 microplots were set up as described in  the earlier studies  (Read, 1969,  see above).
 The test insecticides were spread  evenly 3/4 in below the soil  surface  at a rate
 equivalent to 100 ppm in the upper 1 in of soil.   This concentration  is somewhat
 higher than the recommended commercial  rate of application  for  carbofuran in  the
 area (60 to 70 ppm).  At different time intervals  after treatment, samples of
 the treated soils were taken to the laboratory,  mixed thoroughly, and diluted
 serially with insecticide-free soil to  obtain  desired concentrations  of toxicants
 in a given volume of soil.

      Bioassays with first larval stages of the cabbage maggot,  H. brassicae,
 demonstrated that carbofuran became biologically active soon after application.
 It was the most toxic of the compounds  tested,  and its toxicity persisted longer
 than that of several other insecticides tested at  a given rate  of toxicant per
 acre.   At 30 ppm, carbofuran produced 100% mortality  of H. brassicae  larvae for
 at least 150 days;  at 10 ppm,  it remained 100% effective  for about 80 days; at
 3  ppm,  close to 100% larval mortality was reached  about 15 days after treatment,
 persisting for only about 15 days.  At  1.5 ppm, maximum larval  mortality  (about
 50%)  occurred 15 days after treatment and declined gradually thereafter,  ap-
 proaching zero 80 days after treatment.

      Carbofuran was the only insecticide in the  group that showed readily de-
 tectable upward movement in the soil; flies resting on the surface of the car-
 bofuran-treated soil were killed.   In further  studies of  this observation, car-
 bofuran was  band-applied at different depths below the soil  surface in  ridged
 greenhouse microplots.   The times required for  toxicants  of  carbofuran  to reach
 the soil surface were 1 week, 2 to 3 weeks, and 3  to  4 weeks, respectively, for
 the 1/2-,  3/4-,  and 1 in depth of insecticide  placement.  In a  second greenhouse
 test, dead flies were found on carbofuran-treated  soil containing as  low  as 3
 ppm of  carbofuran.

     Evidence  that  carbofuran toxicants actually moved into  the surface soil
was demonstrated by removing the upper \ in of soil and testing it for  toxicity

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by the cabbage maggot bioassay method.   At  the  field  recommended  rate  for cab-
bage maggot control, sufficient toxic  components  of carbofuran moved from the 1
in depth of application into the upper 1/4  in of  the  soil  to  produce 100% mor-
tality of test larvae after 3 to 4 weeks.   When the upper  1/4 in  of soil  was
transferred to a new area over untreated soil,  toxicants could be detected by
bioassay for 2 months.  However, if left in the original microplots over  the
carbofuran-treated band, the upper layer of the soil  remained toxic for at
least 200 days.  This observation indicates,  according to  Read  (1971a), contin-
ual upward movement of toxic materials into the surface soil  from the  parent
compound.

     In the greenhouse trials, all toxic components of carbofuran decreased to
nondetectable levels  (below 0.5 ppm) within 300 days.

     In another series of tests (Read, 1971b) on  the  bioactivity  and persistence
of insecticides against the cabbage maggot, H^  brassicae,  the performance of
carbofuran essentially confirmed the author's previous findings.   Among the in-
secticides included in this experiment, carbofuran was again  the  most  toxic to
the test organisms 30 days after application to field microplots  at  100 ppm (in
the manner described previously).  Toxicity gradually declined  in the  carbofuran-
treated soil, and toxic residues were  barely detectable the following  spring.

     Hubbell et al. (1973), in studies on the microbiological effects  of  carbo-
furan and other pesticides described previously,  also made observations on the
persistence of the insecticides investigated.  The test pesticides were applied
to field plots at times and rates of application  approximating  agronomic prac-
tices in the growing of shadeleaf tobacco in northern Florida.   Field  plots were
established on a Norfolk loamy fine sand prepared and fertilized  as for a tobac-
co crop.  Carbofuran was applied at the rate of 10 Ib Al/acre (11.2 kg/ha).  The
carbofuran-treated soil was sampled 2, 4, 6, 8, and 10 weeks after application.
Carbofuran was extracted from the soil samples  and analyzed chemically.  Carbo-
furan levels found were as follows:

     Weeks after treatment                         Carbofuran residue

              2                                           0.95
              4                                           0.90
              6                                           1.25
              8                                           1.05
             10                                           0.55

     Caro et al.  (1973) studied the dissipation  of soil-incorporated  carbofuran
in a 2-yr field investigation  in  two small watersheds  at  Coshocton, Ohio.   Water-
shed No. 113 consisted  of Keene and Rayne  silt loam soil  with an average pH of
6.35 and an average slope of  9.3%.  Watershed  No. 118  consisted  of Coshocton
silt loam, average pH 5.2 and  average  slope  9.6%.  Both watersheds were  plowed,
disked, harrowed and  fertilized  in  accordance  with normal corn growing practices.
Carbofuran 10% granules were  applied broadcast at the  rate of 4.83 Ib Al/acre
(5.41 kg/ha) to Watershed No.  113,  followed  within 30  min by disking  into the
7.5 cm depth.  Watershed No.  118  received  carbofuran  10%  granules at  the rate of
3.71 Ib Al/acre  (4.16 kg/ha)  applied  in-furrow 5 cm  deep  in  rows 1 m  apart,
along with the corn seed, without subsequent cultivation. The following year,


                                   123

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 in May of 1972,  an in-furrow application  of  carbofuran 10% granules at the rate
 of 2.77 Ib Al/acre (3.11 kg/ha)  was made  on  Watershed No. 113.  Watershed No.
 118 was not retreated  in 1972.
                                        •;v
      Soil samples were taken from numerous sampling points in each watershed on
 the day of carbofuran  application and  at  4 to 8 week intervals throughout both
 seasons.   Carbofuran persistence in the soil, expressed in milligrams per square
 meter after each of the 3 treatments,  is  shown in Table 25.  The disappearance
 curve in each case approximated  a first-order reaction during the crop season.
 In 1971,  half-lives were estimated to  be  46  and 117 days in the broadcast and
 band applications,  respectively.   In 1972, the band application half-life was 94
 days.   Disappearance was slower  during the cold months of the year.  Despite the
 use of soil sampling techniques  designed  to  minimize variation, variability in
 carbofuran content among samples and standard deviations were quite high.  The
 irregularities parallel those found in similar experiments by the authors and by
 other investigators and are  believed to be largely due to a lack of uniformity
 in pesticide field application.

            Table 25.   Carbofuran Residues in Soil Samples (mg/m2)
Days after
_apj> 1 i ca t io n
Range
Mean
Std.
dev.
. Range Mean
Std.'
dev.
       0
      29
      63
     113
     153
     225
     337
                  Watershed No.  113 broad-
                    cast  application, 1971
215-726
1.46-588
65-244
17-140
9-129
4-97
8-59
404
265
147
69
46
30
22
126
102
50
33
31
25
14
  Watershed No.  118 band
    application, 1971
365-1,508
376-1,558
375-920
126-633
142-551
 28-558
 51-134
775
743
575
343
311
203
 76
353
362
157
143
126
126
 28
                  Band application, 1972
0 .
49
89
138
160
628-1,046
330-866
224-665
116-467
135-537
830
516
392
291
306
177
170
167
126
159
Source:  Adapted from Caro et al. (1973).

     As reported above, the 2 watersheds had soil pH values of 6.35 and 5.20,
respectively.  The half-life of pure carbofuran at these 2 pH levels in solution
                                      124

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was determined to be 140 and 1,600 days, respectively.  Thus,  it  is  apparent
that carbofuran decomposes more rapidly in soil, but it is not known whether
chemical and/or biological mechanisms are responsible.  The  authors  state that
the observed differences in insecticide half-lives  in  the 2  watersheds were the
result of differences in both soil pH and management practices.

     Carbofuran residues disappeared much faster from  certain small  areas in
each of the watersheds where the insecticide was banded.  The residue values at
these sampling points are not included in the data  in  Table  25 because these
sites were obviously atypical.  The factors causing this decreased persistence
are not known, but moisture regime, soil pH, and physical structure  of the soil
are believed to be involved.  The "rapid disappearance" areas were characterized
by 1 or more of the following:  greater runoff  intensity; higher  soil pH level
(about 0.4 pH unit above that of the surrounding area); more clay-like soil tex-
ture; and soil moisture content that was higher by  approximately  1.2% wet weight
basis.

     In an effort to further define the effect  of temperature on  the rate of de-
composition of carbofuran, Caro et al.  (1973) determined  the activation energy
of carbofuran hydrolysis and found it to be 38.5 kcal/mol.   The mean soil tem-
peratures during the season in Watershed No. 113 were  19.8°C in 1971 and 18.7°
in 1972.  Entering these values into the Arrhenius  equation3./ indicates that the
hydrolysis of carbofuran is a sensitive function of temperature,  and that the
half-life of carbofuran should have been about  50%  longer  in 1972 than in 1971.
However, the actual half-life was more  than twice as  long  (94 versus 46 days),
suggesting overriding effects of other  factors, especially  placement.  A sub-
stantial increase in persistence apparently occurred  as  a result  of  the band
application.

     Caro et al.  (1973) also studied the losses of  carbofuran in the runoff
water from the treated watershed  (see  subsection  on Environmental Transport
Mechanisms, p. 129).

     FMC Corporation  (1974),in  commenting  on  the  studies by Caro et al.  (1973)
discussed above, points out  that  the observed  dissipation rates of carbofuran
in soils are not nearly as  sensitive to changes in temperature and pH  as  the
solution kinetic studies predict.   From the  Climatic Atlas of the United  States,
FMC calculated the mean temperatures during  a  typical growing season,  June
through September, for several  areas.   The Arrhenius equation was then used  to
predict the following relative  half-lives  for  the hydrolysis of carbofuran  in
these areas during the summer months:

                                  Average                  Relative
              Area                 temperature (°F)           half-life

          Caribou, Maine                 60.3                  1.000
          Buffalo, New York               66.0                  0.414
          Lincoln, Nebraska               74.8                  0.156
          Amarillo, Texas                77.5                  0.111
          Memphis, Tennessee              79.0                  0.092
          Miami, Florida                 81.5                  0.056
a/   k = Ae E*/RT


                                    125

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      FMC analyzed  the  actual  dissipation rates  of carbofuran after broadcast
 application of  10% granules in a variety of  soils from 6 states.   The most rap-
 id dissipation  rate was  only  about  5  times greater than the  slowest rate.   No
 correlations between climate  and dissipation rates were observed.   A similar
 analysis of the dissipation of carbofuran after in-furrow application of  10%
 granules in soils  from 8 states again showed no correlation  between climate and
 dissipation rate.   Again,  there was approximately a 5-fold difference between
 the slowest and fastest  dissipation rates.

      The discrepancy between  theoretical dissipation rates and those observed
 was considered  to  be due to several factors, including microbial  action,  insuf-
 ficient moisture in the  soil  for true solution  kinetics, catalysis of carbofuran
 decomposition by 1 or  more soil constituent(s)  and/or a complex reaction  mecha-
 nism which does not conform to the  Arrhenius equation.   (The Arrhenius equation
 suggests that catalysis,  i.e.,  lowering  of the  activation energy,  would render
 the reaction less  sensitive to temperature changes.)

      FMC Corporation (1972a and 1974)  conducted studies to evaluate the persis-
 tence of carbofuran in different soils following single applications, and the
 possible buildup of carbofuran residues  in soil from repeated applications in
 successive years.

      In 1 study, carbofuran residues  were determined after single broadcast ap-
 plications of carbofuran  10%  granules in 6 different  states,  representing a
 variety of soils.   The analytical results from  different rates of application
 were normalized to a rate  of  6  Ib Al/acre.   The average residues  (in parts per
 million)  found  were as follows:   6.6  on  day  of  application;  1.9 after 30  days;
 0.31 after 75 days; 0.73  after  95 days;  0.21 after 130  days;  0.31 after 160
 days;  0.06 after 360 days.  The average  variation ranged from 24  to 79% for
 sampling dates  0 to 130 days  after  application.   There  were  no correlations be-
 tween climate and  dissipation rates.

      The  dissipation of carbofuran  following in-furrow  treatment  with 10% gran-
 ules was  studied at 10 different  sites in 8  states,  again representing a  vari-
 ety of different soils.  Analytical results  were normalized  to a  rate of  1 Ib
 Al/acre.   Average  residues (in  ppm) found were  as follows:   20 on the day of
 application;  12  after  40 days;  1.8  after  60  days;  0.52  after  150  days;  0.53
 after 190 days;  0.13 after 360  days.   The average variation  ranged from 42 to
 100%.

      As other investigators have  observed, this  data  indicates that carbofuran
 residues  in  the  soil dissipate more rapidly  following broadcast than following
 band  treatment.

      In a  third set of studies, FMC Corporation  (1974)  evaluated  carbofuran soil
 residues  following  repeated applications  in  successive  years.   The soils  were
 planted with crops  typical for each location.   They were sampled twice  each
 year, once in the  fall at the time of harvest of the crop and once in the spring
 just prior to the next  year's carbofuran  application.   This  sampling schedule
was followed for 4 yr,  from the fall of 1970  through  the fall of  1973.
                                    126

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     There was no indication of an increase in soil residues  following  repeated
applications of carbofuran  in successive years.  Treatments monitored included
5.0 (5 x 1.0) Ib of 4  Ib/gal flowable Al/acre/yr applied  to potatoes in New
York; 3 Ib of 10% granules  Al/acre/yr applied to corn in  New  York  and Nebraska^;
6 Ib of 10% granules Al/acre/yr applied to tobacco in Arkansas;  and 3 Ib of 10%
granules Al/acre/yr applied to peanuts in Arkansas.  Carbofuran  residues in the
New York corn plots snowed  greater variations from year to year  than those from
Nebraska plots.  This  might be related to differences in  method  of application.
Residues from tobacco  plots receiving broadcast applications  were  fairly uniform
from year to year.

     Soil samples from these studies were analyzed by a method that included acid
hydrolysis, methylene  chloride extraction, Nuchar-atta clay  column cleanup, and
detection with a nitrogen-specific microcoulometric  gas chromatograph.   Carbo-
furan was the only carbamate compound detected above the  method sensitivity of
0.10 ppm.


Residues in Water

     The dissipation of carbofuran in flooded rice fields is  summarized in a
report by the FMC Corporation  (1972a).   In California, carbofuran residues in
water were determined  following postflood at  the  rate of  1 Ib Al/acre:  carbo-
furan residues in the  water peaked at 0.7 ppm 8 hr after  application.   In an-
other postflood test,  maximum  residues  (0.3 ppm)  were reached 14 hr after an ap-
plication of carbofuran 2% granules  at  0.5  Ib Al/acre.  When carbofuran granules
were applied to rice fields preflood at  the  rate  of  0.5  Ib Al/acre, maximum resi-
dues in  the water occurred 7  days after  treatment,  and  these maxima were  lower,
for example, 0.1 ppm not tilled,  and 0.05  ppm tilled.

     Similar patterns were observed in tests in Louisiana rice  fields.   When
carbofuran  2%  granules were applied postflood at the rate of 0.5  Ib Al/acre,
carbofuran  residues in the water peaked at 0.3 ppm 8 hr  after treatment.   Fol-
lowing  a preflood  application of carbofuran 3% granules  at 0.5  Ib Al/acre, max-
imum water  residues,  0.2 ppm, were reached 2 days after  application.

     After  peaking, carbofuran water residues dissipated with a half-life of  1
day  or  less.   Residues reached nondetectable (0.01 ppm)  levels  within  a few
days.   No other carbamate  metabolites such as 3-hydroxy-carbofuran or  3-keto-
carbofuran  were detected.
 Phytotoxicity

      Tobacco  plant  responses  to  recommended and excessive rates of application
 of Furadan® 10G were  studied  by  Tappin (1969).   Furadan® 10G was broadcast by
 hand on February 25 at  rates  of  4,  6,  and 10 Ib Al/acre and roto-tilled to a
 depth of 6 to 8 in.  Plots were  bedded and transplanted 27 days later.  An un-
 treated check and a standard  dust treatment were included in the randomized
 block, 4-replicate experiment.   Plant  response was evaluated by measuring the
 stalk height  on the fifteenth and fifty-seventh day and by rating phytotoxicity
 on a scale of 0 to 4  weekly intervals  from April 16 through June 25.

                                     127

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      Plants responded well to Furadan®, as judged by plant height,  but  the 4
 and 6 Ib rates showed slight to moderate injury until early June.   Plants treat-
 ed at the 10 Ib rate showed symptoms of severe phytotoxicity in May,  but again
 had outgrown all effects by early June.

      The author attaches little, if any, economic importance to the phytoxicity
 observed,  especially at the 4 and 6 Ib/acre rates.   At proposed rates of appli-
 cation this has been limited to occasional chlorosis and,  in unusually  severe
 cases, small necrotic spots (flecks) on the lower leaves of the plant.  Since
 these leaves are normally not harvested and usually drop prematurely  due to lack
 of adequate sunlight, injury'to these leaves is of no consequence.  The improved
 growth of treated plants, particularly in the early season, more than offsets
 any possible early season injury to the unharvested older leaves.


 Bioaccumulation and Biomagnification

      The propensity of carbofuran for bioaccumulation and biomagnification was
 recently studied by investigators at the University of Illinois at  Urbana-
 Champaign (Sangha,1972; 53^01^1,1974; and Yu et al., 1974), using a  laboratory
 terrestrial-aquatic model ecosystem developed by Metcalf et al. (1971).  The
 model ecosystem consists of a terrestrial-aquatic interface and a 7-element food
 chain; it can be used to simulate the application of pesticides to  crop plants
 and to study contamination of the aquatic environment.  The system  is housed in
 a  glass aquarium (25 x 30 x 45 cm) and contains a sand-water interface  consist-
 ing of 15 kg of sterilized white quartz sand and 7 liters of standard reference
 water.

      Sorghum (Sorghum halepense) was grown in the sand for 7 days,  followed by
 treatment  with 5 mg (50 uCi)  of ring-l^c- and carbonyl-l^C-labeled  carbofuran
 in 0.5 ml  of acetone (rate equivalent to 1 Ib of carbofuran Al/acre).  After
 treatment  of the sorghum, larvae of the saltmarsh caterpillar,  Estigmene acrea,
 were added to the system and allowed to feed on the treated sorghum plants; the
 larvae simulated the first member of a food chain,  and acted as an  effective
 distributing agent for the labeled pesticides within the system.  The saltmarsh
 caterpillars died after they ate carbofuran-treated sorghum leaves.   As a re-
 sult,  more caterpillars were added for the first 5 days after treatment until
 all  sorghum leaves were consumed.

      The water phase contained several members of a freshwater aquatic  food chain,
 for  example,  frogs (species not identified), snails (Physa species),  freshwater
 clams  (Corbicula manilensis), freshwater crabs (Uca minax), water fleas (Daphnia
magna),  green filamentous algae (Oedogonium cardiacum), and a freshwater plant
 (Elodea canadensis).   After 27 days, mosquito larvae were added to  the  system
 to become  another member of the food chain, and after 3 more days,  mosquito fish
 (Gambusia  affinis) were added to become the final segment of the system.  The
experiment  was carried out in 2 aquaria (tanks) each for ring-^C-  and  carbonyl-
14-c-labeled carbofuran, respectively.

     At  the end  of 33 days, the entire system was taken apart,  and  the  organisms
and water were extracted and  analyzed for radioactivity.  In addition,  extracts
were spotted  on  TLC plates, developed with appropriate solvents,  and  exposed to

                                    128

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x-ray film to locate and identify the chemical composition of the solvent  ex-
tracts.  Metabolites were identified by co-chromatography with proposed  metabo-
lites, as well as by infrared, nuclear magnetic resonance, and mass  spectrometry
techniques.

     At the end of the test period, none of the organisms contained  residues of
carbofuran.  In the test with carbonyl-labeled carbofuran, several unknown com-
pounds were isolated from E._ canadensis along with 3-ketocarbofuran  (35  ppb),
N-hydroxymethyl carbofuran (35 ppb) and 3-hydroxy-carbofuran (11.8 ppb).  Fewer
metabolites were isolated from the experiment with ring-labeled carbofuran.  As
previously observed with 2 other carbamate insecticides, most of the carbofuran
radioactivity was unextractable by acetone; values for ring- and carbonyl-la-
beled carbofuran were 69 and 77%, respectively.  Small amounts of the unchanged
carbonyl-labeled carbofuran (ca. 0.5 ppb) were isolated from the water phase of
the system.  Other metabolites found in identifiable quantities in the water
portion were 3-ketocarbofuran, N-hydroxymethyl carbofuran, carbofuran phenol,
and 3-hydroxycarbofuran, none of them in concentrations higher than  10 parts per
trillion.  It was concluded from these findings that carbofuran is highly bio-
degradable and has low residual activity in the components of the model ecosys-
tem.  Detoxification occurred by hydroxylation of the carbofuran molecule at
several points.  Metabolites were found only in the water phase (Sangha,1972).

     Sanborn's conclusions from these studies on carbofuran and 2 other carba-
mate insecticides are as follows:  "If the data obtained for these carbamates
in this model ecosystem is representative of the behavior of aryl N-methyl car-
bamate insecticides, then it would appear that the use of these insecticides
will not present ecological problems related to persistence and food chain ac-
cumulation" (Sanborn,1974).

     Yu et al. (1974) provided additional details in regard to these carbofuran
model ecosystem studies.  His paper covers sample preparation and analytical
techniques, and presents detailed, tabular data on the concentration of carbo-
furan metabolites and degradation products in solvent extracts and in residue
fractions for ring-labeled and carbonyl-labeled carbofuran.  The authors also
report on the distribution of radioactive metabolites in  solvent extracts  after
TLC analysis for both types of ^C-carbofuran.

     The radioactivity in the water was monitored throughout  the experimental
period.  In both the ring- and carbonyl-labeled experiments,  radioactivity in
the water reached a peak on the  seventh day.  However,  radioactivity  in the
tanks containing the ring-labeled  carbofuran peaked at  about  0.3 ppm, compared
to less than 0.05 ppm in the  tanks containing the carbonyl-labeled  carbofuran.
This indicated the rapid hydrolysis of carbofuran to  carbofuran phenol  and n-
methyl-carbamic acid.  The latter  is  then  further degraded  to C02 and other
metabolites.  To verify this  conclusion, carbonyl-labeled carbofuran was  placed
in a closed aquatic system fitted  with a C02 trap which contained NaOH.  The
radioactivity in the water decreased  rapidly,  while  radioactivity in the  C02
trap steadily increased.  However, the radioactivity collected in the C02 trap
was only about 25% of the total  14c put  into the  system.   The radioactivity
remaining in the water was less  than  10% of  the  introduced radioactivity.   The
authors explain this discrepancy in  the  ^C  balance by the inefficiency of the
C02 trap.

                                      129

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      As reported above, no parent carbofuran was found in any of the living or-
 ganisms analyzed.  However, large amounts of carbofuran were found in 2 crabs
 found dead the second day after applying carbonyl-labeled carbofuran to the
 tanks, and in 1 of the 2 crabs which became moribund after being introduced in-
 to the same tank 20 days after application.  A second crab stocked in this tank
 at the same time did not die, and no intact carbofuran was found in this living
 crab at the end of the experiment on the thirtieth day.  Apparently, the crabs
 did not metabolize carbofuran extensively as 61 to 92% of the radioactivity was
 extractable by acetone from the whole body.  In other organisms, only about 20%
 of the radioactivity was acetone-extractable.

      Insoluble residues remaining after acetone extraction from the water and
 organisms were not analyzed further and, therefore, their chemical nature is
 not known.  The authors presume that they are conjugated with glucose or other
 large molecules because they are very polar.

      In summarizing their findings, Yu et al. (1974) stated that carbofuran was
 rapidly hydrolyzed in water.  Hydroxylation of the benzofuranyl moiety consti-
 tuted the major degradation pathway.

      Wong and Fisher (1975) determined the residues of carbofuran and its meta-
 bolites, 3-hydroxycarbofuran and 3-ketocarbofuran, in animal tissue by gas-liq-
 uid chromatography with electron capture detection as N-trifluroacetyl deriva-
 tives.   The procedure has a minimum sensitivity of approximately 0.5 ppm carbo-
 furan,  0.07 ppm 3-ketocarbofuran, and 0.05 ppm 3-hydroxycarbofuran for the test
 animals which were oyster,  shrimp, mullet, menhaden, skate, and red-winged black-
 bird.   After being fortified with 2.5 to 25.7 ppm carbofuran, 0.12 to 8.2 ppm
 3-hydroxycarbofuran,  and 0.23 to 0.82 ppm 3-ketocarbofuran, the resulting resi-
 dues averaged 84.2, 83.8 and 72.8%, respectively.

      Data on the rate of uptake and excretion of carbofuran by the common dew
 worm,  Lumbricus terrestris, and a manure worm,  Eisenia foetida, is reported in
 the subsection on Interactions with Lower Terrestrial Organisms, p.  109.

      Other studies related  to storage patterns  of carbofuran and its metabolites
 in  plants  and animals can be found in the section on Metabolism and Metabolism
 in  Mammals.
Environmental  Transport  Mechanisms


Lateral Movement  -  Bowling  (1970)  studied  the  lateral  movement,  sites  of  uptake,
and retention  of  carbofuran applied  in different  ways  to rice  plants.   Rice was
planted in rows 20  cm  long  and  7.5 cm apart  in metal trays  kept  under  green-
house conditions.   The trays were  fertilized 18 days after  planting, then flood-
ed to a water  depth of 1 in.  Twenty-one days  after planting,  the  trays were
moved to a growth chamber programmed to a  19 to 36°C daily  temperature cycle
and 14 hr daily illumination coinciding with the  warmer  period.

     When the  trays were placed in the growth  chamber, carbofuran  3% sand-core
granules were  applied  to the first 7.5 cm  at one  end of  the tray at the rate of


                                    130

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1 Ib Al/acre.  Field-collected adult  leafhoppers, Draeculacephala  portola,  were
caged on each of the four rows of rice plants,  and numbers  of  surviving leaf-
hoppers were recorded at 6, 22, 24,  and 48 hr after  application of the carbo-
furan.  The rate of survival of leafhoppers on  the rice  plants in  relation  to
the distances of the plants from the  center of  the area  where  the  carbofuran
granules had been applied indicated  that the insecticide moved laterally 22.5
cm in 22 hr in quantities toxic to the leafhoppers.   Both carbofuran and its
metabolites were absorbed and translocated by the plants, especially when car-
bofuran was placed near the roots prior to flooding,  or  when carbofuran wettable
powder was placed on the leaf sheafs.  The authors concluded that  optimum utili-
zation of carbofuran would be obtained by placement  in dry  soil, near the root
system, followed by flood water.


Leaching Studies - FMC Corporation (1972a) studied the leaching properties  of
carbofuran in 7 different soil types  in the laboratory,  following  the methods
developed by Harris (1969a).  In a segmented column  consisting of  aluminum  tub-
ing, soil was packed in 1-in segments to a height of 7 in,  and 1^C-carbonyl-
labeled carbofuran mixed with soil was placed in the second segment 1-in from
the bottom.  The column was then placed in a container in which water was kept
at a constant level.  Water moved upward in the column by capillary action  to
the soil surface when it was allowed to evaporate.   After 3 days,  each column
segment was analyzed for radioactivity.  The results showed that carbofuran
moved more slowly in columns high in clay or organic matter.  In soils of equal
clay content, carbofuran moved further in soils with lower  exchange capacity.

     In this test, another pesticide' was used  as a  standard, and its upward
movement through comparable soil columns was monitored by bioassay.  The rate
of movement of carbofuran was slightly greater than that of the other pesti-
cide, which Harris (1969a) classified as being "intermediate" in relative soil
mobility.

     Field leaching studies in 3 different soil types using lysimeters were con-
ducted in Illinois.  Carbofuran 10% granules were applied broadcast at the rate
of 4 Ib Al/acre over the top of lysimeters packed with Plainfield  sand  (little
or no organic matter), Blount silt loam  (light forest soil),  and Elliot  (an
agricultural soil, highest among the 3 soils in organic matter).   The  lysime-
ters were embedded in a field exposed to normal year-round weather conditions.

     Initial residues were 0.08 to 0.32  ppm in the runoff water and 0.005  to
0.009 ppm in the sediment.  Some carbofuran residues  percolated through  the
lysimeter containing the sandy  soil.  After 1 yr, negligible  carbofuran  residues
were found in the top 1.5  ft of the  2 heavier soils;  they were  equally distri-
buted throughout 3 ft in the sand.   The  lysimeters were new and had not  fully
settled at the start of the experiment.   Therefore,  the  significance of  the
results is questionable.

     The leaching behavior of carbofuran under field  conditions was studied  by
analysis of soil samples from 2 corn fields in Iowa  and Nebraska  (treated  with
carbofuran 10% granules, at the rate  of  1 Ib Al/acre  banded)  and  from 3 fallow
fields in New York  (treated with carbofuran 50% wettable powder at an exagger-
ated rate of 10 Ib Al/acre broadcast).   Maximum initial  carbofuran residues in


                                        131

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 the corn field soils were 1.1 ppm.  Residues below 6 in did not exceed  0.2  ppm
 during the entire growing season.  In the samples from the fallow fields, ini-
 tial residues of carbofuran were as high &s 10 ppm in the upper 3 in soil layer.
 Residues of less than 0.1 ppm were found below 6 in over the year of sampling
 following treatment except for the muck soil.   In all soil samples,  essentially
 all carbofuran residues dissipated during the 1-yr sampling period.

      In another study, a Nebraska fallow field and a Georgia tobacco field  were
 treated broadcast with carbofuran 10% granules at the rate of 10 Ib  Al/acre.
 Samples from 0 to 6 in and 6 to 12 in depths were an  /zed for carbofuran resi-
 dues.   The results were as follows:

 Days after                  Nebraska fallow field        Georgia tobacco field
 treatment                   0-6 in	6-12 in        0-6 in	6-12 in

     0                       11.0            0.1          10.0           5.0
   124                        -              -             0.5           0.2
   136                        0.3          Nondetect-
                                             able

      The data shows that most of the carbofuran residue remained in  the upper 6
 in of  the soil in both locations, and that the total residue decreased  to less
 than 3% of the initial concentration in the Nebraska soil within 136 days and
 to 5%  of the initial concentration in the Georgia soil within 24 days.


 Runoff  Studies - In the carbofuran dissipation studies discussed above  (see sub-
 section on Field and Combined Field/Laboratory Studies p.  120),  Caro et al.  (1973)
 investigated losses of carbofuran in the runoff water from both of the  watersheds
 treated in 1971 and from the watershed that was retreated in 1972.   The runoff-
 producing rainfalls and carbofuran losses in the runoff water are shown in  Table
 26.   In 1971,  the carbofuran losses occurred almost entirely in 2 heavy rains
 that  fell within 48 hr after the application.   In both watersheds, the  carbofuran
 concentration in the runoff water was much higher in the second rainfall than in
 the  first,  indicating a greatly increased rate of release of carbofuran active
 ingredient from the applied granules by the second day.

      In 1972,  rainfall was more evenly distributed over the season,  with measur-
 able runoff occurring on the treated watershed on 13 occasions.   Once again, the
 major carbofuran losses occurred in the early rainfall events.   The  first runoff-
 producing rainfall did not occur until almost 1 month after the carbofuran  appli-
 cation.   Therefore, the carbofuran concentrations in the runoff water never
 reached the high levels of 1971.   The sudden increase in the carbofuran concen-
 tration that appeared 168, 173,  and 179 days after treatment resulted from  the
 disturbance of the soil surface at corn harvest which took place 154 days after
 application.

     Some  rainfalls were sufficiently intense to produce measurable  quantities
 of carbofuran-bearing sediment  in the runoff.   Fine solids suspended in the
water and  coarser sediment deposited on the floor of the flume collecting the
 runoff were  analyzed  for carbofuran content.   Residues on the suspended solids
 ranged  from 0.46  to 1.64 mg/kg,  and on the flume floor deposit  from  0.98 to 1.11
ppm.
                                     132

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       Table 26.  Runoff-Producing Rainfalls and  Carbofuran Losses in
                    Runoff Water from Carbofuran-Treated  Watersheds
Days after
pesticide
application
     1
     2
    39
    65
    82
   239
Total
     1
     2
   239
Total
Amount of runoff
      (I)
Average carbofuran
concentration
     (ug/£)
               Watershed No. 113 (broacast application).  1971
    31,900
     7,170
     1,480
       120
       300
     3,760
       473
     1,394
       537
        33
        15
         5
    44,730

 Watershed No. 118 (band application), 1971
    40,640
     3,470
     9.190
       272
     1,002
        19
    53,300
 Watershed No. 113 (band application), 1972
Carbofuran in
runoff water
     (tng)
   15,089
    9.995
      795
        4
        5
   	19
   25,907
   11,054
    3,477
      175
   14,706
26
28
53
76
82
91 (a.m.)
91 (p.m.)
119
123
147
168
173
179
Total
35,840
61,320
30,710
630
3,190
12,430
9,170
1,130
6,160
2,710
11,400
33,970
34,020
242,680
191
223
58
8.8
6.9
4.4
2.9
2.8
1.8
2.6
14.2
16.9
19.9

6,845
13,674
1,781
6
22
55
27
3
11
7
162
574
677
23,934
Source:  Adapted  from  Caro  et  al.  (1973)

     In the 1972  runoff  study,  the  concentration  of  3-ketocarbofuran in the run-
off water was also determined.  About  5%  of  the parent  compound was 3-ketocar-
bofuran.  However, peak  3-ketocarbofuran  concentrations were reached earlier in
the runoff water  than  in the soil.

     Overall, from 0.5 to 2.0% of  the  carbofuran  applied was lost in runoff, most
of it in water rather  than  in  sediments.
                                   133

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      Several additional  carbofuran runoff  studies have been reported  by FMC  Cor-
 poration (1972b).   In Illinois,  a 4-acre watershed close to a pond  was  planted
 with corn and treated with carbofuran 10%  granules broadcast at  the rate of  4
 Ib Al/acre.   Soil,  pond  mud,  and pond water samples were analyzed periodically.
 The initial  half-life of carbofuran in the soil  was 1 to 2 weeks on the average
 of 7 sampling stations,  varying  somewhat in relation to soil pH. Initial soil
 residues of  about  1 ppm  reached  levels of  less than 0.1 ppn by the  fall and  were
 nondetectable the  following spring.   Residues of about 1 ppm occurred in the pond
 water following  a  heavy  rainfall 4 days after treatment.  This residue  declined
 to "negligible"  by the next sampling date  (16 days from application and 12 days
 from first sampling),  and was not detectable thereafter.  Highest residues of
 0.2 ppm were found in the pond mud during  the first few weeks after the runoff,
 but they disappeared thereafter.   There was no fish mortality in the  pond.

      In another  runoff study, carbofuran 10% granules were applied  broadcast at
 the rate of  6 Ib Al/acre to the  top  4 ft strip of 24 ft x 24 ft  plot  having  a
 4% slope.  Soil  cores  of 6 in were taken at 1 ft intervals in 3  replicates down-
 slope,  starting in  the treated zone,  down  to 3 water-catch basins at  the  base.
 Soil samples were  taken  periodically throughout  the growing season, and water
 samples were taken from  the catch basins after each significant  rainfall. In
 the treated  zone,  carbofuran  residues declined to 10% of the initial  concen-
 tration within 64  days.   Residues were found in  the first foot below  the treated
 zone,  but  none further downslope.  No detectable residues (0.01  to  0.02 ppm  de-
 tectability)  were  found  at any time  in runoff water collected in the  catch ba-
 sins 25 ft downslope.

      In western  Iowa,  4  watersheds (2 to 4 acres in size with slopes  of 15 to
 20%,  containing alluvial silt with about 2% organic matter content) were treated
 with carbofuran 10% granules  banded  on corn at planting time at  the rate of  1
 Ib Al/acre.   Runoff water  and sediment were collected through flumes  and water-
 wheels.  Three major rainfall events  created measurable runoff on one or more
 of the watersheds  37,  60,  and 70  days after planting.   Analysis  of  the  runoff
 showed carbofuran  residues  of 0.15 ppm or  less in the water and  0.7 ppm or less
 in the sediment.  There  were no significant differences in carbofuran residue
 content between the watersheds.   There was  less  runoff of water  and sediment
 from ridge-planted  than  contour-planted  watersheds.

      In California,  an 8.5  acre tomato  field (sandy loam,  average pH  8.2) was
 sprayed  by air with  a  concentration of carbofuran 4 Ib Al/gal (flowable formu-
 lation)  applied at  the rate of 1  Ib Al/acre.  At the time of treatment  the to-
mato plants provided a canopy that protected from one-third to two-thirds of
 the  soil surface from  the direct  spray.  The treated field was furrow-irrigated
weekly  for 4 weeks.  Soil samples were taken at  weekly intervals from 3 points:
 (a) along the plant beds not covered by  the plant  canopy (exposed bed);  (b)
along  the plant rows in  the area protected  from  the spray by the foliage (pro-
 tected row);  and (c) in  the irrigated  furrows that  were also exposed  to the
direct spray.  Soil samples were  taken to a 6 in depth,  with 25  cores diago-
nally across  the field comprising one sample.  Duplicate samples were taken
along the other diagonal.
                                 134

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     Carbofuran residues in the exposed  bed  (a)  declined from a maximum of 0.3
ppm 4 days after application to below  0.05 ppm after  32 days.  Residues in the
protected row (b) slowly increased  to  a  maximum  of  0.09 ppm within 25 days,
then declined to 0.01 ppm at 32 days.  Residues  in  the exposed irrigation furrow

                  °'3 PPI" ** the *&J °f  treatment to  below °-05 PPm 24 days after
treatment
     Samples of the irrigation water  (pH  8  to  9) were  taken several times during
  A i qnnJ*    al°n8 the  ta±1 ditch  drainin8  the  field  at  distances of 0, 750,
TVh  H  *  *   8 thS ditch'  Maximum carbofuran  residues  of  0.1 ppm were found
at tne head of the ditch 1 day after  spraying.  Residues decreased with distance
along the ditch and declined to undetectable levels  (less than 0.0023 ppm)
throughout the entire length of the ditch within 28  days after treatment.
                                 135

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Hubbell, D. H., D. F.,  Rothwell, W.  B.  Wheeler, W. B. Tappin, and F. M. Rhoads,
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                                   137

-------
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  Kulkarni,  J. H.,  J.  S.  Sardeshpande,  and  D.  J.  Bagyaraj,  "Effect of Four Soil-
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  Lin,  S.,  B.  R.  Funke, and J. T. Shulz,  "Effects of Some Organophosphate and
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  Mauck, B., Annual  Progress  Report: 1972,  U.S. Department  of the Interior, Bureau
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 Metcalf, R. L., G.K.  Sangha, and I. P. Kapoor,  "Model Ecosystem for the Evalua-
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 Onsager, J. A., and  H. W. Rusk, "Potency  of  the Residues  of Some Nonpersistent
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                                     140

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                    PART II.   INITIAL SCIENTIFIC REVIEW

                      SUBPART D.  PRODUCTION AND USE

                                 CONTENTS

                                                                  Page

Registered Uses of Carbofuran	   143


Production and Domestic Supply 	   143

     Volume of Production	   143
     Imports	   143
     Exports	   143
     Domestic Supply 	   144
     Formulations	   144


Use Patterns of Carbofuran in the United States	   144

     General	   144
     Carbofuran Uses in 1971	   145
     Carbofuran Uses in 1972	   145
     Carbofuran Uses in 1974	   146
     Carbofuran Uses in California	   146


References	   160
                                       142

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     This section contains  data on registration and on  production and
uses of carbofuran.   The  section  summarizes  rather than interprets
scientific data reviewed.
Registered Uses of Carbofuran
Federally Registered Uses  -  Carbofuran  is  a broad  spectrum insecticide-
nematicide registered as a contact  insecticide  on  crops  and as a systemic
soil treatment.   The chemical was introduced  for commercial use in
agriculture in the United  States about  1970.  Carbofuran has been
highly effective against corn rootworms and alfalfa weevils.  Dosages,
tolerances and limitations for  currently registered uses are summarized
in Table 27.
Production and Domestic Supply
Volume of Production - Carbofuran is  produced in the United States by a
single manufacturer, the Agricultural Chemical Division of FMC Corporation,
Middleport, New York.

     The United States Tariff Commission (1973b, 1974)  does not report
the production and sales volumes of carbofuran individually.  Carbofuran
is included in the category "All Other Cyclic Insecticides and Rodenticides."

     In comparison to all other pesticides in this category, the production
and sales volumes of carbofuran are so small that Tariff Commission data
is not significant in estimating carbofuran volumes.  However, carbofuran
was one of 25 selected pesticides whose production, distribution, use,
and environmental impact potential was studied by von Rumker et al.
(1974).  Estimates for 1972 placed domestic production of carbofuran at
6.0 million Ib.
Imports - A report by the U.S. Tariff Commission (1973a) shows an
absence of carbofuran imports.  The probability that there were no
imports of carbofuran into the United States in 1972 is further supported
by the fact that the product is the subject of a patent held by the only
U.S. producer, FMC Corporation.
Exports - Carbofuran is not listed in the U.S. Bureau of the  Census  commodity
descriptions on pesticide exports for 1970 (U.S. Bureau of  the  Census,  1971).
This may be due to the fact that, at least in some statistics,  carbofuran is
classified as a nematicide.  The reports do not contain a separate breakdown
of nematicides.
     However, von Rumker et al. (1974) estimated  that,  in 1972, approximately
1.0 million Ib of carbofuran Al were exported from  the  United States.

                                      143

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There are indications that the export volume of carbofuran is increasing.
Carbofuran is an effective, versatile insecticide and nematicide that is
in demand in other parts of the world.  According to von Rumker et al. (1974),
recent increases in carbofuran production capacity have eased supply
problems that limited carbofuran export (as well as domestic) sales in
the early 1970's.  It is considered likely that not only domestic (see
below)  but also export sales of carbofuran have increased since 1972.
 Domestic  Supply - As estimated by von Rumker et al.  (1974), approximately
 5.0 million  Ib of carbofuran Al were used in the United States.
 Formulations - Carbofuran is not available domestically as technical
 active  ingredient.  The only formulations available are those from the
 basic producer, the Agricultural Chemical Division of FMC Corporation.
 FMC  currently offers 4 different carbofuran granular formulations containing,
 respectively, 10, 5, 3, and 2% Al.  In addition, a flowable  formulation
 containing 4 Ib i ^available.  These formulations are marketed under the
 trade name FuradarPP.  Furadan®2, 3, and 10% granules,  and 4 Ib/gal
 flowable  formulation produced by FMC are also marketed by the Chemagro
 Division  of Mobay Chemical Corporation, Kansas City, Missouri.  Most or
 all  of  the carbofuran granular formulations are dense, freeflowing,
 uniform sand-core granules.  Accurate calibration of application equipment
 is essential to distribution of carbofuran at the intended dosage rate.
Use Patterns of Carbofuran in the United States
General - Carbofuran is an insecticide-nematicide with a broad  spectrum
of biological activity.  It can be used either as a contact  insecticide-
applied to the foliage of target crops, or as a soil-applied systemic
insecticide-nematicide.  Applied to the soil, carbofuran controls certain
soil-inhabiting pests.  In addition, it is systemically absorbed by  the
roots and translocated by treated plants to provide control  of  a number
of foliar pests.  It is the most effective insecticide currently available
against corn rootworms and especially against some strains that are  re-
sistant to other insecticides.

     Carbofuran is registered, recommended and used in the United States
primarily on certain agricultural crops, as outlined in greater detail
in the preceding section.   There are only a few nonagricultural uses,
namely, application as a soil treatment to cottonwoods and Siberian
elms, and as a clay slurry for the treatment of pine seedlings.  These
nonagricultural uses account for only very small quantities  of  carbofuran
active ingredient.  The product is not registered or used for any other
industrial,  commercial, or institutional pest control purposes, nor  for
use on ornamentals, in home gardens or indoors.  Thus, most  of  the
quantities of carbofuran currently used in the United States are
agricultural.
                                      144

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     Carbofuran was introduced in the U.S. for commercial agricultural use in
about 1970.  Its use increased rapidly, mainly due to its superior effectiveness
against corn rootworms and alfalfa weevils.  These insects were major economic
problems, becoming resistant to certain other insecticides when carbofuran be-
came available and placing it in great demand.


Carbofuran Uses in 1971 - Carbofuran is reported individually in the U.S.  De-
partment of Agriculture's survey of the quantities of pesticides used by farmers
in 1971 (U.S. Department of Agriculture, 1974).  Table 28 summarizes the uses
of carbofuran in the United States.  Uses are shown both by quantities of carbo-
furan AI and by numbers of acres treated.  According to the U.S. Department of
Agriculture's survey, 93.9% of the total quantity of carbofuran used by farmers
in 1971 was used on corn, followed by rice (5.7%).  Other field crops, vege-
tables and fruit and nut crops accounted for the balance  (0.4%).  The U.S. De-
partment of Agriculture's data indicates that carbofuran was used at an average
rate of 0.73 Ib Al/acre on corn whereas the average use rate on rice was 2.1 Ib
Al/acre.  The latter rate is questionable, however, since it exceeds recommended
rates.  As indicated in the section on Carbofuran Uses in California, there is
approximately a 12-fold discrepancy between the USDA and  California data on
usage for rice.

     Table 29 summarizes the use of carbofuran in the U.S. in  1971 by regions,
by quantity used, and by acreage treated.  This data indicates  that about 90%
of the total quantities of carbofuran used in 1971 were used on corn in the
corn belt, lake and northern plains states.   In the Pacific and delta states,
carbofuran was used primarily on rice.  The remaining quantities  of carbofuran
used by farmers in 1971, according to  the  USDA survey, were used  primarily on
corn in the northeastern, mountain, and Appalachian states.


Carbofuran Uses in 1972 - In. 1973  and  early 1974, von Rumker et al.  (1974) con-
ducted a comprehensive study on  the production, distribution,  use and environ-
mental impact potential of 25 selected pesticides,  including carbofuran.   They
estimated  that,in 1972, 5.0 million Ib  of  carbofuran AI  were used on agricul-
tural crops  in the United States.  Of  this total,  an  estimated 4.4 million Ib
were used  in the north central states,  200,000  Ib  each  in the  south central
and'western  states,  and 100,000  Ib each  in the  northeastern and southeastern
states.  The authors' surveys further  indicated that,in 1972,  uses of carbo-
furan for  industrial, commercial,  institutional,  governmental, or home garden
pest control purposes were negligible,  if used at all.

     Figure  8 presents the materials  flow diagram for carbofuran for 1972 from
the report by von Rumker  et  al.  (1974).   This figure shows the flow of raw
materials  (open arrows)  to  FMC's plant in Baltimore,  Maryland, where 2,3-dihy-
dro-2,2-dimethyl-7-benzofuranol, the  final intermediate in the production of
carbofuran,  was produced in 1972.   This intermediate was then  transported to
                                      145

-------
 another FMC plant in Middleport, New York, where the final reaction step
 and the formulation of the technical active ingredient were carried out.
 Shaded arrows, graduated in proportion to the quantities represented,
 indicate the flow of carbofuran products to the major use areas.   Where
 substantial quantities of carbofuran were used in 1972, the geographic
 distribution is broken down by states or small groups of states (boundaries
 indicated by light shading of the state lines).  Smaller uses in  larger
 geographic areas are broken down to the level of the regions whose
 boundaries are indentified by dark shading of the state lines concerned.


 Carbofuran Uses in 1974 - Von Rumker et al. (1975) studied the use of
 soil insecticides on corn in 1974 in 8 midwestern states (Iowa, Illinois,
 Indiana, Ohio, Missouri, Minnesota, South Dakota, and Nebraska).   These
 8 states accounted for 75% of the total acreage of corn grown for grain
 in the United States in 1974.  It was concluded from a survey of  extension
 entomologists and of pesticide trade sources in these states that, in
 1974,  approximately 5.3 million Ib of carbofuran active ingredient were
 used on corn in the 8 states surveyed.  Taking into account this  information
 and the state use patterns of carbofuran as reported by the U.S.  Department
 of Agriculture (1974) for 1971, it is estimated that, in 1974, approximately
 6.8 million Ib of carbofuran active ingredient were used on corn  in the
 U.S. (6.3 million Ib in the corn belt, lake and northern plains
 states, 500,000 Ib in the remaining corn growing states).


 Carbofuran Uses in California - The California Department of Food and
 Agriculture keeps detailed records of pesticide uses by crops and other
 uses;  the data is published quarterly and summarized annually. Table  30
 summarizes the uses of carbofuran in California by major crops for the
 1970 - 1974 period.   According to the California reports, the annual
 volume of carbofuran used in the state increased from 9,500 Ib AI in
 1970 and 1971 to 10,600 Ib in 1972, 106,000 Ib in 1973, and 146,000 Ib
 in 1974.

     During the 5-year period covered by Table 30, the quantities of
 carbofuran used on rice in California ranged from a low of 7,800  Ib in
 1972 to a high of 11,300 Ib in 1973.   The use of carbofuran on alfalfa
 increased rapidly,  from 100 Ib AI in 1971 to 2,700 Ib in 1972, 94,000  Ib
 in 1973,  and 135,700 Ib in 1974.   There were no significant uses  of
 carbofuran on other  crops during this period,  according to the Department
 of Food and Agriculture's reports.   It should be noted there is a large
 unexplained discrepancy between the quantities of carbofuran used on
 rice in California in 1971 according to the California Department of
 Food and  Agriculture—8,700 Ib,  and that reported by the U.S. Department
 of Agriculture  (1974)--103,000 Ib.

     Table  31 presents  the carbofuran uses in California by crops and
other uses,  number of applications, pounds of active ingredient,  and
number  of acres  treated for 1972,  1973,  and 1974, the 3 most recent
years for which  such data are available.
                                      146

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     Table  32 summarizes the estimated uses of carbofuran in the United
States by regions in 1971, 1972, and 1974, based on reports, estimates
and information sources discussed in the preceding subsections of this
chapter.  It is emphasized that the estimates for 1971 are those reported
by the USDA (1974), whereas those for 1972 and 1974 were obtained by RvR
Consultants.  The RvR data estimates for these 2 yr are not directly
comparable  to those for 1971 from USDA since sources and methods are
different.  RvR's 1972 and 1974 surveys as well as pesticide use reports
from several of the north central states suggest that USDA's reported
total use of carbofuran in 1971, 2,860,000 Ib, may be low.  It is believed
that the use of carbofuran in the United States did not actually increase
by about 75% (from 2.86 to 5.0 million Ib) from 1971 to 1972, but that
the actual  use volume in 1971 was somewhat higher than estimated by USDA
and that, accordingly, the rate of growth from 1971 to 1972 was not
quite as steep.

     It is  estimated that in 1974  7.2 million Ib of carbofuran active
iJ^Zoi?*  Were U86d ** the United States.  Of this total, 6.3 million
Ib (88%) were used in the north central states, primarily on corn.  An
estimated 400,000 Ib were used in the western states primarily on alfalfa
and rice.   About 250,000 Ib were used in the south central states,
mainly on rice.  The remaining 250,000 Ib were used in the northeastern
and southeastern states, mainly on corn.
                                    147

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00
          Ccrbofurcyi
          i«72 estimated:
       Source:  von Rumker et al.  (1974).

                                 Figure 8.    Materials Flow Diagram for Carbofuran  (1972)

-------
                                  Table 27.   Currently Registered Uaee of Carbofuran
  Site and peat

Agricultural crops

Alfalfa
       Dosage
     (Ib actual)'
  Alfalfa blotch leaf mirer

  Alfalfa snout beet'e


  Alfalfa weevil (larvae)


  Alfalfa weevil (adults)

  Egyptian alfalfa weevil
 '   (larvae)

  Grasshoppers

  Lygus bugs

  Pea aphid

  Potato  leafhopper

Bananas
  Banana root borer
  Corn  (field)
 1.0/acre (flow)

 0.25-1.0/acre (flow)


 0.25-1.0/acre (WP, flow)


 0.5-1.0/acre (flow)

 0.25-1.0/acre (UP. flow)


• 0.125-0.25/acre (flow)

 1.0/acre (flow)

 0.2S-1.0 acre (flow)

 1.0/acre (flow)
 1.25-1.5 g/cepa (G)



 2.0 g/cepa  (C)


 2.0-2.5 g/cepo  (G)
               Tolerance,  use,  limitation* .
 10 ppm' (fresh alfalfa)  (not more than 5 ppm carbanates).
'40 ppm (alfalfa hay)  (not more than 20 ppm carbamatea).
 7-Day preharvcst interval through 0.25 Ib/acre.
   Foliage application.
 14-Day preharvest Interval ubove 0.25 through 0.5 Ib/acre.
   Foliage application.
 28-Day preharvest Interval from above 0.5
   through 1.0 Ib/acre.   Foliage application.
 Do not apply more than  once per season.
 Apply only to pure stands of alfalfa.
 Do not move bees into alfalfa fields within
   7 days of application.

 Northeastern states.  Apply when Insects appear.

 Dse restricted to New York state.  Foliage application.
   Apply when insects appear or feeding is first noticed.

 Foliage application.  Apply when larval feeding is  first
   ooticed.

 {ullage application.  Apply when adults appear.

 Foliage application.  Apply when larval feeding is  first
   noticed.

 Use when grasshopper feeding is noticed.

 Foliage application.  Apply prior  to bloom.

 Foliage application.  Apply when Insects appear.

 Apply when Insects appear.

 0.1 ppm.
 No preharvest  Interval  through  3.0 Ib/acre  or
   5.5 g/unlt of  production (cepa).
 For export to  Central and  South America.

 At planting  time treatment.  Apply 0.8-1.0  g to
   planting hole  and  0.45-0.5  g  to  the soil  s.urface
   after  the  hole has been filled  in.
            -plus-
 Soil  treatment.   Apply  4 months and again 8 months
   after  planting.

 Soil  treatment to established plantings.   Apply
   twice  per  year.  For  the first  treatment apply 0.4-0.5 g
   around the base of the mother,  daughter and grand-
   daughter  plants.   For the second treatment apply
    1.6-2.0 g over an  area of 50 cm around the producing
    unit Including the anther,  dunghtcr and granddaughter plants.

 0.2 ppm (grain) (not more than 0.1 ppm cnrbamatce).
  25  ppm (fodder and forage) (not more'than 5 ppm
    carbamates).
 Multiple applications  allowed if l.Olb or less was
    used at planting.
 Source:  U.S.  Environmental  Protection Agency,  EPA Compendium of Rcp.tHtorod
         Poatlclilnd. Vol.  Ill  (1974).
                                                           149

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                                    Table  27. (Continued)
    Site and peat

Corn (continued)

  Armyworm
  Armyvorm,  fill
        Dosage
     (Ib actual)
                                                                Tolerance, use, limitations
0.75-1.0/acre (with 40-ln. (1) Direct granules into planter shoe with iced
  row spacing)               or (2) place applicator Into furrow and mix
           or                with the covering soil or (3) apply granules
0.75-1.0/13,000 linear       In 7-In. band behind planter shoe and incorpo-
  feet of row (C)            rate Into top Inch of soil. Will control army-
                             worn and fall arm/worm for approximately 4-6
                             weeks.
  Corn borer, European
     Second and third
       generations
      First  generation
0.75-l.O/acre (with 40-
  In. row spacing)
           or
0.75-1.0/13,000 linear
  feet of row (G)

1.0/acre (G)
2.0-3.0/13,000 linear
  feet of row (with 40-
  in. row spacing) (G)
  Corn borer, southwestern   1.0/acre  (G)
  Fl«a beetles
  Nematodes (dag'ger,  lance,
    lesion, root-knot,
    spiral, sting,  stubby
    root, stunt)

  Rootvonas,  corn
1.5-3.0/acre (with 40-
  in. row spacing)
           or
1.5-3.0/13,000 linear
  feet of row (C)

0.75-1.0/acre (with 40-
  in. row spacing)
           or
0.75-1.0/13,000 linear
  feet of row (G)

1.5-2.0/13,000 linear
  feet of row
Soil treatment at time of planting.  Apply In •
  7-in. band over the covered seed row.  In-
  corporate Into top Inch of soil. Claims are
  limited to aid in the control of first genera-
  tion European corn borers.

Foliage application. Broadcast by air or direct
  granules into whorls with ground equipment.
  Apply when eggs begin to hatch. Do not make
  over two foliage applications per season.

For control of first generation larvae.  (1)
  Direct granules into planter shoe with seed
  or (2) place applicator Into furrow and mix
  with the covering soil or (3) apply granules
  In 7-ln. band behind planter shoe and in-
  corporate into top Inch of soil.

Foliage application. Broadcast by air or direct
  granules Into whorls with ground equipment.
  Apply when eggs begin to hatch. Claims limited
  to control of second and third generation
  larvae. Do not make foliage application if
  more than 1.0 Ib actual carbofuran was applied
  at planting. Do not make over two foliage ap-
  plication* per season.

Apply in the seed furrow at time of planting.
(1) Direct granules into planter shoe with seed
  or (2) place applicator Into furrow and mix
  with the covering soil or (3) apply granules
  In 7-ln. band behind planter shoe and incorpo-
  rate into top Inch of soil.

Apply at planting time in a 7-15 in. band and
  Incorporate into the top 3 in. of soil.
0.75-1.0/acr*  (with 40-
  in.  row spacing)
            or
0.75-1.0/13.000 llnMr
  f««C of rev  (flow, G)
      susp. in a 7-ln. band over the row, or
  inject It on each sldo of the row. Susp. may
  be mixed with liquid fertilizer. Be certain
  mixture is physically compatible. Do not mix
  until ready to use. Apply G Into the seed
  furrow at time of planting.
                                        150

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                                     Table 27.  (Continued)-
    Site and peit
Corn (field) (Continued)
        Dotage
     (Ib actual)
  Rootworm, northern corn    0.75-1.0/acre (with 40-
                               In. row (pacing)
                                       or
  Rootvorm, southern com    0.73-1.0/13,000 linear
                               feet of row (G)
  Rootwonn, weitern com
   Stalk  rot
0.75-1.0/acre (with 40-
  in. row apaclng)
         or
0.75-1.0/13,000 linear
  feet of row (G)

0.75-1.0/13,000 linear
  feet of row (G)
   Wlreworms
 Peanut*
 2.0-3.0/acre  (with  40-
   In.  row  spacing)
         or
 2.0-3.0/13,000  linear
   feet of  row (G)
  Thrlp*                      2.0-4.0/acre (with 36-
                                in. row spacing)
                                        or
                              0.133-0.275/1,000 linear
                                feet  of row (G)

                              3.0-5.0/acre (with 36-
                                In.  row spacing)
                                        or
                              0.2-0.35/1,000 linear
                                feet  of row (G)

   Nenatodes (lesion, ring,   2.0-4.0/14,520 linear
     root-knot, sting, stunt)   feet of row
   Potatoe leaf hopper


   Rootworm,  southern corn
   Thrlps
  Peppers
 0.033-0.066/1,000  linear
   feet of  row

 0.5-1.0/acre (with 36-in.
   row spacing)
            or
 0.033-0.066/1,000 linear
   feet  of row (C)
                                                                 Tolerance, use, limitations
Soil treatment at tine of planting.  Apply In
  a 7-in. band over the covered seed row.  In-
  corporate into the top Inch of soil.
Postplant soil treatment. Apply by banding over
  the row and Incorporate it Into the soil, or
  by side-dressing on both sides of the row.

Soil treatment at time ot planting.   Apply in
  a 7-in. band over the covered seed row.  In-
  corporate Into the top inch of soil.
Apply a 7-in. band and Incorporate into the
  top 1-in. of aoll. This treatment reduces
  losses due to stalk rot by reducing the
  Incidence of insect wounds which permit
  entry of the stalk rot fungus.

Soil treatment at time of planting. Apply in
  a covered band or in the seed furrow.
                            0.2 ppm (not  more  than 0.1  ppra carbamates)
                              (peanuts).
                            S ppm (not  more than I ppm  carbamates)
                              (peanut hulls).
                            Do not feed treated forage  to dairy  animals  or
                              animals being finished for slaughter.

                            Use restricted to  Southeastern states. Apply
                              In 12-In.  band over the row prior  to plant-
                              Ing.  Incorporate into top 3-6  in.  of soil.
                            Use restricted to Southeastern states.  Apply
                              In 18-in. band over the row prior to plant-
                              ing. Incorporate Into top 3-6 in. of soil.
 Use restricted to Oklahoma, Texas and south-
   eastern states. Apply as a 12-In. band over
   the row and Incorporate  into the top 3-6  in.
   'prior to planting.

 Use restricted to southeastern states. Apply
    In  seed  furrow at  tine of planting.

 Use restricted to  southeastern states. Apply
    in  the  seed furrow at  planting.  This treat-
    ment  will  also aid In  controlling southern
    corn rootworms.
                              1.0 ppa  (not more than O.I ppm carbamates).
                              21-Day preharveat Interval through 3.0 Ib/acre.
                                Slde-dreas  soil application.
                                           151

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                                               Table 27.  (Continued)
   Site «nd peat

 Peppers (continued)

   European corn borer
 Green peach aphid
 Potatoes
   Aphlds
   Colorado potato beetle
   European corn borer
   Potato flea beetle
   Potato leafhopper
   Potato tuberworm
   Wirewonns
   Colorado potato uetle
   Potato flea beetle
   Potato leafhopper
.Rice
   Dark field
   Mosquito (larvae)
   Rice water weevil
       Dosage
     (Ib actual)
2.0 and 3.0/ocre iwith
  38-ln. row spacing)
          or
0.075 and 0.1/500 linear
  feet of row (G)
2.0 and 3.0/acre (with
  38-ln. row spacing)
          or
0.075 and 0.1/500 linear
  feet of row (G)
2.0-3.0/acre (with 38-
  ln. row spacing)
          or
0.143-0.218/1,000 linear
  feet of row (G)
0.5.-1.0/acre (flow)
0.45-0.6/acre (C)
                                           0.5/acre (C)
                                           0.45-0.6/acre (C)
   Shorghun Crecnbug
                                           0.75-1.0/acre (C)
    Toleranid. Use, llnltatlona
Side-dress soil treatment to one or both
  sides of the row.  If application is
- made to both sides, use half the speci-
  fied row dosage per side.  Hake two appli-
  cations.  Apply low dosage 2-4 weeks after
  transplanting and hl&h dosage 4-6 week*
  later.  Incorporate Into soil.

Use restricted to the Delmarva Pennlnsula
  and southern Now Jersey.  Side-dress
  soil treatment to one or both sides of
  row.  Make first application 2-4 weiks
  after transplanting.  Make second appli-
  cation 4-6 weeks later.

2.0 ppm of which no more than 0.1 ppm is
  carbamates.

Use restricted to New York state.  Apply
  directly Into the bottom of the seed
  furrow at planting.
Mortheast, North Central and Colorado only.
  Apply when insects appear. Do not make more
  than 8 applications/season. Do not apply more
  than 3 qt. to foliage If  Furadan 10G were used
  at planting. T)o not apply more than 1 qt./
  application. Do not apply within 10 days of
  harvest. Use ground equipment only;

1.0 ppm  (rice and rice straw)  (not more than
  0.2 ppm carbamates). Do not  apply more than
  once per season.

Use restricted to Arkansas, Louisiana, Missi-
  ssippi, and Texas.  Apply from 1 day before
  to within 2 days after permanent flooding.
  For dark rlcefield mosquito, application
  must be made within 2-4 days after flooding.
  Occasional tip burn may occur if propanil
  la also used.  Do not make more than one
  application per season.   Apply by air or
  ground equipment.

Use restricted to California. Preplant soil
  treatment. Apply to soil  aurface prior to
  flooding. Subsequent use  of propanil may
  result in crop injury.  Do not make more
  than one application per  season.  Apply by
  air or ground equipment.

Use restricted to Arkansas, Louisiana, Missi-
  ssippi, and Texas.  Apply from 1 day before
  to within 21 days after permanent {loading.
  Occasional tip burn may occur if propanil
  'is alao used. Do not make more than one
  application per season. Apply by air or
  ground equipment.

Use only on grain sorghum grown for  forage.
  Apply  in seed furrow or In a 7-inch band
  over the row.
   Strawberry
     Root weevils
 Sugarcane
 1.0-2.0/acre  (flow)
                                                           152
Washington  and Oregon,  apply as 10 to 12
   Inch bond over  the row after lost harvest
   but before Oct.  1. Do not make more than
   one application  per season.

0.1  ppm.
   17-nny  prchnrvont  Intcrvnl through 0.75 lh/
   aero. HromlrnHt  application.
Do not use  In llnwnlt.
4.0 lb/B,500 ft pi-r  Hcnwon.

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                                            Table 27.  (Cci.tlnuad)
      Pest aM site

Sugarcane (continued)

  Meoatodes (root-knot,
    •tunt) .   .
  Sugarcane borer
  Wirovor
  Sugar beet
    Root oaggot

Tobacco (flue cured)

  Flea beetles
  Hornvorms
           Dosage
        (Ib actual)
 2.0-4,0/8, 500 linear
   feet of row (0)
 0.5-0.75/acre (WP,  flow G)
  Nematodea (root-knot,
    atunt)
                             2.0-4.0/acre  (with 60-in.
                               row apaclng)
                                      or
                             0.2i-2.5/1,000 linear
                               feet of row (G)
 20/acre (G)




 6.0/acre .(G)



 4.0/acre  (G)





 6.0/acre  (G)
  Tobacco budworm
  Wireworms
Tobacco (Hurley)

  Flea beetlei
.  6.0/acre  (G)
  3.0-4.0/scre (G)
                                             Toleronee. me. limitations
Apply at planting tine In a 15-ln. band directly
  over planted cane juat before covering with
  •oil.  For atubble cane apply in a 15-ln. band
  over the atubble row within 1-2 weeke following
  harveat then cover with 1-2 in. of toil

Broadcaat application.  Check field weekly from
  early June through Auguat.  Hake firat application
  only after visible joints form and 5Z or more of
  the plants are Infested with young larvae feeding
  In or under the leaf aheath and which have not
  bored Into stalks.  Repeat whenever field checks
  indicate the infeatation rate exceeds St.

At planting soil application.  Apply in a 15-ln.
  band directly over planted cane and cover with
  soil.  Do not use In Hawaii.
Stubble treatment.  Apply in a 15-ln. band over
  the stubble row.  Apply anytime after harvest
  until regrowth reaches 18 in.  Cover with a
  1-2 in. layer of soil.  Covering with more than
  2 in. of soil may reduce stand.  For use
  in Florida only.

Apply in a 6- to 7-ln. band and  Incorporate
  into top one in. of soil.

07

Broadcast soil application before  forming beds.
  Incorporate into  top 4-6  In. of  soil.  Form
  beds and plant as usual.
                 or
Band application after forming beds.   Apply  In a
  14-18 in. band over bed.   Incorporate  Into top
  4-6  In. of  soil  and reform bed.   Plant as  usual.
  This gives  full  season control of flea beetles
  and  controls homworms for approximately 60  days.

Before forming beds,  apply granules broadcast  over
  soil surface and Incorporate 4-6 in. deep.  Form
  beds and plant.
                  or
After  forming beds, apply granules In a 14-18 In.
  band over  the  bed and Incorporate to a depth
  of 4-6  in.  Reform bed and plant.  For flue-cured
  tobacco only.

 Broadcast soil  application before forming beds.
   Incorporate Into top 4-6 In. of aoil.  Form
  beds and plant as usual.  Claims are limited
   to aids In the control of the tobacco budworm.
 Broadcast granules over the soil surface prior
   to transplanting and Incorporate with a suitable
   device.
                                                       153

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                                       Table 27.  (Continued)
    Site «nd post

Ornamentals

(Woody (hrubs, trees  *nd  vines)

Cottonwood
        Dosage
     (Ib actual)
  Cottonwood tvlg borer
  Cottonwood leaf beetle
  Clearwlng borer
Siberian elm
  Elm leaf beetle
0.275-0.55/1,000  linear
  feet of row  12-ln.  row
  spacing - 1.0-2.0/acre
  (C)
                              0.3/1,000 linear feet of
                                row - 40 In.  row spac-
                                ing - 4.0/acre (G)
                              0.003  Ib 01 0.049 oz/ln
                                of girth at 3-4 ft
                                height/tree (soluble
                                packet)
Forest,  nonagricultural and wastelands

Pine  seedlings
  Pales  weevil
  Pitch-eating  weevil
0.05/half  gallon water
   (flow)
                              1 teaspoon 10% (G)/
                                seedling
                                        or
                              1.0 g/seedling (C)
                                                                  Tolerance,  use,  limitations
For use in commercial planting!.  Apply during
  June or July to the root tone of the cutting
  by the use of a subsoil applicator as a  side-
  dress 10-12 in. from the trees  In a continuous
  band on both sides of the trees.

For use in nursery plantings.  Apply In Hay or
  June to the root zone of the cutting by  the
  use of a subsoil applicator  as  a aldedress
  10-12 in. from the trees in  a continuous band
  on both sides of the trees.
Use limited to Arizona,  Colorado,  Kansas,
  Nebraska, New Mexico,  Utah and Wyoming.  Soil
  treatment. Measure circumference (girth)  at
  3-4 ft height and place holes in ground  (us-
  ing probing tool) evenly spaced around treei
                    Locate holes away
If girth is;           from trunk;
  1-10 in.           1 ft
 16-20 in.           3 ft
 24-40 in.           6 and 12 ft (alternating)
 44-80 in.           10 and 12 ft (alternating)
 80 in. and larger  12 and 20 ft (alternating)
Thoroughly soak area under trees.  Determine
  proper location for holes and insert  plugging
  tool in soil with a slight twisting motion.
  If soil is properly soaked, tool will enter
  soil easily. Push tool in soil to depth  of
  black mark on stem of tool. Leave foil plug
  in stem as the next plug will force the  pre-
  ceding one out. Place soil plug by each  hole.
  Drop one packet in each hole unopened. PUce
  small amount of water  on top of  each  packet.
  Replace soil plug Iranediately and compress
  with foot. Keep treated areas soaked  with
  water for 14 days.

 Prctransplant  root  treatment.  For  use  In pine
   plantations.  Prepare  and  apply a  11  (w/w)
   actual slurry of clay  to  roots of pine
   seedlings.  Treat  roots  by  dipping or other
   suitable  method which  allows  for  a thorough
   coating.  Keep  roots moist  until  seedlings
   are  transplanted. This  amount treats  150-200
   seedlings.  Adequate ventilation  Is required
   lor  indoor  treatment.

 Apply  at transplanting.  Distribute  granules
   on  soil  in  a  6-in.  radius  around  each seed-
   ling.  Cover granules  with  soil.
                                        154

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        Table 28.  Use of Carbofuran in the U.S. by Crops, 1971

Quantity used

Crop
Corn
Rice£/
Other field crops
Vegetables
Fruits and nuts
Total
1,000 Lb
active ingredient
2,681
164
4
2
	 3
2,854

Percent
93.9
5.7
0.2
0.1
0.1
100.0
Acreage treated
1,000
Acres
3,677
78
7
8
	 2
3,772

Percent
97.5
2.1
0.2
0.2
Negl.
100.0
aj The quantity of the compound may be upward biased or the rice acreage
   treated may be downward biased since the recommended application rate
   is only 0.5 Ib/acre.

Source:  U.S. Department of Agriculture (1974).
                                  155

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        Table  29.   Use  of  Carbofuran in the U.S. by Regions, 1971
Farm production
   region	

Northeast-/
Appalachian^/
Southeast—'
Delta  States!/
Corn Belt!/
Lake States!/
North  Plains^/
South  Plains]!/
Mountain!.'
Pacific!/

          Total
                           Quantity used
     1,000 Lb
active ingredient    Percent

          59           2.1
          22           0.8
           4           0.1
          62           2.2
       1,140          39.9
         791          27.7
         635          22.3
          38
         103
       2,854         100.0
Acreage treated
1,000
Acres     Percent
            2.1
            0.8
            0.2
            1.0
           38.
           34,
   79
   30
    7
   36
1,443
1,302
  779

   54
   42
 3,772    100.0
           20.7
&l  Maine, New Hampshire, Massachusetts,  Vermont,  Connecticut,  Rhode
      Island, New York, Delaware,  Pennsylvania,  Maryland,  New Jersey.
b/  Kentucky, Tennessee, West Virginia, Virginia,  North  Carolina.
£/  Alabama, Georgia,  South  Carolina,  Florida".
jd/  Arkansas, Louisiana, Mississippi.
£/  Iowa, Missouri, Illinois, Indiana, Ohio.
f/  Minnesota, Wisconsin, Michigan.
£/  North Dakota, South Dakota,  Nebraska, Kansas.
h_/  Texas, Oklahoma.
_i/  Montana, Idaho, Wyoming, Nevada, Utah,  Colorado,  Arizona, New Mexico,
j/  Washington, Oregon, California.
Source:  U.S. Department of Agriculture  (1974).
           acre added by RvR Consultants.)
                              (Application rates per
                                   156

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          Table 30.   Use  of  Carbofuran  in California by Major
                     Crons and Other  Uses,  1970-1974
-•• rr
1 "^""-^ 	 ->_ Year 1970 197
brop/use ' — 	 	 	 1,000 1
Alfalfa!/ - 0.1
Rice 8.8 8.7

1 1972 1973 1974
b of active ingredient
2.7 94.0 135.7
7.8 11.3 10.4
Cotton^' - 0.4 - 1.1
All other crops
and uses 0.7 0.3 0.1 0.2 	 ^_
Total 9.5 9.5 10.6 106.6 146.1

a/  Including alfalfa for hay and for seed.
b_/  Carbofuran is not registered for use on cotton.

Source:  California Department of Agriculture  (1973, 1974 and  1975).
                                   157

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   Table  31.  Use of Carbofuran in California in 1972, 1973 and 1974
           by Crops and Other Uses, Applications, Quantities,
                          and Acres Treated

Commodity
1972
Alfalfa
Alfalfa for seed
Rice
Tomato
University of California
Total
1973
Alfalfa
Alfalfa for seed
Almond
Apple
Apricot
Beans , dry edible
Cotton
Fallow (open ground)
Nonagricultural areas
Peach
Potato
Rice
Soil (fumigation only) '
University of California
Water areas
Total
1974
Alfalfa
Rice
Rice
Total

Applications

187
1
343
1

532

2,744
5
2
1
1
5
1
1
1
1
8
224
1

2
2,997

2,841
241
1
3,082
Pound
active ingredient

2,719.29
21.02
7,849.20
1.87
0.11
10,591.49

93,720.02
229.50
16.19
17.87
15.32
51.66
1,114.27
45.00
0.03
1.75
31.52
11,309.73
5.00
0.28
15.76
106,573.90

135,670.12
10,437.11
0.20
146,107.43

Acres

18,687.50
24.00
15,748.90
50.00

34,510.40

268,279.50
304.00
37.00
51.00
35.00
76.00
53.00
90.00
12.00
8.00
36.00
18,150.70
10.00

18.00
287,160.20

267,605.63
21,075.30
40.00
288,680.93

Source:  California Department of Agriculture (1971 to 1975)
                                  158

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         Table 32.  Estimated Uses of Carbofuran in the U.S.
                   by Regions in 1971, 1972 and 1974

"" ~~~~ 	 — -—— ____J[ear
Region ' • 	 • 	 _
a/
Northeast-'
Southeast—'
1971 I 1972 1 1974
1,000 Lb of active ingredient
60 100 125
30 100 125
c/
North central- 2,570 4,400 6,300
South central—
West^
••
60 200 250
140 200 400
Total 2,860 5,000 7,200

a/  New England States,  New York,  New Jersey, Pennsylvania.
b/  Maryland, Delaware,  Virginia,  West Virginia, North Carolina, South
      Carolina, Georgia, Florida.
c/  Ohio, Indiana, Illinois, Minnesota, Wisconsin, Michigan, Iowa,
      Missouri, North Dakota, South Dakota, Nebraska, Kansas.
d/  Kentucky, Tennessee, Arkansas, Louisiana, Mississippi, Alabama,
      Oklahoma, Texas.
el  rtontana, Idaho, Wyoming, Colorado, Utah, Washington, Oregon, Alaska,
      New Mexico, Nevada, Arizona, California, Hawaii.

Sources:  1971 - U.S.  Department of Agriculture  (1974).
          1972 - von Rumker et al.  (1974).
          1974 - RvR estimates; see text.

Note:  The estimates for 1971 and  those for 1972  and  1974 originate from
         different sources  and were obtained by  different methods  and are
         therefore not directly comparable; see  text.
                                   159

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References

California Department of Agriculture, Pesticide Use Report;  1970. Sacramento,
  Calif.  (1971).

California Department of Agriculture, Pesticide Use Report:  1971, Sacramento,
  Calif.  (1972).

California Department of Agriculture, Pesticide Use Report;  1972. Sacramento,
  Calif.  (1973).

California Department of Agriculture, Pesticide Use Report:  1973. Sacramento,
  Calif.  (1974).

California Department of Agriculture, Pesticide Use Report;  1974. Sacramento,
  Calif.  (1975).

U.S. Bureau of the Census, U.S. Foreign Trade Statistical Classification of
  Domestic and Foreign Commodities Exported from the United States, Schedule
  B, Section 5, Chemicals (1971).

U.S. Department of Agriculture, Farmers' Use of Pesticides in 1971...Quantities/
  Agricultural Economic Report No. 252, Economic Research Service  (1974).

U.S. Environmental Protection Agency, EPA Compendium of Registered Pesticides.
  Vol. Ill, Washington, D.C. (1974).

U.S. Tariff Commission, Imports of Benzenoid Chemicals and Products 1972, TC
  Publication 601 (1973a).

U.S. Tariff Commission, United States Production and Sales of Pesticides and
  Related Products. 1972 Preliminary (1973b).

U.S. Tariff Commission, United States Production and Sales of Pesticides and
  Related Products. 1973 Preliminary (1974).

Von Rumker,  R., E. W. Lawless, and A. F. Meiners, Production, Distribution.
  Use, and Environmental Impact Potential of Selected Pesticides, Contract No.
  EQC-311, Report for the Environmental Protection Agency and Council on
  Environmental Quality, EPA 540/1-74-001 (1974).

Von Rumker,  R., E. S. Raun,  and F. Horay, Substitutes for Aldrin, Dieldrin.
  Chlordane  and Heptachlor for Insect Control on Corn and Apples, U.S.
  Environmental Protection Agency, Contract No. 68-01-2448 (1975).
                                    160

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                      PART III.   MINIECONOMIC REVIEW




                                 CONTENTS




                                                                  Page




Introduction	163




Efficacy of Pest Control on Alfalfa	164




Cost Effectiveness of Pest Control—Alfalfa	165




Efficacy of Pest Control on Field Corn	165




Cost Effectiveness of Pest Control—Field Corn	167




Efficacy of Pest Control on Peanuts	168




Cost Effectiveness of Pest Control—Peanuts	169




Efficacy of Pest Control on Peppers	169




Cost Effectiveness of Pest Control—Peppers	170




Efficacy of Pest Control on Potatoes	170




Cost Effectiveness of Pest Control—Potatoes	171




Efficacy of Pest Control on Rice	171




Cost Effectiveness of Pest Control—Rice	172




Efficacy of Pest Control on Sugarcane	172




Cost Effectiveness of Pest Control—Sugarcane	173




Efficacy of Pest Control on Tobacco	173




Cost Effectiveness of Pest Control—Tobacco	174




References	181
                                        162

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     This section contains a general assessment of the efficacy and cost
effectiveness of carbofuran.  Data on the production of carbofuran in the
United States, as well as an analysis of its use patterns at the regional
level, were developed as part of the Scientific Review (Part II) of this
report.  The section summarizes rather than interprets data reviewed.


Introduction

     The efficacy and cost effectiveness of a specific pesticide applied
to cropland should be measurable in terms_of the value of increased yield
or improved quality or in terms of reduced ^osts associated with the
pesticide's use.  Therefore, one should be able to select a test plot of
a given crop, treat it with a pesticide, and compare its yield with a similar
untreated plot.  The difference in yield should be the increase related to
the use of the pesticide.  The increased income (i.e., the yield increase
multiplied by the selling price of the commodity) less the additional cost
(i.e., the pesticide, its application, and the harvesting of the increased
yield) is the net economic benefit related to the use of the pesticide.

     Unfortunately, this method has many limitations.  The data derived is
incomplete and should be looked on with caution.  Review of the literature
and EPA registration files revealed pesticide-treated versus nontreated
crop experiments are conducted by many of the state agricultural experimental
stations.  Only a few tests, however, have attempted to measure increased
yield and most of the yield information is found with a few crops such as
cotton, corn, potatoes, sorghum, and selected vegetables.  Most crop experi-
ments measure the reduction in pest populations which cannot be directly
related to yield.

     Even yield data from the test plots is  only marginally reliable,  since
these tests are conducted under field conditions that may never be duplicated
again or may not be representative of actual field practices.   Each experi-
ment is somewhat unique  since yield is  affected by rainfall,  fertilizer use,
severe weather conditions, soil type, region of the country, pest infestation
levels, and the rate, frequency and method of pesticide application.

     Because of the above factors, yield tests at different locations  and
in different years will show wide variations ranging  from declines to
significant increases.  For example, in a year of heavy pest  infestation,
pesticide use can result in a high yield increase because of  extensive
damage in the untreated  test plot.  Conversely, in  a  year of  light  infestation,
the yield increase will be slight.

     The use of market price to estimate the value  received by the producer
also has limitations.  If the use of a  pesticide  causes  an  increase in the
national production, then the market price  should  decline.   According to
Headley and Lewis  (1967), a 1%  increase in  quantity marketed has at times
resulted in a greater than  1% decrease  in price.   Thus,  the marginal revenue
from the increased yield would be a better  measure of the value received.
                                     163

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     A third limitation to the quantification of the economic costs and
benefits is the limited data on  the pesticide quantities used by crop
or pest, the number of acres treated, and the number of applications.
In most cases  the  amount of carbofuran used on different crops is not
available.

     As a result of these limitations, an overall  economic benefit for
a crop-pest combination cannot be determined.  Where applicable, a range
of the potential economic benefits derived from *"he use of the pesti-
cide for control of a specific pest on a crop is ieveloped.  This eco-
nomic benefit  or loss is measured in dollars per acre for the highest
and lowest yield found in reviewed experimental tests.  The highest
and lowest yield increases are multiplied by the price of the crop and
reduced by the cost of the pesticide and its application to give a range
of net economic benefits.

     Carbofuran is a broad spectrum insecticide and nematicide available
as a flowable  or granular formulation.  The chemical may be applied at
planting time  or as a foliar treatment (post-planting) depending on the
crop and target pest.  It is registered for use on alfalfa, corn, peanuts,
peppers, potatoes, rice, sugarcane, and tobacco.  Target pests of carbofuran
include armyworms, corn borers,  nematodes, rootworms, wireworms, weevils,
aphids, lygus  bugs, beetles, leafhoppers, tuberworms, grasshoppers, horn
worms, and tobacco budworms.   The degree of control varies with the method,
rate and timing of application,  the specific pest, and the crop.  The use
of carbofuran  has  been shown to  give excellent control of several pests
and to increase yields significantly.

     Carbofuran prices are estimated at $4.55/lb AI for granular formulations
and $6.86/lb AI for 4F formulations (Shmerler, 1975).

     For the purpose of this analysis, carbofuran application costs are
neglected when carbofuran is applied with the seed at the time of planting;
the incremental costs would be insignificant.  Cost for incorporation into
the soil is estimated to be $2.50/acre and the estimated cost for foliar
application is $1.50/acre.  All  application rates are reported in pounds
of active ingredient.


Efficacy of Pest Control on Alfalfa

     Carbofuran is recommended for control of the alfalfa snout beetle,
alfalfa weevil, Egyptian alfalfa weevil larvae, lygus bugs, and the pea
aphid.

     Depew (1969) evaluated several insecticides for control of the weevil
in tests at Garden City, Kansas, during 1967 and 1968.  Carbofuran EC at
0.25 Ib/acre provided 98% control after 14 days.  In a second test, carbo-
furan EC at 0.5 Ib/acre gave 100% control after 7 days and 94% control after
28 days.
                                      164

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     Summers et al. (1971) found in alfalfa weevil tests at Ithaca,
New York, that carbofuran at 1.0 Ib/acre sprayed on alfalfa was su-
perior to other insecticides used in the test and that effects of the
insecticide were evident 4 weeks after application.  The carbofuran-
treated plots looked excellent and rated 1 on a scale of 1 (no visible
damage) to 10 (crop destroyed).   Carbofuran also gave 95% control of
aphids.  Similar results were achieved in a second experiment conducted
later in the season.

     The Egyptian alfalfa weevil is a serious pest of alfalfa in
California.  Losses from this weevil in 1970 exceeded $6 million
(Summers and Cothran, 1972).  Several insecticides for control of the
weevil at Strathmore, California, were evaluated during 1971.  Carbo-
furan sprayed on a plot at a rate of 1 Ib/acre as early as 80 days
prior to cutting gave effective control-.  The mean damage rating on a
scale of 1 (no damage) to 10 (crop destroyed) was 2.0 for carbofuran
and 7.3 for the untreated plot.

     Johansen and Eves (1972) evaluated the effect of aerial applications
at 1.0 Ib/acre of prebloom sprays on lygus bugs and aphids in alfalfa fields
at Zillah, Washington.  Carbofuran was quite effective against lygus bugs
which increased to only 4.4 nymphs per sweep at the end of 33 days.   However,
aphid counts gradually increased  (to 232.0/sweep) after 33 days.  At this
population level, the field needed retreatment for both pests.
Cost Effectiveness of Pest Control

     The yield effects related to the use of carbofuran on alfalfa ranged
from a decline of .08 to an increase of 1.18 tons/acre.  At a 1971 to  1973
average hay price of $33.33/ton  (U.S. Department of Agriculture,  1974),  the
net economic benefits associated with the use of carbofuran on alfalfa
ranged from a loss of $11.03 to  a gain of $34.97/acre.  These results  are
summarized in Table 33.
Efficacy of Pest  Control  on  Field Corn

     Carbofuran formulations are registered  for  control  of  several pests
that attack field corn.   These  include  the armyworm and  fall  armyworm;
European and  southwestern corn  borers;  flea  beetles;  the dagger,  lance,
lesion, root-knot,  spiral, sting, stunt and  stubby  root-knot  nematodes;
corn rootworms  (northern,  southern,  and western) and wireworms.

     The western  corn rootworm  is a  serious  pest in the  midwestern corn belt.
Hills  and  Peters  (1972)  evaluated several insecticides and  application methods
at Newell, Iowa,  in 1969. Carbofuran was applied at a rate of 1.0 Ib/acre in
liquid and granular formulations to  De  Kalb  XL306 seed corn.   With an assumed
acceptable adjusted root  damage rating  equal to  or less  than 2.5, carbofuran
performed  favorably with damage ratings ranging  from 1.62 to 2.23.
                                      165

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      Musick and Fairchild (1968)  concluded  that  carbofuran,  at rates varying
 from 0.25 to 1.0 Ib/acre, would be.recommended for  control of the western
 corn rootworm larvae in Missouri.   Carbofuran was applied with the seed at
 planting and was rated for control of root  damage.   All  tests were signifi-
 cantly better than an untreated check at the 5%  probability  level.

      Apple et al.  (1969) found that 0.84 kg/ha  (0.77 Ib/acre) of carbofuran
 provided outstanding protection from the northern corn rootworm in tests
 during 1968.   The average number of larvae  were  reduced  99.6% compared  to
 an untreated check.

      Petty and Kuhlman (1972)  reported on corn rootworm  control tests in
 Illinois from 1968 to 1971.   For the 1971 tests, carbofuran  10% granules
 banded at 0.8 Ib/acre gave the highest control  (77.7%) of all materials
 evaluated and resulted an 11.4% yield enhancement.   The  summary of tests
 over the 4-yr period showed that carbofuran averaged 84.6% control and
 resulted in a yield  enhancement of 12.3%.   Kuhlman  and Petty (1973) reported
 on 1972 tests in Illinois which demonstrated that carbofuran 10G banded at
 1.0 Ib/acre gave an  average of 92% larvae control and increased yields by
 5.8%.

      The southwestern corn borer is a major pest in certain  states.  In pest
 control tests,  Henderson and Davis (1970) studied 4 insecticides at State
 College and Holly Springs,  Mississippi,  from 1966 to 1968.   The results
 showed that 4 applications of  3% carbofuran granules applied to the foliage
 at 0.5 Ib/acre reduced borer infestation by 48 to 84% and stalk girdling
 by 70 to 95%.   Yield changes compared to untreated  plots ranged from a loss
 of 2.0 bu/acre to a  gain of  18.0 bu/acre.   In 1968  tests with 4 applications
 of 1.0 and 0.5 Ib/acre/application reduced  borer infestation from 58 to 95%.
 Yield changes ranged from a 1.0 bu/acre reduction to a 10.0  bu/acre increase
 over  the untreated plot.   Some of the use rates  in  this  test were above the
 quantities registered for use.

      Keaster  (1972)  found that carbofuran 10G applied at rates of 1.44 to
 2.0 Ib/acre to  the foliage of  corn at Portageville,  Missouri, in 1968 reduced
 the amount of borer  girdling by 49 to 90%.   Yield effects varied from a loss
 of 6.6 bu/acre  to  a  gain of  21.8 bu/acre.

      The European corn borer has been effectively controlled with carbofuran.
 Harding et al.  (1968)  found  that 0.25 Ib/acre provided 91% control of the first-
 generation borer and 78% control of the second-generation borer in field tests
 in 1966.   Berry et al.  (1972)  conducted similar  tests and reported 75 to 81%
 control of first-generation  borers with  a 3% granular formulation at rates of
 0.25,  0.50, and 1.0  Ib/acre.   Control of second-generation borers was not as
 good,  ranging from 21% with  an application  of 0.25  Ib/acre granules to 78%
with  1.0  Ib/acre of  3% granules.
                                     166

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     Wedderburn et al.  (1973)  observed that  carbofuran  granules  applied
at 0.75 Ib/acre to the  whorls  reduced first-generation  corn  borers  by 77%
in tests at Mead, Nebraska,  in 1971.   In a second  test,  carbofuran  10%
granules at 2.0 Ib/acre applied either to the furrow or band reduced  the
number of tunnels by 42 to 71%.

     Kuhlman and Petty  (1972)  found that carbofuran at  1.0 Ib/acre  applied
at planting with corn in Illinois did not control  the first-generation
borer.  However, 90% control was achieved at rates of 2.0 Ib/acre and 100%
control occurred at 3.0 Ib/acre.

     Musick and Suttle  (1973)  evaluated carbofuran for  control of the
annyworm.  Carbofuran 10G was applied at rates of 1.2,  2.4,  and 4.8 oz
AI/1,000 linear feet of row at planting.  They found that the effectiveness
varied with the date of treatment and rate of application.  An application
rate of 2.4 oz/1,000 linear feet of row was  required at planting for  maximum
suppression of the armyworm.

     Kuhlman  (1974)  found that  carbofuran applied with no-till corn at
1.0 Ib/acre achieved 100% control.  These tests were conducted in Illinois
in 1973 when armyworm infestation was light.

     Kuhlman and Petty (1972)  found that wireworm control was poor  with
carbofuran.  Tests in Illinois in 1971 at 1.0 Ib/acre applied with  corn at
planting showed an average control of 13.3%.  These results  were confirmed
by Sechriest and Sherrod (1973) who found that 1.3 Ib/acre of carbofuran
banded on corn for wireworm control was not significantly different at the
5% level from an untreated plot.  The application rates were lower  than the
2.0 to 4.0 Ib/acre recommended rate.

     Nematode control was evaluated by  Dickson and  Johnson  (1972).  Although
control  of sting and lesion nematodes with  10G carbofuran at  a rate  from
1.0 to 2.0 Ib/acre was slightly better  than the untreated plots  it was not
significantly different at  the 5% probability level.  Yield,  however,  in-
creased  from 13  to  22 bu/acre.   Arnett  (1973) found similar results with
carbofuran 10G  at the  2 Ib/acre rate.   Yields increased  from 26.5  to  27.2
bu/acre, but stubby  rootknot  and spiral nematodes were  not  controlled.
Cost Effectiveness of Pest Control

     The range of yield changes due to the use of carbofuran varied  from a
loss of 6.6 to a gain of 49.4 bu/acre as a result of  several tests on corn.
With a 1971 to 1973 average corn price of $2.01/bu  (U.S.  Department  of
Agriculture, 1974), the net economic benefits associated  with  the use of
carbofuran on corn after subtracting pesticide and  application costs ranged
from a loss of $22.44/acre to a gain of  $48.09/acre.   Reduction in yields
only occurred in 2 of the tests.  These  results  are summarized in Table 34.
                                       167

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 Efficacy of Pest Control  on Peanuts

      Carbofuran is registered for control of thrips,  nematodes (lesion,
 ring, root-knot, sting, and stunt), the potato leafhopper,  and the
 southern corn rootworm on peanuts.   Several references on the efficacy
 and yield changes associated with carbofuran applications on peanuts
 were available from tests conducted by the agricultural experiment
 stations at Tifton, Georgia; Virginia Polytechnic Institute at Blacks-
 burg and Holland, Virginia;  and  Oklahoma State University at Stillwater,
 Oklahoma.  Data was available on all of the above pests with the exception
 of the potato leafhopper.   Most  tests measured carbofuran efficacy against
 several pests so that  yield changes could not be identified with control
 of any single pest.

      Osborne (1970)  conducted several tests at various locations in Vir-
 ginia comparing carbofuran to other pesticides for control  of root-knot,
 sting,  stunt,  and ring nematodes  as well as control of thrips on peanuts.
 Application rates varied  from 2  to  5 Ib/acre.   They were applied in an
 18 in wide  band and incorporated  6  to 8  in deep.   Control of sting nema-
 todes at the 2.0 Ib/acre  rate ranged from 72 to 92%,  and only slight
 damage from thrips was noticed.   Thrips damage was rated 15 on a scale
 of 10 (no damage) to 30 (severe  damage).  Yield increases ranged from
 300 to  1,028 Ib/acre.

      Smith  (1972)  conducted  tests at Courtland,  Virginia, and Cyprus Chapel,
 Virginia,  in 1971 comparing  insecticides for control  of thrips and ring
 nematodes on peanuts.  Carbofuran was  applied  in 14-in bands at a depth of
 8  in.   At Courtland, carbofuran 10G was  applied at planting at 1.0 and
 4.0 Ib/acre.   Although thrips  control  increased 63% at both rates,  ring
 nematodes were  not  controlled  at  the 1.0 Ib/acre rate.   Yields were also
 lower by 357 and 412 Ib/acre.  Results were similar at Cyprus Chapel,
 although yield  effects were not reported.

      Smith  (1971) also evaluated  several insecticides  for the control  of
 southern corn  rootworm on peanuts grown  in  Virginia from 1965 to 1967.
 Carbofuran  applied  at planting at rates  from 1.0 to 4.0 Ib/acre (the latter
 rate  being  higher than the current  recommended  rate).   The  1.0 Ib rate pro-
 vided control  ranging from 1.8 to 9.3% damaged  fruit.   The  damage to the
 comparable  test  plots was  7.1 and 29.8%,  respectively.   Yield increase at
 1.0 Ib/acre  was  7.0%.

      Several tests were conducted in Georgia to  evaluate  the ability of
 carbofuran  to control ring, root lesion,  and root-knot  nematodes,  thrips,
 and leafhoppers.  Minton et al. (1969) found that  the  number of ring
nematodes in a peanut plot treated with  3.0 Ib/acre of  carbofuran had
more nematodes than an untreated test plot.  Minton and Morgan (1970)
 reported more effective control of ring nematodes with  carbofuran 10G
applied at planting of 5.0 Ib/acre than at 3.0 Ib/acre.  Control  increased
34% at the 5.0 Ib rate.  (A 4.0 Ib/acre rate is currently recommended.)
                                    168

-------
     Carbofuran effectively controlled  the  lesion nematodes  as measured
by a pod lesion index.   On a scale  of 1 to  3  (3  = severely discolored) ,
carbofuran-treated peanuts were  significantly better  than the untreated
check at the 5% level of significance.   The rating  index ranged from
1.0 to 1.8 at rates of 3.0 to 5.0 Ib/acre.  Yields  increased from 114
to 232 Ib/acre (Minton et al., 1970).

     Morgan and Minton (1970) concluded that  high yields of  peanuts were
directly related to control of root-knot nematodes.  This was supported
by Minton and Morgan (1971).  Carbofuran applied at a rate of 5.0 Ib/acre
(which is higher than registered use rates) in  this test  resulted in a
peanut yield of 2,806 Ib/acre compared  to a rototilled check plot yield
of 1,469 Ib/acre.  Galling of roots was measured by an index of 1 to 5
with 1 representing the least galled and the  5  the  most severely galled.
The index for the carbofuran plot was 2.9,  compared to 4.7 for the check.

     Carbofuran controlled thrips  in most tests, but  little  relation was
found between thrips control and yields (Minton et  al. , 1969).

     Sturgeon and Shackelford (1972)  reported that  carbofuran at 2.0
and 4.0 Ib/acre applied with the seed  effectively reduced nematode popu-
lations and increased yields from 423  to 485  Ib/acre over an untreated
plot.
Cost Effectiveness of Pest Control

     The range of yield changes associated with the use of carbofuran
varied from a loss of 412 Ib/acre to a gain of 1,137 Ib/acre.  At-an
average 1971 to 1973 price of 14.7
-------
      Burbutis et al.  (1972)  tested carbofuran for control of the  green
 peach aphid in several tests in Delaware between 1969 to 1971.  Single
 and double applications of carbofuran granules side-dressed in  a  band at
 rates varying from 1  to 4 Ib/acre reduced aphid populations by  56 to 95%.
 Burbutis  and Lesiewicz (1974), in 1971 tests at Bridgeville, Delaware,
 found that 2 Ib/acre  of carbofuran 10G, followed by a 3 Ib/acre application,
 reduced European corn borer infestation later to 1% (compared to  30% for
 the check) and increased yields by 3.6 tons/acre.  Hale and Shorey (1971)
 conducted tests at Santa Maria, California,  from 1965 to 1969.  They found
 that carbofuran foliar sprays at 0.5 and 1.0 Ib/acre reduced aphids by
 87  to 100% 14 days after treatment and up to 99% 28 days after  treatment.


 Cost Effectiveness of Pest Control

      Pepper yield changes, due to the use of carbofuran, varied from a
 gain of 22 cwt to 82  cwt/acre when compared  to untreated test plots.  At
 a 1971 to 1973 average price of $12.97/cwt for peppers (U.S. Department
 of  Agriculture,  1974)  and a cost of $4.55/lb AI for carbofuran, and an
 application cost of $12.50/acre, the net economic benefits ranged from
 a gain of $269.19 to  $l,035.79/acre.
 Efficacy of Pest Control on Potatoes

     Carbofuran  is  registered for control of aphids,  the Colorado potato
beetle,  European corn borer,  potato  flea beetle,  potato leafhoppers,
potato tuberworm and  wireworms on potatoes.

     Onsager (1969) tested  several insecticides at Quincy, Washington,
in 1966  and George, Washington,  in 1967.   Carbofuran  at rates  of 2.2 lb/
acre provided wireworm control and reduced the degree of injury to tubers
by 71%.  However, there were  no  significant  differences in yields.  Onsager
and Foiles  (1970) found that  carbofuran applied by band application at 2.3
Ib/acre  was 27 to 64% more  effective against wireworms than broadcast
application at 4.0  to 8.0 Ib/acre.   (These latter rates are greater than
registered  uses.)   No significant difference in yields was observed.

     Day (1970)  found that  5.0 Ib/acre  (3.0  Ib/acre is the recommended rate)
carbofuran  granules broadcast on the soil gave 94% initial control of the
southern potato wireworm.   Control,  however, declined to 45% by the end of
53 days.  Day and Crosby (1972)  found that carbofuran at 2.0 Ib/acre pro-
duced erratic results in several experiments between  1965 and  1969 in South
Carolina. '  Control varied from 24 to 100%.
                                    170

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     Hofmaster and Waterfield (1972) evaluated insecticides for control
of the Colorado potato beetle in several tests in Virginia.  At Painter,
Virginia, in 1967, 2.0 Ib/acre of carbofuran were banded on each side of
the row and effectively controlled the beetle for 120 days.  Only 11
larvae/10 hills remained, whereas the plants that were not treated were
defoliated.  Tests during 1968 to 1971 showed similar reductions in
larvae.  In 1970, heavy infestations of the beetle destroyed the check
plot resulting in significantly increased yields in the treated plots.

     Chapman (1971) tested 2 formulations of carbofuran (4F and 10G) at
3 different rates of application (.5 Ib/acre, 1.0 Ib/acre and 3.0 Ib/acre)
to control flea beetles.  Yield increases ranged from 25 cwt/acre for 3.0
Ib/acre of a 10G formulation applied in-furrow to 78 cwt/acre^ for^ ._5
Ib/acre of a 4F formulation that was applied as a spray.  Carbofuran
10G applied at 3.0 Ib/acre gave complete control of the flea beetles
and provided commercial control of aphids for 71 days after treatment.

     FMC (1971) tested a 10G formulation of carbofuran for control of
the green peach aphid and the Colorado potato beetle.  A banded application
of 1.18 Ib/acre enhanced the potato yield by 72 cwt/acre when the green
peach aphid was the target pest.  With an application rate of 3.0 Ib/acre
directed at the Colorado potato beetle, the yield per acre was increased
by 85 cwt.
Cost Effectiveness of Pest Control

     The range of potato  yield  increases  related  to  the  use of carbofuran
varied from 25 to 213 cwt/acre  when  compared  to untreated potato test plots.
At a 1971  to  1973 average price of $2.99/cwt  for  potatoes  (Agricultural
Statistics, 1974), net  economic benefits  after subtracting pesticide and
application costs ranged  from $61.10 to $625.27/acre.  Results are  summarized
in Table 36.
Efficacy  of  Pest  Control on Rice

      Carbofuran is recommended for control of tihe rice water-weevil and
mosquito  larvae.

      Donoso-Lopez and Grigarick (1969) demonstrated that preplant treat-
ment  of rice fields with carbofuran at 1.0 Ib/acre AI effectively controlled
adult weevils (78% mortality)  on rice seedlings up to 4 weeks  following the
applications.  After 6 weeks mortality still occurred, but was reduced to
43%.  At  rates of 0.25 and 0.50 Ib AI, mortality was less but  not signifi-
cantly  so.

      Gifford et al. (1975) evaluated carbofuran in several Louisiana
parishes  between  1970 and 1972.  They concluded that a single broadcast
application  of 3% carbofuran granules at a rate of 0.5 Ib/acre AI applied
                                     171

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as much as 5 weeks after the rice seedlings are flooded will reduce infesta-
tions of the rice water weevil larvae established in the root systems.  Yield
increases per acre of rough rice ranged from 86 to 614 Ib.

     The dark rice field mosquito breeds exclusively in the rice-producing
areas of Louisiana.  Craven and Steelman (1968) evaluated several insecti-
cides for control of the mosquito at Crowley, Louisiana, in 1967.  Propanil
at 3.0 Ib/acre was also applied with all treatments.  The mixture with car-
bofuran EC at 0.1 Ib/acre applied 26 days after planting was phytotoxic
to the plants; the control was only 26.4% which was less than in the check
plot.  Carbofuran at 0.05 Ib/acre gave 47.0% control and phytotoxicity was
not evident.

     Lancaster and Tugwell (1969) found that carbofuran 10% granules applied
to the soil prior to the first watering of rice fields completely eliminated
the larvae of the southern house mosquito in tests at Stuttgart, Arkansas,
in 1967.  Similar results were also obtained in 1968 tests.
Cost Effectiveness of Pest Control

     Several tests were conducted to determine yield effects of carbofuran
for rice water weevil control.  The results of these tests showed that yield
effects ranged from a loss of 199 Ib/acre to a gain of 1,614 Ib/acre.

     With a 1971 to 1973 average price of $8.72/cwt for rice (U.S. Department
of Agriculture, 1974), economic benefits after subtracting pesticide and appli-
cation costs ranged from a loss of $20.88/acre to a gain of $50.01/acre.  Most
of the tests showed positive yield changes.  These results are summarized in
Table 37.

Efficacy of Pest Control on Sugarcane

     Carbofuran is recommended for control of the sugarcane borer, wireworms,
and root-knot and stunt nematodes on sugarcane.  Only one study was found
which evaluated insecticides for control of the sugarcane borer.  Fuchs et al.
(1973) found that carbofuran at 0.75 Ib/acre applied as an aerial spray was
significantly more effective at the 5% level of probability than no treatment.
Control of the borer, as measured by the percent of bored internodes, was
52% better than the untreated check.

     Tests at the Everglades Experimental Station in Belle Glade, Florida, in
1966 showed that carbofuran for nematode control gave a 36.5% yield increase
at an 8.0 Ib/acre rate and 37.8% yield increase at a 16.0 Ib/acre rate
(Applewhite, 1969a).

     Tests at Canal Point, Florida, from 1966 to 1967 showed that a 3.8 lb/-
acre carbofuran in a banded application at planting gave better than 90% cont-
rol of wireworms, and it increased yields by 34,1 tons/acre (Applewhite, 1969b).
                                      172

-------
     In a 1971 Belle Glade,  Florida,  experiment  (Metz,  1973a),  2  granular
formulations (5G and 10G)  of carbofuran were  applied  at rates of  2.0 and
4.0 Ib/acre to control wireworms in stubble crop sugarcane  grown  in a muck
soil.  The 4 Ib/acre rate  was more efficacious than the 2 Ib/acre rate,  with
wireworm control ranging from 52.2% to 82.6%  40  days  after  treatment.  In-
creases in millable stalks/acre for all formulations  ranged from  38.5% to
51.9%.

     In a 1971/1972 Lantana, Florida, test (Metz, 1973a), 1 flowable and 2
granular formulations (4F, 10G, and 5G) of carbofuran were  applied in-furrow
at rates of 2.0 and 4.0 Ib/acre to control wireworms  in sugarcane.  All for-
mulations and application rates completely controlled the wireworms, but the
largest yields resulted from the 4F formulations. Applied  at 2 and 4 Ib/acre,
the 4F formulations increased the millable stalks/acre by  109.6%  and 105.9%,
respectively.
Cost Effectiveness of Pest Control

     Yield increases related to the use of carbofuran on sugarcane ranged
from 2.9 to 15.0 tons/acre.  At a 1971 to 1973 average sugarcane price of
$12.53/ton (U.S. Department of Agriculture, 1974), a carbofuran cost of
$4.55/lb AI and an application cost of $2.50/acre, net economic benefits
ranged  from $38.37 to $172.48/acre.  These results are summarized in Table
38.
Efficacy of Pest Control on Tobacco

     Mistric  and Smith  (1972)  found that foliar damage to newly set  flue-
cured  tobacco plants by overwintered  flea beetles was reduced by 97% with
4.1  Ib/acre of  carbofuran.  Mistric and Smith  (1973) also achieved  76%  flea
beetle control  up  to 16 weeks  with 4.2 Ib/acre of carbofuran applied prior
to transplanting.   The  authors concluded that  carbofuran was effective
against all major  insects  attacking flue-cured tobacco.  These insects  in-
clude  the  tobacco  wireworm, southern  potato wireworm, tobacco  flea  beetle,
tobacco budworm, and tobacco hornworm.

     Dominick (1968) compared  several insecticides  for  the  control  of  the
hornworm on tobacco.  Carbofuran applied as a  foliar spray  at  1.0  Ib/acre
produced tobacco that remained free from hornworms  during  the  21-day test
period. Mistric and Smith (1973) found in  tests  in Clayton, North Carolina,
during 1965-1967 that a pretransplant treatment  of  4.2  Ib/acre (4.0 Ib rate
as recommended) carbofuran gave 96% control 31 days after  transplanting, but
its  effectiveness  decreased rapidly by the  eleventh week.

     Girardeau (1971) evaluated carbofuran  for control  of  the  tobacco bud-
worm in experiments at  Tifton, Georgia,  in  1968 and 1969.   The results of
these  tests  showed that plots  treated with  carbofuran at 6 Ib/acre  had the
lowest number of damaged plants on each observation date throu"^ut the
                                       173

-------
season.  Treatments at 3.0 Ib or less per acre apparently became ineffective
after the seventh and eighth week after application.  They concluded that
rates of 4 to 6 Ib/acre of carbofuran 10G would provide good season-long pro-
tection as measured by percent of leaves lost to the budworm.  This loss
ranged from 2.6 to 4.2%.  Mistric and Smith (1973) applied carbofuran prior
to transplanting at rates of 4.0 to 4.5 Ib/acre and obtained 38 to 52% bud-
worm control for 5 weeks in 2 out of 3 tests when the carbofuran was applied
prior to transplanting.  Carbofuran control of the budworm in one of the 2
post-transplant experiments was 70%.
Cost Effectiveness of Pest Control

     The yield increases related to the use of carbofuran on tobacco ranged
from 102 to 578 dried Ib/acre.  At a 1971 to 1973 average tobacco price of
$.839/lb (U.S. Department of Agriculture, 1974), a carbofuran cost of $4.55/-
Ib AI, and an application cost of $2.50/acre, net economic benefits ranged
from $55.78 to $455.14/acre.  These results are summarized in Table 39.
                                       174

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                                                                  Table 33.  Sunmary of Carbofuran Testa on Alfalfa.
Ul
.
Applications
Feet
Alfalfa veevil
Alfalfa weevil.
Alfalfa veevil
Alfalfa weevil
Alfalfa veevil
Alfalfa weevil
Alfalfa weevil
Alfalfa weevil
Alfalfa weevil
Alfalfa veevil
Foraulation
4F .
4?
4F
4F
4?
4F
4F
. 4F
4F
4F
. Hethodi/
A
A
FS
FS
A
FS
FS
FS
FS
FS
Rate
(Ib/acre)
.5
.5
.5
.5
1.0
1.0
1/0
1.0
1.0
1.0
No.
1
1
1
1
1
1
1
1
1
1
Yield
Increase
(dried
ton»/'acre)b/-
.6
.11
.15
-
.79
1.3
1.18
.3
-
(.08)
Additional
Zncooa at
$33.33/ton
($/acre)
20.00
3.71
5.00
-
26.39
43.33
39.33
10.00
-
(2.67)
Carbofuran
CostaS/
($/acre)
3.43
3.43
3.43
3.43
6/86
6.86
6.86
6.86
6.86
6.86
Application
Coed/
(S/acra)
1.00
1.00
1.50
1.50
1.00
1.50
1.50
. 1.50
1.50
1.50
Economic
Benefit
($/ecre)
15.57
( .72)S/
.07
(4.93)«/
18.53
34.97
30.97
1.64
(8.36)fi/
(11.03)"
Source
Brant aad
Broadus. 1973
Broadua, 1973b
Broadua, 1973a
Keeude and
Broadua. 1973
Broadus, 1973b
Fienkoveki. 1974
Flenkowski, 1974
Broadus, 1973a
Kesuda and
Broadus. 1973
Fienkowski. 1974

          £/  A  • Aerially applied.
              FS  - Foliar spray.
          £/  Yield  is  expressed as a dried weight, which la approxlaataly  25Z of the wet weight.
          e/  4F  formulation - $6.86/lb (Shnerler. 1975).
          i/  Aerial application -  $1.007acre;  Spray  application -  S1.50/acre.
          e/  Data In parentheaea Indicates decreeses in yield.  Incone,  and economic benefit.

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                                                      Table  34.   Sunoary of Carbofu-an Tests on Corn.

Applications

Pest
Xecatodes
Nematodes
Nexatodes
Xesatodes
Nesatodes
Nematodes
Ncoatodes
£exatodes
Neaatodes
Nematodes
Kematodes
Neca Codes
Xecatodee
Southwestern com borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
^~! Southwestern corn borer
CT\ Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Southwestern corn borer
Rootwora
Root worn

Forculatlon
10G
IOC
10G
10G
10G
IOC
4F
IOC
10G
10G
10G
10G
IOC
10G
IOC
IOC
10G
10G
10G
10G
10G
IOC
IOC
10G
10G
3G
3G
3G
3G
3G
IOC
IOC

Methods/
B
B
B
B
B
B
B
B
B
B
B
B
B
F
P .
P
t
P
P
F
P
PC
PC
PC
PC
PC
PC
PC
PC
PC
B
B
Rate
(ib/acre)
1.0
2.0
1.0
1.0
2.0
2.0
2.0
2.0
1.0
2.0
2.0
2.0
2.0
3.0
2.0
3.0
2.0
3.0
2.0
3.0
2.0
1
1
0.72
0.72
0.5
0.5
0.5
O.S
O.S
0.92
0.9

No.
1
1
1
1
1
1
1
1
1
1
1 '
1
1
1
1
1
1
1
1
1
1
2
2
2
2
4
4
4
4
4
1
1
Yltld
Increase]*/
(bu/r.cre)
13
22
22
14
27.2
26.5
37
32
21 '
10
32
20
21
21.9
25.2
15.5
23.0
18.2
19.9
36.6
49.4
21.8
14.7
(t,6)
6.9
9.0
15.0
(2.0)
18.0
16.0
13.8
13.3
Additional
Inconujk/
at $1.67/bu
(S/acre).
21.71
36.74
36.7.'
23.38
45.24
44.26
61.79
53.44
35.07
16.70
53.44
33.40
35.07
36.57
42.08
. 25.88
38.41
30.39
33.23
61.12
82.50
36.41
24.55
(11.02)
11.52
15.03
25.05
(3.34)
30.06
26.72
23.05
22.21
Carbofuran
CostsS./
($/acre)
4.55
9.10
4.55
4.55
9.10
9.10
13.72
9.10
4.55
9.10
9.10
9.10
9.10
13.65
9.10
13.65
9.10
13.65
9.10
13.65
9.10
13.65
9.10
6.55
6.55
9.10
9.10
9.10
9.10
9.10
4.19
4.10
Application
Cosed/
($/acre)
2.50
2.50
-
-
2.50
2.50
_
-
-
-
_
2.50
-
_
-
-
_
_
-
_
-
5.00
5.00
5.00
5.00
10.00
10.00
10.00
10.00
10.00
-

Economic
Benefit^/
($/aere)
14.66
25.14
32.19
18.83
33.64
32.66
48.07
44.34
30.52
7.60
44.34
21.80
25.97
22.92
32.98
12.23
29.31
16.74
24.13
47.47
73.40
17.76
10.45
(22.57)
(.03)
(4.07)
5.95
(22.44)
10.96
7.62
18.86
18.11

Source
Dickaon and Johnson (1972)
Dickson and Johnson (1972)
Dickson and Johnson (1972)
Dickson and Johnson (1972)
Arnett (1973)
Arnect (1973)
Dickson and Johnson (1973)
Dickson and Johnson (1973)
Dickson and Johnson (1973)
Dickson and .Johnson (1973)
Johnson et al. (1973)
Johnson et al. (1973)
Dickson et al. (1973)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster and F&irchild (1968)
Keaster and Fairchild (1968)
Keaster and Fairchild (1968)
Keaster (1.972)
Keaster (1972)
Keaster (1972)
Keaster (1972)
Henderson and Davis (1970)
Henderson and Davis (1970)
Henderson and Davis (1970)
Henderson and Davis (1970)
Henderson and Davis (1970)
Petty and Kuhlnan (1972)
Kuhlman and Petty (197.3)

•/  FS • Foliar granule*
~   B - Banded
    F • Furrow
b/  Data la parenthases Indicate decreases to yield. IncoM, and economic benefit.
c/  Craaules - *4.55/lb; 4 F femulation - $6.86/lb (Shaerler. 197S).
d/  Foliar application - $1.50/acre; granular applications not applied at planting • $2.50/acr«.

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                                                               Table 35.  Suauty of Carbofurao  Teats on Peanuts


Peat
Neaatodea
Se=atodes
Xeaatodes
Xeaatodes
Thrips
Kesacodes
Seaatodes
Senatodes
Kesatodes
Seca codes
XezACodes
Senatodes
Neaatodea
Necatades
Seaatodea
Keaatodes
Xenatader
Xerutodes
Nasa^ades
.'^enatodes
Ke=atodes
XezaCodes



and
and
and
aad
and
and
and
and
and
aad





and



chrips
thrips
chrips
thrips
thrips
thrips
chrips
thrips
Chrips
thrips





thrips

Formulation
IOC
10G
10G
10G
IOC
IOC
IOC
10G
10G
IOC
IOC
10G
IOC
IOC
IOC
IOC
IOC
10G
10G
ICG
IOC
Application
Rate
(Ib/acre)
4.0
3.0
3.0
3.0
• 3.0
3.0 + 2.0
3.0
5.0
3.0 •(• 2.0
5.0
3.0
5.0
3.0
3.0 + 2.0
5.0
3.0
2.0
2.0
4.0
3.0
5.0

Method*/
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
. thrips, and
1— > leafhoppers
—J Xeaatodcs.

10G
5.0
B
Yield
Iiicreaaek/
(Ib/a^.-e)
1.290
105
568
266
764
812
131
62
232
147
114
931
810
692
370
300
1,028
5/2
362
731
1,337

620
. chrips, and
*"J leafhoppers
Sezatcdcs and
Ne=atodes
Se=«todes
S«c*todes
Xezitcdes

Xecatodes

Neeatodea

Seca codes
Xesatoucs
Thrips
Thrips
Thrips
and
and
and.







thrips
thrips
chrips
thrips




.


IOC
IOC
10G
IOC
4F
IOC

IOC

IOC

IOC
IOC
IOC
IOC
IOC
3.0
3.0
5.0
5.0
5.0
4.0

2.0

1.0 + 2.0

2.C + 2.0
2.0
4.0
1.0
1.0
B
B
B
B
S
FU

ru

FD + B

B
B
B
B
B
(11)
392
327
465
443
485

423

105

1.110
261
(357)
(412)
(35)
Additional'
IncOBeb./ at
Carbofuran
Costac/
14.7c/lb (S/acre) .(S/acre)
189.63
15.44
83.50
39.10
112.31
119.36
19.26
9.10
34.10
21.61
16.76
136.86
119.07
101.72
54.39
44.10
151.12
76.73
53.21
107.46
196.54

91.14

(1.62)
57.62
48.07
68.36
65.12
71.30

62.18

15.44

163.17
38.37
(52.48)
(60.56)
(5.14)
18.20
13.65
13.65
13.65
13.65
22.75
13.65
22.75
22.75
22.75
13.65
22.75
13.65
22.75
22.75
13.65
9.10
9.10
18.20
13.65
22.75

22.75

13.65
13.65
22.75
22.75
34.30
18.20

9.10

13.65

18.20
9.10
18.20
4.55
4.55
Application Economic
Cost!/ Benefitb/
(S/acre)
2.50
2.50
2.50
2.50
2.50
2.50
-
-
-
2.50
2.50
2.50
2.50
2.50
••
2.50
2.50

2.50

2.50
2.50
2.50
2.50
1.50

-

2.50

2.50
2.50
($/acre) Source
168.93 Osborne 09681
1.79
67.35
22.95
96.16
94.11
5.61
(13.64)
8.85
(1.14)
3.11
14.11
105.42
76.47
29.14
27.95
139.52
65.13
35.01
91.31
171.29

65.89

(17.77)
41.47
22.82
43.11
29.32
53.10

53.08

(0.71)

142.47
27.27
(70.68)
(65.11)
(12-19)
Laughlin et al. (1969)
Mlnton et al. (1969)
Morgan and Mir ton (1969)
Morgan and Minton (1969)
Mlnton and Morgan (1970)
Minton and Morgan (1970)
Mlnton and Morgan (1970)
Mincon et al. (1970)
Minton et al. (1970)
Minton et al. (1970)
Morgan and Minton (1970)
Morgan and Minton (1970)
Morgan and Minton (1970)
Osborne (1970)
Osborne (1970)
Osborne (1970)
Osborne (1970)
deletion et al. (197i)
Kinloch (1971)
Mlnton and Morgan (1971)

Morgan and Mlnton (1971)

Mor^n and Xlntcn (1971)
Morgan et al. (1571)
Morgan et al. (1971)
Mincer, and Morgan (1972)
Mlnton and Morgan (1972)
Scurgon and Shackdlt'ord
(1972)
Sturgeon and Shackeltbrd
(1972)
Sturgeon and Shaciteiford
(1472)
Sturgeon «t al. (1973)
Sturgton «t al. (1973)
S=ith (1972)
SalLh (1972)
Morgan et al. (1970)

_.  S • Spray
~  FV • Furrov application.
    b • Banded application.
b/  Data in parentheses indicates decreases In yield.  Income  acd  ecocovlc benefit.
£/  Crandl«a - J4.55/lb Al; 4F fonaulatlon - $6.86/lb  Al (ShawrUr.  1975).
4/  Spray application - $1.50/acra; granular application not applied at planting - $2.50/acre.

-------
                                                           Table  ')6.   Summary  of  Carbofuran  Tests on  Potatoes.



Pest Fonaulation
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Colorado potato beetle
Fles beetles
Flea beetles
Flea beetles
Flea beetles
Potato leafhopper
Potato aphlds
Green peach aphid
Colorado potato beetle
Colorado potato beetle
^j Colorado potato beetle
00 Colorado potato beetle
European corn borer
Green peach aphidt
Green peach aphids
IOC
10G
10G
10G
4F
4F
10G
10G
10G
4F
4F
10G
10G
10G
10G
10G
10G
10G
10G
10G "
10G
10G
4F

Method8./
B
B
B
B
B
B
B -
B
B
S
S
FU
FU
B
B
B
B
SD
FU
SD
B
B
S
Rates
(Ib/acre)
2.0
2.0
2.0
J.O
2.0
2.0
2.0
2.0
2.0
0.5
1.0
1.0
3.0
2.0
3.0
1.18
3.0
3.0
3.0
3.0
2.0
2.0
0.5
Yield
"ncreaseA/
(cwt/acre)
187
191
213
209
142
140
171
134
150
78
53
57
25
85
87
72
85
128.4
128.1
194.6
181
174
148
Additional
Income]!/ at
$2.99/cut
($/acre)
559.13
571.09
636.87
624.91
424.58
418.60
511.29
4C0.6o
448.50
233.22
158.47
170.43
74.75
254.15
2f0.14
215.28
254.15
383.92
383.02
581.85
541.19
520.26
442.52
Carbofuran
Cost£/
($/acreL
9.10
9.10
9.10
13.65
13.72
13.72
9.10
9.10
9.10
3.43
6.86
4.55
13.65
9.10
13.65
5.37
13.65
13.65
13.65
13.65
9.10
9.10
3.43
Application Economic
O^sd/ Benefit^/
(S/acre) (S/acre)
2.
2.
2.
2.
1.
1.
2.
2.
2.
1.
1.
-
-
-
—
-
—
2.
-
2.
_
-
1.
50
50
50 "
50
50
50
50
50
50
50
50






50

50


50
547.53
559.49
625.27
608.76
409.36
403.38
499.69
389.06
436.90
228.29
150.11
165.88
61.10
245.05
246.48
209.91
240.50
367.77
369.37
565.70
532.09
511.16
437.59
Source
Hofnaster and Wacerfield
Hotmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Hofmaster and Waterfield
Chapcan (1971)
Chapman (1971)
Chapman (1971)
Chapman (1971)
Wells (1971)
Wells (1971)
FMC (1971)
FMC (1971)
Semel and Wilde (1969)
Semel and Wilde (1969)
Semel and Wilde (1969)
Hoi master and Waterfield
Hofmaster and Waterfield
Ho roaster and Waterfield

(1972)
(1972)
(1972)
(1972)
(1972)
(1972)
(1972)
(1972)
(1972)











(1969)
(1S69)
(1969)

a/  B • Banded application.
    FU - Furrow application.
    S - Spray application.
    SD " Side-dressed.
b/  Data in parentheses Indicate decreases in yield. Income, and economic benefit.
c/  G.-anules - $4.55/lb AI 4F - $6.86/lb AI (Shmerler. 1975).
d/  Spray application - $1.50/acre; granular application, applied at planting - $2.50/acre.

-------
Table 37.  Summary of C*rbofuran Tests on Rice.

. Applications

Pest
Rice water weevil
Rice vater weevil
?.ice vater veevil
Rice vater veevil
Rice vater veevil
Rice vater weevil
Rice vater weevil
Rice water veevil
Rice vater veevil
Rice water weevil
Rice water weevil
Rice water veevil
Rice vater weevil
Rice water weevil
Rice vater weevil

a/ £R • Broadcast.

Foraulation
30
30
30
30
30
30
30
30
30
'30
30
30
30
30
30


Method!/
BR
BR
BR
BR
BR '
BR
BR
BR
ER
BR
BR
BR
BR
BR
BR

It Data in parentheses indicate decrease! in
7/ Sorter (1975)
.
d"/ Broadcast applications - $1.



25/acre.

Rates
(Ib/acrc)
0.5
0.5
- 0.5
0.5 •>
0.5
0.5
0.5
0.5
0.5
0.5
0.25
0.50
0.25
0.50
0.50

Additional Carboturan
Yield Income^/ at Cost— at Application Economic
Increase^/ $8.72/cwt $4.55/lb Cost! Benefit^/
(Ib/ncre)
86
275
246
412
123
400
560
349
235
614
270-
(199)
13
(16)
326
-
yield*, income, and economic


Table


38. Suranary of
(S/acre) (S/acre)
7.50
23.98
21.45
27.21
10.73
34.88
48.83
30.43
20.49
53.54
23.54
(17.35)
1.13
(1.40)
28.43

benefit.


Carbofuran Tests
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
1.
2.
1.
2.
2.




28
'•3
28
28
23
28
28
28
28
28
14
28
14
28
28




($/acre) (S/acreJ
1.25
• 1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25




3.97
20.45
17.92.
32.40
7.20
31.35
45.30
26.90
16.96
50.01
2.15
(20.88)
(1.26)
' (4.93)
24.90




I Source
Clfford
Clffcrd
Cifford
Cifford
Clfford
Cifford
Cifford
Cifford
Clfford
Clfford
Clfford
Cifford
Cifford
Cifford
Cifford





et al. (1975)
ct.al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
et al. (1975)
and Trahan (19£9)
and Trahan (15i»)
and Trahas (1569)
acd Trahaa (1969)
and Trahaa (1969)




on Sugarcane.

Additional
Applications

Pest
Soil insects
Soil infects
Soil Insects
Soil Insects
Soil insects
Soil insects

Formulation
• ice
100
100
100
ICO
100

Methodi/
B
S
B
B
B
B
Rate
(Ib/.icre)
2.85
3.0
3.0
3.0
3.14
3.63
Yield
Increase
Income at
$12.53/ton
No. (tons/acre) • (S/ncre)
1 • 15.0
1 4.7
1 5.0
1 2.9
1 14.7
1 4.58
187.95
58.39
62.65
36.34
184.19
57.39






Carbofuran

(S/acre)
12.97
13.65
13.65
13.65
14.29
16.52








Application
Cost£/
($/acre)
2.50
2.50
2.50
2.50
2.50
2.50

Scntfit

172.48
42.74
46.50
20.19
167.40
38.37



Valdes. 1972a
Eroadus, 1973d
Eroadus, 1973c
Broadus, 1973*
Valdes, 1972a
Valdes. 1972b

-------
                                                   Table 39.
                                                                  ary of Carbofuran Teat* on Tobacco.



Pest
Root-knot
Root-knot
Root-knot
Root-'-not
Root-knot



nematode
nematode
nematode
nematode
nematode
Application*
Rate
Formulation Mvthodi/ (Ib/acre)
IOC
IOC
IOC
IOC
IOC
6.0
6.0
6.0
6.0
6.0


lo.
1
1
1
1
1
Yield
Increaae
(cured
Ib/acre)
578
304
278
138
102
Additional
Income at
$.839/lb
($/acre)
484.94
255.06
233.24
115.78
85.58
Carbofuran
CostsW
(S/acre)
27.30
27.30
27.30
27.30
27.30
Application
Cost c/
(S/acre)
2.50
2.50
2.50
2.50
2.50
Economic
Benefit
.(S/acre)
455.14
225.26
.203.44
85.98
55.78


Source
Nance,
Ketz,
Nance,
Nance,
• Nance,



1972
1973c
1972
1972
1972
     Tobacco flea beetle,
     tobacco thrip,  and
     green peach aphid
IOC
                        4.0
456
                                                         382.58
18.20
                                         2.50
                                                      366.88
                                     Moore, 1971
Not identified
Not identified
IOC
IOC
B
B
5.0
5.0
1
1
161
152
135.08
127.53
22.75
22.75
2.50
2.50
109.83
102.28
Pleaa et al.,
Pleaa at al..
1971
1971

     *f  B • Banded application.
     b/  Cranulea - $4.55/lb Al (Schmerlcr. 1973).
     £/  Banded application! - $2.50/acra.
00
O
                                                     Table 40.
                                            of Carbofuran Tests on Peppers.
Application*

PfSt
European corn
European corn
European corn
European corn
European corn
European corn
European corn
European corn


borer
borer
borer
borer
borer
borer
borer
borer
#
Formulation
10G'
IOC
IGi.
IOC
IOC
IOC
IOC
IOC

Method*!/
SD
SD
SD
SD
SD
SD
SD
SD
Ratea
(Ib/acre)
3.0
2.0 -I- 3.0
2.0 + 3.0
2.0 + 3.0
3.0
4.0
2.0 •»• 2.0
2.0 + 3.0
Yield
Increaae
(cvt/acre)
58
72
82
32
22
78
55.7
54.8
Additional
income at
$12.97/cwt
($/acre)
752.26
933.84
1,063.54
415.04
285.34
1,011.66
722.43
710.76
Carbofuran
coses at Application
$4.55/lb>./
($/acre)
13.65
.'22.75
22.75
18.20
13.65
18.20
18.20
22.75
costc/
($/acre)
2.50
5.00
5.00
5.00
7.50
2.50
5.00
5.00
Economic
benefit
(S/acre)
736.11
906.09
1,035.79
391.84
269.19
990.96
699.23
683.01


Source
Ryder etal.(1969)




Burbutls & Uslevicz (1974)
Burbutis & Kelscy
Burbutls & Kelsey
Burbutis & Kelaey
Burbutla 4 Kelsey
Uofmaater (1971)
Kofmaster (1971)
(1971)
(1971)
(1971)
(1971)
•

      a/  SD • Stdc-dreused.
      b/  Shaerler (1975).
      c/  Slda-dreaaed application*  - $2.50/acre/appllcation

-------
References

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Burbutis,  P.  P., C.  P.  Davis,  L.  P.  Kelsey,  and C.  E. Martin, "Control of
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Burbutis,  P.  P., and L.  P. Kelsey,  "Summary of  Tests at Bridgeville, Delaware,
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-------
 Chapman, K., "Large Plot Potato Trials, Maine, 1970," FMC Corporation, Middle-
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 Craven, B. R.,  and C. D. Steelman, "Studies on a Biological and a Chemical
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 Day, A., "Initial Effectiveness and Residual Toxicity of Several Insecticides
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 Dickson,  D. W.,  G.  C. Smart,  Jr., and L.  C. Cobb, "Peanut," Fungicide and
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 Dominick,  C.  B.,  "Evaluation  of Experimental Insecticides for Control of  Horn-
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 Fuchs,  T. W., J. A. Harding,  and T.  Dupnik,  "Sugarcane Borer Control on Sugar-
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Gifford, J. R., B. F. Oliver,  and G.  B.  Trahan,  "Control of  Larvae of the Rice
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Kuhlman, D. E.,  "Insect  Problems  and  Control  in No-Till Corn," 26th Illinois
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       «U.S. GOVERNMENT PRINTING OFFICE: 1976 210-810/156
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