United Stataj Office of Pesticides and Toxic Substances
Environmental Protection Office of Pesticide Programs (TS-766CI
Agency Washington. DC 2O460
vvEPA Pesticide
Fact Sheet
Name of Chemical: DJFLUBENZURON
Reason for Issuance: UPDATE
Date Issued: MARCH 11, 1937
Fact Sheet Number: 68<1
1. Description of Chemical
Generic name: N-[t(4-chlorophenyl)amino]carbonyl]-
2,6-difluorobenzamide
Common Name: diflubenzuron
Trade Names: Dimilin, Micromite, Vigilante
EPA Shaughnessy Code: 108201
Chemical Abstracts Service (CAS) Number: 35367-38-5
Year of Initial Registration: 1976
Pesticide Type: Benzamide chitin inhibitor
U.S. and Foreign Producers: Duphar B.V., Amsterdam, Holland
2. Use Patterns and Formulations
Application sites:
Agricultural crops:
cotton (boll weevils ; cotton leaf perforator)
soybeans (velvetbean caterpillar; green cloverworm)
Forests:
woodland trees and shrubs including Christmas trees
(gypsy moth; Douglas fir tussock mouth; forest
tent caterpillar; Nantucket pine tipmoth)
Ornamentals:
commercial nursery (gypsy moth)
Pasture:
flood irrigated areas in California only
(floodwater mosquitoes)
Greenhouse:
mushrooms (mushroom flies)
Type of Formulation: 25% Wettable Powder
3. Science Findings
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Summary Science Statement :
Djf]ubenzuron has demonstrated a low acute toxcity to
mammals through the oral, dermal, and inhalation routes. The
Agency has determined that diflubenzuron is not an oncogen,
a teratogen, a mutagen, or a neurotoxin.
The allowable daily intake (ADI) of diflubenzuron is
0.02 mg/kg/day. This is based on a no observable effect level
of 40 ppm (2 mg/kg/day) on changes in the blood of rats. The
tolerances established add up to 2.9% of the ADI.
Diflubenzuron disrupts the normal molting of insects and
other invertebrates by interfering with the deposition of
chitin preventing proper formation of the new exoskeleton
and shedding of the old one.
Chemical Characteristics :
Physical state: solid
Color: white
Odor: none
Boiling point: N/A
Melting point: 210 to 230 °C
Flammability: N/A
Solubility in water: at 20 to 25 °C 0.2 mg/i.
There are no unusual handling
characteristics.
Toxicology Characteristics :
Acute Oral, Rat: > 4640 mg/kg
Toxicity Category IV
Acute Dermal, Rabbit: > 4000 mg/kg
Toxicity Category III
Acute Inhalation, Rat: > 2.88 mg/L
Toxicity Category III
The Major Routes of Exposure in Order of Toxicological Significance:
Chronic Toxicology Results :
Rat Chronic Feeding: NOEL = 40 ppm (2 mg/kg) bwt/day for
met— and suiphemoglobin formation.
Rat Oncogenicity: Not oncogenic to male and female rats
under the conditions of the study; highest dose
tested 10,000 ppm (500 mg/kg bwt/day).
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Mouse Oncogenicity: Not oncogenic to male and female mice
under the conditions of the study; highest dose tested
was 10,000 ppm (500 mg/kg bwt/day).
Rat Teratology: Not fetotoxic or teratogenic to rats at
levels up to 4 mg/kg bwt/day, the highest. dose tested.
Rabbit Teratology: Not fetotoxic or teratogenic to rabbits
at levels up to 4 mg/kg bwt/day, the highest dose tested.
Three—Generation Rat Study: No adverse effects on reproduc-
tive performance at 160 ppm (8 mg/kg/day), the highest
dose tested.
Gene Mutation: At rates up to 1000 ug/plate there was no
evidence of changes in spontaneous revertant frequency
or any mutagenic effect.
Sheep 13—Week Feeding Study: No treatment—related effects
were observed on food consumption, body weight gain,
hematological parameters or urinalysis at 10,000 mg
diflubenzuron/kg in the diet.
Dog 13—Week Feeding Study: No histopathological changes
were reported attributable to feeding diflubenzuron
at rates up to 160 ppm in the diet.
Physiological and Biochemical Behavioral Characteristics :
A. Translocation :
The available plant metabolism data show that diflu—
benzuron, when foliarly applied in doses approximating those
registered or proposed for use on citrus, soybeans, and cotton
will undergo very little, if any, translocation from treated
areas. Additional metabolism data are needed to support the
established mushroom tolerance.
B. Mechanism of Pesticidal Action :
Diflubenzuron interferes with arthropod chitin formation,
thus disrupting the development of a new cuticle in preparation
for molting of the exoskeleton. Exposed insect larvae continue
to feed and otherwise develop normally until growth makes it
necessary to shed the old cuticle. The old exoskeleton is shed,
after which the growing insect swells by taking air into the
respiratory system, expanding the body, and stretching the formed,
elastic new cuticle before it hardens. Insects exposed to
diflubenzuron die while trying to molt since the new cuticle is
not properly - formed.
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C. Metabolism and Persistence in Plants and Animals :
The metabolism of diflubenzurori in plants has been
adequately described for higher plants following foliar
treatments. No residues were found in the milk, fat, kidney,
liver, or meat of cattle fed at 25ppm of the total diet.
In an exaggerated rate study, residues were found in milk,
liver, and kidneys from cattle fed diflubenzuron at 2SOppm
of the diet. Metabolites found included p—chlorophenylurea ,
p—chloroaniline, and 4—chioroacetanilide.
Environmental Characteristics :
Due to rapid binding with soil particles and organic
matter and breakdown by soil biota, ground water contamination
problems are unlikely. In aerobic soil, radio].abeled
dif].ubenzuron with a particle size of approxiinatly 2 microns
had a half—life of less than 2 weeks at 20 DC.
Ecological Characteristics :
Avian Oral Acute Toxicity:
> 5000 mg/kg — Bobwhite quail and mallard duck
Avian Dietary Toxicity:
) 20,000 ppm — Bobwhite quail and mallard duck
Fish Acute Toxicity:
> 25 ppm — Yellow perch
> 50 ppm — Brook trout
> 100 ppm — Rainbow trout, channel catfish and
bluegill sunfish
> 500 ppm — Fathead minnow
Freshwater Invertebrate Acute Toxicity:
560 ppb — Chironomus sp
16 ppb - Daphnia magna
30 ppb — Gammarus pseudolimnaeus
Estuarine/Marine Organism Acute Toxicity:
2.06 ppb - Mysid shrimp
0.64 ppm — Grass shrimp
> 130.00 ppm - Oyster larvae
255.00 ppm - Mumrnichug
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> 1000.00 ppm — Uca pugilator,
Carcinus maenus, Anodonta sp.
and Mercenaria mercenaria
Honeybee Acute Toxicity:
> 114.8 micrograms per bee. (rel. non—toxic)
Based on these studies, diflubenzuron is of low toxicity
to birds, finfish, and honeybees. However, based on current
studies, it is extremely toxic to aquatic invertebrates.
Therefore, additional studies are required to complete a
hazard assessment for aquatic invertebrates.
Tolerance Assessment :
Sufficient data are available to determine that the estab-
lished tolerances for residues of diflubenzuron (DFB) in or on
the following commodities are adequate: cottonseed, pasture
grass, soybeans, soybean hulls, soybean soapstock, milk, eggs,
and the meat, fat, and meat byproducts of cattle, goats, hogs,
horses, sheep, and poultry. However, additional data are
required for complete elucidation of the nature of the residue
in mushrooms to support the established tolerance in mushrooms.
The Theoretical Maximum Residue Concentrate (TMRC) for
diflubenzuron is 0.0352 mg/day based on a 1.5 kg diet. The ADI
is 0.011 mg/kg/day. based on a 1.5 kg/day diet. The tolerances
established add up to 2.9% of the ADI.
4. Summary of Regulatory Position and Rationale
The Agency has determined that it should continue to allow
the registration of diflubenzuron. However, because of gaps in
the data base, additional data are required as specified in the
registration standard whitch was published on September 10, 1985
and is available from the National Technical Information Service
in Springfield Virginia. Additional tolerances and label changes
will be considered as applications are submitted.
Because of toxicity to crab, shrimp, and other aquatic inver-
tebrate animals, diflubenzuron is classified as a restricted
pesticide for use on forests and field crops. Cautionary state-
ments are required on the label warning of hazards to aquatic
invertebrates.
The only geographic limitation for use of products contain-
ing diflubenzuron is for control of mosquitoes in temporarily
flooded areas of pastures in Central California. The primary
concern with these mosquitoes breeding in wastewater from irri-
gation projects is their potential for carrying diseases affect-
ing humans.
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5. Summary of Major Data Gaps
Toxicology :
None.
Environmental Safety: (Data due in 1987)
Avian Reproduction Studies
Freshwater Invertebrate Acute LCS0
Estuarine/Marine Organism Acute EC 50
Freshwater Invertebrate Life—Cycle
Estuarine Invertebrate Life—Cycle.
Residue Chemistry : (Data due in 1987)
Metabolism in mushrooms
Metabolism in cattle, poultry, and swine
6. Contact person at EPA :
Arturo E. Castillo, (PM—17)
Insect icide—Rodenticide Branch (TS—767)
401 M Street, SW
Washington, DC 20460
Telephone: (703) 557—2690
DISCLAIMER: The information presented in this Pesticide Fact
Sheet is for Informational purposes only and may not be used
to fulfill data requirements for pesticide registration and
reregistration.
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