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Volume Three
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&EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternatives
10 Case Studies — Volume 3
Foreword
This is the third EPA publication of case studies describing alternatives to the use of the
pesticide, methyl bromide. As with the first two volumes of case studies, the alternatives listed
here were chosen because of their level of development and availability, and should not be
construed to be the only alternatives to methyl bromide.
The alternatives described in this document are in response to the fact that methyl
bromide is a significant stratospheric ozone depleting chemical, and therefore contributes to
environmental degradation. Because of this, methyl bromide will soon be phased out both in the
United States and internationally. This pesticide has been used since the early 1960's primarily
as a pre-plant soil fumigant (often for high-value crops such as strawberries and tomatoes) as
well as a post-harvest (commodity) and structural treatment.
In it's current use pattern, methyl bromide is an important production component for many
in the agricultural community. Since effective pest management is essential to field agricultural
production, commodity storage, natural resource protection, and public health, alternatives to
methyl bromide which are efficacious, cost effective, and environmentally sound must be
available before methyl bromide is phased out. To assist in this effort, EPA has published this
document, as well as the first two sets of case studies, and has committed to publish additional
case studies.
The alternative materials and methods discussed in these case studies are not intended
to be complete replacements for methyl bromide, but tools which are efficacious against the
pests that are currently controlled by this pesticide. Many of the alternatives described herein are
part of an overall integrated pest management system, and must be combined with other pest
control tools to achieve an economically viable level of management.
All efforts were made to insure that the information in this document is correct and
factual. Comments on this document, as well as your experiences with these and other
alternatives to methyl bromide, are welcome via the contacts listed below.
For additional information, please contact:
Ozone Protection Hotline toll-free (800) 296-1996
Bill Thomas, Methyl Bromide Program
U.S. EPA - 6205J, 401 M Street S.W., Washington, DC 20460
TEL: 202-233-9179, FAX: 202-233-9637
E-MAIL: thomas.bill@epamail.epa.gbv
EPA Methyl Bromide Phase-Out Web Site:
http://www.epa.gov/ozone/mbr/mbrqa.html
This publication discusses specific proprietary products and pest control methods. Some of these alternatives are now commercially available
while others are in an advanced stage of development. In all cases, the information presented does not constitute a recommendation or an
endorsement of these products or methods by the Environmental Protection Agency (EPA) or other involved parlies. Nerlher should the
absence of an Hem or pesl control method necessarily be interpreted as EPA disapproval.
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-------
vvEPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternatives
10 Case Studies --- Voiume 3
Table of Contents
Soil Use:
Compost
Flooding
Grafting
Hydroponics
Metam Sodium
Steam
Telone/Chloropicrin/Tillam
Commodity/Structural Use:
Carbonyl Sulfide
Controlled Atmospheres
Phosphine/Carbon Dioxide
Page numbers have been purposely excluded from this document so individual case studies can be copied and distributed.
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&EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(62O5-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Disease Suppressive Compost as an Alternative to Methyl Bromide
Disease suppressive compost can be an effective and viable alternative to methyl bromide
use in some nursery production systems, and when used in combination with integrated pest
management practices. Disease suppressive compost also has potential for replacing methyl
bromide use in the production of fruit and vegetable crops. Diseases that have been shown to be
effectively suppressed by compost use include those caused by Fusarium, Phytophthora, Pythium,
and Rhizoctonia solani. In addition to suppressing the spread of disease at nurseries and in field
crops, disease suppressive compost mixes provide nutrients and organic matter, thereby
eliminating or reducing the need for fertilizer additions or use of expensive peat mixes. Compost
can also create soil which allows for better water transmission, thereby decreasing the potential
for disease development. Use of compost is particularly valuable as a way to utilize what would
often be considered waste products: tree barks, municipal solid waste components, green wastes,
peanut hulls, and sewage sludge. While compost generally does not contain toxic or potentially
harmful substances, it is critical that compost made from sewage sludge and related municipal or
animal waste must undergo testing on a regular basis, and its use carefully monitored to ensure
that it-will not pose any risks to human health or environmental quality. However, in general,
disease suppressive compost does not require any special care during use and handling, and
therefore eliminates the need for the re-entiy period necessary when using methyl bromide.
While the use of disease suppressive
compost as a pest control tool is
theoretically sound, the science is still new
and not clearly understood. It should be
noted that most greenhouse operations do *
not have the equipment necessary to fully
adopt this technology. In addition, large-
scale field operations may not give
consistent results, as a number of factors
(including the amount of compost necessary
to suppress disease) need additional
research.
-------
mixes have virtually eradicated the use of expensive fungicide drenches and fumigants like methyl
bromide in the greenhouses and nurseries which are using these materials. Research is currently
being conducted to determine the specific interactions that make compost effective and to
determine its usefulness in field applications.
Although there are currently no standards regulating the manufacture of disease
suppressive compost, the process by which it is made and the inoculations some mixes receive
have been shown to be critical to their effectiveness against certain pathogens. For disease
suppressive composts to be marketed as natural pesticides, the U.S. Environmental Protection
Agency is requiring that they be registered and undergo health and safety testing (Segall 1995).
In addition, compost sources tend to be extemely variable with regard to beneficial microorganism
abundance, pathogen presence, and salinity.
Development of Disease Suppressive Compost
There are three main phases in the production of compost. The first phase occurs during
the first few days when temperatures rise and sugars and other easily biodegradable substances are
consumed. Over the next several weeks, in the second phase, the temperature range increases and
cellulose and other less biodegradable substances, pathogens, and some biocontrol agents are
destroyed. In the third phase, temperatures and decomposition rates decline as the supply of
readily biodegradable substances becomes limited. The drop in temperature allows for
microorganisms (e.g. Bacillus, Enterobacter, Flavobacterium balustinum, Pseudomonas, and
Streptomyces) to recolonize the compost's interior layers, thereby creating the natural
suppressiveness.
There are two primary mechanisms by which the colonies of biocontrol organisms in
compost combat disease: general suppression and specific suppression. General suppression
occurs when a high-microbial activity environment is created in which the germination of
pathogen propagules is inhibited. Specific suppression involves the action of a specific microbial
agent in suppressing a specific pathogen. This can be achieved by inoculating the compost with
the desired microbial agent (Hoitink 1993).
To ensure that compost will provide the required suppressive qualities, it has been
determined that the composting process must be carefully monitored (Hoitink 1991 and 1993,
Hoitink and Grebus 1994). Heat levels and anaerobic conditions must be maintained throughout
the composting cycle and the compost should be allowed to mature properly before use. Studies
have shown that immature compost is generally not as effective as mature compost at suppressing
disease (Quarles and Grossman 1995). Assays currently exist that allow the compost to be
monitored and evaluated for its disease suppressive capabilities. In addition, some states, most
notably Georgia are taking steps to regulate the compost industry by creating standards that all
compost manufacturers must meet in order to ensure the quality and performance of their
compost.
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Research Findings
The discovery that compost can be naturally disease suppressive was made when some
nurseries began using composted wood wastes in an effort to reduce their use of expensive and
increasingly scarce peat. As a result, plants grown in the composted mixes showed more vigorous
growth and Phytophthora appeared to be suppressed (Hoitink and Grebus 1994). These findings
triggered formal research that further showed the effectiveness of disease suppressive compost as
a viable replacement for methyl bromide and other fungicides. Composted mixes that have been
shown to have disease suppressive qualities include those based on tree barks, green wastes, and
sewage sludge (Quarles and Grossman 1995).
Because disease suppressive compost growing media has been found to be a viable
alternative to chemical fungicides (methyl bromide) at nurseries, extensive research is now being
conducted to determine whether or not disease suppressive composts can also replace fungicide
use in field fruit and vegetable crops. Preliminary research is already showing that this is a
reasonable possibility. Some of the findings in this area are summarized below:
• Dr. Sally Miller of Ohio State University has observed that use of composted yard waste
can cause pepper plants to grow more vigorously. She believes that use of compost in
combination with hilling will suppress Phytophthora in peppers (Logsdon 1993).
• Nancy Roe of the University of Florida has experimented with various composts and
found that peppers grown using a municipal solid waste or wood chip compost as a mulch
have higher survival rates than those grown on white polyethylene (Logsdon 1993). This
finding is supported by an additional study by Kim et al. that showed that chitosan and
crab shell waste can be effective at controlling Phytophthora stem rot in bell pepper (Kim
etal.1996).
• Results from a study in a San Joaquin Valley peach orchard showed that incidence of
brown rot was notably higher in peach tree plots unamended or grown conventionally than
in plots that were amended with urban yard waste compost (Anonymous 1995).
• Vegetable seedlings grown in composted media were found to develop faster and become
stronger more productive plants than plants grown with conventional methods in a study
performed by Dr. Herbert Biyan at the University of Florida (Logsdon 1993).
Cost of Disease Suppressive Compost
Costs associated with growing plants in nurseries are attributable to the purchase of
growing media, fertilizer, wetting agents, fungicides and herbicides, including methyl bromide,
and to labor. Using disease suppressive compost generally reduces fertilizer inputs and often
results in a reduction in labor costs due to the elimination of labor needed to utilize fumigants and
the subsequent elimination of a re-entry period in which workers must wait to have access to a
fumigated field or area. Therefore, the primary difference in cost between use of disease
-------
suppressive composts versus other growing media is the cost of the material itself. Fumigated
container media range in cost from $18 to $60 per cubic yard plus the cost of methyl bromide
which is $1.64 per cubic yard (Asgrow 1995, Great Lakes 1995). A cubic yard of disease
suppressive compost growing media costs approximately $38 per cubic yard. Cost information is
summarized in Table 1. Manufacturers of disease suppressive compost are attempting to ensure
that their products are approximately equal or less in cost to other growing media that require
fumigation (Southern Importers Inc 1996).
Table 1. Comparison of Costs Among Container Media Used at Nurseries
....
Typical price per cu.yd.
Plus:
Fertilizer
Methyl bromide
Lime
Shrinkage
Actual cost per cu. yd.
Composted Mix :
$30
$6
$0
$0
$2 (6%)
$38.00
Uncompostcd Bark
Mix
$12
$10
$1.64
$1
$4 (30%)
$28.64
TJneompmsted Peat Mix
$56
$6
$1.64
$0
$14 (25%)
$77.64
Sources: BioComp 1996, Asgrow 1995, Great Lakes 1995.
Costs associated with using disease suppressive composts in field applications include the
cost of the compost plus costs resulting from implementation of integrated pest management and
other low-input organic practices. Studies by Gliessman et al. (1990, 1994,1996) compare
conventional and organic methods to grow strawberries. The conventional method includes using
methyl bromide to fumigate the soil. The organic method includes using compost in combination
with integrated pest management approaches to take the place of the methyl bromide. Results
from this study to date show that organic yields relative to conventional yields of strawberries
were 39 percent lower in the first year, 30 percent in the second year, and 28 percent in the third
year (Gliessman et al. 1996).
-------
References
Anonymous. Urban yard waste benefits orchard. California Agriculture 1995, 49(5), 4.
Asgrow Agricultural Supply, Collier County, FL, personal communication, 1995.
BioComp, Inc., Edenton, NC, unpublished materials, 1996.
Gliessman, S.R.; Swezey, S.L.; Allison, J.; Chochran, 1; Parrel, J.; Kluson, R.; Rosado-May, F.;
Werner, M. Strawberry production systems during conversion to organic management.
California Agriculture 1990, 44(4), 4-7.
Gliessman, S.R.; Werner, M.R.; Swezey, S.L.; Caswell, E.; Cochran, J.; Rosado-May, F.
Conversion to organic strawberry management changes ecological processes. California
Agriculture 1996, 50(1), 24-31.
Gliessman, S.R.; Werner, M.R.; Swezey, S.L.; Caswell, E.; Cochran, J.; Rosado-May, F.
Conversion to an organic strawberry production system in coastal central California: a
comparative study"; study by the Agroecology Program, University of California: Santa Cruz,
CA, 1994.
Great Lakes Chemical Corporation. Product specimen label. Great Lakes Chemical Corporation,
West Lafayette, IN., 1995.
Hoitink, H. A. J. Compost can suppress soil-borne disease in container media. American
Nurseryman 1993, pp 91-94.
Hoitink, H. A.J.; Grebus, M.E. In Composting Source Separated Organics; Plant Disease
Control; J.G. Press: Emmaus, PA., 1994; pp 204-209.
Hoitink, H.AJ. Status of compost-amended potting mixes naturally suppressive to soilborae
diseases of floricultural crops. Plant Disease 1991, 75(9), 869-873.
Kim, K.D.; Nemec, S.; Mussen, G. "Effects of composts and soil amendments on soil microflora
and Phytophthora stem rot of pepper"; Indian River Research and Education Center: Fort
Pierce, FL, 1996.
Logsdon, G. Using compost for plant disease control. BioCycle 1993, pp 33-36.
Quarles, W.; Grossman, J. Alternatives to methyl bromide in nurseries-disease suppressive
media. The IPMPractitioner 1995, 17 (8), 25-37.
Segall, L. Marketing compost as a pest control product. BioCycle 1995, pp 65-67.
Southern Importers, Inc., Greensboro, NC, unpublished results, 1996.
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vvEPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(620S-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Flooding As An Alternative to Pre-plant Methyl Bromide Fumigation
Flooding can be a viable alternative to methyl bromide as a preplant soil fumigation in flat,
low-lying areas rich in mineral soils where there are seasonally high water tables (at least 4-6 feet
from the surface) and abundant water supplies (e.g., Florida and in some parts of California).
Approximately 66 percent of Florida soils have high water tables, of which an estimated 30 to 50
percent would be amenable to water table/flooding management practices
(20 percent of all the land surface in Florida) (Buol 1973). Areas in Florida where flooding could
be used as an alternative to methyl bromide include the Florida Peninsula (e.g., potatoes,
tomatoes, bell peppers, and eggplants in Hastings and Bradenton, Florida) and east coast areas
south of Vero Beach. Areas not suitable for flooding include northwest Florida and the Florida
panhandle (Allen and Sotomayor 1996).
Flooding is believed to be as
effective as methyl bromide for the
control of some soil-borne pests and
pathogens, particularly nematodes
and non-aquatic weeds. Flooding
also leaves no toxic residues. With
the proper soil and water-availability
conditions, flooding can be used to
create anaerobic (little to no
available oxygen) soil conditions
which are followed by drainage to
provide an aerated (available
oxygen) root environment. This
sufficiently will alter the soil environment in way that results in conditions which are unfavorable
to pests. It will also conserve carbon in organic matter by slowing decomposition, increases the
availability of certain micronutrients (e.g., magnesium and iodine) to crop plants, and changes the
soil microflora to favor biological pest control (Snyder 1987). Flooding could be used in
conjunction with other control practices, including organic soil amendments and soil solarization.
As an added benefit, instead of leaving flooded fields fallow, it may be possible to grow cash
crops (such as rice) on flooded fields (Allen and Sotomayor 1996).
Benefits of Flooding
Highly effective against soil-borne pests and
pathogens
Eliminates the need for soilfumigants
Conserves soil carbon
Increases levels of mineral nutrients in soils
Promotes biological control
Leaves no toxic residues
Highly efficient and cost-effective pest control method
Can be combined with other pest management practices
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In general, the flooding of soils significantly decreases soil oxygen supplies, causing an
unfavorable environment for most pests, pathogens, and weeds (Maas 1987). Alternating
anaerobic and aerobic conditions through periodic flooding, can cause a decrease in nematode
populations (Dunn and Noting 1995, Wallace 1956), while longer periods of flooding have been
found to be more effective in the control of weeds (Reddy and Patrick 1975 and 1976). Stover
(1979) achieved nematode control by flooding and noted that for Florida organic soils, two weeks
of flooding followed by two weeks of drainage, drying, and disking was as effective in controlling
nematodes as continuous flooding for 9 months.
Flooding has been recognized as a viable means for controlling plant parasitic nematodes
for more than 70 years. As early as 1907, Ernst Bessey (1911) observed control of root-knot
nematodes on vegetables in flooded fields on islands which once existed in Lake Okeechobee
(Synder 1987). More recent research indicates that proper water management and flooding
practices can reduce nematodes and other pests in a variety of crops, including rice, bananas,
corn, soybean, milo, sugarcane, tomatoes, bell papers, and eggplant (Hollis and Rodriguez-
Kabana. 1966, Rodriguez-Kabana and Hollis 1965, Muller et al. 1992, Muller .and Van Aartrijk
1992). For example, flooding has been shown to be effective in the control of Panama disease
and nematodes in bananas (Stover 1962, Maas 1969).
Many vegetable crops in Florida (e.g., eggplants, tomatoes) are grown in high water table
soils that must be drained and managed to prevent anoxic rooting conditions. These high-value
crops are produced in Florida during the fall, winter, and spring seasons. In the summer,
however, fields are either fallowed or managed at a low scale because of seasonally heavy rainfall.
This system of cropping followed by fallow may provide an opportunity for the development of
specific management technologies during the summer off-season, including prolonged soil
flooding (possibly with a water tolerant crop such as rice).
Current Research
Researchers at the USDA, Agricultural Research Service (ARS) in Gainesville, Florida are
conducting experiments to assess the efficacy of soil water-logging for the control of root-knot
nematodes (Meloidogyne arenaria) and purple nutsedge (Cyperus rotundus L.) populations.
Specific issues being investigated regarding the effectiveness of flooding for the control of
nutsedge include: 1) how water-logging affects sprouting of the nutsedge tuber, and 2) once the
nutsedge is established, what becomes of it after flooding. Researchers are working to determine
if tubers remain in a dormant, but viable stage during flooding (after which they can proliferate
when appropriate conditions occur) or if the tubers die because of low soil redox potentials and
unsuitable soil conditions resulting from flooding. Recent results indicate that purple nutsedge is
suppressed in flooded rice fields. Additional research will be necessary to determine if nutsedge
will still be suppressed during the subsequent cropping periods.
Because nematodes are aerobic organisms, they are controlled by asphyxiation in flooded
fields, and by a build-up of H2S and other chemicals produced under anaerobic soil conditions that
result from microbial fermentation reactions (Maas 1987, Hollis and Rodriguez-Kabana 1966).
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Other changes in soil ecology can occur that limit root-knot nematode reproduction or stimulate
predation by beneficial soil organisms (Sotomayor and Allen 1996, Allen and Sotomayor 1996),
however, additional research is needed to determine the exact response of nematodes to long-term
flooding. Since high temperatures during flooding are more effective in conn-oiling root-knot
nematodes than lower temperatures (Stover 1979), combinations of treatments (alternate
flooding, solarization, and high applications of fresh or composted organic matter) may prove to
be more effective than long-term flooding alone in the control of nematodes.
Important Considerations for Flooding
When using flooding as a pest control measure, some basic processes should be
considered (Snyder 1987):
• Time or Season of Flooding: In general, flooding is more effective at higher ambient air
and soil temperatures. This places seasonal and geographic constraints on flooding. For
example, flooding will require additional time to be effective at temperatures below 20 °C
(68 °F) - four to 6 weeks of flooding is effective in warm weather, while 6 to 10 weeks
may be required to achieve effective control in cooler seasons.
• Alternate Flooding with Disking: Because some pathogens can survive flooding by
persisting on plant debris in the soil-water interface or on the soil surface during draining;
pests may be more easily eliminated if they are disked deep into soils before fields are
reflooded.
• Water Depth: Most fallow flooding involves flooding to a depth of 10 cm (4 inches) to
40 cm (16 inches).
• Rice Culture: Because rice can be grown on fields flooded for pest and pathogen control,
flooded fields can both generate revenue and provide opportunities for more efficient
land/water use.
Costs
Flooding can be a viable and cost-effective alternative to methyl bromide in some
situations. Flooding can be many times less expensive than methyl bromide fumigation, however,
capital costs which may be necessary to achieve good pest control from flooding include those
associated construction of retention/detention ponds, digging perimeter ditches and leveling fields,
installing subsurface drains for reversible-flow drainage/irrigation/flooding water control,
installing vertical barriers of low-density-polyethylene around the water management unit
perimeters (i.e., land fill liners 3 to 5 feet below the soil surface to contain the flood waters), and
installing power, pumps, and a pipe system (Allen and Sotomayor 1996). In considering the costs
associated with this technique, it is also important to consider that water costs vary considerably
from region to region. Regions with readily available water supplies will have lower costs, than
areas where water must be pumped from wells or transported long distances.
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Table 1. Cost of Flooding vs. Methyl Bromide as a Preplant Fumigant.
_ % £esis($acrej \
••iff
Capital
Labor/Operating
Materials
(Water/Chemical)
TOTAL
Treatment #1
HootlSng
60
4-39
0-41
64-140
Treatment $2
Met! vl Bromide
54
436
1,936
2,426
Sources: Allen and Sotomayor 1996, Williams ef al. l992,Cookeetal. 1996, Gregory and Winn 1996,Giesler
and Salassi 1995, Lagunas-Solar 1996, Onitsuka Greenhouse 1996.
References
Allen, L.H.; Sotomayor, D., United States Department of Agriculture, Agricultural Research
Service, South Atlantic Area Crop Genetic and Environmental Research Unit, Agronomy
Department, Agronomy Physiology Laboratory, Gainesville, FL, personal communication, 1996.
Bessey, E.A. Root-knot and its Control; United States Department of Agriculture; Bureau of
Plant Industry Bulletin No. 217. U.S. Government Printing Office: Washington, D.C., 1911.
Buol, S.W. Soils of Florida: Soils of the Southern States and Puerto Rico; South Cooperative
Series Bulletin Number 174; joint regional publication of the Agricultural Experimentation
Stations of the Southern States and Puerto Rico Land Grant Universities with Cooperative
Assistance by the Soil Conservation Service of the United States Department of Agriculture;
1973, p 105 and map.
Cooke, F.T.; Caillavet, D.F.; Walker, J.C.. "Rice Water Use and Costs in the Mississippi Delta";
Bulletin #1039; Mississippi State University, Division of Agriculture, Forestry, and Veterinary
Medicine, Delta Research and Extension Center: Stoneville, MS, 1996.
Dunn, R.A.; Noling, J.W. 1995 Florida Nematode Control Guide. Institute of Food and
Agricultural Sciences and Florida Cooperative Extension Service. IF AS Publications. University
of Florida: Gainesville, FL, 1995; SP-54.
Giesler, G.G., Salassi, M.E. "Projected Costs and Returns - Rice, Louisiana, 1995"; A.E.A.
Information Series Number 131; Louisiana State University Agricultural Center, Louisiana
Agricultural Experiment Station, Department of Agricultural Economics and Agribusiness: Baton
Rouge, LA, 1995.
Gregory, E.; Winn, J. "1996 Rice Production Guidelines"; Texas A&M University System D-
1253. Texas Agricultural Extension Service: College Station, TX, 1996.
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Hollis, J.P.; Rodriguez-Kabana, R. Rapid kill of nematodes in flooded soil. Phytopathology
1966, 56, pp 1015-1019.
Lagunas-Solar, M., University of California, Davis, CA, unpublished results, 1996.
Maas, P.W.T. IK Nematodes of Tropical Crops; Peachey, J.E., Ed.; Two Important Cases of
Nematode Infestation in Surinam; Technical Communication 40; Commonw Bur Helminth
1969, pp 149-154.
Maas, P.W.T. In Principles and Practice of Nematode Control in Crops; Brown, R.H; Kerry,
B.R., Eds.; Physical Methods and Quarantine; Academic Press: Orlando, FL, 1987.
Muller, P.J.; Van Aartrijk, J. "Flooding Reduces the Soil Populations of the Stem Nematode
Ditylenchus dipsaci in Sandy Soils"; Bulb Research Center: Lisse, Netherlands, 1992.
Muller, P.J.; Van Beers, T.H.; DeRooy, M. "Flooding, a Non-chemical Soil Treatment to Control
the Root-lesion Nematode Pratylenchuspenetrans"; Bulb Research Center: Lisse, Netherlands
1992.
Onitsuka Greenhouse, Monterey, CA, unpublished results, 1996.
Reddy, K.R.; Patrick, W.H. Jr. Effect of alternation aerobic and anaerobic conditions on redox
potential, organic matter decomposition and nitrogen loss in a flooded soil. Soil Biol Biochem
1975, Vol. 7,87-94.
Reddy, K.R.; Patrick, W.H. Jr. Effect of frequent changes in aerobic and anaerobic conditions on
redox potential and nitrogen loss in a flooded soil. Soil Biol. Biochem. 1976, Vol. 8,491-495.
Rodriguez-Kabana, R.; Hollis, J.P. Biological control of nematodes in rice fields: role of
hydrogen sulfide. Science 1965, Vol. 148, 524-526.
Snyder, G.H. Agricultural Flooding of Organic Soils; Technical Bulletin 870; University of
Florida, Agricultural Experiment Station, Institute of Food and Agricultural Sciences- Gainesville
FL, 1987.
Sotomayor, D.; Allen, L.H., Jr. Presented at the 1996 Annual International Research Conference
on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper
97.
Stover, R.H. "Fusarial Wilt (Panama Disease) of Bananas and other Musa Species";
Commonwealth Mycological Institute Phytopathology Paper: Kew, Surrey, 1962, Vol 4, pp 1-
117.
Stover, R.H. In Soil Disinfestation; Mulder, D.J., Ed.; Flooding of Soil for Disease Control;
Elsevier, Amsterdam, 1979, pp 19-28.
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Wallace, H.R. Soil aeration and the emergence of larvae from cysts of the beet eelworm,
Heteroderma schlachtii schmidt. Ann. Appl. Biol. 1956, 44, pp 57-66.
Williams, J.; Klonsky, K.; Livingston, P. "Sample Costs to Produce Rice in Sutler, Yuba, Placer,
and Sacramento Counties -1992"; U.C. Cooperative Extension: Davis, CA, 1992.
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&EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Plant Grafting as a Tool to Help Reduce the Need for Soil Fumigation with
Methyl Bromide
Expanding the use of resistant rootstocks, in combination with Integrated Pest
Management (IPM) practices, may help to reduce the need for soil fumigation with methyl
bromide for many crops. Grafting currently is used in commercial agricultural production to
achieve higher yielding field and greenhouse crops, repair damaged sections of a plant, increase
temperature or salinity tolerance, produce higher yielding varieties (including dwarf varieties), and
extend the duration of economical harvest time. Research is being conducted to identify disease
resistant germplasm for a variety of crops that currently receive methyl bromide treatments at
planting. It is believed that germplasm with resistant traits may be useful for grafting, as well as
the development of new cultivars. Specifically, with regard to reducing the need for soil
fumigation, the primary use of grafting will be to increase disease and nematode resistance
through the use of select rootstock with known resistance to soilborne pests.
s
s
Commercialization of cultivars with
resistance to diseases caused by nematodes
(e.g., Meloidogyne incognito) and fungi (e.g.,
Fusarium oxysporum) has been achieved by
screening various plant species to identify traits
of potentially resistant stocks that may be useful
for grafting, and through breeding programs. In
addition, field trials have been conducted to
assess whether identified germplasm increases
the ability of crops to withstand soil infestation
as well as whether the crop performance will be
commercially acceptable (i.e., yield,
compatibility, anchorage). Finally, commercialization has been advanced through cooperation
with nurseries and growers to determine the factors affecting commercial adoption of new
rootstocks. Current research efforts to develop additional resistant germplasm for use in grafting
for many of the crops currently treated with methyl bromide may lead to an increased ability to
minimize or prevent yield losses from soil pest pressure (Ledbetter 1996b, Ledbetter 1996a,
McKenry and Kretsch 1995, Lee 1994).
Benefits of Grafting
Increases disease and nematode resistance
Helps to increase yields, extend plant life,
and increase tolerance to temperature and
salinity
Is useful in both nursery and vegetable
applications
Can be used in conjunction with
Integrated Pest Management (IPM)
practices
-------
Grafting Techniques and Applications
Plant grafting is a propagation technique whereby two portions of plant which have similar
organic texture are joined in such a manner so as to continue their development as a single plant.
There are many methods of grafting plants, each involving the joining of the leaf-bearing part
(scion) of one plant with the rootstock of another. Grafting methods include such techniques as
apical-wedge grafting, whip-and-tongue grafting, splice grafting, flat grafting, saddle grafting, bud
grafting, hole insertion grafting, tongue approach grafting, and cleft grafting.
Grafting can be used for nursery, orchard, vineyard, and vegetable crops. The technique
can be particularly useful when there is a specific infestation problem that can be controlled with
available rootstocks, and in situations where disease problems arise after the orchard or vineyard
has already been established (McKenry 1995). In general, grafting is a technology that is readily
accessible to commercial suppliers of nursery and vegetable transplants, can be easily taught to
field technicians, and has a relatively low cost (Ledbetter 1996b, Rodriguez-Kabana 1995). To
enhance the use of grafting, commercial nurseries and growers will need continued access to new
resistant germplasm for field testing and commercial trials. In addition, mechanized grafting
approaches are being developed that rely on small portable machines that can perform the basic
cutting and joining procedures (Maynard 1996).
Currently, grafted plants are widely used in the United States for a variety of orchard and
vineyard crops (e.g., apples, grapes). Other countries also have experience with grafting
techniques. For example, in Japan, where land use is intensive and the availability of new
farmland is scarce, almost 95 percent of the watermelons (Citrullus lamanis), Oriental melons
(Cucumis melo var. makuwa), greenhouse cucumbers (Cucumis sativus), and solanaceous crops
are grafted before being transplanted to the field or greenhouse. In 1992, Japan cultivated almost
24,000 hectares of grafted watermelon seedlings in the field, and over 3,000 hectares in the
greenhouse. Most of the Oriental melons are grafted to squash rootstocks (Curcurbita spp.).
Watermelons and cucumbers are grafted with either gourd stocks (Lagernaria siceraria or C.
ficifolid) or mixed hybrids (e.g., C. maxima x C. moschata) (Lee 1994).
Research, Development, and Use of Resistant Rootstocks
The following research programs and commercial applications further demonstrate the
potential for commercial use of grafting as a means to reduce soil fumigation with methyl
bromide:
• At the U.S. Department of Agriculture/Agricultural Research Service (USDA/ARS)
Horticultural Crops Research Laboratory in Fresno, California, over 200 Primus
accessions were screened for resistance traits that showed promise for grafting.
Germplasm with resistance to root lesion nematodes (Pratylenchus vulnus) were
identified. To determine the acceptability of these rootstocks for commercial production,
several additional factors are being considered, including rootstock performance in the
nurseiy (e.g., vigor, tree anchorage, water use efficiency, and fruit production) and graft
-------
compatibility between the rootstock and the fruit bearing portion of the tree (Ledbetter
1996).
At the USDA/ARS in Davis, California, researchers are evaluating clones, selections, and
hybrids of various germplasm to identify superior resistance to Phytophthora spp. for
walnut. Scientists have determined that Chinese wingnut is highly resistant to
Phytophthora affecting walnuts in California. Additional research is being conducted to
evaluate graft compatibility and potential for hybridization of Chinese wingnut with
English walnut (Anonymous 1996).
At the USDA/ARS in Byron, Georgia, researchers are investigating rootstock resistance
to nematodes, including the ring and root-knot nematodes (Criconemella xenoplax and
Meloidogyne spp.), that frequently cause yield losses in peach orchards. To combat
diseases caused by these pests and to help reduce reliance on soil fumigation with methyl
bromide, researchers have identified a resistant rootstock that has performed well in
research and commercial field trials. Results indicate that the efficacy (in terms of tree
survival) of the Guardian rootstock on non-fumigated plots was comparable to results on
fumigated plots grown with the currently available rootstocks (e.g., Lovell and
Nemaguard) (Nyczepir 1995).
At the University of California, Davis, Dr. H. Andrew Walker and Dr. Jeffrey Granett
have evaluated grape rootstocks for resistance to phylloxera in research and commercial
settings. The insect pest Phylloxera vastratix feeds on grape roots, is quite prolific, and,
once established, can rapidly destroy a vineyard. The primary method of controlling this
insect in vineyards is through the use of resistant rootstocks (Bentley et al. 1996). As a
result, numerous rootstocks with proven resistance to phylloxera have been developed and
are widely used commercially (Walker and Butzke 1997, Wolpert et al. 1992, Walker
1997). According to Walker (1997), "almost all phylloxera resistant rootstocks are
composed of Vitis berlandieri, V. riparia and V. rupestris in various combinations. The
primary stocks in California are 5C, 110R, 3309C, 101-14Mgt, 1103P, and Freedom. In
addition, there are about ten more in general use. Rootstocks are selected based upon the
soils, climate and viticultural needs of a particular area."
Between 1982 and 1991, Dr. Alberto Gomez conducted several extensive grafting studies
on melon plants for the University of Valencia in Spain. The studies showed that, for
melon plants, grafting will produce a larger yield and enable plants to live longer. These
results were based upon a study prepared in 1982, using Roget melons grafted over
Curcurbita moschata, and on a study in 1984 that evaluated the performance of
Tetsukabuto grafted over Just melons. The yield increases achieved through grafting
ranged from 30 to 35 percent. Additionally, Dr. Gomez prepared a study to demonstrate
the benefits of grafting for watermelons. In 1982, he found that watermelons can be
grafted to have a superior resistance to Fusarium oxysporum niveau (Gomez 1992).
-------
Costs
Table 1 presents a cost comparison for grafting and standard methyl bromide fumigation
for vegetable, orchard, and vineyard crops. The grafting cost estimates are for activities
conducted by nurseries to prepare transplant stock for sale to growers. Typically, grafting is
performed by agricultural technicians that can process up to 1,000 grafts per day, therefore, the
relative impact on the price of the transplant to the grower is small (Ledbetter 1996b). The
majority of the costs to nurseries would be to conduct research and development activities after
the completion of university research trials. As shown in Table 1, the costs for grafting orchard
and vineyard rootstocks is less than the cost of fumigation with methyl bromide. This suggests
that grafting technology can be an economical technology to help reduce the need for methyl
bromide fumigation for these crops. Costs of grafting for vegetable crops is more expensive than
fumigation, however, vegetable grafting costs are expected to decrease as the mechanized grafting
technology becomes increasingly commercialized (Maynard 1996).
Table 1. Costs of Grafting and Fumigation for Vegetable and Nursery Crops
-CttJ)^
A .vXs .> s •. f. f s
Vegetables
Orchard
Vineyard
C^tof drafting
^$£ do&arsfojan$r ;
0.41 - 0.92
1.79 - 6.07
2.14-3.33
Sources: Gomez 1992, Ledbetter 1996b, Anonymous 1993, Anonymous 1992.
References
Anonymous. De-bugging the wine industry. Oregon Business 1992, 15(6), 12.
Anonymous. Methyl Bromide Alternatives; United States Department of Agriculture: Beltsville,
MD, Vol. 2, No. 4, 1996.
Anonymous. Sample Costs to Produce Organic Wine Grapes in the North Coast; United States
Department of Agriculture. Cooperative Extension Service. University of California: Davis, CA,
1993.
Bentley, W.J.; Smith, R.; Zalom, F.; Granett, J. Grape pest management guidelines. Internet:
http://www.ipm.ucdavis.edu, 1996.
Gomez, A. Ph.D. Thesis, Polytechnic University of Valencia, 1992.
-------
Ledbetter, C.; Peterson, S. Presented at the 1996 Annual International Conference on Methyl
Bromide Alternatives and Emissions Reductions, November 1996a, Orlando, FL; paper 31.
Ledbetter, C. United States Department of Agriculture, Agricultural Research Service, Fresno,
CA, personal communication, 1996b.
Lee, J. Cultivation of grafted vegetables I. Current status, grafting methods, and benefits
HortScience 1994, 29(4), 235-239.
Maynard, D., Gulf Coast Research and Education Center, University of Florida, Bradenton, FL,
personal communication, 1996.
McKenry, M.; Kretsch, J. Presented at the 1995 Annual International Conference on Methyl
Bromide Alternatives and Emissions Reductions, November 1995, San Diego, CA; paper 32.
Nyczepir, A.P.; Beckman, T.G.; Bertrand, P.P. Presented at the 1995 Annual International
Conference on Methyl Bromide Alternatives and Emissions Reductions, November 1995, San
Diego, CA; paper 105.
Rodriguez-Kabana, R., Department of Plant Pathology, Auburn University, Auburn, Alabama,
personal communication, 1995.
Walker, M. A; Butzke, C. "The grape rootstock breeding program at UC Davis." Internet:
http://wineserver.ucdavis.edu, 1997b.
Walker, M.A., Department of Viticulture and Enology, University of California, Davis, CA,
personal communication, 1997a.
Wolpert, J.A.; Walker, M.A.; Weber, E. Presented at the Rootstock Seminar - A Worldwide
Perspective, Reno, NV, June 1992; American Society for Enology and Viticulture.
-------
-------
EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Hydroponics and Soilless Cultures on Artificial Substrates as an
Alternative to Methyl Bromide Soil Fumigation
The use of hydroponic technology can be a viable alternative to methyl bromide soil
fumigation for greenhouse grown tomatoes, strawberries, cucumbers, peppers, eggplants, and
some flowers. Hydroponics allows crop culturing without soil fumigation by providing a system
where a majority of a plants nutrient needs are met by mixing water soluble nutrients with water,
and eliminating requirements for soil. Hydroponic systems that use only a nutrient solution, are
categorized as water culture or solution culture, however, if the nutrient solution is used in
combination with solid inert matter (i.e., Rockwool, turf stone, clay granules, sawdust, flexible
polyurethane foaming blocks, composed hardwood bark, or peat) to physically support root
systems and hold the hydroponic solution, it is categorized as a substrate culture or aggregate
culture.
s
Benefits of Hydroponics and Artificial Substrates
Eliminates the need for soil fumigants
Absence of competing weeds and soil-borne pests
Leaves no toxic residues
Conserves water
Control over nutrient and oxygen conditions
Highly efficient and cost-effective pest control method
Increases crop quality and yield
If the nutrient solution is
recycled, then the system is
considered to be a closed
hydroponic system. If the solution
is discharged after use, it is
considered to be an open
hydroponic system (Cropking
1996). Hydroponic systems are
usually utilized in indoor
greenhouses in non-tropical
climates, allowing the grower to
have control over climate
conditions. Specialized hydroponic farming systems in the U.S., Canada, and Europe have
demonstrated the technical and economic feasibility of eliminating methyl bromide use in
greenhouses and (under certian climate conditions) in open fields (Braun and Supkoff 1994,
Anonymous 1992b, Anonymous 1992c).
The advantages of hydroponic or soilless cultures on artificial substrates are: 1) an absence
of completing weeds and soilborne pests and toxic residues; 2) water conservation (with recycling
systems, hydroponic systems use one tenth the amount of water used in irrigated agriculture); and
3) conditions that can be altered quickly to suit specific crops, various growth stages, and
environmental/climate conditions. In addition to nutrients, hydroponics also brings fresh oxygen
-------
to the root zone and takes away "off-gases," the waste by-product of the root zone, making it a
highly efficient and cost-effective technology (Anonymous 1992a, Cropking 1996). Because
nutrients are readily available in hydroponic systems, plants have smaller, more efficient root
systems and can spend more energy growing the more valuable above ground stems, foliage, and
fruit. Furthermore, growers can space plants closer together, thus producing more agricultural
products per a given area, while avoiding competition for scarce nutrients in the rootzone (Hydro
Aquatic Technologies 1995, Resh 1993).
All hydroponic systems provide water, nutrients, and oxygen to plants; however,
hydroponic systems differ significantly. Several of the many types of hydroponic systems include
the following: static air techniques, aeroponic systems, nutrient flow techniques, rockwool slab
systems, aquaponic systems, ebb and flow, deep flow techniques, aerated flow techniques,
nutrient flow techniques, drip irrigation techniques, root mist techniques, fog feed techniques,
subaeration methods, gravity flow feeds, and peat bag culture (Hydro Aquatic Technologies
1996).
Hydroponics in the Netherlands
In 1980, the Netherlands decided to phase-out the use of methyl bromide as a soil
fumigant by 1992. The work that was done to achieve this and the alternatives developed
provides an important model for phasing out methyl bromide, as well as a number of good
alternatives to this pesticide (Anonymous 1992a). The Netherlands was formerly one of Europe's
largest users of methyl bromide for soil fumigation. Using this pesticide to control soilborne pests
on greenhouse-grown crops such as tomatoes, lettuce, strawberries, cucumbers, sweet peppers,
eggplants, as well as nursery crops and cut flowers (only a small amount was used to fumigate
soils in field crops). By using alternative cropping methods, such as hydroponics and soilless
culture on artificial substrates, growers in the Netherlands have successfully eliminated the risk of
infestation by soilborne pests, while increasing crop yield and quality (Methyl Bromide Task
Force 1995).
The phase out of methyl bromide allowed the Netherlands to develop greenhouse crop
production systems with a number of economic and environmental advantages. For example,
both strawberries and cucurbits are successfully grown in greenhouses in the Netherlands using
artificial substrates (i.e., peat and Rockwool, respectively) on hanging shelves or on raised shelves
outdoors (Sneh et al. 1983, Braun and Supkoff 1994). Planting densities in greenhouses are
doubled by hanging each tightly-spaced row from cables attached to winches. Alternating rows
are then raised and lowered to gain access for tending or harvesting (Methyl Bromide Task Force
1995, Liebman 1994). The hydroponic solution (nutrient rich water) is pumped to the plants
using a regulated trickle/drip irrigation system. The wastewater from the roots is recaptured,
sterilized, and reused to reduce environmental waste and contamination, and to conserve water.
Growers sterilize the recycled nutrient water by heating it to about 90°C (194°F) (Anonymous
1992b, Anonymous 1992c). Substrates are sterilized for reuse using steam (USDA 1996,
Liebman 1994).
-------
Strawberries
There are approximately 2,072 ha of strawberries grown in the Netherlands. In 1993, production
of greenhouse strawberries in the Netherlands was approximately 31,000 tonnes, of which almost
half (14,000 tonnes) was from greenhouse production. Peat bags are primarily used in the
production of greenhouse strawberries and to cultivate new runners. Young plants are exposed to
short-day lighting to stimulate bud formation, and are then either placed in greenhouse substrates
(or outdoors) to fruit or are stored for up to eight months at -2°C in a dormant state poised for
flower development (Methyl Bromide Task Force 1995). In warmer weather, mature plants may
produce strawberries within 60 days without the use of methyl bromide or any other soil fumigant
(Anonymous 1992b, Anonymous 1992c).
Cucurbits
Approximately 1,020 ha of cucurbits (i.e., cucumbers, eggplant, and melons) are grown in the
Netherlands. In the current post methyl bromide period, more than 90 percent of the cucurbits
were grown on artificial substrates in temperature controlled greenhouses, while the remainder
were grown in steam sterilized soil. The main cucurbit crop is cucumber, of which 484,720
tonnes were produced in greenhouses in 1993. The area used to grow cucumbers has remained
constant since 1970, however, the area of crops grown on artificial substrates has increased from
272 ha in 1991 to 935 ha in 1994 (Banks 1993).
Costs
Hydroponics is an economically viable alternative to methyl bromide fumigation for a
number of crops, including strawberries and cucumbers (See Table la and b). Although materials
and total costs are higher for hydroponic systems compared to methyl bromide fumigation,
operating costs are generally lower (except for double crops of strawberries) and overall crop
yields far exceed those obtained with methyl bromide. In general, strawberry and cucurbit yields
using artificial substrates are double those obtained using soil. In fact, production on one
greenhouse acre is equivalent to that on 8 to 10 field acres with long term production costs being
much lower (Rosselle 1996). Adjusting costs ($/kg yield) to take into account crop yield renders
costs comparable to that of methyl bromide fumigation. Furthermore, hydroponic costs are
expected to decrease as sales continue to increase and these systems become more
commercialized (Rosselle 1996, USDA 1996).
Other economic advantages of hydroponics include a potentially fast and flexible
hydroponic cropping period, which allows growers to quickly change production to take
advantage of market conditions. Because of the short cropping period (4 months total) and the
development of cold storage techniques, growers can increase or decrease production depending
on prices, or select alternative crops if crop prices are not favorable. By marketing produce when
the prices are at a premium, growers can pay off the initial capital investments in as little as 3
years (Methyl Bromide Task Force 1995, Liebman 1994). In fact, Dutch growers have already
reported a 10 to 20 percent increase in cash income with the use of these artificial substrates
(USDA 1996, Banks 1993). Lastly, unlike conventional crops, growers also have the option of
"double cropping" to produce 2 crops/year from one planting, thereby halving the cost of crop
establishment (Banks 1993, Anonymous 1992b, Anonymous 1992c).
-------
Table la. Strawberries: Cost of Hydroponics vs. Methyl Bromide as a Preplant Fumigant.
Cost Factors
i -":{$?fia%&y&ift
Labor/Operating
Materials
(Water/Chemical)
Total
Yield (kg/acre)
Adjusted Cost
($/kg)
Greenhouse
%d^»8Stf Artificial Sufcrtrtfe
Single Crop
4,692
25,844
30,536
20,235
1.51
Doable Crop
15,602
28,604
44,211
36,423
1.21
Greenhouse
Methyl Bromide
8,455
14,553
23,008
23,008
1.14
Source: Banks 1993.
Table Ib. Cucumbers: Cost of Hydroponics vs. Methyl Bromide as a Preplant Fumigant.
- _C0sfF80f0*s
V.C$/aere/year)
Labor/Operating
Materials
(Water/Chemical)
Total
Yield (kg/acre)
Adjusted Cost
(S/kg)
Greenhouse
Hy^ropoBic/AriificiaJ
§#bstrate
11,818
70,381
82,199
274,791
0.30
Greenhouse
Methyl Bromide
12,696
18,216
30,912
107,650
0.29
Source: Banks 1993.
-------
References
Anonymous. Into the Sunlight: Exposing Methyl Bromide's Threat to the Ozone Layer, Friends
of the Earth: Washington, D.C., 1992a.
Anonymous. "Methyl Bromide". Executive Summary, International Workshops on Alternatives
to Methyl Bromide for Soil Fumigation. Rotterdam, The Netherlands, October 1992, and Rome,
Italy, October 1992b; p 32.
Anonymous. "Methyl Bromide: Its Atmospheric Science, Technology and Economics"; synthesis
report of the Methyl Bromide Interim Scientific Assessment and Methyl Bromide Interim
Technology and Economic Assessment, United Nations Environmental Programme, Montreal
Protocol Assessment, 1992c.
Banks, J. Agricultural production without methyl bromide - Four Case Studies. CSIRO Division
of Entomology and UNEP lE's Ozone Action Programme under the Multilateral Fund, 1993.
Braun, A.L.; Supkoff, D.M. "Options to Methyl Bromide for the Control of Soil-borne Diseases
and Pests in California with Reference to the Netherlands"; Pest Management Analysis and
Planning Program; State of California, Environmental Protection Agency, Department of
Pesticide Regulation, Sacramento, CA, 1994.
Cropking, Seville, OH, unpublished material, 1996.
Hydro Aquatic Technologies, Switzerland, 1995, unpublished material.
Liebman, J. Alternatives to methyl bromide in California strawberry production. The IPM
Practitioner 1994, 16(7).
Methyl Bromide Task Force. Alternatives to Methyl Bromide: Research Needs for California;
Department of Pesticide Regulation and The California Department of Food and Agriculture:
Sacramento, CA, 1995.
Resh. Hydroponic Food Production (fourth edition); Woodbride Press Publishing: Santa
Barbara, CA, 1993.
Rosselle, T. Seeing Green Under Glass. The Packer 1996, 103, p. 1 A.
Sneh, B.; Katan, J.; Abdul-Razig, A. Chemical control of soil-borne pathogens in tuff medium for
strawberry cultivation. Pestic. Sci. 1983,14,119-122.
United States Department of Agriculture (USDA). "The Netherlands' Alternatives to Methyl
Bromide." Internet: http://www.ars.usda.gov/is/np/mba/oct96/nether.htm, 1996.
-------
-------
vvEPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Metam Sodium as an Alternative to Methyl Bromide for Fruit and Vegetable Production
and Orchard Replanting
This is an update of a July 1995 EPA report (Alternatives to Methyl Bromide, Ten Case Studies) entitled "Metam
Sodium as an Alternative to Methyl Bromide for Fruit and Vegetable Production". Additional information on this
materials, including new data from field tests, is reported here. This report contains information on the use of this
pesticides in the production of crops where methyl bromide is currently used.
First marketed in the 1950's, metam sodium is a soil pesticide that has been sold under the
trade names Amvac Metam Sodium®, Busan®, Metam CLR™ 42%, Sectagon 42®, and
Vapam®. Once in the soil, this pesticide degrades rapidly to methylisothiocyanate (MITC), the
product's primary bioactive agent (Budavari 1994). Metam sodium is a broad spectrum soil
fumigant that can be used to control plant parasitic nematodes, weeds, germinating weed seeds,
and soil-borne plant pathogenic fungi affecting a variety of economically important fruit and
vegetable crops. This pest control tool can be a cost effective, technically viable alternative to
methyl bromide for controlling soil pests affecting high value fruit, vegetable, and orchard crops.
Benefits of Metam Sodium
- Registered for use of many of the crops
methyl bromide is used
- Widely availability
- Proven effectiveness
- Low cost
- Wide-range of control
Metam sodium is registered and
available to growers. It has no effect on the
stratospheric ozone layer, and with current
use patterns there are no residues left on
crops. For over four decades, metam
sodium has been used in a variety of
experimental and commercial applications
for the control of annual weeds, reduce
nematode populations, and control soil-
borne pathogens. In California, over 15
million pounds of metam sodium were used
in 1995 for the production of melons, peppers, tomatoes, potatoes, strawberries, nurseries,
ornamentals, cut flowers, container plants, forest tree seedlings, citrus, grapes, almonds,
artichokes, asparagus, and carrots (CDPR 1997).
However, it should be noted that metam sodium has a reputation with some growers of
being unforgiving and unreliable if not used carefully. Growers that have used this material note
that correct application procedures are critical to insure success in the control of pest, especially
-------
nematodes and fungi. Current methyl bromide users should bear this in mind as they consider
future utilization of this material.
Commercially Viable Alternative to Methyl Bromide
Table 1 compares methyl bromide and metam sodium soil fumigation use for grapes,
peppers, tomatoes, processed tomatoes and strawberries for California in 1995 (CDPR 1997). As
indicated in table 1, methyl bromide is not used in processing tomatoes — this crop is shown in
this report to show a successful and established use pattern, not to imply substitution in this or
any other crop.
fable 1* 1S£S Pesticide tfs* in Catitoraias libs active tegredtefit
Crop
Grapes
Peppers
Tomatoes
Processed Tomatoes
Strawberries
Methyl Bromide
575,000
49,000
266,000
-0-
4,200,000
Metam Sodium
15,500
7,600
243,000
2,888,000
30,000
Source: CDPR pesticide use summary database, April 1997.
Many researchers have cited metam sodium as a potential alternative to methyl bromide
fumigation, and metam sodium's low cost and wide-range of control makes it a strong candidate
for fumigation on many crops (Braun and Supkoff 1994, Noling and Becker 1994, Yarkin 1994).
Metam sodium is registered for use in controlling a wide array of soil-borne pests, and can be
used to control weeds (e.g., annual bluegrass, bermuda grass, chickweed, dandelion, ragweed,
henbit, nutsedge, and wild morningglory.), nematodes (e.g. root knot, lesion, dagger, lance,
needle, pin, reniform, stunt, stubby root, sting, spiral), and soil diseases caused by species of
Rhizoctonia, Fusarium, Pythium, Phytopthora, Verticillium, Sclerotinia. Metam sodium is also
useful in Integrated Pest Management systems, as it can be used in conjunction with resistant
varieties, improved sanitation techniques, biological control agents, and soil pasteurization (i.e.,
solarization, hot water or steam) (Noling and Becker 1994). It is possible, based upon current
metam sodium use patterns, to see expanded across a wide range of fruit and vegetable crops
including tomatoes, strawberries, and peppers which currently utilize methyl bromide for soil pest
control.
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Fruit and Vegetable Production
Note that not all the crops listed in this section currently utilize methyl bromide in their
production. However, a description of metam sodium efficacy is provided to illustrate the kind of
pest control that can be acheived with this material. While this document assumes that such pest
control efficacy is transferrable to crops that use methyl bromide, this must be established with
field trials where applicaiton methods and production timing can be established. This is especially
important with metam sodium, where application techniques are absolutely critical to success.
Carrots -
In comparisons with methyl bromide, metam sodium has shown good growth responses
and yield increases (Olson and Noling 1994, Cook and Keinath 1994, ICI1992). In the
production of carrots and tomatoes, metam sodium has been used to significantly reduce
populations of stubby root (Paratrichodorous sp.) and root-knot nematode (Meloidogyne
sp.) prior to planting (ICI 1992). Application through drip irrigation on California tomato
and carrot beds before planting significantly reduced nematodes in the soil as well as root
gall ratings at mid-season and harvest and increased yields in most cases (Roberts et. al.
1988). In Florida, use resulted in improved plant vigor and stand, reduced root-knot
nematode damage and increased yields (Johnston et. al. 1991).
Tomatoes -
A fresh market tomato study comparing metam sodium and methyl bromide fumigation to
an untreated control reported that yields and fruit quality obtained with metam sodium
were equivalent to those achieved with methyl bromide fumigation (Cook and Keinath
1994). In the production of tomatoes in southwest Florida, Fusarium crown and root rot
has been the most prevalent soilborne disease. Metam sodium has been demonstrated to
significantly reduce crown rot incidence and when combined with solarization, control was
equivalent to methyl bromide + chloropicrin (McGovern et. al. 1996).
Strawberries -
In California strawberry production, methyl bromide and metam sodium are rated
comparable in chemical effectiveness to control annual and perennial weeds (UC 1996).
Field experiments conducted by the UC Cooperative Extension over a three year period
on broccoli, cauliflower and strawberries demonstrated that metam sodium will effectively
control several annual weeds common in these crops (Agamalian 1990).
In two registrant-supported strawberry field trials, Metam sodium was applied at 240 Ibs
per acre through sprinkler system; methyl bromide/chloropicrin was applied at 325 Ibs per
acre. Overall, during the early part of the season, yields achieved with metam sodium
were 26% greater than those obtained with methyl bromide. Although methyl bromide
yields for the overall season were 14% greater than yields achieved with Metam sodium,
because metam sodium treatment costs were 1/3 less than methyl bromide costs and
higher early season yields achieved by metam sodium received significantly higher prices,
economic returns with metam sodium were greater than those achieved by using methyl
bromide (ICI 1992).
-------
Weed Control -
Haiiy nightshade (Solanum sarachoides Sendter) and black nightshade (Solatium nigrum
L.) are widespread major weed problems in California processing tomatoes causing severe
economic loss to growers. This loss amounts to greater than $68 million due to hand
hoeing costs and yield reductions. A three year study of Solanum species control in
processing tomatoes conducted by University of California Cooperative Extension Farm
Advisor, Mullen, show metam applied preplant subsurface can be effective for control of
Solanum and other weed species (Mullen). It must be noted that processing tomatoes do
not currently use methyl bromide. Reference to this crop is to establish metam sodium as
a good weed control tool, with the broad (and very likely) assumption that such effective
weed control will be transferable to other cropping situations.
Nematode Control -
A statewide investigation into the potential of various nematicidal materials for controlling
root-knot nematodes (Meloidogyne spp.) on processing tomatoes was conducted in
California during 1985. Metam sodium applied via drip irrigation at both 64 and 128
pounds active per acre significantly reduced root galling throughout the season and had
significantly reduced numbers of root-knot nematode second stage juveniles in soil
assessed at planting time. These two treatments gave the highest yields in these
experiments (Roberts and Matthews 1985). Again, it must be noted that processing
tomatoes do not currently used methyl bromide, and reference to this crop establishes
metam sodium as a good nematode control agent, with the assumption that such control
may be transferable to other cropping situations, such as those where methyl bromide is
currently used.
Plant Disease Control -
Metam sodium applied at rates of 10 to 40 gallons per acre greatly reduced pythium and
Fusarium soil levels and root infection in processing tomatoes. Metam sodium also
significantly reduced the "corky-root like" banded lesions on roots in midseason. It was
concluded that the control of these common soil fungi by metam sodium may have
contributed, along with nematode control, to the overall plant growth increase and yield
increase that occurred in most of these experiments.
Fusarium oxysporum causes serious losses in yield and quality of celery. It attacks the
fibrous root system and spreads through the xylem into the crowns. The initial symptom
is a retardation of growth, usually followed by yellowing of the foliage. Field evaluations
conducted during 1989 in California revealed that fumigation of soil with metam sodium
promoted early plant growth and increased yield in fields infected with this disease
(Becker et. al. 1990). Very little celery production currently uses methyl bromide, so here
again, reference to this crop establishes the pesticidal effects of metam sodium, with the
assumption that such control will be transferrable to cropping situations where methyl
bromide is currently used.
In 1990, Johnston and Phillips evaluated soil fumigants for control of Phytophthora and
Pythium blight of peppers. The incidence of Pythium blight was high in this test and this
test was considered definitive. Metam sodium applied via drip irrigation at 160 to 320
-------
pounds active per acre provided significant reduction in Pythium blight and a significant
increase in total yield (Johnston and Phillips 1991).
Orchard Replant Sites -
Pathogenic soil organisms present in the soils of most mature orchards often reduce root
growth of young fruit trees when the site is replanted. Poor root development leads to
reduced vegetative growth and poor fruit yields throughout the life of the replanted
orchard. While many soil fumigants, fungicides, fertilizers and soil amendments have been
tested for effect on the orchard replant disease, only three have shown long-term growth
and yield benefits in Washington orchard trials: methyl bromide, metam sodium, and
fumigants containing chloropicrin (WSU 1996).
To evaluate control of southern blight in apples, UC Farm Advisor Joseph Grant and Greg
Browne, USDA-ARS are evaluating alternatives to methyl bromide + chloropicrin. In year one of
the experiment, metam sodium performed as well as the methyl bromide/chloropicrin mixture for
control of the disease at tree replant sites (USD A 1996).
Trials conducted to evaluate the use of methyl bromide alternatives on orchard replant
sites demonstrated that metam sodium can provide comparable control as methyl bromide
(McKenry 1994). However, the study also noted that metam sodium does not always penetrate
deep roots, and thus may not control nematodes in old roots if the proper soil conditions are not
present. A vineyard with root lesion and root knot nematodes was replanted to strawberries.
Results of this trial revealed that soil drenching replant sites with 300 Ibs of metam sodium gave
equivalent nematode control for 24 months. A 20 year old plum site, with root lesion and ring
nematodes, was replanted to nectarines. Soil drenching with 330 Ibs of metam sodium gave
equivalent nematode control for 24 months. At another site, soil drenching a 15 year old peach
and plum orchard, infested with root lesion and citrus nematode, with metam sodium gave
comparable nematode control. Additionally, at an old almond orchard, infested with root lesion
and ring nematode, replanted to grapes was treated with metam sodium at 327 Ibs. Results
showed comparable nematode control and plant growth when compared to methyl bromide.
Successfully Applying Metam Sodium
Although some growers have been frustrated with metam sodium's soil distribution
characteristics and variations in pest control, research and advances in application techniques have
the potential to increase the consistency and efficacy of metam sodium as a soil fumigant.
Effectively using metam sodium to control pests currently treated with methyl bromide will
require some low-cost modifications of cropping systems, including, in some cases, the adoption
of drip irrigation systems, narrower bed widths, multiple drip tubes per bed, and planting practices
which place plants closer to drip tubes (Noling and Becker 1994).
To use metam sodium effectively, the applicator must follow the recommendations
provided by the product label, including considerations of the soil conditions, methods of
application, application rates, and the factors influencing the release rate. The release rate of
metam sodium depends on several factors including soil temperature, texture, moisture and pH.
-------
Prior to application, the seedbed must be prepared by ensuring that it is free of clods and by
receiving a preplant fertilizer treatment. Additionally, soil moisture must be at least 50 to 75
percent of field capacity, and soil temperatures must be between 40° F and 90° F in the top 2 to 3
inches (ICI1992).
In most cases, 80 to 320 pounds active of metam sodium are applied per treated acre as a
liquid and then incorporated into the soil through tilling and irrigation (Braun and Supkoff 1994).
Metam sodium can also be applied through sprinkler, flood or drip irrigation. Research
trials indicate that application of metam sodium through overhead irrigation water may be a more
effective way to obtain uniform distribution than by injecting with chisels (Adams and Johnson
1983, Adams et. al. 1983, Ben-Yephet and Frank 1984). Additionally, University of Georgia
researchers demonstrated that metam sodium was more effective against Rhizoctonia and Pythium
when applied through overhead sprinkler irrigation than when injected with chisels in a fall
experiment (Sumner and Phatak 1988).
University of Georgia researchers demonstrated that proper placement through adequate
water is important for the efficacy of metam sodium (Sumner and Phatak 1988). Metam sodium
moves in the water phase (opposed to methyl bromide which moves in the air phase) so adequate
watering is essential. Failure to appreciate this fact is one of the major causes of inconsistency in
metam sodium application. These trials demonstrated that the application of metam sodium in 2.5
cm of water was more effective in controlling root diseases in deep-rooted vegetables such as
okra than in 1.3 cm of water. Application in 0.6 cm of water were ineffective. Metam sodium is
most effectively applied through drip tape if it is applied no more than 6 inches off center and 2 to
3 inches deep.
Cost Effective Alternative to Methyl Bromide
An advantage to the use of metam sodium is the low cost. Although supplemental pest
control activities may be required under certain circumstances and may increase the total
application costs, metam sodium is considered by many to be safer and easier to use than methyl
bromide. Table 2. compares the costs of metam sodium and methyl bromide for soil fumigation
treatments. The average cost of metam sodium ranges from $0.41 to $0.88 per pound active
(Johnson Mercantile Co. 1997, Western Farm Service 1997), with typical application rates
ranging from 240 to 320 pounds active per acre (Braun and Supkoff 1994). Total metam sodium
costs can average between $141 to $282 per acre. In comparison, the average cost of methyl
bromide ranges from $3.13 to $4.25 per pound (Shore Chemical 1997, Helena Chemical 1997,
Cal Ag Industrial Supply 1996). Methyl bromide costs are estimated to range from $560 to
$1,700 per acre.
-------
TABU! 2, SUstotive Cms ftf M«%l»ita»i
-------
Cook and Keinath 1994. Metam sodium as an alternative soil fumigant to methyl bromide in fresh
market tomatoes, 1993. F&N Tests 49:160.
CDPR 1997. California Department of Pesticide Regulation, Sacramento, California
California Pesticide Use Report, University of California, Davis, CALIPM, Pesticide Use
Summary Database, April 1997
EPA 1994. Methyl Bromide Consumption Estimates. U.S. Environmental Protection Agency,
Stratsopheric Protection Division, Washington, D.C. May 3,1994.
EPA 1996. Methyl Bromide Consumption Estimates. U.S. Environmental Protection Agency,
Stratsopheric Protection Division, Washington, D.C.
Helena Chemical Company 1997. Price Quote. Active ingredient price for methyl bromide.
Helena Chemical Company, Kerman, CA. 1997.
ICI1992. Vapam® Product Guide, ICI Agricultural Products, Wilmington, DE.
Johnson Mercantile Company 1997. Price Quote. Active ingredient prices for metam sodium and
methyl bromide. Johnson Mercantile Company, Hamilton, NC.
Johnston and Phillips 1991. Evaluation of Soil Fumigants, Fungicides, and a Surfactant for
Control of Phytophtora and Pythium Blights of Peppers, 1991 F&N Tests 47:104.
Johnston et. al. 1991. Evaluation of Fumigants and Nematicides for the Control of Root-Knot
Nematodes on Carrot, 1991. F&N Tests 47:158.
I^arson and Shaw 1994. "Evaluation of Eight Preplant Soil Treatments for Strawberry Production
in California". 1994 International Conference on Methyl Bromide Alternatives and Emissions
Reductions. Kissimmee, FL
McGovera et. al. 1996. Reduction of Fusarium Crown and Root Rot of Tomato by Combining
Soilsolarization and Metam Sodium.
McKenry, Buzo, Kretsch, Kaku, Ashcroft, Lange, Kelly. 1994. "Soil Fumigants provide multiple
benefits; alternatives provide mixed results." California Agriculture. 48:22-28.
Mullen. A Three Year Study of Solanum Control in Processing Tomatoes. Robert Mullen, Farm
Advisor University of California Cooperative Extension, San Joaquin County.
Noling and Becker 1994. "The Challenge of Research and Extension to Define and Implement
Alternatives to Methyl Bromide". Supplement to the Journal ofNematology, Vol. 26, No. 4s,
pp.573-586.
-------
Olson and Noling 1994. "Fumigation Trials for Tomatoes and Strawberries in Northwest
Florida". 1994 International Conference on Methyl Bromide Alternatives and Emission
Reductions. Kissimmee, FL. November 1994.
Roberts and Matthews 1985. Report on 1985 Nematicide Trials. Nematologist and Research
Associate, Kearney Agricultural Center, Parlier, CA.
Roberts et. al. 1988. Effects of Metam Sodium Applied by Drip Irrigation on Root-Knot
Nematodes, Pythium ultimum, and Fusarium sp. in Soil and on Carrot and Tomato Roots. Plant
Disease, Volume 72 No. 3. March 1988.
Shore Chemical 1997. Price Quote. Active ingredient prices for methyl bromide. Shore
Chemical, Turlock, CA. 1997.
Sumner and Phatak 1988. Efficacy of Metam-Sodium Applied Through Overhead Sprinkler
Irrigation for Control of Soilborne Fungi and Root Diseases of Vegetables. Plant Disease, Vol
72, No. 2 Feb. 1988.
UC 1996. Strawberry Integrated Weed Mangement. Strawberry Pest Mangement Guidelines.
April, 1996.
USDA 1996. Technical Reports: Research on Alternatives to Methyl Bromide for Control of
Soilborne Pests of Grapevines and Tree Fruits and Nuts. U.S. Department of Agriculture: Methyl
Bromide Alternatives, October 1996.
Western Farm Service 1997. Price Quote. Active ingredient price for metam sodium and methyl
bromide. Western Farm Service, Fresno, CA. 1997.
WSU 1996. WSU-TFREC Orchard Management Forum: Orchard Fumigation. Washington
State University, 1996.
Yarkin 1994. Methyl Bromide Regulation: All crops should not be treated equally. Cherisa
Yarkin, David Sundling. David Silberman, and Jerry Siebert, University of California, Davis.
California Agriculture, Volume 48, Number 3. May-June 1994.
-------
-------
&EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
Septembeir1997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Steam as an Alternative to Methyl Bromide in Nursery Crops
Steaming can be a viable alternative to methyl bromide for soil and growth media in
greenhouses and some small-scale field nurseries. Steam effectively kills pathogens by heating the
soil to levels that cause protein coagulation or enzyme inactivation (Langhans 1990). Soil steam
sterilization was first discovered in 1888 (by Frank in Germany) and was first commercially used
in the United States (by Rudd) in 1893 (Baker 1962). Since then, a wide variety of steam
machines have been built to disinfest both commercial greenhouse and nursery field soils
(Grossman and Liebman 1995). In the 1950s, for example, steam sterilization technologies
expanded from disinfestation of potting soil and greenhouse mixes to commercial production of
steam rakes and tractor-drawn steam blades for fumigating small acres of cut flowers and other
high-value field crops (Langedijk 1959). Today, even more effective steam technologies are being
developed.
Benefits of Steam Sterilization
Highly efficient and cost-effective control method
Eliminates the need for tarps and soil fumigants
Neat, clean, and easy-to-use '
Leaves no toxic residues or fumes •
Requires little aeration time
Can disinfest non-soil substances
Can be combined with other pest control practices
The advantages of steam
sterilization are that it can be a
highly efficient, cost effective
technology for the control of soil-
borne pathogens, pests, and
weeds; it eliminates the need of
tarps and fumigants; it can be a
neat, clean, and easy-to-use ^
control technology, leaving no
toxic residues or fumes and
therefore less harmful to other
greenhouse crops and growers
(with no toxic fumes, workers can harvest or plant new cuttings in adjacent fields). In addition, it
is non-selective (lethal to all pests). Steam requires little aeration time (steamed soils can be
planted as soon as they cool, whereas chemically treated soils can have a relatively long treatment
and aeration period). Steam can also be used to disinfest non-soil substances such as perlite, peat,
and compost (Szmidt et al. 1989) and can be adaptable to many situations (i.e., most types of
boilers used to heat greenhouses can be adapted to supply steam for sterilizing benches or soil
bins).
-------
However, it should be noted that while there are a number of positives aspects to using
steam as a pest control tool, there are potential pitfalls and shortcomings. This method does not
currently appear to be operationally feasible for large outdoor nurseiy crops due slow application
speed as well as high energy and capital investment costs. Due to limited steam penetration in the
field, surface application may not reach pests in deep rooted trees or crops. It is a very inefficient
methods when soils are very wet (similar with most other fumigants, including methyl bromide).
In addition, steam that is too hot (85°C to 100°C) may increase soil aggregation and destroy soil
structure. A number of these issues may well be resolvable, and efforts by researchers to refine
this technology should continue.
If deemed necessary, steam sterilization can be used in combination with other control
mechanisms, such as nematicides, botanicals, soil amendments, and biological control agents
(Stephens et al. 1983). For example, one possible biocontrol agent is the fungal antagonist,
Trichoderma, which has been shown to increase biological control and horticultural productivity.
Tricoderma. spp. can hasten flowering of periwinkle, increase the number of blooms in petunias
and chrysanthemums, and increase dry weights of flowers and vegetables such as tomato, pepper,
and cucumber (Baker 1992, Chang et al. 1986, Locke et al. 1985, Horst and Lawson 1982).
Nurseiy crops account for 20 percent of the worldwide use of methyl bromide for soil
fumigation (Anonymous 1995a). Steam sterilization can be an effective pest control method for
many nurseiy crops, including ornamental bedding plants, potted foliage and flowering house
plants, fresh cut flowers and greens, bulbs, container perennials, propagating material, vegetable
starts, greenhouse grown vegetables, garden seeds, and sod. Soil used to grow cut Christmas
trees and seedlings for orchards, vine-yards, and forests can also be effectively treated with steam
technologies, depending upon crop value and size of area to be treated. In 1991, the value of
crops produced by floriculture and on environmental horticulture farms was $8.7 billion, or 11
percent of total cash receipt from all crops (Johnson and Johnson 1993). In California, these
industries are worth $2 billion in gross receipts, or about 10 percent of the total value of
California's agricultural commodities (Anonymous 1993).
Steam Pasteurization
To effectively steam treat soils, soil temperatures of at least 70 °C must be achieved for
30 minutes. Temperatures below 70°C will not kill all soil-borne pathogens and steaming for
periods exceeding 30 minutes after the desired temperature has been reached does not further
benefit the soil (Horst and Lawson 1982). Sterilization does not guarantee that disease causing
organisms will not recontaminate the soil, therefore if the soil is not used immediately after it is
treated it should be protected from reintroduced pathogens (i.e., by avoiding contact with non-
sterilized soil and practicing standard sanitation procedures in the greenhouse) (Horst and Lawson
1982).
-------
Steaming Greenhouse and Potting Soils
The use of steam for greenhouse and potting soil mixes is quick and efficient. Boilers
used to heat greenhouses can often be adapted to supply steam for sterilizing greenhouse benches
or soil bins. Bulk and container soils can be easily loaded into steam boxes with removable fronts
and steam pipe grids for treatment. Alternatively, forklifts can load pallets of soil into pressurized
autoclaves for steaming. Another way of disinfesting greenhouse and nursery soils is to cover
perforated steam pipes with soil to be treated (Newhall 1955). Bed or bench treatments are most
effective when perforated pipes are laid in the bottom of the bed because steam supplied from the
top of the bed has limited penetration to about 8 inches depth (Bartok 1993). More recently,
small portable steam generators have been developed and used for greenhouse benches in the U.S.
and the Netherlands (Grossman and Liebman 1995).
Open Fields and Steam
;
Sheet Steaming
In addition to greenhouses, it is also possible to use steam technologies on small nursery fields.
For example, movable steam applicators, such as the steam rake and the steam blade have been
used extensively in nursery fields. Both are pulled through the soil either by a winch or by a self-
propelled unit containing a boiler to produce steam. In Florida, several small ;steam machines
have been developed for field use. Using these machines can be less expensive and in some
conditions may be more effective than methyl bromide fumigation (Grossman and Liebman 1995)
and can disinfest a quarter of an acre of planting bed per work shift. Steam cultivation is also
used in the Netherlands, where methyl bromide soil fumigation has been banned for several years
and where large mobile boilers (that can be moved from farm-to-farm on trucks) have been
developed and used in fields (Grossman and Liebman 1995). To aid steam penetration, soil is
cultivated as deeply as possible. Typically steam is blown under a sheet covering the soil and left
to penetrate. Clay is very easy to disinfest with this steam system, while slightly more energy is
required to achieve high enough soil temperatures in sand, loams, and peat soils because of their
water retaining capacity. To raise the temperature in these soils or in deeper soil layers, steaming
sheets are sometimes covered with nylon nets or bubble foil, so that the pressure under the sheets
can be increased and heat loss can be kept at a minimum. For high value Dutch crops such as
carnations and cut flowers, field soils have also been disinfested by embedded steam pipes directly
in the field. Though fuel costs for steam systems using embedded pipes are less than sheet
steaming, material costs are often higher (Runia 1983).
Negative Pressure Steaming
Negative pressure steaming, the most recent advance in applied steam technologies for soils, was
introduced to the Netherlands in 1981. Using this method, steam is introduced under the steam
sheet and pulled into the soil by negative pressures created by a fan. Specifically, the fan draws
air out of the soil through buried perforated polypropylene pipes (Runia 1983). The fans continue
to move heat from the upper to lower soil layers for several hours after steam treatment. Deep
soil temperatures achieved with negative pressure steaming are considerably higher than those
obtained with sheet steaming, averaging 85 to 100°C (185°F to 212°F) down to 35 cm deep
-------
(sheet steaming produces an average temperature of only 26 °C (78 °F) at the same depth). This
method was found to be more energy efficient, economical (by up to 50 percent), and more
reliable for the cultivation of some crops (i.e., chrysanthemums) than the conventional steaming
methods used to disinfest soil in the Netherlands (Anonymous 1992). By 1982, over 100
nurseries in the Netherlands were using negative pressure steaming (Runia 1983, Banks 1995).
Cool Steaming
Although high-temperature negative pressure steaming has its advocates, some researchers
believe that steam at 85°C to 100°C (185°F to 212°F) kills too many beneficial soil organisms
(i.e., mycrorhizal fungi) along with the pathogens and can lead to the production of phytotoxic
compounds harmful to crop plants. As a result, these researchers advocate the use of lower
temperatures (70°C) (152°F)or cool steam, which does not kill beneficial organisms (i.e.,
nitrifying bacteria) and is less phytotoxic (Langhans 1990, Grossman and Liebman 1995, Baker
1970). To cool steam to the desired temperature (i.e., typically 70°C for 30 minutes), it is mixed
with a stream of air. Since lower temperatures are required, aerated steam is faster and
approximately 40 percent cheaper than hot steam (Baker 1962, Bartok 1993). Likewise, Baker
(1957) calculated that the cost of aerated steaming is 30 to 50 percent cheaper than methyl
bromide (including the boiler costs).
Costs
Steam sterilization can be an economically viable alternative to methyl bromide fumigation
in a number of crops (i.e., ornamental bedding plants, potted foliage and flowering house plants,
fresh cut flowers and greens, bulbs, container perennials, vegetable starts, greenhouse grown
vegetables, and garden seeds). Tables 1 and 2 present a cost analysis for steam compared to
methyl bromide for cucumbers and chrysanthemums, respectively. The formula for calculating the
cost of soil steam sterilization vs. methyl bromide takes into account soil volume and permeability,
soil heat exchange efficiency, boiler efficiency, units of fuel required, the BTU constraints of the
fuel, and water prices (Lawson and Horst 1982). Total steam sterilization costs ($/kg yield or
$^ench) were comparable to that of methyl bromide fumigation for both crops analyzed
(Anonymous 1995a). Furthermore, steaming has the extra advantage of allowing growers to
replant up to three weeks sooner than methyl bromide treated fields (an important economic
advantage in cool climates) (Grossman and Liebman 1995).
Since large steam boilers can cost up to $150,000, it is likely not practical for growers not
currently using boilers to heat their greenhouses to buy new boilers to steam soil once a year.
Instead, outside contractors can be hired for steam treatments (Grossman and Liebman 1995).
This is especially common in the Netherlands, where in addition to stationary on-site boilers,
growers commonly rent or contract for truck-mounted steam generators on an as need basis
(Anonymous 1992 and Anonymous 1995b). As a result, the capital cost to purchase a boiler was
not included in the cost estimates presented in the tables below. Likewise, in Table 2, the cost of
tarps, plastic, canvas, metal pipes, and labor were excluded from analysis since these costs were
found to vaiy significantly from greenhouse to greenhouse depending on the current material
prices and labor rates (Lawson and Horst 1982).
-------
Steam costs are expected to decrease as these systems become more commercialized and
less expensive energy/water sources are utilized. For example, greenhouse heating costs can be
kept at a minimum by tapping alternative fuels such as sawdust, rubber from old tires, methane
from landfills, wind, hot water from electric power plants, and geothermal vests (Davis 1994).
Table 1. Cucumbers: Annual Cost of Steam vs. Methyl Bromide as a Preplant Fumigant
Costs Rasters
Labor/Operating
Materials
Total
Yield (kg/acre)
Adjusted Cost
($/kg)
Greenhoose
Steam
(1&/H«re/year)
11,818
18,969
30,787
107,650
0.28
Greenhouse
Methyl Bromide
($/aere/year)
12,696
18,216
30,912
107,650
0.29
Source: Banks 1995.
Table 2. Chrysanthemums: Annual Cost of Steam vs. Methyl Bromide as a Preplant Fumigant.
Cost Factors ~
Application
Greenhouse
Steam
(S/betteh/year)
8.60
Greenhouse
Methyl Bromide
($/beaeh/ye«r)
20.00
Note: One bench equals 200 square feet.
Source: Lawson and Horst 1982.
References
Anonymous. 1995 Assessment of the Montreal Protocol on Substances that Deplete the Ozone
Layer, Methyl Bromide Technical Options Committee. United Nations Environmental
Programme; 1995; p 304.
Anonymous. California Agricultural Statistics Review 1992; California Department of Food and
Agriculture. California Agricultural Statistics Service: Sacramento, CA, 1993.
-------
Anonymous. Methyl Bromide. Presented at the International Workshops on Alternatives to
Methyl Bromide for Soil Fumigation, Rotterdam, The Netherlands, October 1992 and Rome,
Italy, October 1992a.
Anonymous. Mobile soil sterilizer. Greenhouse Management and Production 1995b, 14(2), 75.
Baker, K.F. Beneficial fungus increases yields, profits in commercial production. Greenhouse
Manager 1992, 10, 105.
Baker, K.F. In Root Diseases and Soil-borne Pathogens; Toussoun, T.A.; Bega, R. V.; Nelson,
P.E., Eds.; Selective killing of soil microorganisms by aerated steam; University of California
Press: Berkeley, CA, 1970.
Baker, K.F. Principles of heat treatment of soil and planting material. J. Austral. Inst. OfAgric.
Sci. 1962,28(2), 118-126.
Baker, K.F. "The U.C. System for Producing Healthy Container-Grown Plants"; Manual 23;
Univ. Calif. Agric. Exp. Sta.: Berkeley, CA, 1957.
Banks, J. "Agricultural Production Without Methyl Bromide - Four Case Studies"; CSIRO
Division of Entomology and UNEP lE's OzonAction Programme under the Multilateral Fund,
1995.
Bartock, J.W. Steaming is still the most effective way of treating contaminated media.
Greenhouse Manager 1993, 110(10), 88-89.
Chang, Y-C; Baker, R.; Kleifield, O.; Chet, I. Increased growth of plants in the presence of
biological control agent Trichoderma harziamum. Plant Dwease 1986, 70,145-148.
Davis, T. If you know where to look, potential heat sources are virtually everywhere.
Greenhouse Manager 1994, 13(6), 60-63.
Grossman, J.; Liebman, J. Alternatives to methyl bromide steam and solarization in nursery
crops. The IPMPractitioner 1995, 17(7), 39-50.
Horst, R.K.; Lawson, R.H. Soil sterilization: an economic decision. Greenhouse Manager 1982.
Johnson, D.C.; Johnson, T.M. Financial Performance of U.S. Floriculture and Environmental
Horticulture Farm Businesses, 1987-91; Statistical Bull. No. 862. United States Department of
Agriculture Economic Research Service: Washington, D.C., 1993
Langedijk, G. Mechanized soil steaming as being developed in Holland. The Calif. State
Florists 'Assoc. Mag (Engl. Transl.) 1959; Groenten en Fruit 1957, 13(9), 253-254.
-------
Langhans, R.W. Greenhouse Management, 3rd ed.; Halcyon Press: Ithaca, NY, 1990; Chapter
Lawson, R.H.; Horst, R.K. Upset with diseases? Let off some steam. Greenhouse Manager
1982, pp 51-54. •
Locke, J.C.; Marois, J.J.; Papavizas, G.C. Biological control ofFusarium wilt of greenhouse-
grown Chrysanthemums. Plant Disease 1985, 69, 167-169.
Newhall, A.G. Disinfestation of soil by heat, flooding, and fumigation. Botanical Review 1955
21(4), 189-250.
Runia, W. Th. A recent development in steam sterilization. Acta Horticulturae (Soil
Disinfestation) 1983, 152, 195-200.
Stephens, C. T.; Hen-, L. J.; Schmitthenner, A. F.; Powell, C. C. Sources of Rhizoctonia solani
and Phytium spp. In a bedding plant greenhouse. Plant Disease 1983, 67, 272-275.
Szmidt, R.A.K.; Hitchon, G.M.; Hall, D.A. Sterilization of perlite growing substances. Acta
Horticulturae (Soil Disinfestation) 1989, pp 197-203. '.,
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-------
&EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Replacing Methyl Bromide for Preplant Soil Fumigation With
Telone®, Chloropicrin and Tillam® Combination Treatments
This is an update of a July 1995 EPA report (Alternatives to Methyl Bromide, Ten Case Studies) entitled "Telone C-17
and Tillam Use on Florida Fresh Market Tomatoes". Considerable work has been done since that report with regard to
these materials, and new data from field tests is reported here. This report contains information on the use of these
pesticides in the production of tomatoes and other crops where methyl bromide is currently used.
Telone® C-17, a DowElanco product registered for preplant fumigation, contains 77.9
percent 1,3-dichloropropene (1,3-D) and 16.5 percent chloropicrin (an effective fungicide).
Telone® C-17 and other Telone® products are recognized as effective preplant nematicides
(Youngson et al. 1981) and have been proven to suppress some plant diseases (e.g., Fusarium
wilt of cotton, Verticillium wilt of mint, and southern stem blight) (Melichar 1994, Dickson
1996). Tillam® 6E, a selective herbicide containing the active ingredient pebulate, is often used
in conjunction with Telone® products for control of weeds (especially nutsedge) (Gilreath 1994,
Gilreath 1996). Used together, these chemicals can achieve control of nematodes, weeds and a
variety of diseases at levels comparable to those achieved with methyl bromide and chloropicrin
combinations (Melichar 1994, Gilreath 1994, Olson etal. 1996, Gilreath 1996).
In a recent study, Telone® C-17
controlled root-knot nematodes and several
diseases, and achieved yields similar to
those obtained by fumigation with methyl
bromide for tomatoes, peppers, and
strawberries in Florida (Melichar et al.
1996b). Another study conducted at the
University of Florida found that a
combination treatment of Telone® C-17 and
Tillam® on Florida tomatoes produced a
significantly higher yield of medium and
large fruit than methyl bromide/chloropicrin
(67/33). There were no significant differences
for total yield in the study (Olson et al. 1996).
Telone® C-17 was found to be as effective as,
Benefits of Telone® C-17 and Tillam®
Combinations
-------
chloropicrin in controlling nematodes and certain soil-borne diseases (Chellemi et al. 1996,
Dickson 1996, Noling et al. 1996, Duniway and Gubler 1996).
Telone® C-17 is a restricted use pesticide licensed for control of nematodes, symphylans,
wireworms and certain soil borne diseases in the preplant fumigation of tomatoes, peppers,
strawberries, melons, grapes, and 112 other crops. Telone® C-17 is also approved for use on
nursery crops. This fumigant may be broadcast or row applied and should be sealed immediately
after application. Sealing may be accomplished by uniformly mixing the soil to a depth of 3 or 4
inches and compacting the soil surface (broadcast fumigation) or by disrupting the chisel trace
using press sealers, ring rollers or by reforming the beds and then using such equipment (row
fumigation). In both application techniques, sealing can be improved by applying polyethylene
film over the entire area or in strips (DowElanco 1994).
Research Summary
Several studies have been conducted comparing control of soil borne pests obtained with
methyl bromide fumigation to that obtained by formulations containing Telone® products.
Highlights of 1,3-D/chloropicrin research are presented in the two subsections below. The first
section describes other formulations of Telone®, and the second section presents information on
combination treatments consisting of Telone® C-17 with certain herbicides or integrated pest
management (IPM) techniques.
Other Formulations of Telone®
Researchers have been investigating formulations of Telone® with varying percentages of
chloropicrin for control of root-knot nematode, soil-borne diseases, and weeds. For example,
Telone® C-25, Telone® C-30, and Telone® C-35 contain 25,30, and 35 percent respectively in
combination with Telone®, while Telone® II contains 1,3-D as the sole active ingredient.
Increases in the percentage of chloropicrin are intended to raise the level of disease control
achievable. In general, these formulations have compared favorably with methyl bromide and
chloropicrin formulations, as described in the following bullets:
• Experiments compared the efficacy of Telone® C-17 and Telone® C-35 to methyl
bromide/chloropicrin formulations. These experiments were conducted in 1996 at
the Agronomy Research Farm at the University of Florida, Gainesville on
tomatoes. Researchers found root-knot nematode galling indices to be lower in
soil treatments of methyl bromide/chloropicrin (98/2), Telone® C-17 (1,3-D + 17
percent chloropicrin) and all treatments containing Telone® C-35 (1,3-D + 35
percent chloropicrin) than in the control. The study also found wilt caused by
Sclerotium rolfsii (southern stem blight) was reduced to one or fewer plant hits
per plot by methyl bromide/chloropicrin (98/2) and by all but one of the Telone®
C-35 treatments (Dickson 1996).
-------
• Telone® II/chloropicrin formulations were tested against methyl
bromide/chloropicrin in a study supported by the California Strawberry
Commission and ARS-USDA. In this study, Telone® II/chloropicrin formulations
were broadcast fumigated and covered with polyethylene tarpaulins for 5 days
before raising the beds. Relative to yields (100%) obtained following standard
fumigation with methyl bromide/chloropicrin (67/33 @ 325 Ib/acre), total yields
for 1994 and 1995 trials, respectively, were 98 and 108 percent with Telone® II
(l,3-D)/chloropicrin (70/30 @ 454-461 Ib/acre), and 109 percent with Telone®
II/Chloropicrin (70/30 @ 410 Ib/acre, 1995 only) (Duniway and Gubler 1996).
• Telone® C-17, Telone® C-25, and Telone® C-35 were compared with methyl
bromide in field tests conducted by the manufacturer of Telone® products in
Florida, California and North Carolina. Researchers compared these three
formulations of 1,3-D and chloropicrin to methyl bromide for nematode and soil-
borne disease control. Telone® C-35 performed similarly to methyl bromide based
on measurements of nematode counts, root damage, disease incidence and disease
severity (Melichar et al. 1996a).
• Research trials compared the efficacy of Telone® C-17 and Telone® C-30 with
methyl bromide on tobacco and peppers in Georgia. Researchers applied Telone®
C-17 (@ 20 gal/acre), Telone® C-30 (@ 20 gal/acre), and methyl
bromide/chloropicrin (@ 9 lbs/300 linear feet) to tobacco beds. They found no
significant differences between the treatments for control of soil borne diseases
(Pythium spp., Fusarium spp., Rhizoctonia solani), nematodes (root knot larvae,
ring, spiral), or weeds (purple cudweed, cutleaf evening primrose, and old field
toneflax) (Melichar et al. 1995).
Combination Treatments with Telone® C-17
Studies have shown the importance of using an herbicide in conjunction with Telone® C-
17 in areas where nutsedge is a problem. For example, a Florida study evaluated the efficacy of
Telone® C-17 on nematodes (Meloidogyne spp.), diseases (fusarium wilt, Fusarium oxysporum
f.sp. lycopersici, and fusarium crown and root rot, Fusarium oxysporum f.sp. radicis-
lycopersici), and weeds (yellow nutsedge, Cyperus esculentus, and purple nutsedge, Cyperus
rotundus). Telone® C-17 disease and nematode control was equivalent to methyl bromide,
however, Telone® C-17 did not provide equivalent weed control (Melichar etal. 1996b).
Although combination treatments with Tillam® have been very effective against weeds,
researchers have been looking into other herbicides and combination treatments for use with
Telone®, because Tillam® is currently registered for only three crops — tobacco, tomato, and
sugarbeets (Helena Chemical Company 1997). Summaries of research results for herbicides
including Tillam® and IPM practices that could be used in combination with Telone® products
are presented below.
-------
One of many studies in which a combination treatment of Telone® C-17 and
Tillam® was proven to be as effective as treatment with methyl
bromide/chloropicrin was conducted at the North Florida Research and Education
Center. Telone® C-17 (@ 35 gal/acre) and Tillam® 6E (@ 4 Ibs a.i./acre) were
applied and covered with black polyethylene mulch immediately after fumigation.
Telone® C-17/Tillam® produced the highest yield of medium and large fruit of all
the treatments and significantly higher yield of these fruits than methyl bromide
(Olson etal. 1996).
Researchers have also combined Telone® C-17 with Vapam®. Experiments
conducted at the University of Florida in 1995 compared the efficacy of methyl
bromide/chloropicrin (98:2 @ 400 Ib/acre), chloropicrin (@ 350 Ib/acre), and
Telone® C-17 (@ 35 gal/acre). Each plot was then treated with 956 ml Vapam®.
Although chloropicrin treatments resulted in numerically higher strawberry yields,
no significant differences in January yields were identified in any of the fumigation
treatments (Noling et al. 1996).
A 1996 study compared the efficacy of methyl bromide/chloropicrin on peppers to
that of Telone® C-17 and Devrinol® (napropamide) herbicide, the only in-bed
herbicide labeled for peppers. The trial was conducted late in the season, thereby
allowing time for only 2 harvests. Telone® C-17 (@ 21 gal/acre) and Devrinol®
(@ 3.4 Ib a.i./acre) produced significantly more peppers than the methyl bromide
treatment during the first harvest, and resulted in a minor cumulative yield
advantage after both harvests (Mueller 1997).
Another study considered the effects of soil solarization in combination with
Telone® C-17. This Florida study compared the efficacy of soil
solarization/Telone® C-17 fumigation with those of standard methyl bromide
application on tomatoes. Soil solarization in combination with reduced rates of
methyl bromide plus chloropicrin or Telone® C-17 provided significantly greater
control of root galling than soil solarization alone. In addition, rows treated with
soil solarization reduced the incidence of southern blight (Sclerotium rolfsii) to
less than 0.1 percent, whereas rows treated with only methyl bromide experienced
a 3.7 percent incidence of disease (Chellemi et al. 1996).
Availability and Regulatory Issues
Telone® products are currently available in Florida. Although regulatory issues (worker
exposure health-related concerns) were once a limiting factor in California (Melichar 1995),
Telone® II is now available in California. The California Department of Pesticide Regulation
draft permit conditions restrict use of Telone® products to 5,000 gallons per township (i.e., 36
square mile range) for application depths less than 18 inches and 9,500 gallons for depths greater
than 18 inches (Duniway 1997, Roby 1997).
-------
DowElanco is considering drip irrigation as a means to deliver Telone®, while reducing
1,3-D loss to the atmosphere. Several field studies have proven 1,3-D/chloropicrin combinations
to be effective nematicides when applied through drip irrigation. Drip irrigation of Telone® n
(1,3-D) is registered for melons in Arizona and studies are underway to determine the extent of
disease control achievable when using drip applied 1,3-D/chloropicrin combinations (Mueller
1995). i
Costs of Alternative
Because Tillam® is frequently used in combination with Telone® C-17 during tomato
production and because both are applied in a manner similar to the application of methyl
bromide/chloropicrin, alternative costs reflect the costs of the raw materials, only. Other costs
associated with Telone® C-17/Tillam® or methyl bromide/chloropicrin fumigation include labor
costs, machinery costs and the costs of time delays associated with protecting against
phytotoxicity and addressing human health concerns. An analysis of the raw material costs
associated with fumigation for tomatoes in Florida is presented in Table 1. Please note that
application rates are presented in terms of bed fumigation rather than broadcast fumigation.
Table 1.
Comparison of Estimated Raw Materials Costs for Row Applications
'fe&$t$$mt-\ '-"-
Application Rates
Cost per Unit
Total Material Cost
Teto»^€~l7/lHlanrt$
Telone® C-17
17.5 gal/acre
Tillam® 6E
2 Ib a.i./acre
Telone® C-17
$12.75-13.75/gal
Tillam® 6E
$7.66/lb a.i.
($45.95/gal)
$247/acre
IVfat&yJ liFeittide/ enloropicnn .;:
MeBr/Pic (98:2)
2001ba.i./acre
MeBr/Pic (98:2)
$1.12/lb
,
$224/acre
Sources: Eger 1997, Gilreath 1997, Helena Chemical 1997, and Asgrow 1995.
-------
References
Asgrow Agricultural Supply, Collier County, FL, personal communication, 1995.
Chellemi, D.; McSorley, R.; Rich, J.R. Presented at the Annual International Conference on
Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 42.
Dickson, D. Presented at the 1996 Annual International Conference on Methyl Bromide
Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 46.
DowElanco, Indianapolis, IN. Label Code 112-70-007, EPA Approval 4/93, 1994.
Duniway, J.M.; Gubler, W.D. Presented at the 1996 Annual International Conference on Methyl
Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 37.
Duniway, J.M., University of California, Davis, CA, personal communication, 1997.
Eger, J., DowElanco, Indianapolis, IN, personal communication, 1997.
Gilreath, J., Gold Coast Research and Education Center, University of Florida, Braedenton, FL,
personal communication, 1997.
Gilreath, J.P.; Jones, J.P.; Noling, J.W. Presented at the 1996 Annual International Conference
on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper
44.
Gilreath, J.P.; Jones, J.P.; Overman, J. "Development of Alternatives to Methyl Bromide in
Tomato Production"; report of Tomato Research: Supported by the Florida Tomato Committee
1993-1994; Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL,
1994.
Helena Chemical Company, personal communication, 1997.
Melichar, M.W.; Eger, J.E.; Huckaba, R.M.; Mueller, J.P.; Peterson, L.G. Presented at the 1995
Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, San
Diego, CA, November 1995; paper 51.
Melichar, M.W.; Huckaba, R.M.; Eger, J.E.; Mueller, J.P. Presented at the 1996 Annual
International Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando,
FL, November 1996a; paper 94.
Melichar, M.W. Presented at the 1996 Annual International Conference on Methyl Bromide
Alternatives and Emissions Reductions, Orlando, FL, November 1996b; paper 93.
-------
Melichar, M. Presented at the 1994 Annual International Conference on Methyl Bromide
Alternatives and Emissions Reductions, Kissimmee, FL, November 1994; paper 15.
Mueller, J.P. Presented at the 1995 Annual International Conference on Methyl Bromide
Alternatives and Emissions Reductions, San Diego, CA, November 1995; paper 28.
Mueller, T., Roger Seed Company, Naples, FL, personal communication, 1997.
Noling, J.W.; Gilreath, J.P.; Chandler, C.K.; Legard, D.E. Presented at the Annual International
Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November,
1996; paper 39.
!
Olson, S.M.; Rich, J.R.; Chellemi, D.O. Presented at the 1996 Annual International Conference
on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper
41.
Roby, D., DowElanco, Indianapolis, IN, personal communication, 1997.
Youngson, C.; Turner, G.; O'Melia, F. Control of plant parasitic nematodes on established tree
and vine crops with Telone II soil fumigant. Down to Earth 1981, 37(3). •
-------
-------
EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
September "4997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Fumigation with Carbonyl Sulfide for Controlling Pests on Perishable and Non-Perishable
Commodities
Carbonyl sulfide (CAS Number 463-58-1) has traditionally been used as a chemical
feedstock; however, recent studies suggest that carbonyl sulfide may be a technically and
economically viable alternative to methyl bromide for use as a non-perishable1 and perishable
commodity fumigant to control insects (e.g., termites, beetles, and moths) and mites, and possibly
as a soil fumigant for control of nematodes. The first research performed on the efficacy of
carbonyl sulfide was conducted by the Commonwealth Scientific and Industrial Research
Organization (CSIRO), which lodged a patent for carbonyl sulfide as a fumigant in July 1993
(CSIRO 1993). Further, the potential to use carbonyl sulfide to control stored product insects in
fruits and nuts is being evaluated through laboratory studies conducted by the United States
Department of Agriculture/Agricultural Research Service (USDA/ARS) Horticultural Research
Laboratory located in Fresno, California. Additional research needed to complete applications for
registering carbonyl sulfide as a pesticide in the U.S. and elsewhere in the world is currently
underway (Zettler et al. 1997, Banks 1996).
Benefits of Carbonyl Sulfide
^Effective method ofdisinfesting non-perishable
commodities.
-------
be useful as a non-perishable commodity fumigant. Recent data generated by USDA/ARS
suggest that carbonyl sulfide could also be useful as a perishable commodity fumigant. Studies
are on-going to determine its potential for use as a soil treatment and to determine potential
effects on commodity quality, if any. (Desmarchelier 1993, Banks 1996).
A number of tests have been conducted to determine the likelihood that carbonyl sulfide
could be used in commodity applications. First, Plarre and Reichmuth (1996) found that a
concentration (C) of 32 mg/liter for 72 hours (T) (CxT value of 2,304 mg/hr/liter) effectively
controlled all life stages of the granary weevil (Sitophilus granarius (L.)). Another study found
that with application rates of 25 mg/L combined with exposure periods of 24 hours (CxT value of
600 mg/hr/liter), over 99.8 percent efficacy could be achieved against some immature stages of
insects, including the rice weevil and lesser grain borer (Rhyzopertha dominica). It was also
determined that application rates could be lowered to 8 mg/L while still obtaining a high efficacy
(98.1 percent) if exposure periods were increased to 48 hours. It was suggested that the shorter
exposure periods with the higher application rates could potentially be used for treating perishable
commodities that require rapid fumigations prior to shipment (Desmarchelier 1993).
In addition to studies on grain pests, a recent USDA/ARS study evaluated carbonyl sulfide
for use on stored product insects affecting dried fruits and nuts (Zettler et al. 1997). The toxicity
of carbonyl sulfide for five economically important pest species was determined. The insects
tested included larval navel orangeworm, Amyelois transitella (Walker); adult sawtooth grain
beetle, Oryzaephilus surinamensis (L.); adult driedfruit beetle, Carpophilus hemipterus (L.); adult
cigarette beetle, Lasioderma serricorne (F.); and adult confused flour beetle, Tribolwn confusum
(Jacquelin duVal). Each pest had different susceptibilities to fumigation with carbonyl sulfide,
with LC90 toxicities ranging from 2.66 to 15.4 mg/liter. The CxT value which resulted in
complete mortality for the most resistant life stage of the least susceptible insect tested (i.e., the
egg and pupal stage of the adult confused flour beetle) ranged from 750 to 1,008 mg/hr/liter for a
24 hour exposure. Based on these results, it was concluded that carbonyl sulfide could be an
effective fumigant for dried fruits and nuts.
The CSIRO Stored Grain Research Laboratory has also conducted tests to identify the
effects of carbonyl sulfide treatment on the quality of malting barley, wheat (various types),
sultanas, chickpeas, and canola (Desmarchelier 1993). The results of these tests are as follows:
• Barley displayed no significant loss of malting quality when treated with carbonyl
sulfide. Similarly, no significant effects have been found on wheat or flour
properties with the exception of marginal effects on dough properties. None of
these commodities displayed a foreign odor.
• Although research on canola and chickpeas is still underway, researchers found
little or no sorption after 24 hour exposures and no detectable odor after 24 hours
airing.
• Sultanas fumigated with carbonyl sulfide were assessed for quality by taste, odor,
and color change. Fumigated fruit had a distinctive odor, which diminished over
time. There were no taste or color changes detected.
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Additional research (Desmarchelier 1993) on wheat fumigated with carbonyl sulfide has revealed
the following. ;
• Studies of the sorption of carbonyl sulfide by wheat have been conducted, with the
detection of very low levels of possibly naturally occurring carbonyl sulfide in
untreated controls. As carbonyl sulfide concentrations in fumigated wheat decline,
it becomes increasingly difficult to distinguish carbonyl sulfide in fumigated wheat
from that in untreated wheat.
• A comparative study on the effects of carbonyl sulfide and hydrogen cyanide
(HCN) on germination and plumule length of wheat indicates that carbonyl sulfide
can be used to control insect infestation in wheat without affecting seed viability or
plumule length (i.e., it has no effect on seedling vigor and thus potentially is a
valuable treatment for seed for planting).
Additional studies being conducted to support carbonyl sulfide registration as a fumigant
are evaluations of soil and commodity residue potential, flarnmability, and the potential for worker
exposure. Many of the toxicity, emission, and environmental fate studies needed to complete
registration have been completed (Banks 1996, Desmarchelier 1993). Studies to more accurately
determine the efficacy of carbonyl sulfide for controlling specific insect species are also being
initiated (Zettler et al. 1997).
Performance Characteristics
With regard to its potential as a commodity fumigant, carbonyl sulfide has what is
considered to be excellent physical and chemical characteristics (Banks 1994, Desmarchelier
1993, Kluczewski et al. 1985). Its spectrum of activity, mobility and penetration, efficacy, and
environmental fate characteristics are briefly discussed below.
• Spectrum of activity - Carbonyl sulfide effectively controls insect pests and mites. It may
also be useful for controlling soil borne pests such as nematodes; additional research is
pending.
• Mobility and penetration - Carbonyl sulfide has a high penetration and mobility rate;
thereby increasing distribution and efficacy. This characteristic may be particularly useful
for fumigation of logs and lumber, where its penetration is much superior to methyl
bromide.
• Efficacy - In ten comparative efficacy studies using the rice weevil and lesser grain borer,
carbonyl sulfide consistently out-performed carbon disulfide at application rates ranging
from 8 mg/L to 24 mg/L and exposure periods of up to two days. Data on direct efficacy
comparisons with methyl bromide generally are not available. Efficacy, comparisons for
treatment of logs indicate that carbonyl sulfide may be comparable to methyl bromide.
Further, studies evaluating the efficacy of carbonyl sulfide for controlling stored product
insects in dried fruits and nuts indicate the potential for carbonyl sulfide to replace methyl
bromide in these applications.
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Environmental fate - Carbonyl sulfide is biodegradable, is a natural part of the sulfur-
cycle, and has low water solubility.
Cost Comparison Data
Although cost data for the use of carbonyl sulfide are not currently available because
research and development is still in the early stages, it is believed that carbonyl sulfide will be both
a technically and economically viable alternative to methyl bromide (Banks 1996 and 1994,
Desmarchelier 1993).
References
Banks, H.J., Commonwealth Scientific and Industrial Research Organization (CSIRO), Stored
Grain Research Laboratory, Canberra, Australia, personal communication, 1996.
Banks, HJ. Presented at the International CFC and Halon Alternatives Conference, Washington,
D.C., October 1994; notes on presentation.
Commonwealth Scientific and Industrial Research Organization (CSIRO). "Carbonyl Sulphide as
a Furnigant for Control of Insects and Mites"; CSIRO report, p 1; CISRO: Canberra, Australia,
1993.
Desmarchelier, J.M. "Carbonyl Sulphide as a Furnigant for Control of Insects and Mites";
Commonwealth Scientific and Industrial Research Organization (CSIRO); CISRO report; CISRO:
Canberra, Australia, 1993.
Desmarchelier, J.M. Presented at the 6th International Working Conference, Canberra, Australia,
1994; pp 78-82.
Kluczewski, S.M.; Brown, K.A.; Bell, J.N.B. Deposition of carbonyl sulphide to soils;
Atmospheric Environment 1985, 19(8).
Plarre, R.; Reichmuth, C. Effects of carbonyl sulfide (COS) on Sitophilus granarius, Fusarium
avenaceum, and Fusarium culmorum, and possible corrosion on copper. Nachrichtenblatt des
Deutschen Pflanzenschutzdienstes 1996,48(5), 105-112.
Zettler, L.; Leesch, J.G.; Gill, R.F.; Mackey, B.E. Toxicity of carbonyl sulfide to stored product
insects. Journal of Economic Entomology, submitted for publication.
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&EPA
United States
Environmental
Office of Air and Radiation
(6205-J)
September 1997
Protection Agency
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Use of Controlled Atmospheres As A Quarantine Treatment for Table Grapes
Controlled atmosphere technology with elevated carbon dioxide and/or reduced oxygen
concentrations can be a viable alternative to methyl bromide as a post harvest quarantine
treatment for table grapes. It is effective against insect pests and pathogens (Carpenter and Potter
1994) and has the added benefit of improving the quality of grapes and extending their shelf life
by lowering respiration rates (Mitcham et al. 1994). Other benefits include the prevention of
color change and softening and the maintenance of fruit composition and nutritional value.
Furthermore, the gas used in this technology are chemically inert and will not corrode handling
equipment (Ke and Kader 1992, Calderon and Barkai-Golan 1990). Unlike some other
fumigants, controlled atmosphere treatments (with carbon dioxide and/or nitrogen) do not leave
toxic residues on grapes. The treatment also penetrates more easily than most fumigants because
of its small molecular size (Smith and Newton 1992). Furthermore, grapes are ideally suited for
this treatment technique because they produce very little ethylene (a compound emitted from fruit
which stimulates ripening) and are highly resistant to its effects (Lamb 1996).
Technological advances have
led to the development of refrigerated
controlled atmosphere sea transport
shipping containers used by
commercial exporters for storage
treatment. These containers can be
equipped with controlled atmosphere
units that control insects and other
pathogens. As a result, controlled
atmosphere technologies could be
used as quarantine treatments. By
maintaining low oxygen levels and
refrigerated temperatures, decreased
commodity spoilage and pest control
can be accomplished (Gay 1995).
Furthermore, because of the demonstrated benefits of sulfur dioxide in combination with carbon
dioxide in the control of black widow spiders (Shorey and Wood 1993), omnivorous leafrollers,
and other grape pests, it may be possible to combine these two treatments to achieve even more
effective control of grape pests (Mitcham et al. 1994).
Benefits of Using Controlled Atmospheres on Grapes
^ Penetrates easily to reduce or eliminate insects and
pathogens
f Increases product value by extending shelf life and
enhancing fruit quality
*^ Prevents color change and softening
t^ Maintains fruit composition and nutritional value
V* Does not corrode handling equipment
*^ Leaves no toxic residues
<^ Allows use of more economical surface transport
for shipping commodities
f Can be used in conjunction with other treatments,
such as sulfur dioxide
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Controlled Atmosphere Technologies
Controlled atmosphere technology has been used to control a variety of economically
important pest species including thrips, aphids, and beetles infesting a wide variety of fruits and
vegetables, including grapes (Anonymous 1993b). Controlled atmosphere technology works by
reducing the respiration of grapes, inhibiting pathogen reproduction, and killing insects and
pathogens. The greatest impact on insects is achieved by maintaining low oxygen levels for an
extended period of time, leading to oxygen depravation in insect body tissues (Gay 1995).
Controlled atmospheres are most effective at preserving grapes when they exhibit no signs of
senescence or damage from handling; therefore field packaging, purchase of physiologically
younger, less ripe commodities, and installation of ripening rooms may reduce difficulties in using
controlled atmosphere technologies for grapes (Anonymous 1993b).
The effectiveness of controlled atmospheres varies depending on the insect species and
developmental stage, temperature, oxygen and carbon dioxide levels, and relative humidity.
Likewise, factors influencing the grapes treated with controlled atmosphere technology include
storage temperature, oxygen concentration, respiration rate, resistance of gas diffusion, soluble
solids content, and ethanol accumulation rate of the commodity under a low oxygen treatment
(Ke and Kader 1992, Calderon and Barkai-Golan 1990).
Current Research
Current research on the use of controlled atmospheres on grapes is being conducted at the
University of California at Davis. The main focus of this research is the development of a
quarantine treatment technique for export of grapes from California to Australia (although the
same research may later be applied to U.S. imported grapes from Chile). Currently, U.S. grapes
are not exported to Australia; however, a proposal for use of controlled atmospheres as a
quarantine commodity treatment for grapes snipped to Australia is currently under review (Kader
1996, Christie 1996). Pests of quarantine concern to Australia include the omnivorous leaf roller
(Platynota stultand), western flower thrips (Frankliniella occidentalis), spider mites, and grape
mealy bug (Pseudococcus maritimus) (Mitcham et al. 1994).
Initial studies indicate that table grapes can tolerate and are effectively disinfested by
carbon dioxide. For example, Mitcham et al. (1995) demonstrated that by increasing the carbon
dioxide levels and lowering temperatures to 45 percent and 0°C to 5°C, respectively, over an 8 to
10 day period results in 100 percent mortality of all life stages in the pests of economic concern.
Research is still pending for the Grape Mealy Bug. Grapes have also been evaluated for firmness,
soluble solids, berry shatter, browning, and weight loss of the cluster. In general, controlled
atmospheres have only minimal effects on grape quality. The most notable difference between
treated and non-treated grapes was a decrease in titratable acidity in treated grapes; however,
there was not consistent effect on berry shatter, weight loss, or soluble solids. Future research
will include consumer taste tests (Mitcham et al. 1994 and 1995).
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Potential to Use Controlled Atmospheres as Quarantine Control Technology in Grapes
Current U.S. regulation requires that grapes be fumigated with methyl bromide as a
condition of entry (i.e., Chilean grapes-which undergo treatment because of a mite).
Furthermore, grapes exported by the United States must be fumigated with methyl bromide in
order to comply with the quarantine requirements of recipient countries (i.e., Japan). Finding
alternatives to methyl bromide as a quarantine commodity treatment is critical because large
quantities of grapes are both imported to and exported from the United States and may cany non-
indigenous insects and pathogens. In 1989 to 1990, for example, the United States imported an
annual average of approximately 372,135 tonnes of grapes of which 302,502 tonnes (92 percent)
were fumigated with methyl bromide. In fact, grapes flimigated with methyl bromide represented
34 percent of the annual U.S. fresh grape supplies in that same year (Anonymous 1993a). By
comparison, currently 80 percent (1,488,540 tonnes) of table grapes are consumed domestically,
while 20 percent (372,135 tonnes) are shipped overseas; therefore, the use of controlled
atmospheres could increase trade by lowering costs and extending shelf life (Wineman 1996,
Anonymous 1993a).
After a disinfestation treatment, the majority of controlled atmosphere shipments do not
require methyl bromide fumigation for quarantine control of pests (Gay 1995b). However,
controlled atmospheres are not currently recognized by USDA's Animal and Plant Health
Inspection Service (APHIS) as a quarantine treatment, and therefore if a quarantine pest was
found on the shipment, fumigation with methyl bromide would be required for quarantine
purposes (Gay 1995b). Industry, government, and academic partnerships are currently compiling
data on pest control efficacy required to secure quarantine approval. If successful, controlled
atmosphere technology for grapes may become an important quarantine treatment technology.
Continued research is expected to lead to effective methods to achieve insect control that will
satisfy strict international quarantine regulations (Gay 1995, Mueller 1994, Delate and Brecht
1989).
Costs
Although controlled atmosphere technologies require significant operating, labor, and
capital investments in hardware required to customize containers, the benefits in these investments
far outweigh the costs, making it an economically viable alternative to methyl bromide
(Anonymous 1993b). Estimating costs for application of controlled atmosphere technology
compared to methyl bromide use is presented in Table 1 below. Two standard methods used to
conduct controlled atmosphere treatments are presented independently. Although capital, labor,
and operating costs vary between these two methods, their total costs are similar. The first
method has low capital costs but high labor and operating costs, while the opposite is true for the
second method.
In the first treatment method, the controlled atmosphere unit partially displaces air in the
container by purging the container with carbon dioxide (usually supplied via a compressor) and
closing the system until the container has reached its final destination. The second method is
believed to be more effective because it is more automated. The process generates nitrogen from
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surrounding air, which is then pumped into the chamber. Gas concentrations in the containers are
then monitored and maintained throughout transport in an open system which vents gases to the
atmosphere (Lamb 1996, Calderon and Barkai-Golan 1990). In general, the cost to adapt a
shipping container for controlled atmosphere treatments cost between $800 to $7,000 per
container, depending on which type of treatment method is used, the number of containers
shipped, the type of commodity, destination, place of origin, and pests of concern (Cea 1996, Gay
1995). Typically controlled atmosphere equipment has a useful life of about 10 years and is used
between 6 and 12 times a year. Currently commercial facilities only use controlled atmospheres
to improve grape quality and extend shelf life; however, it was assumed that storage treatment
costs (operating and labor costs) would be comparable to the costs of disinfestation treatments
with controlled atmospheres. As a result, treatment costs range from $800 to $1,200 per
container. Fumigating grapes with methyl bromide, on the other hand, costs nearly twice as much
as controlled atmosphere treatments. Specifically, operating/labor costs for methyl bromide
fumigation represents a large percentage of the total costs, while capital and chemical costs are
relatively minor.
If controlled atmosphere technology becomes an approved quarantine treatment, shippers
will quickly recover their initial investment as expensive methyl bromide treatments will no longer
be required. Furthermore, methyl bromide can often damage, destroy, or shorten the shelf life of
grapes. Therefore, the risks associated with reduced inventory due to fumigation can partially
offset the costs of using controlled atmosphere technology (Murphy 1995). Lastly, controlled
atmosphere treatments add significant value to grapes by extending and improving both their
quality and shelf life and enabling them to be shipped using surface transport where aircraft or
airlift transport was required previously (Gay 1995).
Table 1. Costs Comparison for Controlled Atmospheres vs. Methyl Bromide.
^|iyFafett*$. - """ ,„
Annualized Capital
Labor & Operating
Chemical
Total
CsntroHed Atm&$bfer$$
- e^sfctand^
•(ponne)
<1
45-58
N/A
46-59
8
66
N/A
74
Methyl bromide
{PKM»$
5
100-150
<1
106-156
Notes: N/A = Not applicable.
Sources: Rodde 1996, Lamb 1996, Cea 1996, Folwell 1996.
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References
Anonymous. "The Biological and Economic Assessment of Methyl Bromide"; report of the
National Agricultural Pesticide Impact Assessment Program; United States Department of
Agriculture: Washington, D.C., 1993a. ;
Anonymous. "Pacific Surface Initiative and Produce Shipment Losses To Guam"; Defense
Subsistence Region Pacific, Defense Logistics Agency, Department of Defense: Alameda, CA,
1993b.
Carpenter, A.; Potter, M. In Quarantine Treatments for Pests of Food Plants; Sharp, J.L. and
Hallman, G.J., Eds.; Western Press: San Francisco, CA, 1994, pp 171-198.
Cea, M.A., Ag-Fume Services Inc., Downey, CA, personal communication, 1996.
Christie, J., W.L. Bryant Corp., Seattle, WA, personal communication, 1996.
Calderon, M.; Barkai-Golan, R. Food Preservation by Modified Atmospheres; CRC Press: Boca
Raton, FL, 1990.
Delate, K.; Brecht, J. Quality of tropical sweet potatoes exposed to controlled-atmosphere
treatments for postharvest insect control. Journal of the American Society for Horticultural
Science 1989, 114(6).
Folwell, R., Department of Agricultural Economics, Washington State University, Pullman, WA,
personal communication, 1996.
Gay, R., LCDR, MSC, USN, Staff Entomologist, Quality Assurance Division, Directorate of
Subsistence, Alameda, CA, personal communication, 1995.
Kader, A.A., Department of Pomology, University of California, Davis, CA, personal
communication, 1996.
Ke, D.; Kader, A. A. Potential of Controlled Atmospheres for Postharvest Insect Disinfestation of
Fruits and Vegetables. Postharvest News and Information 1992, 3 (2), p 31N-37N.
Lamb, J., Carrier Transicold, Syracuse, NY, personal communication, 1996.
Mitcham, E.J.; Ahumada, M.; Shorey, H. Presented at the 1994 Annual International Research
Conference on Methyl Bromide Alternatives and Emissions Reductions, Kissimmee, FL,
November 1994; paper 77.
Mitcham, E.J.; Ahumada, M.; Bikoba, V. Presented at the 1995 Annual International Research
Conference on Methyl Bromide Alternatives and Emissions Reductions, San Diego, CA,
November 1995, paper 10.
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Mueller, D., Fumigation Services and Supply, Indianapolis, IN, personal communication, 1994.
Murphy, K., Transfresh, Salinas, CA, personal communication, 1995.
Rodde, K., Transfresh, Salinas, CA, personal communication, 1996.
Shorey; Wood. "Control of Black Widow Spiders in Table Grapes"; 1992-93 research report for
California table grapes, Vol. 21, 1993.
Smith, C.P.; Newton, J. "Carbon Dioxide: The fumigant of the future"; white paper for Rentokil
Group Inc.: West Sussex, United Kingdom, 1992
Wineman, D., California Table Grape Commission, Fresno, CA, personal communication, 1996.
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&EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
September 1997
Stratospheric Ozone Protection
Methyl Bromide Alternative
Case Study
Phosphine/Carbon Dioxide Combinations As Alternatives to Methyl Bromide
in Structural and Commodity Fumigation
This is an update of a July 1995 EPA report (Alternatives to Methyl Bromide, Ten Case Studies) entitled "Structural
Fumigation Using a Combined Treatment of Phosphine, Heat, and Carbon Dioxide". Considerable work has been done
since that report with regard to the described pest control method, as well as two other methods which also use
significantly reduced amounts of phosphine combined with carbon dioxide. This report presents these methods as viable
alternatives to the use of methyl bromide in appropriate treatment situations.
Currently seven percent of domestic methyl bromide consumption is for commodity and
quarantine fumigation (Anonymous 1994b). Phosphine, another fumigant gas, has been used
successfully to control insects in a number of plant and animal commodities (especially stored
products), and therefore can be a viable alternative to methyl bromide treatments. Compared to
methyl bromide, phosphine treatments can be more economical and easier to use in some
situations . When used correctly, phosphine can have a broader spectrum of activity, penetrate
more effectively and deeper into commodity storages (thus reducing the number of fumigations
required and the amount of shut down time needed to perform the fumigation) and can exceed the
95 percent minimum kill rate required for methyl bromide fumigations (Sloane Group 1996).
Existing phosphine formulations
available on the market include air-tight
packages of pellets, tablets and plates
(sachets) which contain and inert
ingredients. Once the package is
opened, the metallic phosphides contacts
with moisture in the air, and phosphine
gas is slowly produced. The metallic
phosphides most commonly used
include: magnesium phosphide (used
primarily in the United States because it
is safer and releases phosphine faster
than other phosphine compounds), calcium phosphide, and aluminum phosphide (primarily used in
Canada) (Phosphume™ 1996, AAC 1996, Sloane Group 1996). During conventional phosphine
commodity treatments, structures are first sealed and then the solid fumigant is placed in the
container or structure in several places to assure complete gas dispersion. Phosphine levels reach
Benefits of Phosphine Treatments
S Economical and easy to use
/" Has a broad spectrum of activity
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the desired concentration in 3 to 10 days to achieve the proper effect. Following treatment, the
structure is aerated and the inert ingredient residue disposed of properly (Kelley 1997).
Although conventional phosphine treatments are convenient to use, there are use
limitations as a commodity treatment. For example, conventional phosphine treatments can take
up to two days to reach required concentrations, leave residual dust after the treatment, and can
be corrosive to precious metals or alloys (i.e., copper, brass, gold, silver). There are also health
and safety concerns associated with handling products that emit phosphine when exposed to the
air (sometimes at flammable concentrations leading to unexpected fires and possible explosions)
(Phosphume™ 1996, AAC 1996, Kelley 1997, Sloane Group 1996).
Because of these disadvantages to conventional phosphine treatments, recently improved
phosphine treatment methods: such as the combination method (using heat, phosphine, and
carbon dioxide); the cylinderized phosphine gas ECO2FUME; and the TURBO HORN
(phosphine) GENERATOR, may be more appealing alternatives to methyl bromide treatments in
the future. A more detailed description of these treatment techniques is presented below.
Phosphine Treatment Techniques
COMBINA TION TREA TMENT
Combining heat, phosphine, and carbon dioxide as a commodity treatment technique was
first tested in 1992 and refined and patented by David Mueller of Fumigation Service & Supply
Inc. (FSS) in Indianapolis. Since then researchers in the United States at Purdue University and
Oklahoma State University, and in Canada, South America, and Europe have demonstrated the
effectiveness of combination treatments as a pest control method in flour mills (e.g., Hawaiian
Flour Mill in Honolulu and the Quaker Oats Company of Canada Limited), food processing
plants, and museums (Anonymous 1994a, AAC 1996, McCarthy 1996). The combined treatment
consists of 50 to 100 ppm phosphine (9 to 18 percent of the standard phosphine concentration),
heat (89.6-98.6°F, 32-37°C), combined with 4 to 6 percent carbon dioxide. Using low
concentrations of phosphine reduces the chance of corrosion of metallic materials at facilities, a
common problem associated with conventional phosphine treatment techniques. Furthermore,
heat and carbon dioxide help reduce moisture, thereby limiting corrosion. The process relies on
heat and carbon dioxide to increase the susceptibility of pests to phosphine by interfering with
insect metabolism (i.e, by dilating insect spiracles, increasing respiration and interfering with
cellular energy cycles). This stress on the insect allows for low levels of phosphine to more
effectively kill all insect life stages, including the egg stage (Anonymous 1994a, Mueller 1994a).
Experiments have shown that combined treatments can produce 100 percent mortality within 24
hours or less for the egg, larvae, pupae, and adult stages of stored-product insects, including the
Angoumois grain moth, red flour beetle, warehouse beetle, and rice weevil (Mueller 1994b).
Over the last five years, more than 40 successful combination fumigations have been
performed. Twenty-four of these have been for flour mills, resulting in use reductions of over
100,000 Ibs. of methyl bromide (Mueller 1994b, Mueller 1994c, Mueller 1996a). This patented
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process is less expensive than heat, more practical than carbon dioxide, and safer and more
effective than phosphine alone (AAC 1996, Mueller 1994c). As a result, the combination
technique shows promise as a replacement for methyl bromide in flour mills and food processing
facilities (Anonymous 1994a).
ECOfVME
BOC Gases Group has developed and patented ECO2FUME, a gaseous phosphine
fumigation mixture that can be used as an alternative to in-situ generation of phosphine from
metallic phosphides. It consists of 2.6 percent by volume of phosphine in carbon dioxide
premixed in a cylinder and can be used on a wide variety of products, including foods, tobacco,
timber and cane products, buildings, and other structures (Phosphume™ 1996, Carmi et al. 1995,
Sloane Group 1996).
Eco2Fume appears to offer many advantages over other phosphine fumigation techniques,
including improved health and worker safety, environmental benefits, and product quality (Ryan
1991, Phosphume™ 1996, Carmi et al. 1995, Sloane Group 1996). Since Eco2Fume is premixed
and ready to use, the need for on-site mixing is eliminated. The gas is dispensed directly from the
cylinder into a sealed structure to be fumigated. The technique achieves the required
concentration in a matter of hours, allowing for greater and more immediate control of phosphine
concentrations during the entire fumigation period. Because the gas is dispersed quickly and
reaches the desired concentration in a short period of time, the treatment itself is shorter, and
may result in less frequent fumigations, thus reducing the risk of corrosion. The treatment
prevents incomplete or variable phosphine generation (such as that acquired with the use of
metallic phosphides), eliminates the need for disposal of residual product, and reduces worker
exposure.
As of the date of this publication, Eco2Fume does not have a label which allows use as a
commodity or quarantine treatment technique in the United States. However researchers are
collecting data and developing the necessary information to meet regulatory requirements.
Studies are also being conducted on the use of Eco2Fume in quarantine situations (e.g. pre-
shipment, pre-marketing fumigations). Furthermore, BOC has initiated plans for plant production
and sourcing of phosphine. The registration process to receive use labels has been initiated in the
U.S., Canada, Europe, and other parts of the world. The product is expected to be available on
the global market by the end of 1997, registered as Eco2Fume in the U.S. and Canada, and
Phosfume™ in Australia and Europe (Mueller 1996b, Anonymous 1997). Although Eco2Fume
has not been used extensively in the United States, over 9 million metric tons of grain are
fumigated in Australia each year using the Phosfume™ process (Sloane Group 1996, Anonymous
1997). Eco2Fume also has proven to be highly effective and beneficial to the cut flower industry
(MacDonald and Mills 1995), and as a result, this pest control tool has good potential to be a
viable substitute for methyl bromide in this and other commodity fumigation applications (Mueller
1996b, Kelley 1997, Carmi et al. 1995)).
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TURBO HORN GENERATOR
A new method of generating phosphine gas, the Turbo Horn Generator (manufactured by
Fosfoquim S.A. in Santiago, Chile) has been developed, field tested, and patented by Degesch de
Chile. The method involves an apparatus that rapidly produces phosphine on site when
magnesium phosphide granules (a new, product) are placed in the unit with water, producing
hydrogen phosphide under controlled conditions. The gas is then mixed in the apparatus with air
and carbon dioxide until hydrogen phosphide concentrations reach approximately 2.5 percent.
The gas then is pumped directly into the structure to be fumigated, while air is drawn from the
structure and recirculated through the system to maintain a constant pressure and distribution.
The system quickly produces large amounts of gas from a relatively small amount of reactants and
can quickly be reloaded to produce more gas if necessaiy. Residues or any remaining reaction
products remain in the apparatus and can easily be disposed of following treatment. Lastly, the
generator is computerized to operate automatically or manually and will stop automatically if any
irregularity or technical problems occur (Fosfoquim S.A. and Degesch De Chile Ltda 1996).
Advantages of the Turbo Horn Generator include a flexible system where gas
concentrations can be adjusted at any time during the fumigation, and allows gas generation under
various temperatures and humidities. Furthermore, the system is easy to use and cost effective.
This technique has already been successfully utilized in several flour mills, granaries, and silos
(Fosfoquim S.A. and Degesch De Chile Ltda. 1996).
Costs
In general, the cost of phosphine treatments are only slightly higher than those using
methyl bromide. This is attributed to the fact that phosphine treatments require marginally more
equipment, labor, and technical expertise than methyl bromide treatments (Table 1). However,
phosphine treatment costs are expected to decrease in the future as new advances in phosphine
gas generation technology are made. For example, after initial capital costs, the Turbo Horn
Generator is less expensive than conventional phosphine treatment techniques. Furthermore,
because much of the cost for conventional fumigations is that associated with the facility
shutdown time necessary to complete disinfestation, phosphine treatments, when correctly
applied, are cost effective because they can require a shorter shutdown than required for methyl
bromide treatments (Mueller 1994c).
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Table 1. Comparison of Phosphine and Methyl Bromide Treatment Costs
($ per 1,000 cubic feet)
Labor
$4.25
$4.50
NA
$4.50
$4.75
$5.10
Equipment
$0.25
$0.75
NA
$1.25
Chemical
$1.15
$1.00
NA
$1.50
$2.00
$4.50
Additional
$1.75
$1.85
NA
$2.00
$1.50
$1.50
TOTAL
$7.40
$8.15
NA
$9.25
$8.25
$11.10
Notes: NA = not available at this time.
Source: Mueller 1994c, Sullivan 1997.
References
Anonymous. ECO2FUME: a new furnigant. Fwnigants & Pheromones 1997, No. 41, 1-2.
Anonymous. Methyl bromide phase-out. Fwnigants & Pheromones 1994a, No. 34, 4-5.
Anonymous. Montreal Protocol on Substances that Deplete the Ozone Layer; Methyl Bromide
Technical Options Committee (MBTOC), 1995 Assessment. United Nations Environment
Programme, 1994b; EPA 430/K94/029.
Agriculture and Agri-Food Canada (AAC). "Heat, Phosphine, and CO2 Collaborative
Experimental Structural Fumigation"; report to the Canadian Leadership in the Development of
Methyl Bromide Alternatives; Ottawa, Canada, 1996.
Carmi, Y.; Kostjukovsky, M.; Binenboim, I.; Golani, Y.; Frandji, H. Presented at the 1996
Annual International Research Conference on Methyl Bromide Alternatives and Emissions
Reductions, Orlando, FL, November 1996; paper 76.
Fosfoquim S.A. and Degesch De Chile Ltda., Santiago, Chile, unpublished results, 1996.
Kelley, P., Fumigation Service & Supply, Inc., unpublished results, 1997.
-------
Macdonald, O.C.; Mills, K.A. Presented at the 1995 Annual International Research Conference
on Methyl Bromide Alternatives and Emissions Reductions, San Diego, CA, November 1995;
paper 95.
McCarthy, B. Presented at the 1996 Annual International Research Conference on Methyl
Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996; paper 60.
Mueller, D.K., Fumigation Services & Supply, Indianapolis, IN, personal communication, 1994c.
Mueller, D.K. In Stored Product Protection: Proceedings of the 6th International Working
Conference on Stored-product Protection. Volume I; Highley, E.; Wright, E.J.; Banks, H.J.;
Champ, B.R., Eds.; Canberra, Australia, 1994b; paper 55.
Mueller, D.K. Methyl bromide alternative update. Fumigants & Pheromones 1994a, No. 34, p 2.
Mueller, D.K. Presented at the 1996 Annual International Research Conference on Methyl
Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996a; paper 68.
Mueller, D.K. Presented at the 1996 Annual International Research Conference on Methyl
Bromide Alternatives and Emissions Reductions, Orlando, FL, November 1996b; paper 75.
Phosphume™. BOC Gases Label, HOR020116, MSVAUS, 1195,10k, BOC Gases Australia
Limited, Chatswood, New South Wales, 1996.
Ryan, R.F. Presented at the Australian Institute of Food Science and Technology 24th Annual
Convention, Hobart, Australia, July, 1991.
Slone Group, The. "ECO2FUME: Executive Summary. ECO2FUME Tolerance Data"; Report
by the Slone Group: Greenwich, CT, 1996.
Sullivan, J.B., Sullivan and Associates, Inc., Harrisonburg, VA, personal communication, 1997.
•U.S. Government Printing Office: 1997 - 521-100/90228
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