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Introduction Methyl bromide is one of the most widely used pesticides in the world. It is used as a preplant soil treatment to kill soilborne pathogens, nematodes, weeds, and insects, and as a postharvest treatment to kill insects and other arthropods infesting harvested commodities. In many cases shipment of commodities is contingent on methyl bromide fumigation to avoid introduction of quarantined pests to new locations. The Montreal Protocol and the U.S. Clean Air Act require that methyl bromide be banned for most uses in the United States and other developed countries in 2005. This will be accomplished by a prohibition on the manufacture or importation of methyl bromide except for quarantine and essential uses. ARS conducts a $14.8 million research program to find alternatives for the many current methyl bromide uses. ARS works closely with the U.S. Environmental Protection Agency to facilitate the approval and registration of new chemical and biological alternatives to methyl bromide. The USDA is a sponsor for the Annual International Methyl Bromide Alternatives Conference. In addition, ARS holds numerous meetings with client groups to get input about the methyl bromide alternative program. ARS also held two large meetings to review the methyl bromide alternatives research programs, one in Florida and one in California. Input received from these two meetings was incorporated into an implementation plan currently being developed to guide the research programs for the next 5 years. Selected Accomplishments for Fiscal Year 1999 (Listed by Component) Preplant Soil Fumigation Alternatives Approximately 75 percent of the methyl bromide used in the United States is used to fumigate soil before planting crops to kill weeds, plant pathogens, nematodes, and insects. There is currently no registered fumigant that can directly replace methyl bromide for all uses. An array of alternative control measures will be required. Such measures include combinations of fungicides, herbicides, and insecticides; replacement fumigants; and nonchemical alternatives, such as cultural changes in cropping systems, development of resistant crops, biological control, and integrated pest management to prevent a buildup of plant pathogens, nematodes, weeds, and insect pests. Methyl iodide and Telone-Vapam control parasitic nematodes on grape replants . Methyl bromide is used to fumigate soil before replanting grapes and other perennial crops to control nematodes and other soil-dwelling plant pest organisms that cause replant disease. Parasitic nematode levels in soil were below detectable limits 18 months after the soil, which was previously planted to grapes, was treated with methyl bromide, methyl iodide and Telone-Vapam. ARS scientists at Fresno, California, also showed that fallow and fallow with cover crops were ineffective in control of these replant disease-causing organisms. This research provides alternatives to methyl bromide, which is scheduled to be banned in 2005, provided that regulatory problems restricting or preventing their use can be overcome. Methyl bromide alternative for squash, bell peppers, and cucumbers. The impending ban on use of methyl bromide as a soil fumigant for
vegetable crop production has led to the formation of a team comprised of
scientists from the ARS facility in Tifton, Georgia and the University of
Georgia. The research team demonstrated that Telone + chloropicrin chisel
injected + metam sodium under plastic film mulch and drip irrigation effectively
controlled root-knot nematodes and soil-borne diseases on squash and cucumbers.
Similar treatments plus the integration of a root-knot nematode-resistant bell
pepper cultivar (developed and released by the ARS Vegetable Laboratory in Charleston, South Carolina) indicates that this is a promising alternative to methyl bromide for peppers, as well. This research shows promise that an integrated approach to manage root-knot nematodes and soil-borne diseases in vegetable crop rotations under film mulch and drip irrigation provides an effective and practical alternative to methyl bromide for these crops in south Georgia. Natural products show promise as methyl bromide alternatives in an integrated pest control system. Because methyl bromide is such a highly effective soil fumigant, it is used in the production of over 100 crops, including ornamental nurseries, bulbs, and cut flowers. The development of alternatives to methyl bromide will have a major impact on the U.S. agricultural industry. A scientist at Beltsville, Maryland, conducted laboratory and greenhouse experiments with several proprietary natural product formulations in soil systems infested with two major pathogens, Fusarium oxysporum and Phytophthora nicotianae, and showed that
several of the formulations were efficacious in reducing populations of test pathogens to levels below detection. In addition, seed or seedlings planted into the treated soils grew with little or no disease expression. Demonstration of the efficacy of these botanical formulations provides the basis for further development of natural products, alone or in combination with other components, as alternatives to preplant methyl bromide fumigation. Identification of a gene that aids colonization of plants by biocontrol agents . A gene that plays an important role in suppression of
damping-off of cucumber was determined by ARS scientists in Beltsville,
Maryland, to be important in the colonization of plants by beneficial biocontrol
agents. Identification of this gene will help in understanding the process of
root colonization and disease suppression, important to the use of biocontrol agents. Biocontrol agents evaluated against nematode pests of tomatoes and peppers. Isolates of the biocontrol bacterium Burkholderia cepacia and the fungus Gliocladium virens were evaluated by ARS scientists in Beltsville, Maryland, for suppression of the nematode Meloidigyne incognita on peppers and on tomatoes. It was found that certain isolates of B. cepacia and G. virens have potential as biocontrol agents for control of this important pathogenic nematode. Demonstration tests for methyl bromide alternatives for strawberry production in Florida and California . ARS sponsors demonstration
tests of the most promising methyl bromide alternatives in grower fields in
California and Florida. These tests, conducted by ARS, University of Florida,
and University of California scientists, test alternatives under actual grower
conditions to test the efficacy and practicality of proposed alternatives. One
of the most promising alternatives involves the use of Telone using drip
application. Testing strawberry germplasm for tolerance or resistance to pathogenic soil organisms. Various cultivars of strawberry were grown in
nonfumigated demonstration plots by ARS scientists in Salinas, California.
Cultivars are being rated for disease resistance in these long-term tests. The
outcome of this research should assist growers in cultivar selection after the
loss of methyl bromide and identify traits for strawberry breeders to select in
future cultivar development. Verticillium treatment in strawberry nurseries. In
ARS-sponsored research, a University of California scientist showed that
chloropicrin and a combination of chloropicrin and Telone were as effective as
methyl bromide in controlling the important pathogen Verticillium wilt in
California strawberry nurseries. Cover crop treatments of rye or rye and mustard
were ineffective. Development of treatments to cover the entire spectrum of
strawberry pests in nurseries is critical to the profitable production of
strawberries in California. Postharvest Commodity Treatment (Including Structural) About 12 to 15 percent of the methyl bromide used in the United States is used to disinfest harvested commodities of insects and other arthropod pests. About 10 percent of this (1 to 2 percent of total use) is used as quarantine treatments. In 1994, the last year for which accurate data are available, $431 million of U.S. commodities were treated with methyl bromide as a condition of entry of the importing country to prevent inadvertent introduction of new species of insects into their country. These commodities included apples and cherries to Japan, cotton and peaches to Mexico, oak logs to Europe, and strawberries to Australia. Methyl bromide is also used extensively at U.S. ports of entry to disinfest commodities that are found on inspection to be infested with exotic pests, the introduction of which would cause irreparable harm to U.S. agriculture. Methyl bromide is currently the only emergency fumigant available to disinfest commodities from growing area quarantined as a result of the invasion of exotic pests, such as Mediterranean fruit fly. The other 90 percent of methyl bromide used for postharvest commodity fumigation is used to control nonquarantine insects and other arthropods on a wide range of commodities to maintain quality during storage and processing. Sulfuryl floride as an alternative to methyl bromide fumigation for in-shell walnuts. Walnuts must be vacuum fumigated with
methyl bromide in order to enter the very important European Union market. Tests
have determined that sulfuryl floride can replace methyl bromide, a fumigant
that will be banned in 2005 by the Montreal Protocol because of damage to the
stratospheric ozone layer. Efficacy against codling moth and navel orange worm
was comparable to methyl bromide. This work by scientists at the Horticultural
Crops Research Laboratory, Fresno, California, will provide an incentive to the
maker of sulfuryl floride to register this material for use on walnuts and
potentially will have a major impact on U.S. walnut growers by keeping open the
lucrative European market after the loss of methyl bromide. Methyl iodide, sulfuryl floride, and carbonyl sulfide, tested as alternative fumigants for methyl bromide for use on dried fruits and nuts. The primary fumigant for dried fruit and nuts, methyl bromide, is
scheduled to be banned in 2005 because of unacceptable damage to the
stratospheric ozone layer. Methyl iodide gives insect control with fumigation
times and chemical doses comparable to methyl bromide. The other chemicals,
while not as effective as methyl bromide, gave acceptable performance in
specific situations. None of these chemicals are presently registered for use on
dried fruits and nuts but this work by scientists at the Horticultural Crops
Research Laboratory, Fresno, California, provides efficacy data, which will
encourage manufacturers of these chemicals to register them. Cold treatment controls egg stage of Indian meal moth in dried fruit and nuts. Dried fruit and nut processors currently rely on the
fumigants methyl bromide and phosphine to disinfest their product of postharvest
insects. An alternative strategy relies on cold treatment to protect the product
after fumigation or another treatment disinfests the commodity. ARS scientists
in Fresno, California, showed that cold treatment is also effective as a
disinfestation treatment for Indian meal moth eggs. This research shows that
cold treatment may be a practical way to disinfest relatively uninfested
commodities when used in an integrated pest management system and may
effectively replace methyl bromide fumigation in some circumstances. Hawaii-produced bananas approved for shipment to U.S. mainland, Guam, and Japan without methyl bromide fumigation. Concern that
unfumigated bananas might serve to transport Mediterranean fruit flies and other
pests from Hawaii to the Mainland and countries where these pests don't
occur have prevented development of oversees markets for Hawaii-grown bananas.
ARS scientists in Hilo, Hawaii, demonstrated that harvest-ready green bananas
were not hosts for fruit flies, and they developed a protocol that allows export
of bananas to the U.S. mainland, Guam, and Japan without fumigation or any other
postharvest disinfestation treatment. Developments of strategies that open or
increase export markets for Hawaii-grown products is critical to Hawaii's
initiative to diversify agriculture to replace the sugar and pineapple
industries, which are on the decline. New cold treatment allows faster access to Mexico market for U.S. apples. Mexico requires a 90-day cold storage at 3.3 degrees C as a
treatment against apple maggot and oriental fruit moth in apples. Reducing the
temperature of the treatment from 3.3 degrees C to 1.1 degrees C, consistent
with present commercial temperatures in cold storage facilities, significantly
shortens the time required to get complete control of both pests. An ARS
scientist in Weslaco, Texas, determined that treatment time could reduce by more
than 50 percent to 6 weeks, thereby providing earlier access to the Mexico
market each year after harvest. Treatment for green mold of lemons. Postharvest green
mold of lemons was reduced more than 80 percent by immersion of the fruit for 1
minute in a solution of 3-percent lime-sulfur solution in water in laboratory
and simulated field trials conducted by ARS scientists in Fresno, California,
and was equal to other approved treatments, including synthetic fungicides. This
provides a practical alternative to chemical fungicides that are being banned
for health or environmental reasons. Granulosis virus as protectant of almonds and walnuts against insect attack in storage. A 2-year study by ARS scientists in
Fresno, California, showed that the virus persisted on stored nuts for at least
2 years and gave good levels of Indian meal moth mortality. These findings could
result in long-term insect protection and reduce the need for methyl bromide and
other chemical fumigants. New pesticide registered for fruit fly bait spray.
Research conducted by ARS scientists in Weslaco, Texas, proved that Spinosid was
as effective as malathion in killing fruit flies when combined with an
attractive bait. Spinosid was registered by the U.S. Environmental Protection
Agency for this use. Effective eradication technology is critical, with the
regulation of methyl bromide to lessen the impacts of exotic pest quarantines of
domestically produced commodities.
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