SAREP Funds Methyl Bromide Alternatives

by Lyra Halprin and Bev Ransom, SAREP

Alternatives to the ozone-depleting agricultural fumigant methyl bromide are the focus of six new grants funded by SAREP.

"We can immediately address one of the most pressing problems of production agriculture with the methyl bromide projects, which will target farming systems where it has been a crucial tool," said Sean L. Swezey, SAREP director.

Methyl bromide is often used as a pre-plant fumigant to eliminate nematodes, weeds and pathogens in agricultural systems such as strawberries and orchard crops including almonds, walnuts and stone fruits; it is also commonly used as a post-harvest treatment to control insect pests. Methyl bromide is designated a Class I ozone depleter scheduled for a 100 percent use reduction in the U.S. by 2005.

"Our major concern in this new grants program is to assure funding for researchers and industries interested in biologically based solutions relying on microorganisms, farming rotations that suppress harmful soil-borne pathogens and nematodes, the use of clean nursery material, and resistant root stocks, which we believe we have done," Swezey said.

Projects funded include:

• "Cultural Control and Etiology of Replant Disorder of Prunus spp.," Greg Browne, USDA-Agricultural Research Service/UC Davis plant pathology department; Andreas Westphal, UC Davis plant pathology department; Tom Trout, USDA-Agricultural Research Service/Fresno. $150,638 for three years. This project addresses orchard replacement strategies for almonds, nectarines, peaches, plums, and prunes. The major benefit of methyl bromide fumigation is the control of "replant disorder." Replant disorder delays economic production and can lead to tree death. This project will determine the underlying causes of replant disorder, the level of specificity of replant disorder between two types of crops that may follow each other on large acreage, and the possible contributions of pre-plant fallow periods and cover crops to replant disorder control. An improved understanding of replant disorder etiology may be one of the most important keys to development of methyl bromide alternatives. (530) 754-9351, gtbrowne@ucdavis.edu

• "Microbiological Improvement of Root Health, Growth, and Yield of Strawberry," John Duniway, UC Davis plant pathology department. $118,780 for three years. The research objective of this project is to find microorganisms to improve root health, growth, and yield of strawberry plants without soil fumigation, which can be integrated with other cultural, biological and chemical treatments. While no individual microorganism or combination of beneficial microorganisms is likely to reproduce the large yield increases obtained by methyl bromide/chloropicrin fumigation of soil, inoculations with specific microorganisms are likely to increase yield significantly. These yield increases are most likely when inoculations are combined with other alternatives to methyl bromide, including fumigants other than methyl bromide, crop rotations, organic amendments of soils, solarization, and/or other cultural practices. The project will use microorganisms recently isolated from strawberry roots growing in fumigated soils in California which have been found to promote growth of strawberry plants in the greenhouse. These microorganisms will be used to inoculate transplants and plants grown for field production. Researchers will look at methods of field application and resulting growth and yield responses will be measured relative to those obtained by normal farming practices with and without fumigation. (530) 752-0324, jmduniway@ucdavis.edu

• "Development of Grape Rootstocks with Multiple Nematode Resistance," Howard Ferris, UC Davis nematology department; Andrew Walker, UC Davis viticulture and enology department. $100,744 for three years. The phase-out of methyl bromide will present California grape growers with a critical problem-lack of suitable rootstocks with nematode resistance. This problem will be particularly severe where new vineyards are replanted over a previous vineyard with high levels of grape-damaging nematodes. Currently available rootstocks have either inappropriate horticultural characteristics, including excessive vigor in scions which leads to poor production and quality, or they have insufficient resistance against aggressive nematode strains and species. This resistance breeding project will be integrated into a larger industry-supported grape rootstock breeding program at UC Davis. The project proposes a new approach to broad and durable nematode resistance in grape rootstocks. Researchers will develop, employ, and evaluate new rootstocks with resistance to a broad range of key nematode species as a sustainable alternative to the use of preplant fumigation. (530) 752-8432, hferris@ucdavis.edu

• "Containerized Strawberry Transplants as a Replacement for Methyl Bromide Soil Fumigation in California Strawberry Nurseries," Kirk Larson, UC Davis pomology department; Curt Gaines, Lassen Nursery. $107,969 for three years. California farmers plant 500,000,000 new strawberry transplants each year; annual plantings of pathogen- and pest-free transplants have been the basis for high productivity and successful strawberry IPM programs for decades. Strawberry plant propagation in California consists of at least three field propagation cycles, with preplant soil fumigation used in advance of each cycle. Currently, strawberry nurseries fumigate with mixtures of methyl bromide and chloropicrin to ensure the production of pathogen- and nematode-free transplants. The use of containerized transplants produced in disease-free, soil-less media would eliminate the need for nursery soil fumigation. This project will determine the potential for using containerized strawberry transplants (plugs) to produce pathogen- and pest-free planting stock without the use of methyl bromide soil fumigation. Although strawberry plugs are used in other parts of the U.S., there is little information regarding propagation and use of plugs for strawberry production in California. Project researchers will determine suitable methods for propagating and conditioning strawberry plugs under California conditions, and evaluate plug performance in thestate's major strawberry production regions. (949) 857-0136, kdlarson@ucdavis.edu

• "Alternatives to Methyl Bromide for Control of Soil-borne Fungi, Bacteria and Weeds in Coastal Ornamental Crops," James MacDonald, UC Davis plant pathology department; Clyde Elmore, UC Davis vegetable crops/weed science department, Steve Tjosvold, UC Cooperative Extension, Watsonville. $76,228 for three years. This project studies non-chemical alternatives to methyl bromide for coastal field-grown ornamentals (cut flowers, bulbs and greens). This is a highly productive and valued component of California's ornamental industry, and is seriously threatened by the pending loss of methyl bromide. Since solarization does not create enough soil heating to be useful by itself in the coastal regions, researchers will combine solarization with the addition of organic amendments to stimulate the phenomenon of bio fumigation. This project will focus on controlling the soil-borne fungus Fusarium oxysporum, the soil-borne bacterium Erwinia carotovora and several weed species. Microplot experiments will be conducted in several locations; in-field experiments will be carried out using two different bulb crops, Dutch iris and Calla. (530)752-6897, jdmacdonald@ucdavis.edu

• "Acetaldehyde and Carbon Dioxide Fumigation for Postharvest Control of Insects on Strawberry Fruit," Elizabeth Mitcham, UC Davis pomology department.  $75,986 for two years. The export market for strawberry fruit to Japan and Australia is valued at approximately $20 million annually. Fumigation with methyl bromide is used prior to export to these countries. Previous studies have shown that fumigation with acetaldehyde and carbon dioxide(CO2) is promising as an alternative to methyl bromide for postharvest insect and mite control. This project will determine the efficacy of acetaldehyde fumigation alone and in combination with carbon dioxide to kill western flower thrips and two-spotted spider mites. Researchers will then determine the affect of acetaldehyde and CO2 fumigation on fruit quality and postharvest life. They will also demonstrate the commercial feasibility of this treatment within existing methyl bromide fumigation facilities. (530)752-7512, ejmitcham@ucdavis.edu

The remainder of the funds will be used to support a Monterey Bay region on-farm demonstration project addressing biointensive alternatives to methyl bromide in strawberries. The project is called "BASIS - Biological Agriculture Systems in Strawberries: A biointensive production methods innovators group in the Monterey Bay region," Carolee Bull, USDA-Agricultural Research Service/Salinas.$180,000 for three years.

"There was a tremendous amount of interest from many different commodities for developing alternatives to methyl bromide," according to Jenny Broome, SAREP associate director and lead scientist on the methyl bromide alternatives grants program. "We received 20 full proposals requesting a total of more than $3 million; unfortunately, we could not fund all the worthwhile proposals submitted."

Last fall SAREP was allocated $1 million from the state legislature via the Department of Pesticide Regulation specifically to support a new grants program to develop and extend alternatives to methyl bromide. Most of the funds will go directly to researchers, however, a proportion is used to administer and implement the grants program. The grants program grew out of negotiations on Assembly Bill 1998 which expanded SAREP's Biologically Integrated Farming Systems grant program.

Assemblymember Helen Thomson(D-Yolo County), the author of AB 1998, said she is "pleased by the large number of project proposals generated by this state funding to develop alternatives to methyl bromide so California agriculture can remain competitive in the world market while improving environmental safeguards."

The bill was supported by a wide range of agricultural organizations and institutions including the Community Alliance with Family Farmers, Farm Bureau, and the University of California.