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United States Department of Agriculture

Agricultural Research Service


Location: Crops Pathology and Genetics Research

2011 Annual Report

1a.Objectives (from AD-416)
1. Demonstrate alternatives to MB in key crop systems and regions dependent upon MB. This will be accomplished by conducting replicated, large-scale field trials that will compare standard treatments with MB to the best available alternatives. The alternatives will include substitute fumigants and supporting integrated pest management (IPM) practices. The trials will be conducted by multi-disciplinary teams in partnership with commercial growers at field locations that collectively represent the diversity of the commercial production systems.

2. Conduct comprehensive assessments of alternatives to MB in key crop systems and regions dependent upon MB. This will be accomplished by multi-disciplinary collection and analysis of biological, environmental, and economic data from the trials described above.

3. Identify key variables affecting the efficacy of MB alternatives and demonstrate management and predictive use of the variables to optimize performance of the alternatives.

4. Assess and demonstrate emissions reduction technologies and strategies for fumigant alternatives to MB.

5. Conduct multi-regional education programs that instruct growers, farm workers, and associated members of the agricultural community on optimized, IPM-supported use of MB alternatives.

1b.Approach (from AD-416)
The project will achieve its objectives by using a collaborative, inter-disciplinary approach and will include operational, assessment, and educational components. The operational component will involve horticulturists, soil and atmospheric chemists, plant pathologists, nematologists, weed specialists, engineers, economists, extension educators, and regulatory specialists working together with commercial growers, nurserymen, advisors, and other agricultural workers. The teams will demonstrate, assess, and optimize use of MB alternatives in commercial fields. The optimizations will focus on identifying and managing variables that maximize fumigant efficacy and minimize fumigant emissions. Where appropriate, integrated pest management practices will be demonstrated and evaluated for contributions to optimizing MB alternatives. The assessment component of the project will involve advanced analysis of economic, environmental, and social data obtained from the field trials. As information accumulates from activities in the operational and assessment components, it will be extended to end users in the educational component of the project. Educational outreach will be achieved via indoor and outdoor extension meetings, newsletters, educational websites, and peer-reviewed and popular publications. Teams involved in the operational, assessment, and educational components will be drawn from diverse public and private institutions, including, but not limited to: USDA-ARS (Davis, Parlier, Riverside, and Salinas locations, with possible contributions from Corvallis and Wenatchee); University of California, including UC Cooperative Extension; California Environmental Protection Agency; California Department of Food and Agriculture; commercial fumigant applicators and manufacturers; marketing and research boards for horticultural commodities; and producers.

3.Progress Report
Twelve research and outreach projects were conducted under the Pacific Area-Wide Program for Integrated Methyl Bromide (MB) Alternatives in FY 2011. The projects include: perennial fruit, nut and rose nurseries (in CA); raspberry nursery (WA); forest nursery (OR, WA); cut flowers and ornamentals (CA); sweet potato hot bed (CA); almonds and stone fruits (CA) ; grape (CA); strawberry (CA); walnut (CA); fumigant emissions management; economic analysis; and website and special issue publication outreach. Each nursery project and the cut flowers/ornamentals project established or completed two or more research and demonstration trials that focused on fumigant alternatives to MB (e.g., 1,3-dichloropropene [1,3-D], mixtures of 1,3-D + chloropcrin, methyl iodide + chloropicrin, and metam sodium + chloropicrin; drip and shank applied). Efficacy of the alternatives was assessed according to control of soilborne pathogens (e.g., Pythium, Phytophthora, nematodes and weeds)and yield of salable plants. The sweet potato project evaluated combinations of alternative fumigants, pre-emergence herbicides, and fungicides as MB alternatives for control of soilborne pests. The almond/stone fruit project established a new orchard replant trial testing fumigant and non-fumigant alternatives to MB for control of replant disease (RD); the non-fumigant treatments includedspot steam and spot fungicide treatments, and rootstocks reportedly tolerant to RD. Growth yield and light interception assessments were completed six almond and peach replant trials. The grape project conducted growth and yield assessments for three previously established replant trials testing pre-plant drip and shank-applied fumigant alternatives to MB and a mustard crop rotation for control of nematodes and stimulating crop productivity. The 2011 strawberry project evaluated a “raised-bed trough system” for field production of strawberry fruit. The trough system avoids exposure of the strawberry plants to soilborne pathogens (e.g., Verticillim, Phytophthora, Fusarium) that are controlled primarily by soil fumigation in the conventional production system. The troughs are lined with mesh that confines strawberry roots to a rooting medium (coir or amended field soil) that is relatively free from soilborne pathogens. The walnut project continued a trial in the San Joaquin Valley examining integration of a nematode-tolerant rootstock and alternative fumigants (1,3-D and 1,3-D + chloropicrin) for reestablishing walnuts in soil infested with plant parasitic nematodes. A second walnut replant trial was established in the Sacramento Valley. Cost-benefit analyses were completed for MB alternative treatments in the almond and stone fruit and grape projects. Two fumigant emissions trials were completed to quantify reduction in non-target fumigant emissions and improvement in soilborne pathogen control achieved using “totally impermeable film”, compared to standard high-density polyethylene plastic mulch. All projects conducted educational outreach at field demonstrations, extension meetings, and scientific conferences.

1. Methyl bromide (MB) alternatives were optimized and demonstrated for production of forest nursery seedlings in the western U.S. Each year well over 300 million seedlings are grown for regeneration purposes in the Southeastern and Western United States. Although fumigant alternatives have been partially successful in replacing MB for this production system, regulatory stipulations are reducing allowed soil application rates and increasing the size of surrounding non-treated buffer zones for the alternative fumigants. At three forest nurseries, ARS Areawide IPM scientists determined that reduced rates of alternative fumigant mixtures of chloropicrin + 1,3-dichloropropene were as effective as full-rate treatments with MB in reducing soilborne pathogen and weed populations. The project also characterized the identity and pathogenicity of previously uninvestigated populations of Pythium species affecting forest nursery seedling production in the Western United States. The effective alternative treatments and the new knowledge on contributions of Pythium species to disease losses in forest nurseries are being implemented in the management of commercial forest seedling nurseries in the Pacific Northwest United States.

2. Non-target fumigant emissions reduction strategies were evaluated. Pre-plant soil fumigation is essential for economical production of many of our nation’s fruit and nut crops, valued at over 12 billion dollars annually in the Central Valley of California alone. Although research is underway to reduce reliance on soil fumigation in the long term, health and air quality concerns and state and federal regulations are requiring immediate reductions in non-target fumigant emissions. Field research and demonstration trials determined that use of new plastic mulches (e.g., virtually impermeable and “totally” impermeable films, known as VIF and TIF, respectively) was the most effective strategy for reducing non-target emissions (by approximately 90%, compared to standard mulch). Fumigant emission reductions were achieved by other strategies (e.g., soil surface sealing with light, frequent irrigations or drip fumigation; application of chemicals to degrade fumigants at the soil surface; using strip or spot fumigation to reduce treated area)with 0 to 90% reductions achieved, depending on method and trial, and costs of all current emissions reduction strategies were reviewed. The findings will help grower and regulatory stakeholders to sustain economical crop production while reducing non-target fumigant emissions.

3. Methods for production of strawberries without pre-plant fumigation were tested and demonstrated. The vast majority of California’s strawberry crop is produced using pre-plant soil fumigation, but the fumigant of choice, methyl bromide (MB) used in mixtures with chloropicrin, is being phased out. Although alternative fumigants are now used on about 50% of California’s strawberry acreage, they are under increasing regulatory restrictions, and the industry is in need of non-fumigant-based strategies for production of strawberries. Non-fumigant approaches (e.g., pre-plant soil steaming; pre-plant Brassica seed meal soil amendment; use of soil fungicides) for management of soilborne pests such as weeds, Phytophthora, and Verticillium, were evaluated in comparison to pre-plant soil fumigation with MB:chloropicrin. Steam treatments, although expensive, were determined to be as effective as MB:chloropicrin in improving strawberry yields at most sites. These findings suggest that steam treatments, with further optimization, may be useful for production of strawberries where fumigants cannot be used as in buffer zones.

Review Publications
Cabrera, A., Wang, D., Schneider, S.M., Hanson, B. 2011. Effect of potential methyl bromide alternatives on plant parasitic nematodes and grape yield under vineyard replant conditions. American Journal of Enology and Viticulture. 62(1):42-48.

Qin, R., Gao, S., Ajwa, H., Sullivan, D., Wang, D., Hanson, B.D. 2011. Field evaluation of a new plastic film (Vapor SafeTM) to reduce soil fumigant emission and improve distribution in soil. Journal of Environmental Quality. 40: 1195-1203.

Gao, S., Hanson, B.D., Wang, D., Browne, G.T., Qin, R., Ajwa, H., Yates, S.R. 2011. Methods evaluated to minmize emissions from preplant soil fumigation. California Agriculture. 65(1):41-46.

Hanson, B., Gao, S., Gerik, J.S., Shrestha, A., Qin, R., Mc Donnald, J.A. 2011. Effects of emission reduction surface seal treatments on pest control with shank-injected 1,3-dichloropropene and chloropicrin. Crop Protection Journal. 30(2):203-207.

Weiland, G.E. 2011. Influence of isolation method on recovery of Pythium species from forest nursery soils in Oregon and Washington. Plant Disease. 95:547-553.

Last Modified: 9/22/2014
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