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United States Department of Agriculture

Agricultural Research Service

Research Project: Alternatives to methyl bromide soil fumigation for vegetable and floriculture production

Location: Subtropical Plant Pathology Research

2011 Annual Report

1a. Objectives (from AD-416)
Identify impact of pest management tactics on functional diversity of soil microflora and weed populations, their competitive interactions, and effects on crop health. Conceive, develop, and test tactics for the control of plant diseases, parasitic nematodes and weed pests of vegetable and floriculture crops. Research efforts will concentrate on the testing of novel chemical, biological, biorational, cultural, and organic pest conrol tactics and on improving their application technology. Identify combinations of pest control tactics that interact synergistically to improve pest control, are practical to implement, and will minimize environmental disruption. Research activities will focus on identifying combinations of pest control tactics that produce synergistic effects and minimize disruption to conventional crop production practices. Define the impacts of pest management and crop production practices on soil health including the suppression of soilborne pests.

1b. Approach (from AD-416)
A rational and sustainable approach to finding viable alternatives to methyl bromide is to utilize integrated pest management (IPM) programs where combinations of tactics are used to maintain economic damage from key pests below a tolerable threshold. Another approach is to redesign production systems minimizing the potential for outbreaks of soilborne pests. Availability of biologically-based pest management tactics must be increased for successful IPM programs for soilborne pests to be implemented. Growers must have the option of choosing tactics that fit the needs and constraints of their individual programs. Deployment of multiple or companion tactics is essential to alleviate selection pressure and manage potential increases in resistant pest populations. Synergistic effects from combinations of pest management tactics need to be determined. Specific research methodology will include combinations of cultural practices, biotechnology, biological, and conventional control methods.

3. Progress Report
Field trials were conducted to evaluate camelina (Camelina sativa) and chia (Salvia hispanica) as beneficial cover crops for vegetable growers currently relying upon soil fumigation for managing soilborne pests and as source of locally produced biodiesel feedstock. On-farm trials were completed to evaluate deep placement of steam for control of root knot nematodes and weeds in commercial flower production. Field demonstration trials were conducted to facilitate adoption of soil solarization by vegetable and cut-flower growers as a nonchemical alternative to methyl bromide. Changes in soil microbial communities, populations of purple nutsedge populations and the soil density of root-knot nematodes were evaluated under continuous tomato monocultures or a sunn hemp cover crop and under various application rates of broiler litter and urban plant debris. Greenhouse and microplot trials were conducted to continue evaluation of summer cover crops and weed species for nematode susceptibility.

4. Accomplishments
1. Anaerobic soil disinfestation as an alternative to methyl bromide fumigation. Non-chemical alternatives to methyl bromide must provide effective control of pest complexes found in vegetable production systems. A cooperative research project between ARS researchers in Fort Pierce, FL, in cooperation with the University of California, Santa Cruz has resulted in the generation of new information on a technique that utilizes the combination of composted broiler litter and a carbon source with soil saturation and heating to create an anaerobic condition that induces weed, nematode, and soilborne plant pathogen control. When soil was amended with both litter and molasses, the effect on anaerobicity was stronger than that of either broiler litter or molasses alone and control of the pest complex exceeded that achieved by soil solarization alone. The method has been expanded to evaluate oxygen impermeable plastic as a substitute for solarization plastic and to evaluate additional sources of organic nitrogen. Multiple on-farm research trials, grower demonstration plots, and home and school gardens have been established using this method.

2. Reduced risk chemicals for weed, nematode, and pathogen control. Crop protection materials are needed that provide broad-spectrum control of pests, but do not pose a risk to workers or the environment. Research was conducted in cooperation with University of Florida faculty to continue evaluation of a novel, reduced-risk compound for control of weeds, plant pathogenic fungi and bacteria, and plant parasitic nematodes. The compound’s broad-spectrum pest control activity at relatively low application rates was further defined.

3. Alternative crop rotational strategies for methyl bromide dependent vegetable growers. Crop rotation can be an effective non-chemical approach to managing soilborne pests. An annual crop rotational program was developed for vegetable growers dependent upon soil fumigation for the management of soilborne pests. The rotation consisted of 3 crops planted in consecutive order in the same field. A summer legume (Aeschynomene americana) was planted in July, mowed and disked in September. Oilseed sunflower was planted in October. Oilseed camelina was planted in February. It was shown that after 67 days of growth, Aeschynomene plowed under green can contribute 161 lbs of nitrogen and 1.25 tons of carbon back to the soil. Subsequent sunflower and camelina crops planted into the plots can be grown with reduced fertilizer inputs. No damage to crops from soilborne pests were observed in the alternative rotation crops.

4. Identification and assessment of soil edaphic factors responsible for crop injury associated with the application of soil fumigants. Crop protection materials are needed that provide broad-spectrum control of pests, but do not pose a risk of injury to the intended cash crop. ARS researchers at Fort Pierce, FL, conducted a field trial to assess soil environmental and edaphic factors associated with crop injury from iodomethane and chloropicrin ands to identify the compounds responsible. Inorganic chemical breakdown compounds of iodomethane responsible for crop injury were identified and quantified in the soil profile following application of iodomethane and subsequent cultivation of a pepper crop. The role of soil physical and edaphic factors contributing to the accumulation of toxic breakdown compounds was established.

5. Soil solarization as a viable nonchemical commercial alternative for cut-flower growers. Soil solarization is a nonchemical approach to managing soilborne pests using clear plastic and high soil moisture to heat soil to lethal temperatures. Unfortunately, very few pest management specialists have understood the concepts well enough to integrate it into commercial crop production applications. A clear plastic film with Ultra violet light stabilizers, anti-fogging, and infra-red retentive compounds was formulated for solid-tarp applications and evaluated on commercial cut-flower farms for 3 years. Soil solarization was shown to be effective in managing damage from soilborne pests up to 2 years in row when used behind an effective soil fumigation programs. It is recommended that solid-tarp solarization be used by commercial cut–flower growers to extend the interval between annual soil fumigant application to every other year.

Review Publications
Burelle, N.K., Rosskopf, E.N., Hartman, R.D. 2010. Evaluation of soil treatments for control of Meloidogyne Arenaria in caladium tubers (Caladium × Hortulanum) and nematode susceptibility of selected cultivars. Nematropica. 40(2):177-189.

Last Modified: 06/24/2017
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