Progress 01/01/09 to 12/31/10
Outputs
Progress Report Objectives (from AD-416) To determine the required exposure to the fumigant DMDS to achieve reliable control of various soil-borne pests including weed seed, parasitic nematodes, and fungal pathogens Approach (from AD-416) Laboratory and greenhouse dose-response experiments will be used to control both the DMDS concentration and exposure time to the fumigant. Documnets Trust with Arkema. Log 37819. This agreement was established in support of the in-house project, the goal being to determine the effects of dimethyl disulfide (DMDS) exposure time and concentration on soil-borne pests which contributes directly to Objective 2 of the in-house project. Soil fumigation is used to promote plant productivity by controlling pests such as weeds, nematodes, and soil-borne pathogens. Methyl bromide, which has been used for years as a soil fumigant, is being phased out due to its potential depletion to the stratospheric ozone. One potential alternative to methyl bromide, dimethyl disulfide (DMDS), is being considered for registration in California under the trade name of Paladin. Relatively little data for DMDS is available regarding its broad-spectrum pest control. Therefore, the objective of this research was to obtain preliminary results on DMDS pest control efficacy using a laboratory dose-response bioassay experiment with several exposure time intervals. A second objective was to determine residual DMDS after application and potential degradation products using gas chromatography methods. Bioassays were conducted using 40-ml glass vials filled with 35 grams of soil naturally infested with nematodes and soil pathogens. Half of the vials were amended with 25 seeds each of little mallow, common purslane, redroot pigweed, and annual ryegrass. Aqueous DMDS was added to soil to achieve final concentrations of 0, 4, 8, 16, 31, 63, 125, and 250 mg / L air space. Vials were immediately capped, shaken, and incubated at room temperature. Quadruplicate samples at each concentration were assayed and chemically analyzed after exposure periods of 6, 24, 96, 192 hours. Nematodes were extracted by the Baermann funnel technique, colony forming units of pathogens were counted by dilution plating, and weed viability was determined through germination. Poor control of Fusarium and Pythium was observed throughout all DMDS concentrations although at higher concentrations and longer exposure times, pathogen populations were slightly reduced. Control of weeds was also poor although this may have been due to experimental artifacts. Nematode control was very good at rates of 31 mg / L with 96 hours of exposure time and longer.
Impacts
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) To determine the required exposure to the fumigant DMDS to achieve reliable control of various soil-borne pests including weed seed, parasitic nematodes, and fungal pathogens Approach (from AD-416) Laboratory and greenhouse dose-response experiments will be used to control both the DMDS concentration and exposure time to the fumigant. Documnets Trust with Arkema. Log 37819. Significant Activities that Support Special Target Populations Relatively few fumigant active ingredients are available to serve as alternatives to methyl bromide for pre-plant soil fumigation. In FY2009, preliminary laboratory research to determine dimethyl disulfide exposure- concentration requirements to provide acceptable control of a broad range of soil-borne pests was initiated and is currently underway. Analytical protocols utilizing GC-MS have been finalized and field soil containing plant parasitic nematodes have been exposed to a wide range of dimethyl disulfide gas concentrations. The ongoing research will lead to finalization of the dimethyl disulfide rates and exposure duration treatments to be used in more detailed pest control studies to be conducted in FY2010. This project is monitored by the granting agency through annual reports and a final project report.
Impacts
(N/A)
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