1a.Objectives (from AD-416):
To develop, test, and demonstrate effective and practical field management techniques for nematode pest control with minimal air and water quality concerns in soil fumigation with methyl bromide alternatives.
1b.Approach (from AD-416):
Surface barriers such as extremely low permeability plastic films will be used under field conditions to enhance pest nematode control and reduce fumigant emissions to the air. Soil amendments with natural organic materials such as animal manure or synthetic chemicals will be evaluated alone or in combination with the low permeability films to enhance fumigant decomposition thus reducing emission potential and protect air quality. Application of fumigants with irrigation systems will be tested in comparison with shank injection methods and potential for deep percolation and surface runoff will be evaluated. Impact of soil organic and inorganic amendments on air and water quality will also be measured.
This project supports objective 3 of the parent project. Pre-plant soil fumigation is a common agricultural practice in nursery production of fruit and nut trees as well as in orchard and vineyards replanting in California. The use of fumigants is highly regulated in the state for several reasons, including toxicological and environmental concerns such as air and water quality. A field investigation was carried out to evaluate the performance of reduced rates of a mixture of 1,3-dichloropropene and chloropicrin under a polyethylene or a low impermeable film against soil-borne plant-parasitic nematodes and pathogens. The fumigants applied at full rate, three fourths, half, and one fourth of full rate, were all highly effective in controlling nematodes under both plastic films. The reduced rates performed well against Pythium spp. and Verticillium spp. but lacked control for Fusarium spp., and Phytophtora spp. Soil gas evaluations demonstrated that the low permeable film increased the chemical concentrations in soil compared to polyethylene film. A manuscript summarizing this field experiment was submitted for publication. During this reporting period, additional data collection and analyses were also carried on the efficacy of drip-applied dimethyl disulfide against nematodes in existing vineyards and crop responses to the chemical, as a therapeutic treatment. Preliminary results showed reductions in nematode numbers in treated plots and no difference in cluster counts and leaf stomatal conductance between treated and untreated plots.