Location: Water Management Research2010 Annual Report
1a. Objectives (from AD-416)
Test emerging methyl bromide alternative chemicals for their efficacy in controlling various soilborne plant pathogens in cut flowers and other ornamental crops. Test methyl bromide alternative chemicals, rates, and application methods to meet California certification standards for nematode-free production of tree, vine, and rose nurseries. Develop various application methods, soil amendments, and physical barriers to reduce the emissions and enhance efficacy of the chemical alternatives to methyl bromide. Develop integrated weed control strategies using combinations of methyl bromide alternative fumigants with herbicides and non-chemical management techniques to improve weed control.
1b. Approach (from AD-416)
Research techniques will include extraction of soil fungal pathogens and nematodes, isolation and identification, population assessment and identification of native weeds, in-situ measurements of fumigant emissions and fumigant gas dispersion in soils, and determining impacts of various combinations of fumigant formulation and surface containment on efficacy and emission reductions. Experimental platforms will range from laboratory microcosms, soil columns, greenhouse pots, to small field plots and demonstration-scale field trials. Stakeholder participation in planning and implementation of research trials will be crucial. Outcomes from these research activities will be transferred to the stakeholders. Formerly 5302-13220-003-00D (12/07).
3. Progress Report
Laboratory dose response studies with acrolein and dimethyl disulfide were completed for control of various soilborne pathogens and weeds. Pathogen control evaluations were made on cooperating methyl bromide alternatives field trials. Ornamental crop field trials using steam as a methyl bromide alternative were initiated in Nipomo, Carlsbad, and Oxnard, CA. An ornamental crop field trial on methyl bromide alternatives using dimethyl disulfide was initiated in Oxnard, CA. Data analysis and report writing were carried out on two multi-year fumigation projects in vineyards and nematode control assessments using various methyl bromide alternative treatments. A manuscript was completed and will be submitted in 2010. Crop response and nematode control efficacy were also measured from three ongoing grape replant field trials. A new study was initiated to test dimethyl disulfide for controlling nematodes in grapes. A greenhouse and a companion field study was initiated to determine nematode control in strawberries using substrate media and landscape fabrics. Emission reduction studies from soil fumigation were conducted through laboratory experiments and field trials. A soil column study was completed to investigate the relationship between soil water content and fumigant emissions in three different textured soils (sand, sandy loam and loam). Data for all three soils were compiled and a manuscript is in preparation. The data show how increasing soil water content up to field capacity affects 1,3-dichloropropene and chloropicrin emissions (flux and cumulative emission loss). A laboratory batch experiment was also initiated to determine fumigant persistence in soils from different application rates. Three field trials were conducted to evaluate the potential of a new low permeable tarp (totally impermeable film or TIF) to reduce emissions, improve fumigant distribution in soil profile, and/or reduce application rates. A report was prepared and a manuscript is being developed. Two field trials using small field plots were conducted in the San Joaquin Valley to determine the potential of TIF tarp to reduce emissions, improve fumigant distribution in soil and reduce fumigant application rate for perennial orchards and nurseries. Sample analyses or data compiling are on-going for these two trials. Ten herbicide trials in tree and rose nurseries established in 2009 were completed. Weed control and crop safety evaluations of pendimethalin, oryzalin, and dithiopyr which were generally safe to nursery stock and controlled many weed species. Relatively new or reformulated products including: indaziflam, penoxsulam, sulfosulfuron, halosulfuron, prodiamine, oxyfluorfen, also were evaluated in small-scale nursery tests.
Wang, D., C. Rosen, L. Kinkel, A. Cao, N. Tharayil, J. Gerik. 2009. Production of methyl sulfide and dimethyl disulfide from soil-incorporated plant materials and implications for controlling soil-borne pathogens. Plant Soil. 324:185-197.