Submitted to: Proceedings of Methyl Bromide Alternatives Conference
Publication Type: Proceedings
Publication Acceptance Date: 8/31/2007
Publication Date: 10/1/2007
Citation: Shennan, C., Muramoto, J., Bolda, M., Koike, S.T., Daugovish, O., Rosskopf, E.N., Burelle, N.K., Klonsky, K. 2007. Optimizing anaerobic soil disinfestation: an alternative to soil fumigation?. Proceedings of Methyl Bromide Alternatives Conference. 40:1-4. Interpretive Summary:
Technical Abstract: Soil disinfestation methods using anaerobic decomposition of organic matter were developed in the Netherlands and Japan as an ecological alternative to MeBr. Anaerobic soil disinfestation (ASD) works by creating a combination of anaerobic soil conditions and readily available carbon pools to stimulate decomposition of organic matter via the anaerobic pathway. These conditions are created by incorporating a carbon source into the soil, irrigating to saturation, then covering with an oxygen impermeable tarp. The tarp is then left in place for sufficient time for anaerobic decomposers to create a period of reducing conditions where products of decomposition accumulate and are toxic to a range of weeds, fungi, nematodes and other organisms. The goal of this project is to test anaerobic soil disinfestation (ASD) as an economic alternative to MeBr for U.S. growers; using strawberry (coastal California) and pepper/eggplant double crop (southeast Florida) as model production systems. We will manipulate different carbon sources, application methods, irrigation techniques, tarp materials, and timing/length of the tarping period to optimize control of key soilborne pathogens and nematodes, and weeds. Further we will test a model that predicts the creation of anaerobic conditions and hence pathogen suppression under different soil conditions. The economic feasibility of ASD compared to MeBr treatments will also be assessed for each production system. Most biologically-based pest management systems target one or a few pests only, yet ASD affects a broad range of pest types and species making it functionally similar to current fumigant-based pest management. The potential for commercial application of ASD in the U.S. is extremely high given the relative ease of incorporating ASD into existing production systems. To optimize ASD for suppressing Verticillium wilt in organic strawberries we are conducting a series of field and pot experiments at the Center for Agroecology and Sustainable Food Systems (CASFS) organic research farm at UC Santa Cruz, and in the future will do on-farm trials with grower cooperators. Early results are very promising. In a replicated flat field application trial, we compared incorporation of different cover crop residues with or without 12 weeks of tarping and found highly significant reduction of V. dahliae microsclerotia in retrieved inocula in tarped plots regardless of cover crop type (mortality 98%, P=0.0001). The following bioassay with a strawberry crop confirmed significantly lower level of wilting symptoms in tarped plots compared to non-tarped plots. Successive field and pot experiments found significant reduction of numbers of inoculated V. dahliae propagules retrieved even after a tarping period of only 3 weeks. Further, in a recent trial, stronger anaerobic conditions were developed when we adapted the system for use with the raised bed system currently used in strawberry production, than in the flat application ASD. If consistently effective, a fall-bed ASD treatment would fit into the current winter-planting strawberry production system in California, and fall/winter vegetable production system in Florida, with minimal adjustments.