Anaerobic Soil Disinfestation
Developed in Japan (Shinmura, 2000; Momma, 2008) and the Netherlands (Blok et al., 2000; Messiha et al., 2007), anaerobic soil disinfestation (ASD), a non-chemical alternative to MeBr,can control soilborne pathogens and nematodes in strawberries and vegetables. ASD integrates principles behind solarization and flooding to control nematodes and pathogens in situations where neither is effective or feasible. ASD works by creating anaerobic soil conditions by incorporating readily available carbon-sources into topsoil that is covered with plastic tarp then irrigated to field capacity. The tarp is then left in place to maintain soil moisture above field capacity and to sustain anaerobic conditions. Anaerobic decomposers are then able to respire using the added carbon, which results in the build-up of anaerobic by-products that are toxic to pathogens (Katase et al., 2009), but that are degraded rapidly once the tarp is removed or holes are made through the tarp for planting. Studies were conducted over the past four years in an attempt to optimize ASD for use in California strawberry and Florida vegetable production systems. Overall, ASD was very effective in suppressing V. dahliae in soils and resulted in 85 to 100% of the marketable fruit yield observed with fumigated controls in coastal California strawberries when 9 t/Aof rice bran was pre-plant incorporated and 3 to 4 acre-inches of irrigation was applied in sandy-loam to clay-loam soils (Shennan et al., 2011). Under the semi-tropical climate of Florida, when composted broiler litter (to improve water holding capacity of FL sandy soil) and heavy blackstrap molasses were incorporated as substrate, ASD treatments provided good control of nutsedge, and excellent control of grass, broadleaf weeds, Phytophthora capsici, and Fusarium oxysporum f. sp. lycopersici (Rosskopf et al., 2010). In the cooler conditions of the Central Coast, however, ASD may not provide effective control of many weed species (unpublished data).To ensure consistency of pest suppression across varying locations, effects of soil temperatures and treatment length, and the mechanisms of pest suppression by ASD are being further elucidated. Integration of ASD with other non-fumigant approaches may also have promise; a combination of ASD and brassicaceae seed meal application is currently being tested..