USDA awards $2.5 million grant to UC Santa Cruz to expand organic strawberry research

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UC Santa Cruz researchers who have pioneered alternatives to methyl bromide in commercial strawberry production have received a $2.5 million grant from the U.S. Department of Agriculture that will take their work national.Carol Shennan, professor of environmental studies, will lead a team of researchers and stakeholders around the country who are optimizing biological methods to manage soil-borne diseases and pests. The grant builds on Shennan’s leadership in the development of alternatives to methyl bromide and other environmentally harmful soil fumigants used to combat soil pathogens. She and UC Santa Cruz research scientist Joji Muramoto have adapted a clever strategy called anaerobic soil disinfestation (ASD) for strawberries. ASD combines short-term saturation with the application of an organic amendment like rice bran under plastic mulch to temporarily create anaerobic conditions in the soil; that results in “fermentation” processes and changes the microbial activity in the soil prior to planting, killing off pathogens like Verticillium dahliae that can devastate berry fields. Unlike methyl bromide, which dramatically reduces microbial activity in the soil, ASD shifts microbial populations in ways that suppress targeted pathogens. “It stimulates disease-suppressing mechanisms,” explained Shennan. The technique has received significant interest in California, which produces more than 80 percent of the nation’s strawberries; more than 20 percent of the state’s organic strawberry acreage uses ASD to manage soil disease, said Shennan.”Because it’s a biological process, its effectiveness depends on the environmental conditions—soil type, soil temperature, carbon sources, pathogens, and water management,” she said. “Heavier soils are more difficult because you don’t want clods. Farmers also have to do this at the right time to get the soil temperatures needed to kill off pathogens, and they may need different carbon sources depending on which pathogens they have.”The goal of the USDA project is to develop region- and pathogen-specific management systems so farmers can use ASD in combination with crop …

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