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The 2011 ASHS Annual Conference

7280:
Non-Fumigant Alternatives for Managing Macrophomina phaseolina and Fusarium oxysporum In California Strawberry

Tuesday, September 27, 2011: 11:45 AM
Kohala 2
Oleg Daugovish, University of California Cooperative Extension, Ventura, CA
Steven A. Fennimore, Extension Specialist and Weed Ecophysiologist, Department of Plant Sciences, University of California, Davis, Salinas, CA
Fungal pathogens Macrophomina phaseolina and Fusarium oxysporum have become increasingly troublesome in California strawberry production valued annually at $ 1.8 billion. These pathogens can be controlled with pre-plant soil fumigation; however, they proliferate in the refuge created by the non-fumigated buffer zones, causing plant decline and yield losses and can spread from infested zones to non-infested areas. In a buffer zone with the history of both pathogens in a field at Ventura, CA we have evaluated three non-fumigant combinations: mustard seed meal at 2200 kg/ha incorporated into beds and followed by solarization via standard clear polyethylene mulch, mustard meal supplemented by steaming for 10 min at 60 C to 25cm depth and steaming followed by solarization for 2 months. Average day/night soil temperature at 15 cm depth under clear mulch was 33 C in August and 27 C in September, 2011. In November, 1.5-months old ‘San Andreas’ strawberry plants were similar in size among all the tested combinations and 26% larger than untreated. Number of germinated weeds under clear mulch was 3-4 times greater for combination with mustard than with steam. Only combinations that included steam reduced Macrophomina phaseolina sclerotia colonies in soil compared to untreated check: 43% at 0-15 cm depth and 88% at 16-30 cm. However, early fruit yields (January-February) were similar for all combinations and 73% greater than in untreated check. Whole-season yields, Fusarium oxysporum survival in soil and pathogen-related plant mortality are currently under investigation. Preliminary results suggest that these non-fumigant treatments may not eliminate pathogens from strawberry rooting depths but may provide substantial yield improvements in non-fumigated areas.