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Poster: Biology & Disease Mgmt: Integrated Pest Mgmt


Novel approaches for the integrated control of the soilborne strawberry pathogens Macrophomina phaseolina and Fusarium oxysporum f. sp. fragariae
M. Carter (1), H. Smith (2), G. Holmes (3), K. Ivors (1) (1) California Polytechnic State University, U.S.A.; (2) California Polytechnic State University, Statistics, U.S.A.; (3) California Polytechnic State University Strawberry Center, U.S.A.

Macrophomina phaseolina (Mp) and Fusarium oxysporum f. sp. fragariae (Fof) are emerging soilborne pathogens causing crown rot and Fusarium wilt in commercial strawberry fields in California. Fungicides representing eight active ingredients from four different FRAC groups were evaluated for their efficacy against each pathogen in greenhouse bioassays. Twenty-four fungicide treatments (eight fungicides at three rates) were drench applied to pathogen infested potting media two days prior to planting and 19 days after planting. Tea bags of buried inoculum were recovered two days after each fungicide application and plated on semi-selective medium to quantify each pathogen; disease severity was assessed weekly. Differences in the colony forming units (CFUs) and disease severity (AUDPC) for all treatments and the inoculated water-drench control for both Mp and Fof were not statistically significant, although there were differences among the CFUs for Mp. In addition, a strawberry plant extract was assessed for its ability to stimulate germination of Mp microsclerotia in vitro. Preliminary results showed that the number of germinating microsclerotia was significantly higher after the application of the strawberry extract. Germinated microsclerotia may be more sensitive to fungicides and offer a means of increasing fungicide efficacy against soilborne pathogens.