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Poster: Biology & Disease Mgmt: Oomycetes


Cold stress at planting increase susceptibility to damping-off caused by Pythium sylvaticum
M. SERRANO (1), A. Robertson (1) (1) Iowa State University, U.S.A.

Pythium sylvaticum is an Oomycete that causes damping-off of soybeans in Iowa, particularly when cool weather occurs at planting. Seed treatments are applied to over 90 percent of soybean seed in Iowa to protect germinating seedlings and consequently plant stand. The objectives of this experiment were to (i) evaluate the effect cold stress at different times after planting, and (ii) the effect of seed treatments on damping off. Soybean seed was treated with Intego Suite, Intego Suite + mandestrobin or left untreated and planted into 8 oz cups inoculated with P. sylvaticum or non-inoculated. The cups were placed in growth chamber and subjected to 96h of cold stress (4oC) at 0h or 24h after planting. A significant three-way interaction was detected between cold stress, inoculation and seed treatment (P<0.0001). In general, emergence of untreated seeds was reduced more than 70% when subjected to periods of cold stress (P<0.05). Emergence was improved with seed treatments (P<0.0001). These data indicate that periods of cold stress at planting increases the susceptibility of soybean to damping-off caused by P. sylvaticum and that seed treatments reduce damping-off under these adverse conditions.