Damping-off caused by Pythium sylvaticum on soybeans subjected to periods of cold stress is reduced by seed treatments

Soybean damping-off caused by Pythium spp. is frequently associated with the occurrence of cold weather fronts soon after spring planting. In this study, we evaluated the efficacy of a commercial seed treatment with metalaxyl and ethaboxam on emergence during various simulated cold stress conditions. A growth chamber experiment utilized a five-way factorial design with two cold stress temperatures (4ºC and 10ºC), two cold stress timings (initiated 24 and 96 h after planting), three durations of cold stress (24, 48 and 96 h), and two levels of seed treatment (INTEGO SUITE^TM and untreated). Cups planted with soybean seeds IA 2094 were inoculated with P. sylvaticum or not inoculated. Cups were incubated at 18ºC and evaluated 21 days after planting. Seedling emergence was reduced when the pathogen was present compared with the non-inoculated controls. In untreated seed, cold stress duration reduced seedling emergence, but no differences in emergence were detected in response to either initiation of cold stress or cold stress temperature. The seed treatment improved seedling emergence, reduced root rot severity and increased shoot weight. There was no significant effect of seed treatment on root weight. Data from this study confirm that cold stress soon after planting can increase the risk of reduced crop stands in Iowa and suggest that seed treatment with metalaxyl and ethaboxam protects seedlings when cold conditions are expected soon after planting.