Soybean (Glycine max) and common bean (Phaseolus vulgaris) are two of the most globally important leguminous crops. Yields can be reduced by high incidence of soilborne pathogens that cause seedling disease. Seed treatments are often used for management of soybean seedling disease, but profitability of seed treatment use remains unclear. To examine this in Michigan, seed treatments were evaluated at seven field sites each year from 2013 to 2015. Across sites in 2013, no seed treatment significantly improved partial returns relative to the non-treated control (NTC); across sites in both 2014 and 2015, the fungicide+insecticide+nematode protectant (FIN) treatment significantly reduced partial returns relative to the NTC. Seed treatment may control soybean seedling pathogens, but seed treatment use did not show improved profitability. Along with chemical control, genetic control is often used to reduce losses from root rot pathogens in common bean. Breeders have aimed to develop Pythium root rot-resistant bean varieties; however, relationships between common bean and most Pythium species remain uncharacterized. Pythium species (n=28) were tested in a growth chamber assay at 20°C and petri dish assay at 20°C and 26°C to describe their pathogenicity and virulence on two bean varieties from the Middle American and Andean gene pools. Root growth or disease severity was significantly impacted by 17 Pythium species, although results varied by bean variety, temperature, and assay used. Improved understanding of Pythium interactions with bean will help breeders and pathologists to control Pythium-induced seedling disease more effectively.
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