Characterization of Pythium spp. from three Ohio fields for pathogenicity on corn and soybean and metalaxyl sensitivity.
Pythium spp. were baited with maize and soyabean seeds from soils collected from 3 locations (Defiance, Sandusky and Wood) in Ohio, USA where soyabean and maize stand establishment was a concern. Five species, P. catenulatum, P. irregulare, P. paroecandrum, P. splendens, and P. torulosum, were recovered and a subset of these isolates was then tested for pathogenicity on maize and soyabean seed and sensitivity to the seed treatment fungicide metalaxyl. There was a range of both pathogenicity and sensitivity to metalaxyl within and among the Pythium spp. recovered from the 3 locations. It is suggested that repeated use of metalaxyl as a seed treatment to manage Pythium spp. may be selecting for insensitive strains of these species.