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Failure of Metalaxyl to Control Pythium Blight on Turfgrass in Pennsylvania. P. L. Sanders, Senior Research Associate, Pennsylvania State University, University Park 16802. Plant Dis. 68:776-777. Accepted for publication 1 March 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-776.

Sixty to 75% of the propagules of Pythium aphanidermatum recovered from a site where metalaxyl failed to control Pythium blight on turfgrass grew without inhibition on a medium containing 50 and 100 ppm of metalaxyl. Representative isolates were pathogenic on pot-grown bentgrass, producing symptoms typical of Pythium blight. These isolates were more aggressive than a pool of wild-type P. aphanidermatum and were not controlled by the commercial rate of metalaxyl on pot-grown bentgrass. They were adequately controlled in vivo by propamocarb and fosetyl Al.