Disease Note

A Seedling Epiphytotic of Sorghum in South Texas Caused by Pythium arrhenomanes. G. A. Forbes, Department of Plant Pathology & Microbiology, Texas Agricultural Experiment Station, College Station 77843. D. C. Collins, Department of Plant Pathology & Microbiology, Texas Agricultural Experiment Station, College Station 77843; G. N. Odvody, Texas Agricultural Research and Extension Center, Corpus Christi 78410; and R. A. Frederiksen, Department of Plant Pathology and Microbiology, Texas Agricultural Experiment Station, College Station. Plant Dis. 69:726. Accepted for publication 9 May 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-726d.

Severe seedling disease of grain sorghum (Sorghum bicolor (L.) Moench) affected several thousand hectares in South Texas in 1983. Many fields were replanted after preemergence and postemergence seedling death. The disease occurred after several days of rain and low soil temperature (often below 15 C). Pythium arrhenomanes Drechs., Fusarium moniliforme Sheld., and Fusarium spp. were isolated from lesions. Only P. arrhenomanes was pathogenic on sorghum seedlings in infested pasteurized soil. The pathogen is morphologically different from P. graminicola Subram., a similar species causing root rot of mature sorghum plants. Sorghum lines BTX3197 and IS9530 were resistant to postemergence damping-off caused by P. arrhenomanes in one South Texas nursery.