Increased Endomycorrhizal Infection of Maize and Soybeans After Soil Treatment and Metalaxyl. D. E. Groth, Graduate Student, Department of Plant Pathology, Seed and Weed Sciences, Iowa State University, Ames 50011. C. A. Martinson, Associate Professor, Department of Plant Pathology, Seed and Weed Sciences, Iowa State University, Ames 50011. Plant Dis. 67:1377-1378. Accepted for publication 4 July 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1377.

Soil incorporation of metalaxyl increased the vesicular-arbuscular mycorrhizal (VAM) infection of maize roots from 57 to 72% after 30 days in greenhouse experiments. Infestation of soil with inoculum of Glomus fasciculatum also increased VAM infection frequency but had no additional effect in combination with metalaxyl. In a 90-day experiment with maize, metalaxyl was associated with increased VAM infection after 30 and 60 days, but after 90 days, the differences in VAM infection between metalaxyl and control treatments were insignificant. Spore production by VAM fungi was not significantly affected. Metalaxyl soil treatment was also related to an increase in VAM infection of soybean roots.