Incidence of Colletotrichum spp. on Soybeans and Weeds in Illinois and Pathogenicity of Colletotrichum truncatum. G. L. Hartman, Graduate Research Assistant, Department of Plant Pathology, University of Illinois at Urbana-Champaign, Urbana 61801. J. B. Manandhar, Graduate Research Assistant, and J. B. Sinclair, Professor, Department of Plant Pathology, University of Illinois at Urbana-Champaign, Urbana 61801. Plant Dis. 70:780-782. Accepted for publication 27 January 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-780.

Colletotrichum destructivum, C. truncatum, and Glomerella glycines occurred on 22% of stubble samples collected in 1984 and on 100% of samples from all but one of 50 fields of soybean (Glycine max) planted in 1983 in three Illinois counties. Colletotrichum spp. were recovered from 50% of soybean leaflets and from 48% of either stem pieces or leaf samples of 17 weeds from 18 fields. C. truncatum was recovered from 14 genera of weed hosts. Single-conidium isolates of C. truncatum from 11 weeds and soybeans varied significantly (P = 0.05) in pathogenicity on two soybean cultivars; one soybean isolate and four weed isolates were pathogenic on four of the weed hosts.