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Weeds as Hosts for Colletotrichum coccodes. R. N. Raid, Graduate Research Assistant, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. S. P. Pennypacker, Associate Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Plant Dis. 71:643-646. Accepted for publication 12 December 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0643.

Eighteen weed species classified within 10 families were tested under greenhouse conditions for their susceptibility to Colletotrichum coccodes, the causal agent of tomato anthracnose. Foliar and root inoculation of these plants has led to the identification of 10 new records of hosts for C. coccodes. The number of infected weed species increased with plant age; 6, 9, and 15 species were infected when the plants were inoculated at the seedling, vegetative, and senescent stages, respectively. The percentage of plants infected also increased with plant maturity. More than 50% of the infected plants were symptomless; however, when symptoms were evident, they generally appeared as inconspicuous chlorotic or necrotic flecks. Premature senescence and defoliation were also observed. Microscopic examination of infected tissue often revealed the presence of brown setae, a characteristic of C. coccodes acervuli and sclerotia, predominantly on senescent foliar and root tissue. These tissues supported profuse sporulation when placed in a moist chamber. Results of this investigation support the hypothesis that weeds may serve as hosts for C. coccodes between crop rotations. The ability of C. coccodes to produce acervuli and sclerotia on infected weed tissue could be important with respect to both primary and secondary inoculum levels.