Colletotrichum coccodes, a Potential Bioherbicide for Control of Velvetleaf (Abutilon theophrasti). L. A. Wymore, Research Associate, Department of Plant Science, Macdonald College of McGill University, Ste-Anne-de-Bellevue, Quebec H9X 1C0. C. Poirier, A. K. Watson, and A. R. Gotlieb. Former Graduate Research Assistant, Professor, Department of Plant Science, Macdonald College of McGill University, Ste-Anne-de-Bellevue, Quebec H9X 1C0, and Associate Professor, Department of Plant & Soil Science, University of Vermont, Burlington 05405. Plant Dis. 72:534-538. Accepted for publication 1 February 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0534.

A velvetleaf (Abutilon theophrasti) isolate of Colletotrichum coccodes was evaluated as a potential bioherbicide for velvetleaf. On velvetleaf, disease caused by this isolate developed over a wide range of dew period durations and temperatures, but the most rapid and destructive disease development occurred following a 24-hr dew period at 24 C. With cooler temperatures and/or shorter dew durations, the pathogen caused premature defoliation of inoculated leaves. An inoculum density of 10⁷ spores/ml applied to runoff or an application rate of 2.3 × 10⁸ spores/m² was necessary to produce the most destructive levels of disease. Velvetleaf plants at all growth stages were susceptible and were reduced in vigor following inoculation. Plants inoculated at the cotyledon stage were killed.

Keyword(s): biological weed control.