Biological Control of Grey Mold of Snap Beans by Trichoderma hamatum. M. E. Nelson, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. M. L. Powelson, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. Plant Dis. 72:727-729. Accepted for publication 22 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0727.

Isolates of Trichoderma spp. from snap bean foliage were tested for their capacity to suppress grey mold of snap bean pods caused by Botrytis cinerea. In a detached blossom-pod assay, an isolate of Trichoderma hamatum reduced pod rot by 94% compared with the nontreated control, which was comparable to that obtained with the fungicide vinclozolin. Forty-two colony-forming units (cfu) of T. hamatum per blossom reduced pod rot by 77% compared with the nontreated control. Control was 97% when 233 cfu per blossom were applied. Grey mold was reduced only when spores of T. hamatum were applied to blossoms before, or simultaneously with, application of conidia of B. cinerea. Volatile compounds produced by one isolate of T. hamatum reduced mean radial growth of B. cinerea to 0.6 mm on potato-dextrose agar, while growth on nontreated plates averaged 23.6 mm. These results suggest the production of inhibitory volatiles as one possible mechanism of biocontrol.

Keyword(s): Sclerotinia sclerotiorum.