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Biological Control of Turfgrass Diseases with a Rhizosphere Competent Strain of Trichoderma harzianum . C. T. Lo, Department of Plant Pathology and Horticultural Sciences, Cornell University, Geneva, NY 14456. E. B. Nelson, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; and G. E. Harman, Department of Plant Pathology and Horticultural Sciences, Cornell University, Geneva, NY 14456. Plant Dis. 80:736-741. Accepted for publication 15 March 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0736.

Trichoderma harzianum strain 1295-22 is a commercially available biocontrol agent that is strongly rhizosphere competent and able to control several plant pathogenic fungi. Two formulations were tested for their ability to control brown patch caused by Rhizoctonia solani, dollar spot caused by Sclerotinia homoeocarpa, and Pythium root rot and blight caused by Pythium graminicola. In growth chamber trials, soils planted with creeping bentgrass were amended with the granular formulation to give 106 cfu/g. All three diseases were significantly reduced by this treatment. Populations of Pythium spp. were suppressed under laboratory conditions by strain 1295-22. In field trials conducted over 4 years, strain 1295-22 reduced dollar spot severity relative to untreated plots. Monthly applications of granular or peat-based formulations of T. harzianum 1295-22 reduced initial disease severity by as much as 71% and delayed disease development by up to 30 days. The persistence of strain 1295-22 in soil core samples from treated creeping bentgrass greens was also measured. After application of strain 1295-22, soil populations of Trichoderma spp. increased 100-fold relative to populations in untreated plots. Population levels remained at least an order of magnitude greater in treated than in untreated plots. Even after overwintering, population levels remained at or above 105 cfu/g of dry weight of the sample.

Keyword(s): IPM, soilborne pathogen, topdressing