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Disease Control and Pest Management

Trichoderma spp. as Biocontrol Agents of Rhizoctonia Damping-off of Radish in Organic Soil and Comparison of Four Delivery Systems. L. Mihuta- Grimm, Former graduate student, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691, Present address of senior author: Research and Extension Center, University of Idaho, Route 1, Kimberley 83341; R. C. Rowe, professor, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 76:306-312. Accepted for publication 2 October 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-306.

Two hundred twenty-five isolates of Trichoderma were tested in the greenhouse as antagonists for biocontrol of Rhizoctonia solani on radish. Isolates were obtained from organic and mineral rhizosphere soils of radish, from organic and mineral surface soils, by baiting techniques, or from other laboratories. Seven isolates were chosen for use in two field studies in 1983, and three isolates were used in four 1984 field studies. At one location in 1983, two isolates of T. hamatum resulted in disease indices of 34 and 43, compared with 82 in the control. In 1984, the same two isolates resulted in disease indices of 23 and 25, compared with 52, 57, and 58 in controls. Four delivery systems were evaluated at two locations for applying antagonists in the field: fluid drilling a gel matrix containing seed and a 5-day-old liquid culture of antagonist produced on a shake table; coating ungerminated conidia onto seed with 2% methylcellulose before planting: applying germinated conidia in a wheat bran/sand preparation to the seed furrow before planting; and drenching the furrow before planting with a 5-day-old liquid culture of the antagonist produced on a shake table. The fluid drilling technique was superior to the others in both 1983 and 1984 Hartville field studies. Isolates of Trichoderma obtained from organic soils were better antagonists in organic soil field trials than those from mineral soils. Many biocontrol treatments provided better control of Rhizoctonia damping-off than treatment with pentachloronitrobenzene at 5.3 kg a.i./ha in 1984 tests.