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Ecology and Epidemiology

Factors Affecting the Biological Control of Cercosporidium Leaf Spot of Peanuts by Dicyma pulvinata. James K. Mitchell, Former graduate student, Department of Plant Pathology and Microbiology, Texas Agricultural Experiment Station, Texas A & M University, College Station 77843, Present address: Department of Plant Pathology, University of Arkansas, Fayetteville 72701; Ruth A. Taber, research scientist, Department of Plant Pathology and Microbiology, Texas Agricultural Experiment Station, Texas A & M University, College Station 77843. Phytopathology 76:990-994. Accepted for publication 29 April 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-990.

The survival and/or growth of Dicyma pulvinata, a mycoparasite on Cercosporidium personatum, was determined in culture media and on host tissue invaded by C. personatum. Variables tested included temperature, pesticide concentration, pH, and relative humidity. Potential carriers for spray formulations of the mycoparasite were tested also. In broth culture, maximal growth occurred at 23-25 C. On detached peanut leaflets infected with C. personatum maximal colonization occurred at 23-28 C. No colonization was noted at constant temperatures above 30 C, and no sporulation occurred at 31.5 C. Of nine pesticides tested, D. pulvinata was most sensitive to benomyl, mancozeb, and triphenyltin hydroxide; however a benomyl-tolerant isolate was obtained that grew in culture media containing 10 μg/ml benomyl. D. pulvinata grew over a broad pH range with maximal growth in the range of 3.3-7.7. Viability of spores of D. pulvinata was assessed at relative humidities (RH) ranging near 0-100% RH at three different temperature regimes. At 10 C D. pulvinata remained viable for at least 72 days under all relative humidities tested.