Ethanol-Potassium Nitrate Medium for Enumerating Rhizoctonia solani-like Fungi from Soil. E. E. Trujillo, Professor, Department of Plant Pathology, University of Hawaii, 3190 Maile Way, Honolulu 96822. C. A. Cavin, M. Aragaki, and M. A. Yoshimura. Research Associate, Professor, Department of Plant Pathology, University of Hawaii, 3190 Maile Way, Honolulu 96822, and Professor, Department of Biological Sciences, California Polytechnic State University, San Luis Obispo 93407. Plant Dis. 71:1098-1100. Accepted for publication 29 July 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-1098.

A medium consisting of 0.2 g of potassium nitrate, 30 g of agar, 947 ml of distilled water, 53 ml of 95% ethyl alcohol, 0.38 ml of metalaxyl 2E, 0.02 ml of prochloraz 40EC, 100 mg of tobramycin, and 300 mg of streptomycin was developed for enumerating Rhizoctonia solani-like fungi from soil. Ethyl alcohol was mixed with the cooled medium at 50 C before antibiotics and fungicides were added. Selectivity decreased with age of the medium, thus freshly made media should be used. Most colony-forming units of R. solani-like fungi in field soils were present in organic matter and retained by a 65-mesh sieve when soil suspensions were screened. A few colony-forming units collected on a 200- or 270-mesh sieve were microsclerotia and resting hyphae free of organic matter.