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Ecology and Epidemiology

Comparative Sensitivity of Rhizoctonia solani and Rhizoctonia-like Fungi to Selected Fungicides In Vitro. S. Bruce Martin, Former graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650; Leon T. Lucas(2), and C. Lee Campbell(3). (2)(3)Professor, and assistant professor, respectively, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 74:778-781. Accepted for publication 1 March 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-778.

Benomyl, carboxin, PCNB, iprodione, chlorothalonil, and triadimefon were added to potato-dextrose agar at 0, 1, 10, and 100 mg a.i./L. The in vitro growth response (inhibition of linear growth) of 16 isolates of Rhizoctonia solani, binucleate Rhizoctonia-like fungi, and R. zeae from several sources were tested on fungicide-amended media. Rhizoctonia solani and binucleate Rhizoctonia-like fungi were sensitive to benomyl (EC₅₀[effective concentration for 50% inhibition of linear growth] <10 mg a.i./L), whereas isolates of R. zeae were tolerant to benomyl (EC₅₀>50 mg a.i./L) but sensitive to the other fungicides. Fungi were most sensitive to iprodione (EC₅₀ generally <1 mg a.i./L), but growth inhibition in response to other fungicides (especially PCNB) differed considerably. Anastomosis group tester isolates of R. solani were variable in response to carboxin, PCNB, chlorothalonil, and triadimefon.