Effect of Dichloran, Iprodione, Procymidone, and Vinclozolin on the Mycelial Growth, Sporulation, and Isolation of Resistant Strains of Monilinia fructicola. David F. Ritchie, Assistant Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Plant Dis. 66:484-486. Accepted for publication 14 August 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-484.

Incubation of Monilinia fructicola mycelial plugs on potato-dextrose agar (PDA) amended with dichloran, iprodione, procymidone, or vinclozolin (25 µg a.i./ml) reduced but did not always prevent mycelial growth. Incubation for 7 days on amended PDA followed by transfer to and incubation on nonamended PDA resulted in an initial increase of sporulation compared with the cultures transferred from nonamended PDA. Isolation of fungicide-resistant strains increased from 8.1% after 4 days to 42% after 21 days of incubation on amended PDA. No resistant strains were detected in cultures incubated on nonamended PDA. Strains resistant to one of the dichloronitroaniline fungicides were cross-resistant to the other dichloronitroaniline fungicides but not to benomyl or CGA-64251 (Vangard). The resistant strains produced a black mycelium; the wild-type strains produced brown mycelium.

Keyword(s): aromatic hydrocarbon fungicides, brown rot, dicarboximides, stone fruits.