Pathogenicity and Benzimidazole Resistance in Penicillium Species Recovered from Flotation Tanks in Apple Packinghouses. D. A. Rosenberger, Associate Professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva, NY. D. T. Wicklow, V. A. Korjagin, and S. M. Rondinaro. United States Department of Agriculture, Northern Regional Research Center, Peoria, IL; and Research Technicians, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva, NY. Plant Dis. 75:712-715. Accepted for publication 8 January 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0712.

Three hundred and sixty-eight isolates of Penicillium were recovered from water collected from flotation tanks in four apple packinghouses in southeastern New York. The 345 isolates, which caused blue mold in inoculated apples (Malus domestica), were identified to species and tested for sensitivity to methyl 2-benzimidazolecarbamate (MBC) and diphenylamine (DPA). Sixty-five isolates were P. expansum, 277 were P. aurantiogriseum, two were P. citreonigrum, and one was P. dendriticum. Thirty-one isolates of P. expansum were sensitive to MBC, 27 were resistant to MBC but sensitive to DPA, and seven were resistant to both MBC and DPA when tested in vitro. Ninety-five percent of the 277 isolates of P. aurantiogriseum were resistant to both MBC and DPA. P. aurantiogriseum was the predominant species recovered on all five sampling dates (November to March). Seventy-four percent of the isolates of P. expansum were recovered in the November and December sampling dates.

Keyword(s): negative cross-resistance, P. solitum.