APS Abstracts of Presentations

Sensitivity of Penicillium expansum isolates to the phenylpyrrole fungicide fludioxonil
Presenter: G. Olaya, Syngenta Crop Protection, Vero Beach, FL
Co-Author(s): T. Heidel, Syngenta Crop Protection, Vero Beach, FL; R. Spotts, Oregon State University MCAREC, Hood River, OR; P. Sanderson, Pace International, Wenatchee, WA; D. Rosenberger, Cornell University, Highland, NY; A. Tally, Syngenta Crop Protection, Greensboro, NC
Phytopathology 95:S77

The sensitivity to the phenylpyrrole fungicide fludioxonil of 120 monoconidial isolates of Penicillium expansum was determined under in-vitro conditions. Isolates were recovered from apples in WA and NY and pears in OR that had not been previously exposed to fludioxonil. Sensitivity of each isolate was determined by comparing the colony radial growth on 1/4 strength potato dextrose agar plates either amended or not with fludioxonil. The sensitivity distributions (ED50 values) of P. expansum isolates collected from each state were different. Sensitivities of isolates collected from pears in OR ranged from 0.027 to 0.171 (mean: 0.056) mg/L, whereas sensitivities of isolates collected from apples in WA ranged from 0.015 to 0.058 (mean: 0.045) mg/L, and that of isolates collected from apples in NY ranged from 0.006 to 0.047 (mean: 0.028) mg/L. Fludioxonil baseline information will be used in future fludioxonil sensitivity monitoring studies looking for the early detection of changes in sensitivity of P. expansum to fludioxonil. Fludioxonil (SCHOLAR®) is a new reduced risk fungicide registered by EPA and is labelled for postharvest application to control diseases on pome fruit caused by Penicillium, Botrytis, Rhizopus and Pezicula.

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