Tests were conducted to determine levels of tolerance of 10 Botrytis cinerea isolates from the Flathead Indian Reservation greenhouse (Ronan, MT) to six fungicides. In vitro growth and conidial germination on fungicide-amended potato dextrose agar were used as criteria for assessing tolerance. All tested isolates were tolerant to benomyl and chlorothalonil, the fungicides routinely used in this greenhouse prior to the test. Most isolates displayed slight tolerance to captan; four were slightly tolerant to vinclozolin. Dicloran and iprodione were the most effective fungicides in limiting growth and spore germination of the Botrytis isolates tested. Field performance tests are needed to evaluate control efficacy of vinclozolin and iprodione. A rotating fungicide spray schedule coupled with good cultural practices such as sanitation, adequate air circulation, and limiting irrigation should provide adequate control for this disease.
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