BENZIMIDAZOLE-RESISTANT AND DICARBOXIMIDE-RESISTANT BOTRYTIS-CINEREA FROM PENNSYLVANIA GREENHOUSES

Botrytis cinerea was isolated from infected plants collected in 13 different greenhouses in Pennsylvania. The linear growth rates of the isolates and sensitivities to the benzimidazole fungicide, benomyl, and the dicarboximide fungicide, vinclozolin, were assessed in vitro. The area under the disease progress curve and sensitivity to benomyl and vinclozolin were assessed on geranium leaf disks (Pelargonium x hortorum cv. Red Elite). Isolates with resistance to benomyl were found in all 13 facilities, and double resistance to benomyl and vinclozolin was detected in isolates from six greenhouses. All isolates with EC50 values greater than 70-mu-g/ml for benomyl or approximately 1.0-mu-g/ml for vinclozolin in vitro overcame the presence of those fungicides and caused disease on geranium leaf disks. One isolate with an EC50 value near 0.1-mu-g/ml for vinclozolin infected vinclozolin-treated leaf disks, but nine others with EC50 values between 0.1 and 0.4-mu-g/ml did not infect treated disks. Neither the area under the disease progress curve nor linear growth rates were correlated with vinclozolin resistance.