Baseline sensitivity and control efficacy of pyrisoxazole against Botrytis cinerea

Botrytis cinerea is an important airborne plant pathogen with a wide host range. Gray mold caused by B. cinerea usually leads to both yield and quality reduction and causes severe losses. In China, the percentage of yield loss caused by B. cinerea gray mold in vegetable production is generally 10 to 20 %, sometimes up to over 60 % in some severely infected regions. The novel fungicide pyrisoxazole was registered for the control of tomato gray mold in China and has not been put into widespread use. In this study, baseline sensitivity of B. cinerea to pyrisoxazole was established based on EC50 values of 165 isolates sampled from tomato from Liaoning Province of China in 2012. Results showed that the frequency distribution of pyrisoxazole EC50 values was a unimodal curve with a right-hand tail. The mean EC50 value was 0.0676 ± 0.0409 (SD) μg/ml and the range of individual EC50 values was 0.0128 to 0.1987 μg/ml. There was no cross-resistance between pyrisoxazole, carbendazim and procymidone. The control efficacy of pyrisoxazole was assessed on detached leaves and in pot experiments. Pyrisoxazole provided over 80 % preventive control efficacy and over 50 % curative control efficacy at 100, 200, 400 μg/ml on detached leaves. It also provided over 80 % preventive control efficacy and over 60 % curative control efficacy at 100, 200, 400 μg/ml in pot experiments. These results indicate that pyrisoxazole is a highly effective fungicide with both preventive and curative effect for the control of B. cinerea.