REDUCED SENSITIVITY TO CARBENDAZIM IN ISOLATES OF BOTRYTIS ALLII

摘要

Fifty isolates of Botrytis allii, causing onion botrytis neck rot, were obtained from onion seed and bulbs throughout New Zealand and tested for their sensitivity to carbendazim (benzimidazole) fungicide in a mycelial growth study. Agar plates amendedwith carbendazim at 6 or 8 different concentrations were inoculated with an 8 mm disc of mycelium of each of the isolates and incubated in the dark at 20 deg C. Radial growth of the colonies was measured after 4 days. EC_(50) (effective concentration required to give half of maximum growth) values were estimated by fitting logistic curves, with growth as a proportion of the maximum growth. Of the 50 isolates, 16 were identified as resistant, 32 as sensitive and two had a variable response. The estimated EC_(50) values for the isolates that were sensitive ranged from 0.006 to 0.053 mu g/ml active ingredient. It is recommended that New Zealand onion growers closely follow the current benzimidazole resistance management strategy.