Baseline sensitivity and efficacy of fluazinam in controlling Sclerotinia stem rot of rapeseed

Abstract

Baseline sensitivity of Sclerotinia sclerotiorum to fluazinam was determined using 150 isolates collected during 2011 and 2013 from the rapeseed fields without a previous history of fluazinam usage in Jiangsu province of China. The median effective concentration (EC50) values for fluazinam inhibiting mycelial growth on agar plates ranged from 0.0019 to 0.0115 μg/mL (mean of 0.0069 μg/ml). Neither cross-resistance between fluazinam and carbendazim or dimethachlon was detected. None of the tested isolates displayed reduced sensitivity to fluazinam. On detached rapeseed leaves and pot experiments, fluazinam at 150 μg/ml provided over 80 % control efficacy and exhibited excellent protective activity. In field trials, fluazinam at 187.5 g a.i. ha−1 provided over 70 % control efficacy, higher than other traditional fungicides, suggesting excellent activity against Sclerotinia stem rot (SSR). These results suggest that fluazinam has strong antifungal activity and could be a good alternative fungicide to carbendazim or dimethachlon in controlling Sclerotinia stem rot.