Baseline sensitivity of isopyrazam against Sclerotinia sclerotiorum and its efficacy for the control of Sclerotinia stem rot in vegetables

Abstract

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is a devastating fungal disease that infects a wide range of agriculturally important crops. An important approach to manage Sclerotinia stem rot is the use of fungicides. This study was conducted to determine the efficacy of isopyrazam in controlling Sclerotinia stem rot in vegetables. The baseline sensitivity of S. sclerotiorum to isopyrazam was established using 178 isolates collected from different vegetable crops during 2016 and 2017 in China. The results showed that the frequency distribution of the EC50 values of isopyrazam was a unimodal curve with a mean EC50 value of 0.039 ± 0.002 μg ml−1, which could be used in the future to detect changes in S. sclerotiorum population sensitivity to isopyrazam. Furthermore, sclerotial production and germination were strongly inhibited by isopyrazam. On detached eggplant leaves, the preventative and curative performance of 40 μg ml−1 isopyrazam against S. sclerotiorum was 100% and 87.78%, respectively. In polytunnel trials, the disease incidence of S. sclerotiorum significantly decreased when isopyrazam was applied at a concentration of 200 g a.i. ha−1. These results suggest that isopyrazam is very effective in managing S. sclerotiorum and could serve as an alternative fungicide to control the Sclerotinia stem rot of vegetables in the future.