Files
Abstract
Grapevine powdery mildew (GPM), caused by the fungus Erysiphe necator, is a devastating disease of wine grapes. E. necator is highly efficient at developing fungicide resistance with reports of resistance to both quinone outside inhibitors (QoIs) and demethylation inhibitors (DMIs) throughout the world. In this research, a survey was conducted to determine the frequency of QoI and DMI resistance-associated alleles in Georgia. Field trials were conducted to determine the efficacy of currently available fungicides to control GPM, if there was control synergy between sulfur and DMI mixtures, and if cross-resistance among DMIs is present in E. necator. Resistance to QoIs and DMIs was observed to be widespread in Georgia. There was variability in efficacy among the DMI fungicides tested, showing that cross-resistance is incomplete. Additionally, synergy between DMIs and sulfur was not observed, but sulfur can still be used in tank mixtures as an effective additive.