First Report of Resistance to Quinoxyfen in Podosphaera xanthii, Causal Agent of Cucurbit Powdery Mildew, in the United States

Abstract

This brief reports the first known occurrence of resistance to quinoxyfen, a quinoline (FRAC Group 13) fungicide, in Podosphaera xanthii in the United States. This fungus causes powdery mildew in cucurbit crops, the most common disease of this important crop group. Mobile, targeted fungicides, which have moderate or high resistance risk, are the most effective management tool for this disease. The pathogen is a documented high resistance-risk organism, having already developed resistance to fungicides in FRAC Groups 1, 3, 7, and 11.