Monitoring of the primary inoculum of the grape powdery mildew (Erysiphe necator) revealed that ascospores were caught almost continuously between bud break and fruit set, and release was best described as a function of degree-days. Monitoring of ascocarp production in the fall showed peaks in mid- to late September. This information can be used to optimize timing of fall eradicant sprays. A survey of fungicide sensitivity in E. necator in Michigan vineyards showed that strobilurin (QoI)-resistant isolates were most prevalent in research plots and some commercial wine grape vineyards and least prevalent in juice grape vineyards. The G143A mutation that confers resistance was detected in every isolate with an EC50
Read
