Leaf removal improves fungicide control of powdery mildew in SJV grapes

Basal leaf removal, which has been used to reduce damage from bunch rots and seasonal leafhopper infestations, was tested for its effects on powdery mildew in the San Joaquin Valley. Powdery mildew is one of the most damaging diseases of wine grapes in California. On-farm experiments showed that leaf removal reduced the disease in two of five experiments and facilitated improved spray coverage in grapevine fruiting zones. Leaf removal can improve the effectiveness of fungicide programs in reducing powdery mildew damage, but should not be relied upon alone to control the disease.