If leaves are not removed and weather is dry in spring, one fungicide application should be made sometime between bloom and pea-size berries. Otherwise, apply sprays before rainfall especially at bloom or after veraison. Remove leaves around clusters at late bloom-cluster set. If leaves are not removed, apply fungicides in northern and coastal production areas to prevent flower infections. Research data shows a trend toward better control if fungicides are applied at bloom, preclose, and veraison.
Thorough coverage is essential for all fungicide treatments.
A fungicide application may also be warranted on late season grapes if a major rain is expected. The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies. Benomyl-resistant strains occur in some areas. . . . Do not apply in combination with, immediately before, or closely following oil sprays. Do not apply in combination with, immediately before, or closely following oil sprays.