A Gardeners Forum Forums General Discussion Plant pests and problems Powdery mildew taking over tree seedling and brittle

Control Measures - A fungicide spray program is necessary to control the disease when powdery mildew susceptible varieties are grown. The major objectives of the spray program are to: 1) reduce the number of spores produced on newly-developing infected tissues in the spring (primary infection), 2) prevent infections of new shoots, buds, and leaves during the growing season (secondary infection), and 3) prevent fruit infections. Normally, spray programs will include a fungicide for powdery mildew around petal fall. On susceptible varieties and when conditions favor the development of the disease, sprays at 5-7 day intervals starting at tight cluster and continuing through petal fall are recommended. Cover sprays should also be applied until terminal buds have set and are no longer susceptible to infection. Since the fungus is infective during dry periods of high relative humidity when redistribution of fungicides by rain does not occur, spray coverage is extremely important. Refer to the Pest Management Guidelines for Commercial Tree-Fruit Production for proper fungicides and spray timings.