Powdery Mildew Technical Report

A Technical Report from The Bartlett Tree Research Laboratories

Powdery mildew is a foliage disease, which occurs on virtually all species of ornamental plants. Rose, oak, hawthorn, lilac, sycamore, laurel, and crabapple are commonly affected. Heavy infection can cause premature defoliation, growth reduction and render the host aesthetically unpleasing. Powdery mildew may occur at any time during the growing season; however, it is usually most severe in the late summer months. Unlike most foliage diseases, powdery mildew is inhibited by extremely wet weather.