Powdery Mildew

Abstract

Powdery mildew of roses, a disease thought to have been first described by Theophrastus in 300 BC, is a problem worldwide, in greenhouses or outdoors, wherever roses are grown. Nearly 40% of the fungicide sprayed on roses is to control powdery mildew. The disease can cause distortion and death of leaves and shoots, but even a mild case makes plants unsightly. Powdery mildew reduces the quality of cut flowers and makes nursery stock less saleable to consumers. Its ubiquity causes gardeners and landscapers to think twice about planting roses. In a time when many parks are cutting maintenance budgets and limiting the use of pesticides in public places and when the use of many pesticides is restricted or not allowed for many breeders and growers of cut and garden roses in Europe, this disease continues to be one of the major scourges of roses. In this article we will describe the pathogen causing powdery mildew, its hosts, symptoms of the disease and how it spreads and the means of controlling it.