The Australian Wine Research Institute

Powdery mildew is the common term for a group of plant diseases. In grapevines the disease is caused by the fungus originally named Uncinula necator, now renamed Erysiphe necator. Infection and subsequent disease development is influenced by many factors including the presence of infected grapevine tissue, spores, and the occurrence of particular weather conditions. Disease progress early in the season may be slow depending on weather conditions, but is not usually impeded in most areas of Australia. Development of the disease can be slow in the early part of the season when conditions are less favourable for the fungus. The critical time for development of powdery mildew falls in the period just prior to flowering through to fruit set. The disease can be carried over from season to season in infected buds, or as ‘resting spores’, called chasmothecia (formally known as cleistothecia). Many commercially important grapevine species and varieties are prone to infection by powdery mildew. Early season control is important to prevent a build-up of the disease.