2019 Daniel McAlpine Memorial Lecture. Grapevine powdery mildew: from fundamental plant pathology to new and future technologies

Grapevine powdery mildew, caused by the fungus Erysiphe necator (formerly Uncinula necator), is a widespread disease which can reduce yield and quality of grapes and compromise wine quality. As an obligately biotrophic pathogen of a woody perennial crop, E. necator presents challenges for researchers studying aspects of biology, epidemiology and management. The disease can be difficult to detect, especially in the early stages, as signs and symptoms are often inconspicuous. Failure to control powdery mildew early, inadequate spray coverage and or fungicide resistance may lead to significant damage. Because of the negative effects of disease on wine quality, many wineries set thresholds for acceptability of grapes for winemaking, typically 3–5% of the surface area of bunches affected. This is usually determined by visual inspection in the vineyard close to harvest or at the winery. Visual assessment is subjective and prone to inaccuracy, and the wine industry seeks a rapid and reliable objective measure for disease severity. In this paper, I describe some of the challenges of research on the biology and management of grapevine powdery mildew and how these have been addressed using fundamental approaches in plant pathology. Recent research towards development of objective measures is presented and technologies that have potential for application in the vineyard or winery in the future to facilitate disease diagnosis, quantification and management are considered.