Fungicide programs used to manage powdery mildew (Erysiphe necator) in Australian vineyards

Powdery mildew (Erysiphe necator Schwein) is a major disease of grapevines. Extensive empirical information is available on the performance of fungicide programs, but little is known about the influence of cultivar, management system and especially the climate on grape growers’ fungicide use practices. Fungicide use records were analysed from a database that covered fifteen Australian production regions, seven seasons, and eight cultivars. Sulphur was the predominant fungicide used. Differences in fungicide programs were small between cultivars relative to differences between seasons. Fungicides were applied later in the season than recommended; after fruit set. The evapotranspiration during the 30-days following the separation of the first leaf from the shoot tip was a good predictor of the number of agrochemicals applied in all but the cooler regions. Growers overwhelmingly conformed to guidelines to prevent the development of fungicide resistance. The effectiveness of fungicide programs may be further improved by increasing the proportion of applications early in the season, targeting more susceptible cultivars, and using evapotranspiration to help identify and respond to seasons with high disease pressure. A better understanding of the practices of grape-growers may allow the refinement of fungicide use recommendations.