Powdery mildew is one of the most persistent diseases confronting wine grape growers. Caused by Erysiphe necator, the disease can infect leaves, shoots, inflorescences and berries, with infections established early in the season capable of developing into significant disease pressure around flowering and fruit set. The challenge with powdery mildew is that by the time it becomes obvious in the vineyard, the grower may already be behind. This is why early-season control is so