Integrated Pest Management for Powdery Mildew of Grapes in Arizona

Due to its ubiquitous nature and prolific reproduction potential, powdery mildew (PM) is arguably the most economically important disease of wine and table grapes in many parts of the world. The pathogen that is responsible for this disease, Erysyphe necator (Schw.) Burr. (synonym Uncinula necator) is a fungus, which if not held in check by chemical and/or cultural intervention, can compromise fruit quality and quantity in the vineyard. Although cultural practices such as shoot thinning and proper irrigation management are key to limiting infections, in most cases without the use of fungicides, PM would likely be responsible for greater losses than any other single pathogen of grapes, worldwide (Moyer and O’Neal, 2013, Pearson and Goheen, 2009). The disease was first described in North America (where it is believed to have evolved with North American Vitis species) in the early 19th century and was later observed in Europe, outside its native range (Gadoury et al., 2011). The introduction of PM caused severe crop losses in European wine grapes (Vitis vinifera L.), which were highly susceptible to the disease, and it was not long before the vast majority of grape growers in France were applying regular anti-microbial sulfur or copper treatments in order to keep the disease at bay.