Assessing the Curative and Protective Impacts of Select Fungicides for Control of Powdery Mildew of Wheat

Powdery mildew, caused by the obligate fungal pathogen Blumeria graminis, has been increasing in incidence and severity on wheat in the Chesapeake Bay region of the mid-Atlantic United States. Although fungicides are used for in-season management of powdery mildew, no studies to date have assessed the ability of these products to control disease after pathogen arrival/infection (curative activity) and the duration of disease control provided after fungicide application (protective activity) under controlled conditions. Five commercially available fungicide products, including Caramba, Stratego YLD, Priaxor, Prosaro, and Trivapro, were applied at either 3 or 5 days after inoculation with B. graminis spores to assess curative activity. In a separate study, protective activity for these fungicides was assessed by applying fungicides and inoculating with B. graminis spores the same day and 21 and 42 days after fungicide application. All fungicides reduced powdery mildew severity on foliage compared with nontreated controls. Priaxor provided 11 to 18% less activity than other fungicides when applied curatively. All products provided protective control up to 42 days after inoculation, with Stratego YLD and Priaxor providing the greatest level of control at 68 and 56%, respectively. Our data indicate that different fungicides can have subtle differences in overall efficacy profiles that may translate to improved control or an extended control window in some situations, but all tested products provide very good to excellent control of powdery mildew on wheat.