Assessing the United States grape industry’s understanding of fungicide resistance mitigation practices

Authors: OLIVER, CHARLOTTE - Washington State University; COOPER, MONICA - University Of California - Cooperative Extension Service; LEWIS-IVEY, MELANIE - The Ohio State University; BRANNEN, PHILLIP - University Of Georgia; MILES, TIMOTHY - Michigan State University; Mahaffee, Walter - Walt; MOYER, MICHELLE - Washington State University

Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2021
Publication Date: 3/1/2021
Citation: Oliver, C.L., Cooper, M., Lewis-Ivey, M.L., Brannen, P., Miles, T., Mahaffee, W.F., Moyer, M.M. 2021. Assessing the wine grape industry’s understanding of fungicide resistance mitigation practices for grapevine powdery mildew (erysiphe necator) in the United States. American Journal of Enology and Viticulture. 72(2):181-193. https://doi.org/10.5344/ajev.2021.20062.
DOI: https://doi.org/10.5344/ajev.2021.20062

Interpretive Summary: The U.S. grape industry was surveyed to assess their understanding of factors involved in the management of fungicide resistance. In general, industry members were more knowledgeable with increased years of experience and size of operation. The survey indicated that while members had a sophisticated understanding of factors involved in managing fungicide resistance, they were less confident in their ability to practically implement this knowledge. This result indicate that outreach efforts should employ approaches that focus on transfer theory to practice and are geared to industry members early in their careers.

Technical Abstract: Grape powdery mildew (Erysiphe necator) fungicide resistance is a persistent concern in the United States (US). In 2019, a national survey of 252 members of the USA grape industry from 20 U.S. states assessed knowledge perception of fungicide resistance management, application of that knowledge to vineyard practices, and knowledge acquisition sources. Overall, respondents demonstrated clear understanding of resistance management practices. The specific distribution of responses was influenced by the respondent's job role, years of experience in the industry, and the size of their farming operation. Nationally, respondents were moderately familiar with the acronym FRAC (Fungicide Resistance Action Committee), with nearly 75% indicatingthey could identify the FRAC group of a fungicide. They felt moderately competent they could design a fungicide program that adhered to resistance management principles. Respondents identified fungicide resistance as a serious problem nationally, and a moderate problem in their own vineyards. They ranked practices that include rotating FRAC groups, avoiding multiple sequential applications of the same trade name or FRAC group, tank mixing with different FRAC groups, using multisite products in a spray program, routine sprayer maintenance and calibration, and good canopy management as very to extremely important in managing fungicide resistance; whereas practices such as rotating between trade names and tank mixing different trade names ranked slightly important. Respondents identified University Extension programs as the primary information resource for fungicide efficacy and fungicide stewardship (resistance management). These results suggest that future educational efforts aimed at improving practices for fungicide resistance stewardship should align with the knowledge base and demographic factors of the target audience, particularly their job role, experience and size of operation to maximize potential impact.