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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #429832
Research Project: Development of Superior Hops and Resilient Hop Production Systems

Location: Forage Seed and Cereal Research Unit

Title: Relative efficacy of fungicide modes of action for hop downy mildew: an individual participant data meta-analysis

Author
item Hwang, Jae Young
item Gent, David

Submitted to: PhytoFrontiers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2026
Publication Date: 3/9/2026
Citation: Hwang, J., Gent, D.H. 2026. Relative efficacy of fungicide modes of action for hop downy mildew: an individual participant data meta-analysis. PhytoFrontiers. https://doi.org/10.1094/PHYTOFR-11-25-0129-R.
DOI: https://doi.org/10.1094/PHYTOFR-11-25-0129-R

Interpretive Summary: Hop downy mildew is one of the most important diseases of hop for U.S. producers. Fungicides and biological control agents are routinely used to manage the disease. In this research, we quantitatively summarized efficacy of all public sector field trials with fungicides and biological control agents conducted in Oregon and Washington over the past 18 years. The results of this analysis are important because they can guide growers and others on the most effective treatment options in each state, and also help growers avoid treatments that may be ineffective.

Technical Abstract: Hop downy mildew, caused by Pseudoperonospora humuli, is routinely managed using fungicides. We analyzed plot-level data from public fungicide efficacy trials for downy mildew conducted in Oregon and Washington between 1997 to 2024 in an individual participant data (IPD) network meta-analysis. Data was aggregated by mode of action (MOA) inferred from the Fungicide Resistance Action Committee Group and analyzed when a given MOA appeared at least five times in trials. All MOA except for biologicals (BM) and various copper formulations (M1) were more effective than non-treated controls. In Oregon, fungicide MOA was resolved into three overlapping groups, with the most effective group being MOA 4, 40, 43, the premix of 49 + 40, and the premix of 49 + 4, providing estimated disease control of 63.9% to 79.7%. In Washington, the four MOA analyzed were more effective than the non-treated but had similar efficacy, with estimated disease control 76.8 to 89.3%. State had an additive effect on disease control; a given fungicide provided 10.5% (95% confidence interval -12.8 - 31.4) greater disease control in Washington versus Oregon. Multiplicative interactions of MOA × State were usually trivial, apart from P 07. Inconsistency testing indicated network comparisons were consistent in Oregon or for observations over both states, but were inconsistent in Washington because the efficacy MOA 11 depended on study design. Overall, these analyses provide a foundation for designing fungicide programs that are effective and follow resistance management principles. The analyses also demonstrate the utility of IPD network meta-analysis and inconsistency testing approaches.