The Diversity and Determinants of Fungicide Programs for Hop Powdery Mildew

Area of Science:

• Agricultural Science
• Plant Pathology
• Entomology

Background:

• Plant disease monitoring generates valuable metadata for predicting pesticide use and associated costs.
• Hop powdery mildew (Podosphaera macularis) management in Oregon involves diverse fungicide application strategies among growers.

Purpose of the Study:

• To summarize pesticide use patterns for hop powdery mildew management in Oregon.
• To identify and categorize distinct fungicide use programs employed by growers.
• To quantify the impact of these programs on pesticide application frequency and costs.

Main Methods:

• Analysis of pesticide use frequency based on active ingredients and Fungicide Resistance Action Committee (FRAC) codes.
• Hierarchical cluster analysis to group diverse pesticide use patterns into distinct programs.
• Random forest regression and Shapley values to determine the predictive importance of fungicide programs on pesticide use and costs.

Main Results:

• Significant variation in active ingredient and FRAC code usage among growers, with mean applications ranging from 0 to 2.41 per yard.
• Identification of three distinct pesticide programs based on hierarchical cluster analysis.
• Fungicide program emerged as a key predictor, ranking third for annual costs and fifth for the number of active ingredients applied.

Conclusions:

• Pesticide use patterns for hop powdery mildew are highly variable and can be categorized into distinct programs.
• Fungicide programs significantly influence pesticide application frequency and costs.
• Growers may adapt their pesticide programs based on the observed incidence of powdery mildew, suggesting a responsive management approach.