Raise a Glass: New Report Shows IPM Gains in Hops

A new report by the Western IPM Center shows that the U.S. hops industry made significant advances in integrated pest management in recent years.

In 2008, the Pacific Northwest hop industry came together and produced a Pest Management Strategic Plan for hops in the region, highlighting pest-management priorities for the industry. The 2008 PMSP identified spider mites, prionus beetle and downy and powdery mildews as significant pests in Pacific Northwest hops.

In 2015, the industry repeated the PMSP process, updating the 2008 plan and expanding the scope beyond the Pacific Northwest to reflect the growth of hopyards across the country.

The Western IPM Center compared the two documents, and found significant IPM improvements in the management of spider mites, prionus beetles and mildew diseases, and regulatory changes promoting the use of reduced-risk pesticides.

For instance, research on spider mite economic thresholds demonstrated that hops tolerate larger mite populations without economic loss than previously thought possible as long as the cones are not infested. Acequinocyl was identified as an effective spider mite control material with low impacts on beneficial insects. Growers now use acequinocyl in their spider mite programs.

Research on the interactions between powdery mildew fungicide programs and arthropods found that minimizing or eliminating sulfur or parafinic oil for disease control, especially applications later in the season, conserves predatory mites and minimizes the severity of spider mite outbreaks. This is a key finding for IPM in hops and has led to improved conservation of predatory mites and management of spider mites.

In mildew control, a period of juvenile susceptibility to powdery mildew on hop cones was discovered. The outcome of entire disease-management programs largely depend on the efficacy of disease-control measures applied during a three-week period in the early stages of cone development. Targeting control measures to this critical period nearly doubles the degree of disease control observed at harvest. This finding has impacted production practices used by over half of producers. Yield loss from powdery mildew in susceptible varieties has been reduced significantly, with savings conservatively estimated at over $2 million annually based on grower estimates of yield damage obtained from surveys.

The four-page report is available on the Western IPM Center website. Download it here