Responding to a new threat to Cascade from Powdery Mildew

As long as the Brewers Association (BA) has been conducting the Annual Hop Usage Survey, the Cascade hop variety has occupied the top spot as the most widely used hop by U.S. craft brewers. Clearly the work horse hop for small and independent brewers, the flavors and aromas of Cascade has long been considered to be the distinctive signature of craft beer. Not incidental to the widespread cultivation and use of Cascade has been the hops’ inherent genetic resistance to powdery mildew.

Powdery mildew is the most costly disease to the U.S. hop industry and, by extension, brewers. Rapid expansion of planting of Cascade has facilitated powdery mildew fungus to develop greater virulence on Cascade in just the past 3-4 years.  Studies have confirmed that Cascade-virulent strains of the fungus are present in the Pacific Northwest.  In short, it appears that the signature hop used in a very large number of craft beers is in danger of losing its resistant to a very common and costly disease. This development could lead to decreased yields, higher prices and lower quality in the Cascade hop.

Grant

With support from the BA, David Gent’s (Research Plant Pathologist, US Department of Agriculture, (Agricultural Research Service) work in 2012 and 2013 confirmed occurrence of powdery mildew on Cascade in the field and infection of Cascade in the lab. In 2014, outbreaks of powdery mildew, sometimes serious outbreaks, were documented in Cascade yards established with planting material sourced from virus-free true to type planting stock. In a continuation of this work, funding was awarded in 2015 to develop new knowledge, understanding, and approaches to mitigate damage from powdery mildew on Cascade.

In addition, the research will focus on the susceptibility of other varieties derived from Cascade to virulent strains of powdery mildew and identify powdery mildew resistance in males that could be useful parents in breeding efforts to develop new, powdery mildew resistant varieties as Cascade replacements. Resistant cultivars are thought to offer a long-term, sustainable solution to powdery mildew’s negative impact. Gent’s project will give growers tools to ensure BA members have access to Cascade in the near term, and will support development of disease resistant, economically viable, sustainable hop varieties in the future.

Grant Awarded: 2015
Grant Submitted by: David Gent, Research Plant Pathologist, US Department of Agriculture (Agricultural Research Service)