Growing hops is stressful!

Technical Session 13: Hops III Session
Douglas B Walsh, Washington State University, Prosser, WA, USA

ABSTRACT: Today’s beer consumer knows that hops are a key ingredient in beer. An increasing population of connoisseurs has gained an appreciation for hops’ essential role in creating the distinctive flavors that characterize specialty brews. Yet, few consumers are aware that producing hops is stressful. Hop growers face the stress of uncertain market demand, shifting price structure, consolidation of key customers, cancellation of contracts, increasing input costs for labor and fuel, and environmental regulation, along with the often stressful challenge of growing this unique specialty crop. Hop plants are subject to stress, as well, from a variety of biotic and abiotic factors. Biotic stress comes from pests and diseases, while abiotic stress comes from bright sunshine, high temperatures, wind, and dust that are typical of summer conditions in the inland Pacific Northwestern United States, in addition to water availability. To assist growers in understanding and overcoming stress factors, a transdisciplinary team sought and received USDA Specialty Crop Research Initiative (SCRI) Coordinated Agricultural Project (CAP) funding to study the plant stresses resulting from spider mites, aphids, downy mildew, powdery mildew, and varying levels of deficit irrigation with respect to impacts on hop quality and quantity and also on the subsequent quality of the beer brewed with hops subjected to controlled amounts of various stresses. The team includes entomologists, plant pathologists, weed scientists, irrigation specialists, economists, a sociologist, a sensory scientist, and an outreach specialist, with researchers from Washington State University, Oregon State University, the University of Idaho, and the USDA Agricultural Research Service. The impacts of the various stresses have been measured quantitatively on yield (kg/ha) and on the levels of alpha- and beta-acids (determined by high-performance liquid chromatography) and qualitatively in controlled laboratory sensory (taste) analysis. In general, results thus far indicate that aphid feeding had no impact on alpha- and beta-acids. Spider mite feeding reduced alpha- and beta-acids, and powdery and downy mildews increased alpha- and beta-acid levels. Deficit irrigation (water stress) decreased yield and tended to decrease alpha- and beta-acids. The interaction of mite spider mite feeding and deficit irrigation did not have a significant effect on alpha- and beta-acids. Single-hop ales were brewed within each hop stress type, with the amount of hops adjusted to compensate for the variability in alpha-acids content. These brews were evaluated by sensory panels at the School of Food Science at Washington State University. Flavor panels rated brews that sustained mite and aphid feeding or infection with downy mildew as inferior to brews made with undamaged hops. Flavor panels preferred brews made with powdery mildew damaged hops. At the submission of this abstract the brews made from deficit irrigated hops had yet to be evaluated by the sensory panel. The results of these beer studies will be described in greater detail in the presentation.

Douglas B. Walsh is the integrated pest management coordinator for Washington State, a professor in WSU’s Department of Entomology, and the research director of the Environmental and Agricultural Entomology Laboratory at the Irrigated Agriculture Research and Extension Center in Prosser, WA. He functions as the overall coordinator and director of the SCRI-CAP project and directs the activities relating to arthropod management. Douglas works closely with and has research supported by the Washington Hop Commission and the Hop Research Council.