ARS | Publication request: THE RISE AND FALL OF HOP POWDERY MILDEW IN THE PACIFIC NORTHWEST

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: June 29, 2005
Publication Date: October 5, 2005
Citation: Mahaffee, W.F., Turechek, W., Thomas, C.S., Grove, G.G., Galloway, H., Nelson, M., Ocamb, C.M. The rise and fall of hop powdery mildew in the pacific northwest. Phytopathology.

Technical Abstract: In 1996, hop powdery mildew was found in a greenhouse in the Yakima Valley of Washington. By July 1998, it was found in all hop growing regions of Idaho, Oregon, and Washington. Over the past six years, laboratory and field research has determined the impacts of diurnal temperature fluctuations, humidity, and host on disease development, spatial dynamics of disease spread, cultural practices that reduce disease development, and pathogen distribution. These efforts have culminated in an infection risk forecasting model and an integrated management system that is used on approximately 75% of US hop acreage. In 2002-2004, growers using the model to assist in fungicide applications reported 2.5 fewer applications and had 55% less incidence of cone infection per year. Combining the model with other cultural practices has helped reduce control costs from $980 to $230-490 per hectare depending on variety and grower risk aversion.