Of the seven dealers, six are owned by European firms. Trellis collapse is one of the most frequently-cited production perils. A collapse occurs when one or more of the poles snap or break, causing the wires to sag and permitting the vines to slump to the ground. The danger of collapse increases after about August 1, when the mature vines place the greatest weight on the trellis. Heavy dew or rain adds to vine weight, further increasing stress on the trellis.
Excessive moisture is a hazard to hop production because it increases the incidence of mildew.
Rain-related mildew is a more serious concern in Oregon than in either Washington or Idaho. Oregon's hops are grown in the Willamette Valley west of the Cascade Mountain range, and experience rainy periods more frequently than the areas east of the Cascades, including the Yakima Valley and southwestern Idaho. The incidence of mildew infections increase rapidly during wet weather. As a practical matter, drought is not a production peril because all U.S. hop production is irrigated. Hops have a high water requirement, however, and a lack of sufficient irrigation water would result in low yields.