Midwest faces special threats: Multi-state event addresses herbicide drift and more

Wines & Vines, Sept, 2008 by Loretta Sorensen

Northwest Missouri--Midwest grapegrowers are almost certain to experience herbicide drift during their growing season. Herbicides control weeds, and grapes are especially sensitive to herbicides commonly used on other crops.

Drift occurs when herbicide is blown into neighboring acreage, injuring sensitive plants. If injury is repeated or severe, drift can reduce yields and result in poor fruit quality--occasionally even killing vines.

"As we've studied our vineyards, we've documented instances of herbicide drift," Dr. Paul Domoto, professor of horticulture at Iowa State University, told attendees at a recent Multi-State Viticulture Field Day. Hosted by the University of Missouri, the event drew about 150 industry members and academics, who toured vineyards and heard researchers from the University of Missouri, Iowa State University and the University of Nebraska-Lincoln. "Usually, the growing season is well under way before herbicide drift becomes a problem," Domoto observed. "However, we were surprised to note that we had herbicide drift damage at one of our sites very early last year."

Injury symptoms usually appear within 48 hours of the drift incident, including fan-shaped leaves with sharp points at leaf margins, downward bending leaves, leaf strapping with deep sinuses, and leaf puckering with constricted veins. Injuries from fall herbicide applications affect vine roots.

Domoto also talked about variety selection for Midwestern vineyards. He pointed out that growers must throughly understand many aspects of their sites in order to successfully produce grapes. "You really need to consult researchers in your state or area and take advantage of their scientific data," Domoto stressed. "There are too many variables, such as soil, air flow, herbicide concerns and elevation." States represented at the event included Missouri, Kansas, Nebraska, Iowa, Arkansas, Oklahoma and South Dakota.

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