Grape growers face drift, weather challenges

VINCENNES, Ind. — The most important weather conditions for grapes are the last four weeks before harvest.

“The temperature during that time is critical for sugar and acid balance and for flavor and aroma compounds,” said Bruce Bordelon, horticulture professor at Purdue University, during the virtual Southwest Purdue Agriculture Center field day.

“Traminette, our Indiana signature grape, is much better when we have warm, sunny days, but cool nights,” he said.

The summer weather will play a critical role in grape development.

Grape farmers also have to deal with the potential for herbicide drift from corn and soybean fields.

“Some of the herbicides used in corn and soybean production are growth regulator herbicides,” Bordelon explained. “Those are volatile compounds that can vaporize off of a field during or after applications and drift miles away.

“Grapes are about 1,000 times more sensitive than other plants. They’re very likely to be damaged by those compounds if they drift into the vineyard at the appropriate time of year.”

If exposed to herbicide drift, the vine may fail to flower normally, affecting its ability to set fruit.

“One of the problems about drift for a grape or tomato growers is there’s really no recourse,” Bordelon said. “There’s really nothing you can do to regrow or reset fruit. It’s a onetime deal.

“We’re at the mercy of the weather and commercial applicators.”

In an effort to help farmers, the Driftwatch website was established. There, growers can post the location of their herbicide-sensitive plants.

“The applicator industry can go online before applying to see if there’s a crop that’s sensitive to herbicides nearby,” Bordelon said. “There are fact sheets to help them make wise decisions.”

Learn more at www.driftwatch.org.