Grape growers in eastern Washington who thought last year’s harvest was early could be in for another surprise.
An unseasonably warm winter and hot spring means the grape harvest date could be two weeks earlier than last year, according to Michelle Moyer, assistant professor and Extension viticulturist at Washington State University in Prosser, WA. That would put harvests about a month ahead of the regular schedule, in which grapes are generally starting to be picked in early to mid-September.
Moyer says a late spring temperature spike, which pushed the mercury to triple digits for a few days, is not a major concern for grapes. In fact, the temperature may have helped in a couple ways.
Just a few weeks ago, viticulturists were warning about the likelihood of powdery mildew on fruit, but that issue was greatly alleviated with the heat spike.
“When we hit 100͒F, we enter mildew-killing temperatures,” she says. It’s been a really weird year for disease management.”
Grape canopies that flourished from a wet winter and spring are slowing growth under the hot sun. Growers can now turn their attention to deficit irrigation plans.
Moyer said another temperature spike or a period of unseasonably cool weather could still move the needle on harvest dates. But temperatures were expected to be back near average, in the 70s and 80s, at the end of the week.
And she doesn’t think fruit would have been damaged by the high temperatures.
“It’s when we get the really prolonged periods like we did last year that we have problems,” Moyer says.