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Frost cripples grape crop

By Staff | Apr 18, 2012

Richard Black, of Farnhamville, shows the dead grape shoots that followed last week’s three nights of freezing temperatures. Black said the damage “is severe” and estimates at least 75 percent of his crop was ruined.


Farm News news editor

FARNHAMVILLE – Richard Black said he knew the killing frost was possible, even to be expected, but some part of him was hoping it wouldn’t happen.

But it did.

Last week, with the first primary grape buds out and a month ahead of schedule, temperatures dipped at official measuring sites to 29 degrees and to 24 degrees on April 10. At 28 degrees for four hours is considered a hard frost in farming terms.

Most of the shoots on this Marquette variety grape vine were killed by the frost. However, the vine shows that possibly the second shoots may still be viable. Grower Richard Black said it’ll be a few weeks until he can make an educated estimate on his actual 2012 harvest will yield.

But according to Black, his thermometer read 17 degrees overnight on April 9, 16 degrees overnight April 10 and and in the 20s overnight April 11. That was enough, he said, to cause significant yield losses to his grapes, especially his early-budding varieties.

“It was bad,” Black said, who manages 1,600 grape vines in a three-acre site around his rural Farnhamville home. “It was devastating.”

When told that Mike White, Iowa State University’s viticulturist estimated the statewide grape yield loss was 50 percent, Black said, “that would be good news. But Mike is looking at the entire state.”

White said vineyards north of I-80 sustained frostbit more severely than those in southern Iowa counties.

White said some growers attempted to keep heat among their vines, or continually spray water on their vines and some tried spraying liquid potassium, which acts like an antifreeze to protect the buds during the freezing period. Black said he didn’t try any of those measures.

“There’s not a whole lot you can do,” he said. “Most efforts are not effective.

“The most you can do is give the vulnerable buds a 3- to 5-degree protection.” Once the temperature slips to below 25 degrees, all bets are off.

“And it’s not like flowers, you can’t just throw a blanket over them,” Black said. “And we’re not the only ones, the same happened to orchards, too.”

He said the primary buds of Marquette varieties were out to 3 inches long on Sunday. They looked green and lush. Some of the secondary buds were out, as well.

White and Black agreed frost damage varies by cultivar and location. Early budbreak varieties, including Marquette, and and low-lying areas normally receive the worst damage.

Black said before the frost, “It would be easy for someone to get overly optimistic. You look at the (vines) and think here’s a chance to do a really good job by-the-book all season long.

“And well, here we are …”

Black said he fully expects to see a 75 percent yield loss on his grapes. “But we’ll be able to tell better in about two weeks.”

He hires three workers throughout the growing season to tend his vineyard. Are they out of work now?

Not at all, Black said. Half of all the work on vine husbandry is for the current crop and half is for the next year’s crop.

“The crop is gone,” he said, “but we still have to do everything as if it’s otherwise; only there’s no income coming in.”

Crop insurance on grapes? Forget about it, Black said.

“There is insurance, but you can’t afford it,” he said. The reason is that unlike corn and soybeans, the sheer numbers of growers are not sufficient to share the risk, so insurance rates are high on grapes.

According to White, there are only 300 Iowa vineyards, cultivating grapes on 1,200 acres statewide.

“This frost did not kill any vines,” White said. “It only set us back. The industry will continue to grow.”

Disappointed to the frost damage and the lost yields, Black said he tries not to get too down. “I’m not the only one this happened to.”

Ajay Nair, an ISU Extension vegetable specialist, said he noticed damage to fruit blossoms at the Horticulture Research Station near Gilbert after the April 10 frost and temperatures were even colder April 11.

Paul Domoto, n ISU Extension fruit specialist, said the temperature dipped to 20 degrees at the horticultural station, a temperature that damages plants, but especially those near the ground, like strawberries. Strawberries are most vulnerable at bloom, however, only the earliest cultivars have reached this stage of development.

The problem with the fruit crops is that the early spring weather sped up blooming, which is a particularly sensitive stage for the plants. Domoto said although there has been damage it’s too early to say how bad the freezes were until growers can assess the conditions in their areas, because site conditions and stage of bud and/or shoot development will have a significant influence on the extent of injury.

Nick Howell, superintendent of the Horticultural Research Station, doesn’t expect much of an apple crop because of the freezes. He confirmed there was “significant damage” to the station’s vineyard and strawberries. Apple trees typically are “in jeopardy” until the middle of May, he said.

Unfortunately, Howell said the expense of pest management in the apple orchard must be maintained even though there are few, if any, apples produced.

Contact Larry Kershner at (515) 573-2141, ext. 453 or kersh@farm-news.com.

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