California wine grape growers and vintners are tallying up the damage caused earlier this month when a bitter-cold Alaskan weather front slowly moved through a large chunk of the state’s Central Coast premium wine grape growing area.

Damage is unquestionably extensive in the northern San Luis Obispo and Southern Monterey counties around Paso Robles, Calif., and north to the King City area where tender 2011 crop buds were fried from hours of mid-20 degree temperatures.

Some vineyards may not have a crop to harvest this fall due to the April 8-10 frost.

Vintners and growers from Solano to Santa Barbara counties are assessing the damage. Although the vines may push secondary buds to set a crop, Stacie Jacob, executive director of the Paso Robles Wine Alliance, reports growers are estimating the loss could range from 30 percent to 50 percent of the 2011 crop from the area’s 26,000 acres of vineyards.

“Although the magnitude of the frost was widespread and prolonged, it is too soon to tell exactly what the loss will be. It all depends on what the secondary and tertiary buds do from now on,” she noted.

Viticulture consultant Lowell Zelinski of Templeton, Calif., estimates that more than half of vineyard acreage in the Paso Robles area was damaged by frosts.

“15,000 of the 26,000 acres in the area suffered some damage,” said Zelinski. “Right now I would estimate 25 percent of the total acreage suffered a 90 percent crop loss. Losses will be so heavy that it will not pay to harvest some vineyards.”

“I have seen vineyards that look like they have been sprayed with paraquat. Buds are black. It is going to be bad.” Zelinski estimated only about half the vineyards in the Paso Robles area were covered by crop insurance when the frost hit.

Richard Smith of Valley Farm Management in Soledad, Calif., in Monterey County said it was a “hyper cooling” event. Low spots prone to frost were spared while upslope vineyards were hit.

“The morning of Friday, April 8, we hung ice from nine to nine. We had all 400 acres of frost protection (overhead sprinklers) running in Hames Valley,” Smith said. This is near the small southern Monterey community of Bradley, Calif., just north of Paso Robles.

“The coldest five acres were beyond our ability to protect. My neighbors were less fortunate,” Smith said.

In a northern Monterey County wine grape growing area called Arroyo Seco, a “real unexpected cold cell-hyper cooling-thunderstorm-cloud-clearing event” hit at an elevation 100 feet higher than the valley floor.

“We have 100 acres of virtually 100 percent shoot burn, and my neighbors on the adjacent west side of the road have another 100-150 acres of damage,” Smith said.

A number of places had cold air dropping down draws and canyons and delivering a cold shot to areas where there are not normally frost issues.

Smith said he was fortunate to suffer what looks to be a 50 percent crop loss on 100 acres out of the 3,000 he farms. The most significant damage was in an area from King City, Calif., south to Paso Robles.

Devastating frost

What made the frost so devastating were low dew points and no inversion layer as temperatures dipped to 24-25 F and stayed there for hours. Wind machines are useless without an inversion layer.

It was the most damaging frost one viticulturist had seen in 25 years. Another said it has been 40 years since the area had experienced a frost like this one. The coastal influence normally lessens the chance of frost, but that influence disappeared with the frigid Alaskan cold.

Dale Hampton of Santa Maria, Calif., veteran coastal wine grape grower, said so far none of his vineyards in the Santa Maria area are showing damage.

“Protecting with sprinklers definitely did the trick. We had the cold for a long time; 11 hours. If we have frost, it is normally for about five hours at most,” he said.

“Our sprinkler frost protection systems are not engineered for protecting against frost for that long. If we had had another night of frost, we would have run out of water in our reservoirs,” he said. Others did, according to Zelinski who has heard reports of drained reservoirs and lost wells in the middle of frost protection.

Hampton added that he has heard reports that the Santa Ynez Valley wine grape crop in Santa Barbara County was “banged up a little bit by the frost.”

Nat DiBuduo, president of Allied Grape Growers in Fresno, Calif., said he has also had reports of frost damage west of Lodi in the Delta area, as well as farther north in Solano County. “I have not heard of any damage on the North Coast,” he added.

“Damage was sporadic and some was significant,” he said. However, it was not as bad in the Lodi area as the 2009 frost.

DiBuduo also said there was hail damage in areas throughout the state from the same Alaskan storm, but it was not widespread.

The frost and hail came as the demand and price for wine grapes were on the upswing.

“The interest has been there early for 2011 grapes for the first time in the 12 years I have been at Allied,” he said. That is expected to heighten in the wake of the frost. There is no question frost has reduced the California crop. How much is the $64 question.

Pullback from finalizing sales

Growers are waiting for the vines to give them the answer. In the meantime, growers and wineries are pulling back from finalizing sales until the full extent of the damage and possible crop loss can be ascertained. Zelinski said many wineries may be surprised in a month to find out just how extensive the damage has been.

“Wineries are in the vineyards trying to find out what happened to the crop. It is definitely going to tighten things up in the grape market. Wineries had been looking for grapes for six weeks before the frost. It has been a pretty lonely three years up until this year,” he joked, adding wineries are also dangling long term contracts before growers to plant new vineyards. However, the prices so far have not warranted grabbing those deals, said Hampton and Smith.

“There is a buzz going on in the market, but it is a little early in the game to determine just how much damage was done. It will be an interesting couple of weeks ahead,” Hampton said. “However, there is no question there has been a significant crop loss,” in the Paso Robles area.

While the frost was relatively widespread, not all varietals were hit. Smith, Hampton and other growers held off pruning late emerging varietals like Cabernet and Zinfandel. Late pruning can delay bud break and give growers extra time to avoid frost.

Like all growers, Hampton will pay special attention to what happens with secondary buds, which are not typically as fruitful as the primary buds. One grower said secondary buds are good for only about half a normal crop.

There are things growers can do to prune off damaged buds and encourage other buds to replace those frosted. This and other post-frost practices will be discussed in a meeting May 10, sponsored by the Independent Grape Growers of The Paso Robles Area.

The meeting is scheduled for 1:30 – 3 p.m. at Silver Horse Vineyard and Winery in San Miguel, Calif., according to Zelinski.

Among those scheduled to speak is Dana Merrill, owner of Mesa Vineyard Management. Merrill manages 6,000 acres of vineyards, many of which were hit hard by the frost.

Chief Deputy County Agricultural Commissioner Brenda Ouwerkerk and Jennifer Anderson from the USDA Farm Service Agency also will speak.

Jacob said the county agricultural commissioner is evaluating the extent of the damage to determine if the county is eligible to declare it a disaster area.

The meeting is free to association members and $20 for others. Participants can RSVP to Precision Ag Consulting at 805-434-3331.