Most local orchardists and grape growers dodged a frosty bullet over the past weekend as a blanket of clouds prevented temperatures from falling too far below freezing.

Most local orchardists and grape growers dodged a frosty bullet over the past weekend as a blanket of clouds prevented temperatures from falling too far below freezing.

Weather forecasters had farmers scrambling over the weekend to protect their crops from temperatures that were predicted to dive into the 20s. On clear nights, heat that collects at the ground during the day radiates into the atmosphere, but clouds reduce the heat loss.

Pears and wine grapes, Jackson County's primary cash crops, are at different stages of development. Pears already have begun to appear, although they are growing more slowly than normal because of persistent cool, wet weather. Grapes are in the flower-bud stage and fruit has yet to set for most varietals.

"We had no frost damage, but we've had hail at various times," said Mike Naumes, president of Naumes Inc. in Medford. "I was out doing crop estimating on Sunday, and I didn't see where there has been any major damage. You can see scratching and marking on some pears. But for the kind of weather we're having, we can count our blessings that it hasn't been worse."

Horticulturist David Sugar at the Oregon State University Experiment Station in Central Point said frost over Memorial Day Weekend is not unheard of in the Rogue Valley. Sugar, who has worked here 32 years, said he has heard anecdotal reports of frost as late as June 6 in some cold pockets.

"We rarely have late frosts damaging pears," Sugar said. "Cloud cover was key to keeping temperatures above the critical zone."

Still, orchardists were taking no chances.

"We've had almost every heater we have going," said Luis Balero, orchard superintendent at Associated Fruit, which grows pears on 1,400 acres. "We had the wind machines and overhead sprinklers going for frost control on Friday night, but otherwise by Sunday night we were safe."

Marcus Buchanan, a soil expert at the experiment station, said the coldest areas affecting grape growers were in the Illinois Valley area in Josephine County.

"In general, the frost was pretty spotty," Buchanan said. "The negative impact was limited to specific sites. There was some bud kill, but only in small percentages at random sites in the three-county (Jackson, Josephine and Douglas) region."

Telephone calls to several Illinois Valley wineries seeking information about frost were not returned Monday. Kate Bendock, of Windridge Vineyard, said despite the cool and rainy temperatures there wasn't much problem outside Cave Junction, where she has worked 8 acres of grapes for a dozen years.

"Our alarms went off for about 20 minutes Saturday morning," she said. "So we didn't have to do anything unusual."

At Deer Creek Vineyards in Selma, the temperature fell to 26 degrees, said Ann Garnett, who has tended 70 acres of grapes for 22 years.

"We use overhead sprinklers for frost control," Garnett said. "The buds are slow coming out, but from what I can tell there may have been a little frost that nipped a few buds. Overall, we're fine."

The long-term concern, Buchanan said, is canopy development, the growth of leaves on the vines.

"We're not seeing early-season heat, so we're not seeing typical amount of canopy development," Buchanan said. "As a result, flowering and fruit-set pollination will also be late."

Pear crop development is running more than a week behind normal, Balero said.

"Right now the fruit is a half-inch to five-eighths in diameter," he said.

Naumes, whose company operates 15 pear orchards covering 1,600 acres in Jackson County, said there are still long-term concerns over the size of the 2010 crop.

"The biggest thing is that we're not getting warm temperatures to get the fruit out and growing." Naumes said. "That could affect our fruit size (and value) ultimately."

Continued wet weather has its own consequences — a fungus disease known as scab that spreads through the air, Sugar said.

"Every time it rains, if there is infection it will get worse and attack more fruit and there will be more loss," Sugar said.

Growers are forced to apply a protective coat to the pears, but it only lasts about a week.

"From a grower's perspective," he said, "as long as we are in a rain-risk period, a conservative grower would apply a protective layer every seven to 10 days."

Reach reporter Greg Stiles at 776-4463 or e-mail business@mailtribune.com.