The bone-chilling cold of early January was exactly what Georgia peach and blueberry growers need, say University of Georgia experts. But they need a lot more.

"At the moment, we're praying for cold weather," said Gerard Krewer, an Extension Service fruit horticulturist with the UGA College of Agricultural and Environmental Sciences.

An unseasonably mild fall brought middle- and south Georgia into the new year with the fewest chill hours to this point in 40 years. Chill hours are the time below 45 degrees between Oct. 1 and Feb. 15.

"The chill hours are running about half of the normal accumulation across most of south Georgia," Krewer said.

Without the needed chill hours, the trees will bloom and set some fruit, Krewer said. But they'll lose the fruit when the leaves don't develop quickly after fruit set. Without leaves that photosynthesize to create sugars, the tree can't support the fruit.

If we're just 100 or so chill hours short, we may get some of a crop, he said. But it probably won't be a good one. At 200 hours short, the crop would be very poor.

However, it's still early in the winter - too early to make a solid prediction of crop yields. Chill hours can accumulate at a rate of 168 every week.

But with six weeks remaining before the cutoff date, Krewer calculates that growers we need a solid month of below-45 temperatures to get enough chill to make a good crop.

"And we rarely receive continuous chilling in south Georgia," he said.

Chill requirements vary by the peach and blueberry type. But so far, no varieties grown in middle and south Georgia have enough chill hours to properly set and develop fruit.

Peach trees can still benefit from chill hours after Feb. 15, Krewer said, but they aren't as effective as those before.

At this point, Krewer and Georgia peach farmers are hoping for cold weather and a state registration for a chemical called "Dormex."

This material, already widely used around the world, can substitute for 100 to 150 chill hours. Farmers may be able to supplement natural chill hours with Dormex and get a good crop.

Krewer and Kathryn Taylor, a UGA stone fruit horticulturist, will lead a meeting on Dormex applications at the Jan. 24 business meeting of the National Peach Convention in Myrtle Beach, S.C.

Call Bob McCurry of the South Carolina Peach Council at (803) 734-2215 for more information about that meeting.

Farmers in upper north Georgia have been more fortunate. They're on track to get enough chilling hours for rabbiteye blueberries and most peach types grown in their area.