Last year, Southern pine beetle populations surged in Georgia’s Oconee National Forest. Drought stress may have contributed to the infestation, said Keith Douce, an entomologist the University of Georgia’s College of Agricultural and Environmental Sciences.
“We’ve been under drought stress for several years,” he said. “Even if you get adequate rainfalls, it takes two or three years for a tree to get back to full health.”
Douce said the increased activity of Southern pine beetles last year was “undoubtedly due to a lot of stress from drought and over-maturing of trees that haven’t been harvested.”
The Southern pine beetle is particularly good at finding trees in decline, he said.
A healthy tree produces large amounts of resin to keep the beetles out. The beetles stick in the resin and don’t enter the tree.
“As you have drought, the tree produces less resin,” Douce said. “You also get things like lightening strikes that cause a tree to decline, and the beetles can detect that and attack the tree.
“If you go through that cycle two or three times over a summer, you have literally thousands of beetles flying around and attacking trees under stress. Lightening itself can fry the tap root of a tree and it’s a goner. But beetles can find that tree because it’s under stress and they can attack and finish it off.”
Several beetles attack trees in Georgia. The most common are the Southern pine beetle, the black turpentine beetle and three species of ips beetles.
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April 2008