Athens, Ga. Thousands of broken trees line the banks of the Chattooga River. The dead gray stabs were once evergreen monsters offering shade to trout and picturesque views to visitors. These Eastern hemlocks are dying rapidly, and University of Georgia researchers are working to save them.
One tiny insect, the hemlock woolly adelgid, is to blame. The Asian insect first appeared in the eastern U.S. in Richmond, Va., in the 1950s. In 2003, it crossed the river from South Carolina and started feeding on Georgia trees.
The tiny pests suck up cells from the tree's needles, which prevent them from transferring water and conducting photosynthesis. The first obvious sign of an infestation is thinning foliage. Needles fall off, and the crown starts thinning. From a distance, trees look gray.
Researchers working to find ways to combat the adelgid have focused on releasing ladybird beetles, which eat adelgids. A new UGA study brings some of the logistical issues to light and offers hope for more successful control in the future. The results were published in the December issue of the Journal of Economic Entomology.
"Because the trees being attacked live mostly in remote forests where insecticide application is impractical, predators may be the best hope for tree survival," said Shimat Joseph, former UGA doctoral student who authored the journal article.
Previous studies have shown widely released predator beetles, Laricobius nigrinus and Sasajiscymnus tsugae, have been successful in controlling hemlock wooly adelgid populations, but they have not survived well through multiple seasons.
"Adelgid populations are not concentrated where we are releasing the predators," Joseph said. "Previous studies assumed populations are evenly distributed, but we are seeing that is not the case."
According to the study, adelgid populations tend to be more abundant in the upper crown, especially early in the infes
|Contact: Kris Braman|
University of Georgia