"Chemical control can slow the spread of adelgids, but beetles provide some hope that we will be able to manage the adelgids and bring them into balance. We may never be able to eliminate them," said Kris Braman, an entomologist with the UGA College of Agricultural and Environmental Sciences and co-author of the paper.
The three-year study looked at the population rates of adelgids in hemlocks located in the Chattahoochee National Forest. The 60 north Georgia trees selected for the study were 25 to 70 years old.
Predator beetles are reared on infested hemlock branches in labs. When released, the branches, saturated with about 100 beetles, are tied to living trees where populations have been identified. Strategic placement of the predators is important for successful control of the adelgidand for the bottom line.
"Because the beetles are so expensive to grow, every single little beetle is like releasing diamonds over the canopy," Braman said.
A cocktail of fertilizer and insecticide was applied to the trees included in the study to develop an application ratio that would maintain tree health while keeping enough adelgids alive to serve as sustainable food for the beetles but not enough to kill the tree.
"Part of the problem with maintaining predator beetles has to do with the declining tree health," said study co-author Jim Hanula, an entomologist with the U.S. Forest Service and adjunct faculty in the UGA department of entomology. "As tree health declines, adelgids produce fewer eggs and, in turn, less food for the predators."
Georgia trees decline faster than those found in northern states due to a lack of winter weather, which kills back adelgid populations in the North.
|Contact: Kris Braman|
University of Georgia