Some county residents have seen an unusual number of small branches under their trees this year, a sign of an insect pest. The twig girdler beetle, Oncideres cingulata, cuts branches with a diameter about three-eighths of an inch, and those twigs are cut cleanly.
Carroll County Cooperative Extension Service Agent Olivia Foster said the insects are not new to this area, even though people may not have noticed them before.
Some years bring higher levels of activity. Because of the late fall, the twigs didn’t start piling until November. It may be that the mild, wet weather aided the infestation.
The beetles emerge in August, and the adults live six to 10 weeks. After mating, the females will lay an egg in a slit in the bark. The eggs cannot develop inside a live tree, so the beetle chews a perfect circle around the twig. The branch will then fall, either from its own weight or from the wind. The egg will hatch inside the fallen twig, and the larva will live on the wood inside the twig. The hollowed-out twig then becomes a shell to protect the larva during its pupation stage.
The girdlers prefer persimmons, hickory, and pecan, but they will attack other hardwoods, including oak and honey locust. Since the fallen branches carry eggs, picking up and burning those branches provides the most effective control. This measure will have limited effectiveness if nearby woods are infested but burning the twigs will still have positive effects.
Spraying has not proven effective, because few homeowners have the capacity to treat the full canopy. Trees will usually recover, although smaller trees may suffer more.
Foster said the Extension office will help with any kind of plant problems. People will sometimes bring cell phone pictures of problems, and Foster encourages those people to take multiple pictures to illustrate the problem. Agents can also schedule farm visits to address problems. The Extension website also has many resources.
Pic courtesy of Tahlequah Daily Press via OSU Extension