Twig pruner eats trees from inside out

Q. I have TONS of leaves falling off my oak trees. Are they dying? Is there anything I can do about it?

Don from Canfield

A. Twig pruner (Elaphidionoides villosus) is the culprit.

First, you can tell by noticing the bark is intact. There are no visible signs of chewing on the outside of the branch. The end of the twig will have a ragged edge, though.

Next, look at the end of the twig. This insect leaves a “plug” in the center of the fallen branches. This plug is frass (sawdust) from the insect and is used to keep out predators.

Oak seems to be the favorite tree of this insect, although other nut trees such as walnut and hickory can be attacked. Even maple, linden and sweetgum can be affected.

Since oaks are the dominant tree species in our area, we tend to notice them more when they affect oak trees.

The adult beetle laid an egg near the tip when the leaves began to emerge on these trees. When the egg hatched, a larva emerged to chew on the inner wood. This larvae grows inside the twig all spring, then makes a conscious effort to chew through the sapwood.

When it gets to the bark, it stops and moves to the outer, weakened part of the branch.

This weakened branch soon succumbs to wind and falls to the ground. The larva continues to develop inside the twig that fell to the ground. It stays there all winter. It will emerge in the spring as an adult beetle.

So, what to you do?

Simple! Rake up all those fallen twigs and bunches of leaves in your yard. Destroy them to destroy the larva inside. There may be some “hanging” branches in the tree with the larva inside that have not fallen to the ground, though. There are no other recommended control options for this insect.

There is a different insect, the twig girdler (Oncideres cingulata), that emerges in August and causes similar damage. But a discussion of this beetle shall wait for another day.

To learn more about the twig girdler, go to http://go.osu.edu/twigpruner

To add to the great twig debate, we’ve had samples since Don’s a couple of weeks back that were similar. The homeowners had tons of small twigs littering their lawns. But the difference was the lack of larvae and frass, the twigs were less than º-inch in diameter and the end of the twigs were mostly clean cuts. This problem is caused by our numerous squirrels. The squirrels are in a nest-building frenzy. There is no cause for alarm, and no real harm is done to the tree.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office hotline at 330-533-5538 to submit your questions. Regular clinic hours are 9 a.m. to noon Mondays and Thursdays.