Q: Leaf-covered twigs are littering my lawn under my large oaks. What is causing this "pruning" without my permission? Should I worry?
A: There are two main culprits that could be the "pruners" of your oaks.
One is the rather dramatic-looking longhorned beetle that you may see in its large mature form in May or June. It is dark, glossy and has two very large feelers that are cast back and give it a very scary appearance.
The other possibility is your local population of squirrels. Either one will cause short and leafy twigs to fall off the tree to the ground.
These tips of branches may be full of leaves and appear to be perfectly healthy. Why did they fall? The longhorned beetle has a larval form that chews over the summer. They are called round-headed borers. Their life's work is to burrow through the twigs of trees like the oaks, and they are fat and happy in the fall. Since they burrow through the narrow stems of branches, they weaken them. Fall weather, with its rain-soaked leaves and intermittent winds, can cause these weakened small stems to break.
Examine the fallen twigs. If you see a concave end break, cut the twig open; you should find the fat white round-headed borer. You can reduce the numbers of these native pests in your oaks by collecting and burning the fallen twigs.
There is an invasive new plant pest called the Asian longhorned beetle that is a serious pest to maples. Report this pest, if you find it, to your Agricultural Extension agent (855-6113 in Hamilton County).
However, if the twigs have a slanted cut end or a sheared-looking end, then the squirrels are your culprits. They bite the stems to use the leafy twigs to make their nests for winter. They also may be smart enough to cut off the acorn-laden branches so they can bury or nibble the nuts in a more comfortable location than the wobbly, twiggy end of a branch.
Your squirrels won't kill the tree, but they may make it slightly bushier with their "pruning." Of course, they do add to yard cleanup chores, but they should cause no worry about the health of your trees.
Email Pat Lea at firstname.lastname@example.org.