FINDING ANSWERS

FALL TWIGS

Q

For the third year in a row, I am seeing short branches fall from my oak trees. Seems to happen every year in the fall. The trees are otherwise healthy and the branches that fall don't have leaf spots. What is causing this to happen? — Via the Internet

A

There are several possible causes for seemingly healthy twigs to fall off trees. To determine the cause, consider the time of year and inspect the cut ends of the twigs. There are two major types of long-horned beetles that lay their eggs towards the ends of branches — twig girdlers and twig pruners. The host-range for both insects are numerous species of broadleaved trees. The twig girdler emerges in late August and lays its eggs in a tiny slit. The adult then cuts a channel around the twig to stop the flow of sap to the branch. Eventually, wind will blow the cut twig off the tree. The end looks like beaver damage, with the outside cone-shaped and the very center ragged from the tear. Twig pruners lay their eggs in the spring, in a hole at a leaf axil. The larva spends the summer feeding on the twig and working its way to the tip. In late summer, the full-grown larva makes concentric cuts through the twig, stopping just inside the bark layer. Again, wind will blow the twig off the tree. The damaged end is smooth inside with ragged bark around the outside. In general, damage is not severe enough from either insect to harm the tree or need chemical control unless the trees are small. In most cases, gathering the fallen twigs and burning or discarding them into a landfill should reduce the adult population for the following season. Do not discard into an unmanaged compost pile, as the larvae will be able to pupate and emerge as adults. Squirrels also damage twigs, usually in the spring, though it can occur anytime. The twig end is tattered and cut at an angle.

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In regard to the discussion on cattail control from the August 2004 "Finding Answers," a reader notes “I let the plants grow until just before they bloom, then cut the stalks cleanly below water level. The plants will take water down their hollow stalks and drown. The plants above the water line, I just mow and when the regrowth is a couple of inches tall, I hit them with Roundup.”

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