Twig girdlers are gray-brown wood boring beetles with a pair of antennae that are about as long as their ¾ inch long bodies. They are active from mid-August into early October when the female lays her eggs. Twig girdlers can be responsible for hanging or fallen twigs on or around a variety of trees including hackberry poplar, linden, redbud, dogwood, and various fruit and nut trees. Heavy infestations can disfigure landscape trees.
The female twig girdler begins the process by chewing a deep V-shaped groove around a small twig and laying an egg in the twig beyond the cut. The girdled portion of the twig that contains the egg will soon fall to the ground. It can be recognized by a smooth cut on the outside of the twig near the bark and a ragged center where the twig breaks. The larva will tunnel into the dead twig and feed until winter. Development will resume in the spring. Ultimately, the larva will pupate in the twig and emerge as an adult late in the summer.
Fallen twigs contain the larvae of this insect so they should be collected and destroyed as soon as practical but before early May of the following year. Hanging twigs should be pruned out and destroyed if practical. An application of Sevin at the first sign of girdling, and repeated twice at two-week intervals, may reduce damage to infested trees. The insecticide kills the adult females before they can lay eggs but will not penetrate the twigs to kill deposited eggs or live larvae.
Several closely related species of beetles damage twigs in a similar manner but are less common. This includes mulberry bark borers, oak stem borers, spined bark borer, and the mulberry borer. These may all cause the same damage as the twig pruner and girdler.
Twig Girdler. Photo from Virginia Tech.Information taken from "TWIG GIRDLERS" By Lee Townsend in the July 24, 2006 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture and from a fact sheet from Virginia Tech on twig girdlers.
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