|Twig Girdler - Oncideres cingulata - Dave Rintoul|
I have never caught these beetles in action, but their evidence is especially easy to find on young trees whose branches are at eye level. They work in two separate ways, each an interesting method of reproduction.
Twig girdlers feed on the tender bark at the tips of branches, the rapidly growing portion which must be juicy and tender. After mating, the female works from the outside in, making a smooth cut around the branch, somewhat V-shaped while the center remnant remains intact for a while. Next she deposits an egg under the bark in the distal or outer half of the branch. Her larva requires dead wood to develop and the cut effectively blocks the branch's circulation.
The larvae of various species are white legless grubs that reach 5/8 to 1 inch long.With time the branch falls to the ground while the larva emerges and bores into the dead branch. After over-wintering in a resting phase, it consumes the rest of the branch in the spring, creating a chamber filled with wood shavings and frass. Following pupation, the adult beetle emerges in the fall, mates and starts the process again.
|Twig Pruner -USFS|
Twig Pruner - Anelaphus villosus- tom murray
Along Bull Creek they do not produce serious damage. If you had a heavy infestation on your urban tree, it would pay to pick up and destroy them by burning the pruned branches to decrease next year's infestation. Pruning the cut branches before they fall is also an option. Meanwhile, nature has a way of maintaining a balance with parasites such as Eurytoma magdalidis, Iphiaulax agrili, and Horismenus sp., and a checkered flower beetle, Cymatodera undulata.
Drawings from MU Extension Brochure
There are lots of species shown in the twig girdler identification guide.