The twig girdler, Oncideres cingulata, and twig pruner, Elaphidionoides villosus, can be problems in nurseries and landscapes. The main difference between these two pests is that girdlers cause damage when adults sever a twig from the outside, whereas pruner damage occurs when the larvae sever the twig from the inside. Both the twig girdler and pruner attack a variety of trees including elm, oak, linden, honeylocust, hackberry, redbud, poplar, sweetgum, and sassafras. Branches up to 3 feet long may drop from the tree because of attack by these insects. They can be a problem in landscapes and nurseries when excessive damage alters the shape of a tree or reduces plant salability.
The twig girdler inflicts damage to twigs or branches as an adult. In the fall, adult females chew circular notches around a twig, girdling it. The females lay eggs singly underneath the bark in a hole created by the adult in terminal and lateral twigs or branches. Females can lay three to eight eggs into a single twig. Leaves on trees turn brown after the adult has fed and laid eggs. The eggs are placed beyond the girdled area. Girdled twigs soon die, break off the plant, and fall to the ground. The eggs hatch into larvae that overwinter inside twigs lying on the ground. Larvae tunnel toward the severed end and feed on woody tissue. Full-grown larvae are cylindrical and 18 to 25 millimeters long when mature. In spring and summer, larvae undergo a pupal stage. Development is complete in late summer and fall, after which the adult beetle emerges and repeats the cycle. The females live about 6 to 10 weeks and can lay a total of 50 to 200 eggs. There is one generation per year.
The twig pruner adult attacks twigs and small branches 6 to 50 millimeters in diameter. The adult female chews a small hole in the bark of a twig near the leaf axil where eggs are laid. The eggs hatch into larvae that are covered with long lemon-yellow hairs. The larvae enter trees and feed within the center of a small branch or twig, creating a tunnel toward the base. The larvae then move from the center to the sapwood, making concentric circular cuts. Eventually the larvae move back into the center tunnel and plug it with frass. Wind causes the branches or twigs to break and drop to the ground. The larvae continue to feed inside the broken branch and overwinter as pupae. In spring, the adult emerges from the hollowed-out branch. There is one generation per year.
Management of both the twig girdler and pruner involves removing and destroying fallen twigs and branches. The use of insecticides is not recommended for these two pests because it is difficult to control the larvae that are inside twigs and branches.