In the past week, I have had many calls about twigs and limbs falling off pecan and hickory trees. A twig pruner or a twig girdler, both long-horned beetles, can cause this neat phenomenon. These beetles can also cause similar damage to oaks and other hardwoods. Although the result is the same, twigs and branches are cut, the difference is who chews the branch.
If it is a twig girdler, the adult female beetle lays an egg in the twig and chews around the outside of the twig until it is almost severed; the twig may eventually fall to the ground or hang on the tree. On the other hand, the grub (larvae) of the twig pruner beetle chews from the inside of the branch, and often the chewed area is not noticeable.
The grubs of both species spend the winter in the twigs and will emerge as adult beetles in the spring. The best control is to pick up the fallen twigs and branches and, if possible, burn them. If burning is not possible, the twigs or branches can be collected and placed into a sealed bag and thrown away. This sanitation should take place throughout the winter as the twigs and branches fall.