BY Polk County Extension Office
I’ve already had a few cases of these brought in to the office, so I thought I would tell the tale of the twig girdler. Let me start….About this time every year, homeowners report that their pecans, hickory, and other hardwood trees are losing branches, sometimes several every day. Is it a squirrel? Is it an overzealous gardener with pruning shears? NO. It’s the handy work of the twig girdler (Oncideres cingulata). Pecan, hickories, and persimmon are the preferred hosts but other hardwoods, including oak and honeylocust, may be attacked.
In late summer and early fall, after mating occurs, female twig girdlers select a small twig with about a 3/8 of an inch in diameter and covered with just a thin layer of bark. The female beetle chews around the entire outside of the twig until the twig is almost separated from the tree. This causes part of the twig to die and this process is called girdling.
The female beetle then gnaws a V-shaped small notch in the dead or dying part of the twig and lays her eggs in the notch. The twig usually falls to the ground. When the eggs hatch, the emerging larvae continue to live in the twig, feeding on the dead wood of the twig. The larvae grow and eventually construct a mass of frass in which they pupate. After they pupate, the larvae have changed into adult beetles and they chew their way out of their twig. Adult beetles fly away to new host trees.
Initially, the foliage at the ends of the twigs turn brown prematurely and the damage can be scattered throughout the crown of the tree. Shortly afterwards, especially after a windy day, the twigs fall to the ground. The dropped twigs look like they’ve been neatly cut from the tree with a pruning shear. The injury will have slightly rounded edges and will feel a little rough from the beetles chewing on it. Trees damaged by the twig girdler will usually recover. Older, larger trees might have smaller twigs damaged resulting in minimal damage to the crown. However, in young trees damage can be severe from the resulting deformed stems and reduced vigor. No control is recommended although gathering and destroying the damaged twigs will help reduce future infestations. For more information contact the Polk County Ext. Office at 479-394-6018.