For Release October 2, 2005

Twig Girdlers are Busy Girdling Twigs

AGRI-VIEWS
by Chuck Otte, Geary County Extension Agent

It's a nice autumn weekend. You are out working around the backyard and you notice there's a couple of small branches on the lawn. You pick them up and suddenly notice that there aren't just a couple, there are a couple of dozen. As you pick them up you look up into the tree and notice that for every one on the ground, there's three or four more that are dead in the tree, but haven't fallen out yet. You start to get that panic stricken knot in your stomach as you search in vain for the squirrel with stainless steel teeth.

Then you look more closely at the ends of the branches and find that they have not been sliced off at an angle like a squirrel will do. Instead it's almost like a miniature beaver went around the small branch, roughly the size of a lead pencil, with a nice clean cut on the edges and a broken matchstick look in the middle. You think to yourself, "this can't be a squirrel!" and you are right.

The damage that you are looking at is the handiwork, or rather the jaw work, of a small insect known as the twig girdler, (Oncideres cingulata). This beetle is about ¾ of an inch long, has antenna almost as long as it's body and is grayish brown in color. While we most often see the twig girdler attacking elms, specifically American and red elms, it is also known to attack hickory, oak, linden, hackberry, apple, pecan, persimmon, poplar,honeylocust, and some flowering fruit trees.

Specifically, the female beetle has been busy in your tree. Prior to chewing around the branch, she has chewed some tiny notches on the branch and laid eggs in them. Then she moves slightly closer to the tree and chews almost through the branch so the eggs will fall off with the branch. The branches blow around in the wind and the eggs are dispersed all around the countryside or neighborhood. If you find one of these trees away from a yard or park setting, there can be hundreds of small branches on the ground.

The eggs hatch in the fall and the small larvae burrow into the branch where they go dormant through the winter. In the spring the larvae start feeding and develop rapidly. Apparently, the reason for cutting the branch off the tree is because the sap impedes the development and growth of the larvae. The larvae feeds in a tunnel inside this branch all summer long and in late summer pupates. The adult emerges in the late summer or early fall, finds a mate and the females go to work laying eggs and girdling branches while the male goes off to parts unknown. The adult beetles feed on tree bark but other than girdling the branches their feeding does no damage.

The twig girdlers are very active right now and I have received a lot of questions on them and their damage. Chemical controls are quite inefficient and are not recommended. While the branches on the ground are cause for concern, their is little long term damage inflicted on the tree. The clipped ends will sprout new buds next spring and the tree continues to grow. The most effective method to reduce damage is to gather the branches this fall and see that they are burned up before spring, or deposited in the trash and removed from the area. This will reduce the population for next year. Pictures of the insect and their damage can be viewed on the Geary County Extension Office's web page at http://www.oznet.ksu.edu/geary/Hort/twiggirdler.htm.

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