What is Cutting the Limbs on My Trees?
October 9, 2007
Brian Pugh, Haskell County Extension Educator, Ag/4-H & CED
I have received a number of calls over the last two weeks from Haskell County residents concerned about their trees losing limb tips. And most callers go on to say it looks like a miniature beaver has chewed through the limb, making it fall off the tree. I usually conclude after hearing the latter comment that the culprit is not a miniature beaver, but the Twig Girdler. Twig Girdlers are common in Haskell County, and usually present on trees every year. However, some years the population is high enough, that most people with trees experience the problem. Twig Girdlers are most commonly found on pecan, hickory, persimmon, and elm. But have been known to attack oaks, honeylocust, hackberry, and various fruit trees.
How do you know you have Twig Girdlers? The most obvious sign is limb tips (terminal branches) lying on the ground with dead leaves still attached. These limbs are usually 12-24 inches in length and ¼” to ½” in diameter. Upon closer inspection, the limb will show signs of being “cut” from the tree in a circular ring. This resembles a “small beaver cutting” or the result of a pencil sharpener. These cuttings can seriously affect the aesthetic quality of ornamentals, and can significantly reduce pecan yields the following year. Repeated girdling of terminal branches results in forks, crooks, and other stem deformities.
So why is this insect girdling limbs off of my trees? The Twig Girdler is simply trying to complete its life cycle. Adults emerge from late August to early October, and feed on tender bark near branch ends. Twigs are girdled and killed because the larvae (young worms) are unable to survive in living twigs. The adult lays eggs during the cutting process into the now dying terminal branch. Some branches are cut completely through and immediately fall, others will hang in the tree for some time. The small larvae hatch from the eggs, and overwinter in the dead stem. When spring arrives, the larvae grow rapidly and migrate towards the girdled end of the stem, where the transformation into an adult beetle occurs over a 14 day period. This is usually around August, when the adult emerges and begins the cycle anew. There is only one generation per year!
How do I control these Twig Girdlers? Insecticidal control is difficult since the insect is protected in the stem most of the year. There are insecticides labeled for use on trees to prevent adults from feeding and laying eggs, however these methods don’t always control the problem. The best method of controlling Twig Girdlers is to accept this year’s loss, and look towards next year. Proper sanitation will eliminate most of next year’s population. Try to rake up all terminal branches off the ground, and remember that some are still hanging in the tree. Since the larvae are present in these branches, burning all terminal limbs will eliminate next years Twig Girdlers.
If you live close to an oak/hickory forest (most of S. Haskell County), this will help but will not totally eliminate Girdlers. Adult Girdlers will migrate in from the woods where they are feeding on hickory. In short, good housekeeping this fall will reduce Girdler problems next year.
Contact the OSU Cooperative Extension Office if you would like more information about Twig Girdlers at 918-967-4330.
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