WESLACO — If your trees are being pruned without your knowledge or consent, fear not. The culprit is not some deranged gardener.
The pruning is most likely the work of an insect commonly known by various names including twig girdlers, twig pruners or long-horned beetles, for their extra long antennae.
John Norman, a cotton integrated pest management (IPM) entomologist at the Texas A&M Agricultural Research and Extension Center at Weslaco, said several species are common and native to the Lower Rio Grande Valley, and their populations seem to peak in cycles.
“We’re getting a lot of calls from Valley homeowners with this problem this year, so the populations of these insects must be high right now,” he said. “They make such a clean cut on a branch that it’s hard to imagine an insect could do this kind of damage, but they do.”
Norman says the insects girdle a branch, or travel around and around the circumference, cutting through the bark and into the hard wood until the branch is weak enough to be snapped off by wind.
“These twig gridlers lay their eggs on that part of the branch that will eventually snap off,” he said. “The larvae, or immatures, are half an inch to an inch long, and they tunnel and feed on the inside of the broken branch until they become adults. Then they exit the branch, climb up nearby trees and the process starts all over again.”
Unfortunately, insecticides are not effective against these insects. Norman suggests stepping on adult insects that fall off trees and burning or disposing of the broken branches that harbor their eggs.
“If you just toss those broken-off branches into a brush pile near your home,” Norman said, “new adults will eventually emerge from those branches to cause more problems. The best solution is to remove those branches from your property, or take them where they can be safely and legally burned.”
Several species thrive in the Valley, and the larger the insect, the larger the branch they cut.
“They’ll work on branches from as thick as a pencil to branches about two inches in diameter, depending on the size of the insect,” said Norman. “Some species here are larger than others, but they all look the same, and they all seem to prefer the same type of trees: hackberry, retama, huisache, mesquite, ponsianas, both royal and dwarf, and probably a lot of other native and common trees here.”
Norman said the insects likely won’t cut all the branches from a tree, but they can hit some trees so hard that the tree loses its appealing shape.
And he offered another solution. “As kids, we used to look for the broken branches on the ground, split ’em open and pull out the grubs which we used as bait for fishing,” he said. They worked pretty good, as I recall.”