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Janet Laminack: Check for signs of mutli-legged invader

Agriculture

We are being invaded by a hackberry-chomping caterpillar!

The southern parts of Denton County are experiencing an impressive display of an insect at work. My observations of this caterpillar are that it’s no bigger than a half-inch long, and it’s a light green color. It loves hackberry trees and doesn’t seem to be eating anything else — caterpillars tend to be very host specific.

The damage caused by the caterpillar is a skeletonizing of the leaf. This gives the tree a lacy and white appearance. Also, these caterpillars produce a type of silk that can be seen on trunks or hanging from the trees.

This caterpillar is not known for being a pest. It doesn’t even have a common name that our Extension entomologists know of, going only by its scientific name Sciota celtidella. When the caterpillar matures, it will be a small pyralid moth. We haven’t had this insect as a problem before, and we don’t expect it to return next year. It’s actually fairly common for an insect to be relatively unknown and then wreak havoc over a small area in large numbers for a short time.

But for now, the damage is extensive. Some of the trees hit are completely defoliated or are rapidly losing most of their leaves. Will the trees recover? This is a good question for which we don’t have an answer.

If the trees were stressed before this happened, they may be goners. This has been a tough season for trees with the flooding in spring and then the hot, dry summer. However, if a tree is going to lose all of its leaves prematurely, this is a pretty good time to do it. The trees may go into dormancy now and bounce back in the spring.

If you have a tree that is being attacked but still has some green foliage on it, you may want to spray. One spray probably will knock out the caterpillar. We are recommending using a spray containing spinosad, which is made by soil bacteria and specifically targets caterpillars.

Another option would be to use a pyrethroid insecticide that is labeled for caterpillars on trees. Pyrethroid insecticides are those with an active ingredient that end in “-thrin” or “-ate” such as bifenthrin, cyfluthrin or esfenvalerate.

And finally, reducing the stress of your tree will help its survivability chances. Although we are not receiving rainfall, supplemental water needs to be applied.

We recommend an inch of water every week (infrequent, deep watering is best). Adding mulch and/or organic material will help the tree, but wait on fertilizing until the spring.

For more information about this pest, our office can assist you at 940-349-2892 or master.gardener@dentoncounty.com, or visit citybugs.tamu.edu.

 

JANET LAMINACK is the horticulture county extension agent with Texas AgriLife Extension. She can be reached at 940-349-2883 or jelaminack@ag.tamu.edu.