April 25, 2001 | By: Aimee D. Heald

Look around the Commonwealth and you're bound to see fuzzy creatures spinning their spring webs on countless Kentucky trees, stripping them of new leaves then crawling around on plants and walkways. What you are seeing are the effects of the Eastern Tent Caterpillar, often confused with fall webworms.

The difference is webworms make their nests at the ends of branches, enclosing foliage and the caterpillars spin their silky webs closer to the trunk, in the crotches of limbs. wild cherry, apple, and crabapple trees are the caterpillar's favorite dwelling places, however, it also will inhabit hawthorn, maple, cherry, peach, pear and plum trees.

University of Kentucky Extension Entomologist, Lee Townsend, said the caterpillars are on the move this year for two reasons.

"First of all, they have stripped the leaves off of the trees on which they have been feeding but still need more food, so they are looking for something to eat," he said. "They will move to nearby trees in search of acceptable leaves."

Townsend said this larval stage will last four to six weeks.

"Secondly, after they have finished feeding and are about two inches long, they are crawling in search of a rough surface so they can spin a white to yellow cocoon and pupate," he said. "This will be the real wave of caterpillars we should see as a nuisance in the next two to three weeks. The adult or moth will emerge in a few weeks but there will not be another generation of this insect until next year."

If you see caterpillars in your landscapes, there are some steps you can take to control the springtime pest. Sometimes nature helps out and various wasp species eat the eastern tent caterpillar.

Townsend said sweeping and destroying is an option where they are massed on accessible places. It is likely that this will need to be done anyway if an insecticide is applied that kills many of the caterpillars in place. It is a greater challenge to kill or remove caterpillars dispersed over a wide area.

You can use Dipel or Bt-based insecticides on foliage where larvae are still feeding but it will not control mature larvae or those that have stopped feeding.

"For wandering caterpillars on sides of houses and decks, you can apply fast-acting, residual formulations of synthetic pyrethroids (permethrin, esfenvalerate, cypermethrin, cyfluthrin, lambda cyhalothrin, bifenthrin, deltamethrin), Townsend said. "Retail formulations with similar effective ingredients include Spectracide, Bug Stop™, and Ortho Home Defense™, sold in lawn and garden shops. These are likely to be more satisfactory than Sevin, malathion, or diazion because they have a very fast ‘knock-down' effect."

Townsend said last year was also a very active year for the eastern tent caterpillar. He said there is usually two to three years of high populations, followed by a crash, with several ‘boom to bust' cycles in the last 20 years.

Early removal and destruction of egg masses on fruit trees in the winter can reduce spring populations of the caterpillar. The good news is that infested trees will usually recover and produce a fresh crop of leaves.

Note: Mention or display of a trademark, proprietary product, or firm in text or figure does not constitute an endorsement and does not imply approval to the exclusion of other suitable products or firms.


Lee Townsend 859-257-7455