The Eastern Tent Caterpillar
You may be seeing whitish, thick webbing in the crotches of wild cherry trees. These are formed by the Eastern Tent Caterpillar. They are already actively feeding on the foliage. They will travel to adjacent plants and trees in the nursery by floating on long silk threads. They love the tender foliage of ornamental cherries and a few others.
The web nests or tents that can be reached can be rubbed with a gloved hand to mash the young caterpillars. This is extremely effective, avoids use of an insecticide, but applies only to the reachable tents. Cut wild cherry trees for firewood and to reduce black knot of plum.
Do not allow horses to eat the caterpillars; due to a strong suspicion of abortion. Once mature they crawl to the ground to pupae in leaf litter and horses may find them.
The best time to control tent caterpillars is while they are small and before the leaves are half grown on wild cherry trees. A good application of insecticide at this time can completely eliminate the tent caterpillar. Several insecticides are labeled: Tempo, Decathlon, Talstar, Scimitar, Conserve SC, 50% WP Sevin at 2 tablespoons per gallon or 2 pounds per 100 gallon; 80% WP Sevin at 1 1/4 tablespoon per gallon or 1 1/2 pounds per 100 gallon; Dursban 2E at 1 teaspoon per gallon or 1 pint per 100 gallon; Orthene at 1 1/2 tablespoon per gallon or 2 quarts per 100 gallon; Dipel at 2 tablespoon per gallon or half pound per 100 gallon; or 57% Malathion at 2 tablespoons per gallon or 1 quart per 100 gallon. Spray the foliage around each web and the larvae will die soon after consuming the sprayed foliage. Dipel is a biological control containing Bacillus thuringiensis and is the least toxic to honeybees. Spraying after 5 pm will also protect honeybees.
The tents are enlarged as the caterpillars grow and are built several layers thick. The spray will not penetrate the web unless tore open with a stick. The larvae leave the tents to feed several times a day but return to the tents when not feeding. The larvae become full-grown about six weeks after hatching and are nearly two inches long, black, sparsely hairy, with some white and blue markings on their sides. There is a white stripe down the middle of the back. Eggs (200) are laid in a black foamy mass-like structure that forms a collar around tree branches later. Fortunately, only one generation occurs each year.
If you need information on controlling woolly apple aphid, contact me at (phone) 931-473-8484, (fax) 931-473-8089 or (e-mail) mhalcomb@utk.edu
Mark Halcomb
University of Tennessee Agriculture Extension
Area Nursery Specialist
Comm/Consumer Hort./Holly Uses at Xmas Dec, 1999
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