Eastern Tent Caterpillar C.F

ees A2933 uit tr Flowering fr Eastern tent caterpillar C.F. KOVAL and S.W. BINNIE Life cycle The eastern tent caterpillar is native to North America, and records The eastern tent caterpillar of its existence go back as far as 1646. spends the winter on the twigs of its While severe infestations occur at hosts in egg masses of 150 to 350 approximately 10-year intervals, the eggs. These egg masses are tapered at caterpillars are found easily through- both ends and partially encircle the out Wisconsin every year. Wild twig. The eggs are cemented together cherry, choke cherry, apple, and orna- and coated with a dark brown, glue- mental crabapple are their favorite like substance which hardens to a hosts. However, they also will attack varnished finish. hawthorn, mountain ash, box elder, The larvae (caterpillars) hatch in elm, maple, birch, willow, poplar, and the early spring when the leaves of oak trees. wild cherry trees begin to unfold. The Eastern tent caterpillar is fre- larvae then feed in colonies. Shortly quently confused with gypsy moth. after hatching, the caterpillars con- Gypsy moth does not spin silk and is struct their silken tents and remain in incapable of producing tents. Thus, it them when not feeding. On warm is readily distinguished from eastern and sunny days, they go out on the tent caterpillar. foliage and feed. About 6 weeks after Young tree defoliated by Symptoms and effects hatching the larvae are full grown. eastern tent caterpillar in May. Note that several tents are The silvery, conical tents of the located in branch crotches. eastern tent caterpillar can be Larval feeding will end in June, and the tree will releaf. observed on trees in Wisconsin during May and June. The larvae feed on the foliage of host trees, fre- quently defoliating wide areas of trees completely. The caterpillars’ dense, silken tents are constructed in the crotches of the trees and grow as the larvae feed. By early June, the host trees may be stripped of leaves, and the caterpillars will begin to wander about for additional food. When severe outbreaks occur, entire trees may be covered with a silken mantle spun by the caterpillars as they pass to and from their tents.

Fully grown eastern tent caterpillar. EASTERN TENT CATERPILLAR

Cultural and mechanical control The head and body of the eastern from many garden centers and is sold tent caterpillar are deep black, and a When the tree is dormant, under several brand names. Be sure white stripe runs down the cater- examine the twigs and small branches the product you select is the variety pillar’s back. Many short, diagonal, for egg masses. These can be easily kurstaki or has caterpillars on the brownish marks are on the sides of its destroyed by rubbing them off or by label. Bt is mixed and sprayed as a body. On each side is a row of pale snipping the twig off the tree. chemical insecticide. Because it works blue spots nearly surrounded by Eggs hatch as the trees start to only as a stomach poison, be certain black. The caterpillar’s body is leaf out in spring. Examine the trees to thoroughly spray the leaves rather sparsely covered with fine, long, light again at this time for the colonies of than the caterpillars or their tents. brown hairs. When fully grown, it small caterpillars and their small Follow label directions for proper use. may range in length from 2.0 to 2.5 tents. If you have just a few colonies, Chemical control inches. When done feeding in late these can be easily removed by hand May or early June, the caterpillar or with a forked stick or similar tool. If chemical controls are used, spins white or yellowish parchment- Make sure all of the small caterpillars spraying the entire tree is unnecessary like cocoons on fences, tree trunks or have been removed or destroyed. unless the tents are numerous. Spray other available objects. Do not attempt to burn the tents only the tent and foliage within an The adult moths emerge in about and caterpillars. This is a hazardous area of 1.5 feet of the tent. Apply 3 weeks. They are reddish-brown and procedure that will seriously injure sprays as soon as you find tents. have two almost parallel whitish lines the tree. A number of chemical insecti- on their wings. Their wingspread Trees may be weakened by severe cides and natural insecticides like Bt varies in size from 1.5 to 1.75 inches, defoliation, allowing attack by other are available at local garden centers. with the males usually the smaller in insects or disease organisms. This is As there are a number of different for- size. A single generation per year especially true of young and unthrifty mulations of these insecticides, you occurs in Wisconsin. trees. Maintain tree vigor by proper should follow the detailed instruc- Control watering, fertilization and pruning. tions provided on the product label. Biological control Where label directions differ from the Populations of the eastern tent suggestions in this publication, follow caterpillar are normally kept below You can control tent caterpillars, the label directions. damaging levels by many natural especially young ones, with a com- enemies such as birds and parasitic mercial preparation of spores of the and predatory insects. However, occa- bacterium Bacillus thuringiensis var. sionally these natural enemies are not kurstaki (Bt). This bacterium is harm- fully effective, allowing tent cater- less to people, animals, and plants, pillar populations to build with resul- but causes a lethal disease in many tant tree defoliation. types of caterpillars. Bt is available

Copyright © 1999 University of Wisconsin System Board of Regents and University of Wisconsin-Extension, Cooperative Extension. Authors: C.F. Koval is professor emeritus of entomology, College of Agricultural and Life Sciences, University of Wisconsin- Madison and University of Wisconsin-Extension, Cooperative Extension and S.W. Binnie is Extension horticulture agent, Waukesha County. Produced by Cooperative Extension Publications, University of Wisconsin-Extension. University of Wisconsin-Extension, Cooperative Extension, in cooperation with the U.S. Department of Agriculture and Wisconsin counties, publishes this information to further the purpose of the May 8 and June 30, 1914 Acts of Congress; and provides equal opportunities and affirmative action in employment and programming. If you need this material in an alternative format, contact the Office of Equal Opportunity and Diversity Programs or call Cooperative Extension Publishing at 608-262-2655. This publication is available from your Wisconsin countycecommerce.uwex.edu Extension office or from Cooperative Extension Publishing. To order, call toll free 877-WIS-PUBS (947-7827) or visit our web site at . A2933 Eastern Tent Caterpillar RP-12-03