Crop & Pest Report

Accessibility


| Share

Webs in my Trees (05/04/17)

Look for webs in the forks of trees or branches in the spring, especially on cherry, chokecherry and plum trees. You may see webbing and small caterpillars crawling around on webs.

Webs in my Trees

Look for webs in the forks of trees or branches in the spring, especially on cherry, chokecherry and plum trees. You may see webbing and small caterpillars crawling around on webs. These caterpillars are Eastern tent caterpillars (Malacosoma americanum). The webbed tents are used as shelters and resting places for caterpillars. Other trees hosts infested include: ash, aspen, basswood, birch, cottonwood, elm, maple, oak, poplar, and other hardwoods. People consider the webbed tents unsightly in trees, but the caterpillars do not bite.

There is one generation per year. Tent caterpillars overwinter as eggs in egg masses. Larvae hatch in early spring. Larvae of the eastern tent caterpillar are black and somewhat hairy with a whitish-yellow stripe down the middle of the back, narrow broken orange-colored subdorsal stripes, and lateral white and blue markings. In five to six weeks, larvae pass through five larval instars and about 2 inches long when mature. Then, they form silken cocoons to pupate. Adult moths will emerge from cocoons during early summer (late June or early July).

Damage: Defoliation is caused by larvae feeding on the foliage. Light defoliation has little effect on tree health. When populations of eastern tent caterpillars are high, whole trees can become covered with webbing and completely defoliated.

Pest Management: Bt (or Bacillus thuringiensis var. kurstaki; Dipel, Thuricide), a natural occurring soil bacterium, works well to control young caterpillars and conserves beneficial insects. Other insecticides available to homeowners include: acephate (Orthene), azadiracthin (Azatin), carbaryl (Sevin), esfenvalerate (Bug-B-Gon), malathion, permethrin, spinosad (Conserve), or other insecticides registered for trees. Always read, understand and follow the insecticide label directions.

 hsci.knodel.1

hsci.knodel.2 3

 

 Janet J. Knodel

Extension Entomologist

 

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.