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Home >> Departments/Offices >> Cooperative Extension >> Pest of the Month >> April

April

EASTERN TENT CATERPILLARS

The nests, or tents, of the eastern tent caterpillar, Malacosoma americanum (Fabricius), are a common sight in black cherry trees along roadsides and in yards. The eastern tent caterpillar is easily identified when it builds its white silk nest in the crotch of small trees or where several limbs meet on larger trees. Eastern tent caterpillars are black, with white and blue spots and a white stripe along its back.

The larvae lay down silk trails wherever they go and these trails serve as roadways for other larvae. Feeding continues for four to six weeks until the larvae are about two inches long. Mature larvae usually leave the nest in mass to search for a suitable place to spin a cocoon. The adults emerge in two to four weeks. There is only one generation per year.

The eastern tent caterpillars prefer wild cherry, but it can be found feeding on crabapple, plum, peach, and ornamental cherry trees in landscapes. Occasionally it will form nests in ash, birch, willow, maple, oak and poplar.

Is Control Necessary?

There are several control alternatives for tent caterpillars.

  • Alternative 1: Do nothing. Eastern tent caterpillars rarely require any control, as their damage is generally considered aesthetic. Parasites, predators and unfavorable weather usually take care of these insects. Tent caterpillar defoliated trees usually refoliate after being attacked. Tree health can be adversely affected when trees are defoliated year after year though.
  • Alternative 2: Scout and destroy egg masses and nests. Tent caterpillars form over winter in the egg stage. Egg masses are attached to small twigs and appear as a shiny, dark gray foam rapped around the twig. These masses are about one inch long and contain 150 to 350 eggs. Look for trees that were attacked in the previous spring. Egg masses are easy to spot after the leaves have dropped in the fall. Simply clip off and crush or dispose. Hand remove any nests in the spring. It is suggested that gloves be used, as the caterpillar hairs are irritating to some people. Simply scrape the nest off onto the ground and crush the caterpillars or drop them into a pan of soapy water. Early morning or late afternoon is best because most of the caterpillars will be in the tent. Do not burn the tent.
  • Alternative 3: Biological controls. Bacillus thuringiensis (Bt) works best on these caterpillars when applications are made while the larvae are small. There are several predators and parasites, such as tachinid flies, that attack tent caterpillars.
  • Alternative 4: Insecticide sprays. Most contact and stomach insecticides rapidly control tent caterpillars. Direct sprays to the plant foliage and nest during late morning when the caterpillars are found sunning themselves on the outside of the tent.