Eastern tent caterpillar US Forest Service	"Tent" made by eastern tent caterpillars US Forest Service

Introduction

The eastern tent caterpillar (Malacosoma americanum) is more a nuisance than a threat. While heavy infestations can cause serious defoliation, eastern tent caterpillars rarely kill trees except those already weakened by disease or climate and environmental stresses. These caterpillars get their name from the ugly tent-like nests that they spin in the crotches of host trees. They are native to North America east of the Rockies.

What trees are affected?

The preferred tree for these pests is the black cherry but they will also infest other cherry trees as well as fruit trees such as apple and a variety of shade trees.

What do they look like?

Eastern tent caterpillars are black and hairy with a white stripe and a series of blue dots along the length of the body. At maturity, they range from 2 to 2 ½  inches (5 to 7 cm) in length. The moth is reddish in colour with white bands on the forewings. Females can be double the size of the males with a wingspan of 2 ½ inches (7 cm).

What is their life cycle?

Eastern tent caterpillars survive the winter in masses of 100 to 300 eggs noticeable as shiny black bands encircling twigs. Eggs hatch in spring at about the same time as the host tree comes into leaf. The young caterpillars then begin to consume leaves and spin the characteristic ‘tent’ nest in the crotch of the tree. The nest continues to grow as long as the caterpillars keep feeding. When the caterpillars reach maturity, after about six weeks, they pupate in silken cocoons visible on trees, on the sides of buildings and on fences. Moths emerge in July to mate, lay eggs and then die.

Control

Eastern tent caterpillar infestations rarely threaten the lives of trees so control is generally for aesthetic purposes. There are commercially insecticides available to combat heavy infestations of these insects. Consult with a local landscape or garden professional for details. 

To prevent the caterpillars from reaching the foliage, use TreeHelp Bug Band.   You should use TreeHelp Bug Band to protect nearby trees as well.

Tents are sometimes burned or otherwise destroyed at night after the caterpillars have returned from feeding. However, given the dangers involved, this is not generally recommended.

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