Johnson’s Flower and Garden Center

Pest Bulletin #7

 

EASTERN TENT CATERPILLAR

(Malacosoina americanum)

 

How to Identify Damage

Look for silken cocoons or webbing appearing in tree forks early in the spring. The webbing will increase during the spring, and defoliation of the tree will occur. By late May the tree may be entirely defoliated. The caterpillar chews the leaves and excretes large amounts of pellet-like excreta on the ground.

 

Life Cycle

The insect over winters as an egg in a very distinctive egg mass. The egg mass is easy to see and is oval in shape, encircling a small twig on the host plant. They are shiny metallic black and can contain up to 350 eggs. The eggs hatch at the time of leaf opening, and the larvae rather quickly gather at a branch fork and begin building a web. The young caterpillars emerge from the nest to feed and range rather far from the nest during the day. In late May to early June, they leave the tent and find other suitable locations to cocoon and pupate. Reddish brown moths emerge in late June to early July. They mate and produce the egg masses for the following year. There is only one generation in a year.

 

Critical Control Time and Strategies

This pest prefers wild cherry, crabapple, and apple trees. These will be the first trees attacked, so monitor these frees to get a good indication of possible infestations, If you can find the egg masses in winter, destroy them manually or remove them by pruning. In early April when the nest begins to form, physically destroy the nest with high-pressure water or a long pole. The caterpillars will die if you do this just before or during cool, rainy weather. If you cannot reach the web to do this, spray the surrounding foliage with BT to kill the caterpillars as they feed. Other sprays can be used, but be sure to penetrate the nest for good control. Spray the nest as early as possible before the caterpillars reach full size because they are more susceptible to sprays as juveniles.

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