- Eastern tent caterpillars (Malacosoma americanum) are black with a white or orange stripe down the back and distinctive, bright blue dots along the sides. Other regional species of Malacosoma also infest and defoliate ornamental trees.
- In late June and early July, the adult moths, which are reddish-brown, lay their eggs on the Eastern redbud trees. The eggs are laid in groups, with as many as 400 or more in one group. This makes them relatively easy to see; they appear as dark-brown, shiny-looking clumps that can encircle twigs. The larvae overwinter in the eggs and emerge in early spring. Once out in the open, the larvae build tent-like structures out of silk. These webs protect them from the elements as they devour the emerging foliage of the tree. They do this for about a month and half before pupating.
- Severe infestations of these caterpillars can leave tree almost completely covered in webs and defoliated. This is especially true in young trees. In fact, it may only take one colony of these caterpillars to defoliate a small tree, according to the University of Nebraska-Lincoln website. Such infestations not only decrease the aesthetic value of the tree, but reduce its strength, leaving it vulnerable to other health problems. This can shorten the tree's life.
- Spraying the tree with insecticide is one way to control the population of tent caterpillars. Spray when you first see the larvae and spray in the morning, when they are sometimes outside their web tents. Sprays may not be effective on mature larvae and are not effective on pupating caterpillars. In the winter, remove the hard egg masses by hand and prune away branches covered with webs in early spring. Or, wind the tents up on a stick. You can even remove the insects by hand in the case of small infestations in young trees. Pluck off the caterpillars and drop them in a bucket of water to drown them.
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