Damage

• A single tent caterpillar tends to eat all leaves within reach, moving from branch to branch along a section of a tree. The tent web acts as its base, and even one tent can house enough caterpillars to eat through a fifth of an ornamental tree's leaves. This significantly slows down the growth of that tree and makes it much more susceptible to disease. Fruit trees such as crabapple, cherry or apple are the most common targets (western varieties prefer oak or plum trees).
  
  

Common Types

• Two of the most common types of tent caterpillars present in the United States are forest and western caterpillars. Forest tent caterpillars actually spin wide webs instead of true tents, but can still be very damaging to the tree. They are blue and black in color, with small white markings. They are one of the few tent caterpillar species that avoid certain trees, specifically red maple, pear, buffalo berry and silverberry. The western tent caterpillar is orange and black, and forms tents at the top branches of trees.
  
  

Natural Predators

• Sometimes natural predators of tent caterpillars are introduced in a tree to slow down the caterpillar growth. The tachinid fly, for instance, lays its eggs in the caterpillar. When the eggs hatch, the fly offspring feeds off the caterpillar and kills it. Some nurseries offer tachinid eggs for sale that you can place on your ornamental tree. As a long-range strategy, this can be effective as long as the predators balance out correctly with the number of available tent caterpillars. Wilt, a virus deadly to the caterpillars, is also used in ornamental trees. Wilt will not harm the tree.
  
  

Egg Removal and Control

• The caterpillar eggs are deposited by female moths in the branches of young trees, often hundreds at one time. They resemble a mass of hardened foam and are brownish gray in color. They are typically laid in half-inch bands on small twigs. These must be removed from delicate trees before they hatch. Particularly dense nesting sites can be burned off the trees as well, but this can create a fire hazard and is not recommended.
  
  

Insecticide

• One of the popular insecticides for tent caterpillars is the Bacillus thuringiensis bacteria. It kills the tent caterpillars but will not harm other insects, plants or animals. The bacteria can be sprayed from a bottle in a water solution. If it is not available, then a hose can be used to wash off the webs on ornamental trees that are strong enough to survive the high pressure without breaking branches.