The tree in my yard has webbing in some of the branches and I think I see caterpillars. What should I do? KW

The webs you are describing are probably the webs of tent caterpillars. Tent caterpillars are kind of the spring variation of fall webworms. It is easy to tell them apart by their webs.

The tent caterpillars build their webs in the v’s between branches while fall webworms construct their webs out toward the end of the branch. That, and tent caterpillars are active in the spring while fall webworms are active in the fall.

There are two varieties of tent caterpillars in our area: the eastern tent caterpillar and the forest tent caterpillar. Despite the name of the eastern tent caterpillar, it can be found as far west as the Rocky Mountains. They prefer to feed on the leaves of cherry, plum, and crabapples. If these trees are in short supply, they will feed on the leaves of poplar, will, and birch trees. Forest tent caterpillars can be found throughout the United States and prefer hardwood trees.

The eastern tent caterpillar is predominately black with a white strip visible down the middle of the back. They also have several blue spots on their sides. Forest tent capillaries are blue with keyhole shaped markings down their backs.

These caterpillars grow to be about 1 to 1.5 inches in length and have overwintered in protective egg masses. The egg masses are dark in color and hard, encircling smaller twigs on the tree. They almost appear shiny. Each of the egg masses can hold between 150 to 300 eggs hatching in mid-February to mid-March. As they eat, the caterpillars will grow and so will the size of their webs.

Feeding lasts about 6 to 8 weeks. After feeding they migrate to a protected spot, spin cocoons, and begin their pupal stage which lasts about 3 weeks. When the moths emerge in late June and July, the females deposit their eggs on branches. Tent caterpillar moths only live a few days.

During the day, the caterpillars emerge from the webs to eat but return to the webs at night. With sufficient numbers, tent caterpillars can defoliate a tree, but this defoliation rarely kills the tree. These caterpillars also serve as a food source for other insects, birds, and toads.

Since they rarely kill a tree, you really don’t need to do anything to reduce their population. However, there are several strategies if you just can’t stand it.

First of all, you can just cut and remove a branch that contains their webbing during the early stages of their life cycle or break apart the webbing to enable birds to have access to a meal or two. The webs make it hard for the birds to reach them.

If you want to make further efforts to eliminate these caterpillars, you can spray the leaves surrounding the webbing with an organic pesticide called bacillus thuringiensis. They will eat the leaves you have sprayed and die. Unfortunately, this strategy is difficult for homeowners if a large tree is playing host to tent caterpillars. In this case, a professional would need to be brought in. Our advice is to just live and let live. Good Luck!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org.

Photo Courtesy: Ansel Oommen, Bugwood.org