Question
I have two dwarf cherry trees and both of them are developing webs.  Inside the webs it looks as if there are caterpillars.  What is wrong with my trees and how do I treat them?  I live in northern Indiana

Answer
These are eastern tent caterpillers.
The eastern tent caterpillar, Malacosoma americanum, is a pest native to North America.

Populations fluctuate from year to year, with outbreaks occurring every several years. Defoliation of trees, building of unsightly silken nests in trees, and wandering caterpillars crawling over plants, walkways, and roads cause this insect to be a pest in the late spring and early summer.Eastern tent caterpillar nests are commonly found on wild cherry, apple, and crabapple, but may be found on hawthorn, maple, cherry, peach, pear and plum as well.

While tent caterpillars can nearly defoliate a tree when numerous, the tree will usually recover and put out a new crop of leaves. In the landscape, however, nests can become an eyesore, particularly when exposed by excessive defoliation. The silken nests are built in the crotches of limbs and can become quite large.

Control can be mechanically or using chemicals.

Hand remove any nests in the spring. It is suggested that a glove be used as the caterpillar hairs are irritating to some people. Simply scrape the nest off onto the ground and crush the caterpillars or drop them into a pan of soapy water. Early morning or late afternoon is best because most of the caterpillars will be in the tent.
One should not use fire to burn out these webs; this can cause much greater injury to the host than this pest ever could.
Young caterpillars can be killed by applying an insecticide containing Bacillus thuringiensis var kurstaki. Other insecticides include carbaryl, methoxychlor, and malathion. Larvae within the tents are protected beneath the webbing and are more difficult to kill with an insecticide.