I look for the egg sacks when pruning. A Google search will give you images of them. Any I find are pruned off and burned. Then I inspect for the webbed nests right around last frost date, again pruning and burning any I find. I found 2 of each this year, then noticed some leaves were being eaten. Expanded my search outside of the orchard and found a nest on a serviceberry bush. I couldn't cut and remove that one, so mixed up some Seven and sprayed them. I'll continue watching my trees for damage. As the caterpillars get larger they travel farther.