Answer: Insects can make holes in leaves and if enough of the leaf is damaged it will fall from the tree. Caterpillars actually consume the leaves. It sounds as though there is a population of caterpillars feeding on the apple tree leaves. If so, a product called bacillus thuringensis which is sold as Dipel and Thuricide will help control caterpillars. Field mice can gnaw on the bark of trees and especially like to hide in the snow and chew on tree bark over the winter months. Now that the damage is done you will want to check the injury for insect activity and make sure they don't nest in the damaged bark. The branches coming from the ground near your cherry tree are called suckers. These are non-productive and should be cut down at ground level.
Good luck with your trees.
Q&A Library Searching Tips