For biological control of webworms, you can put out wasp larva. Most natural garden supply stores carry the wasp larva and you put those out in early spring. They control the worms before they even get there. If you start noticing webs in your tree, the best method is to cut them out. If the tree is not too large, take a long pole and poke a hole in the webs. That will allow wasps to be able to fly in there and eat the caterpillars. If that doesn't work, you can spray them. You need to have a heavy equipment sprayer to spray that high if it is a large tree. If it gets bad enough, you may lose some branches. You definitely lose some foliage because webworms eat foliage. They have been around for years, hundreds of years, and probably few tree deaths result from them. They are more unsightly than anything. They are not usually detrimental to the tree.
