|On one branch of my oak tree is a covering of a clear webbing or cocoon. The whole branch is covered with it. I don't see any bugs or worms.|
|Without having an opportunity to inspect the tree, I can only offer an educated guess. What you describe sounds like the signs of barklice. Pseudocaeciliitae, to be exact. Populations make unsightly silken webs on tree trunks and branches These webs can completely wrap a tree's trunk to the tips of each branch. Underneath this protective webbing, the barklice feed on lichens and fungi. Host trees commonly include oaks and pecans, although any tree with lichen and fungal growth on the bark can support a barklouse population. Silk-wrapped trees harboring this barklouse appear to occur at specific periods of the summer (July and August) when conditions are favorable for their development.
Now for the good news: Pseudocaeciliid barklice are harmless to trees and no insecticides are recommended for their control. You can remove the webbing by hosing it off with a strong stream of water from the hose. Or you can simply leave the webbing alone. Research shows that the barklice apparently remove the silken webbing at the end of the summer.