Greetings, 

Based on the description, there are a few different issues that might be affecting your tree. So we can best understand what's up with your tree, would you be able to share some photos? It would be helpful to get images of: 

--the entire tree and its surroundings

--close up of affected parts on a white background in bright light

--close up of any insects found

If you have insects and/or an affected branch you could also bring them to Benton County Extension and we can take a look under a microscope. Insects should be alive/undamaged and placed in a jar or container.