I had a few trees removed the other day, and got to talking with the very knowledgeable Paul Anthony of Advanced Tree Care in Newtown (215) 968-9161. We were talking bugs, rot, and redemption of local trees. I asked Paul about some of the more prevalent diseases he's been seeing in the area. Here are a few of the ones he called out. I've included links to more information, so that you read up on the symptoms and treatment:
Maple trees can be afflicted with verticillium wilt, which is a soil born vascular disease. There is no cure for this disease, so it may result in losing the tree if it is afflicted.
Birch trees are susceptible to the bronze birch borer which can kill the tree within 2 to 3 years if left untreated. Keep an eye out for Birch Leafminer attacks, since they can weaken the trees and leave them open to borer attacks.
Ash trees have their own borer, who traveled overseas from Asia in packing crates. These exotic bugs have been causing damage in Pennsylvania ash trees, and have even resulted in quarantines in an attempt to stop their infiltration into the US.
Oak trees can be afflicted by bacterial leaf scorch, and since there's no known cure, and stopping infestation is difficult, this could be a "hope and pray" that you don't lose a tree to this infection.
Anyway, the parting advice I got from Paul, is that if you see a tree that looks in distress, call an arborist to evaluate the tree. They can take a specimen of the tree to the lab, correctly identify the problem, and make recommendations for a course of action.
If all else fails, and you lose the tree, perhaps you'll meet Paul during the removal. He's a wealth of information. It's also a lot of fun to see him and his crew climb the trees. My kids thought it was really cool - you will too. Check out the the hair raising picture below: