Have you looked carefully at the leaves? Sounds like you might have spider mites, or some other insect that makes a web around the leaf. If it's isolated to a small area of the tree, you can go organic by spraying that area with Safer soap, or some other insecticidal soap. You have to spray it top and bottom of each leaf. Your local Extension Office will be able to tell you what the problem is if you bring in a leaf for them to see. I would suggest you call first to make sure what their hours are and if they offer this service.