Answer: It is challenging to diagnose problems such as these. Try to imagine anything that might have affected this tree and not the others... such as overspray from an herbicide application, for example. If you don't see evidence of insects, you might want to contact a professional arborist to evalutate the situation. It sounds like these trees are an important part of your landscape and it might be worth the expense to have them evaluated. Sorry I can't be of more help!
Q&A Library Searching Tips