You've got to kind of wonder about the training of a 'master gardener' who believes fungal problems are only directly related to rain and lack of summer heat.......There are many causes to fungal issues and heat and dryness can certainly be contributing factors, just as much as damp, rainy weather. Heat and dry conditions are primary contributors to the development of powdery mildew, for example.

It is impossible to be certain without an accurate diagnosis, but the symptoms resemble those of verticillium wilt, which is a soil borne fungal pathogen (no water or mild temperatures required - it just exists). It typically will affect only selected portions of the tree, leaving the rest looking fine. Until it fails completely :-(( Take a sample of the affected branches in to your local Cooperative extension office for diagnosis and ID. If it is VW, there's not much you can do other than remove the tree.

And if you take a sample to be examined, it must be a branch of at least a 1/2-inch diameter.

As for the comment "You've got to kind of wonder about the training of a 'master gardener' who believes fungal problems are only directly related to rain and lack of summer heat..."

Master Gardeners receive a crash course during which they are trained to do research to locate the needed answers.

Far too often, they are persons who truly want to help other gardeners but who lack the background -- because of the very brief, very hurried crash course -- to know when they have gone astray.

And still others are impressed with their own importance and offer what they "know" to be true but is, instead, folklore and popular wisdom.

Thank you very much for your assistance. I will follow up on that.