I have a bald cypress and oak and box shrubs and a bradford pear all with yellowing, then brown, and dead leaves. My local nursery - twin oaks in sherman, told me a fungus, but the treatment did nothing. I water, I feed, nothing is stopping this. I have photos I can send for a response. Thank you all...Douglas

Sounds like you might have more of a bacterial problem. Too much water and not enough light and oxygen are usually the culprits here. Tight soil and lots of rain can cause negative bacterial activity.

What treatment(s) did you try and we'll try to give you alternatives.
Is the tree itself dying or just particular limbs? Give more information and we'll try to help.

Also, I'd post your question on the Trees forum where more tree people will read it. Good luck!

kathe