I have a large red Japanese maple - don't know what kind - about 2 stories tall. My understanding is that it's 15-20 years old. Last year the leaves were sparse. the rhodies didn't bloom well either, so we thought soil, maybe water. We hadn't feed the plants the previous fall, but only use organic food, and I didn't really expect that the soil would become sterile over a couple of seasons (!), but was careful to feed and water as per our previous habit. This year it's worse - completely defoliated in the center, though growing fine on the outsides. One of the nearby rhodies is fine, the other virtually dead. The viburnun davidii under is thriving.
We took a some samples to the local master gardeners. They didn't have a clue - it doesn't have the striations you'd expect to see in verticillium wilt, nor is the damage one sided. I know I need to get samples off to a lab, but in the meantime - has anyone had this happen?