Question
I have grown Japanese Maples for years and on an occasion I have found that the stems turn black and the leaves wilt on the upper branches. They seem healthy and are for a few years then this happens--I usually check the drip system and then cut the stems back to healthy growth--Can you shed some light on this---The area in the PNW us supposed to be a healthy climate for the species--Thanks

Answer
Brad:
The black stems may be a result of "sooty mold" a condition caused by an insect infestation.  Insects like scale and aphids are common insects that can lead to sooty mold.  Google sooty mold images to compare what you see.  A suitable insecticide can prevent sooty mold from forming.

Steve