Part of Japanese maple dying - disease or pest?
My Japanese maple (Acer palmatum 'Atropurureum') in front of my house has a disease or something. I'm worried about it. This one main branch and all the smaller branches that shoot off of it are dying (you can click the image for a larger version). It started with some leaves turning red about a month ago, and now they've shriveled up. Some of the smaller twigs turned black, but the thicker part of the branch is still green.
The rest of the tree looks just fine, as shown in this photo. What should I do? Should I cut off that branch as far down the tree as I can go? How will I know the disease or pest hasn't started attacking other parts of the tree? Is there a pesticide that could help inoculate the rest of the tree against whatever is harming this branch?