Issues with Japanese Maple

Question: Our ~30 year Japanese Maple showed brown leaves in spots all of a sudden (see picture). Most of the tree looks great, just these patches of dead leaves. While the dead leaves are in two seemingly different spots, we traced it back to the same main branch off the trunk. Everything on that branch is dead. There's no signs of being broken or bark stripped off. I can find no sign of insects (e.g. bag worms or such) except for a few minor spider webs elsewhere on the tree. No other limbs seem to have any issues.

I can certainly cut off this branch (if I should, is it OK to do that since it's dead anyway or wait until another time with less stress given the heat and drought?). But my concern is more is there something wrong that will eventually impact the rest of this tree.

I should also note that there's a Japanese maple of the same variety 15 feet away (we bought and planted them at the same time). It looks fine.

So in summary, should I cut this off now or wait?
Is there, and if so what, an issue that will spread to the rest of the tree? What could it be? What should I look for?

responder: Answered by theHome and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 08, 2024, 11:57 AM EDT
response: You can prune out dead wood on trees can be pruned out at any time, but do it on a dry day. Check for discolored, wedge-shaped wood in the branch, and prune back to 6" below that.  Were you able to check for watering needs this year and last year? We had pretty serious and prolonged drought conditions in central Maryland last season and it's been very hot and dry again recently. Heat, drought stress, and winter injury can allow an opportunistic canker disease called Botryosphaeria to arise, which causes scattered branch dieback. Here is our page that discusses it:  https://extension.umd.edu/resource/botryosphaeria-canker-shrubs/ No fungicides are recommended.  Here is our watering information too:  https://extension.umd.edu/resource/watering-trees-and-shrubs/   Christine

responder: The Question Asker Replied July 08, 2024, 1:44 PM EDT
response: Thanks. So we pruned the tree. We saw no signs when we cut the branches of any deterioration inside. I’ve attached a picture of the cross section (the slight yellow streak  you might see is actually the paint off the saw blade). We cut it in a few areas and it was all the same, seemed fine. There was one area with some discoloration on the outside (see photo), but it was fine on the inside. Not sure it matters, but the leaves on the branch that are dead showed 2 different colors of dead. One grey one burnt orange.This tree is all one color (no grafted branches) a bright green. Does this impact your diagnosis? Might it be something else? Thoughts? We're paying close attention to watering now.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 08, 2024, 6:01 PM EDT
response: Thank you for the photos and additional information. The lesion on the side of the branch looks like a canker, though we can't determine from which pathogen or when it began (likely awhile ago). The photo of the dead foliage on the removed branch is unfortunately too small for us to see enough detail, but the two different colors of dead leaves might be due to unrelated factors like how recently they dried out, if powdery mildew was present (a very common but generally non-serious leaf infection), or if an overlapping condition caused some to die off earlier in the season than others. Going forward, monitoring for watering needs can help to reduce the plant's vulnerability to future canker infections.  Miri