not fire blight....but almost appears to be a fungus. does not appear to be black knot though either...from my handbook i couldn't identify.....if it is me i'm trimming that piece away few inches from source and then using pruning compound over the open wound
Looks like tent worms to me. My bet is that, left unattended, they will over winter and hatch to coincide with spring greenup, where upon they will have the potential to devour a large portion of new growth. Tent worms are now out of season here in Michigan, however, this year I have seen a late summer variety. I just dusted several oaks last weekend. The worms were dead the next day.