One section of the top of my dwarf Japanese maple has yellow drying leaves scattered over it.
What Is the Yellow Dryness on My Japanese Maple?
Certified GKH Gardening Expert
This can be caused by either a fungus or a pest. But there are several of each that it could be. I would recommend treating it with a general pesticide and fungicide. Consider using neem oil as it is both a pesticide and a fungicide, so you would only need to apply one spray. Plus it is safe for people and pets.