Where's all our fruit tree people??
I'll try to answer--my peach tree does this every year, and I get a good harvest anyway.
Since the peaches turned out ok, I never looked into the spot issue.
Not saying you should ignore it, but that's my experience. I'm guessing it's a fungus that never progresses to a serious stage because Kansas, like So California, won't have many rains after the spring rains. The dry weather seems to limit fungal activity. Hopefully someone else will pop in and give a more scientific answer! I garden organically, so I wouldn't know what to recommend if you needed to spray.
