I think peach trees do that when stressed. One of mine is doing that...and leaking sap. Maybe somebody with more knowledge about this condition will pipe up.

think I have gummosis....google that. It may be what you have too. My trees could be water-stressed for sure.

Fireduck is correct some Prunus cultivars leak sap for no particular reason. Doesn't seem to harm them. Kind of like Maple trees I guess.

As long as there is no mechanical reason---about the right height for weed whackers, etc.

I have several plums and apricots that have done this...though it seems to be on the south-southwest side so I always assumed sun.

There are some insects like cicada that gnaw/slice into the bark and lay their eggs. Again usually not a big deal unless the larvae of a given species are known to threaten to girdle the tree. Depends what is in your area.

Thank you for all your responses. I'm glad to hear that it's probably nothing more than stress. In fact, last year the tree was producing dozens of peaches, and that may have added to its stress (not to mention the severe winter we had up here in Western Mass.) I'm sure the weed whacker hasn't gotten near it, so I'll just wait and see if the tree recovers on its own. Thank you all again!