Q.chokecherry tree has sap balls
This spring we had a hard freeze after my chokecherry tree had its white flowers. Now the leaves are purple and there are sap balls oozing on the bark. What do I do? Its never done this before. Tree is from 5-8 years old.
This is likely a Eriophyid mite.
The mite damage is mostly cosmetic, and it typically won't stress the tree or plant to severely.
I recommend cleaning up any leaves or foliage under the tree and dispose of.
Then next spring spray the trees with a dormant oil spray prior to bud break to smother out the little darlings that might have survived. If it's a particularly severe infestation a second dose of a horticultural or insecticidal soap spray just as the leaves are beginning to unfurl should do the trick.