chokecherry tree has sap balls

Question

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.

Answer 1

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.

https://www.gardeningknowhow.com/ornamental/trees/chokecherry/chokecherries-in-the-landscape.htm