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Plum tree #931709

Asked May 14, 2026, 2:31 PM EDT

We have some sort of fungal disease on our plum tree(in picture). I am wondering what it is and if there are any organic solutions for it?

Allegan County Michigan

Expert Response

Hello,

This is black knot. You can read this article on managing black knot:

https://www.canr.msu.edu/news/controlling_black_knot_in_michigan


Black knot will eventually kill trees, but by pruning it out (especially in winter) you can keep the tree alive for many more seasons. Make sure to sanitize your equipment in between cuts.

An Ask Extension Expert Replied May 14, 2026, 4:21 PM EDT

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