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What Fungicide to use on black knot #924375

Asked February 09, 2026, 2:02 PM EST

What fungicide do I use on black knot? What intervals and solution rate do I use when treating for black knot?

Osceola County Michigan

Expert Response

Hello Chelsea!

Fungicides with one of the following active ingredients are effective in protecting trees from black knot: captan, chlorothalonil, thiophanate-methyl, lime sulfur. Please read the label on the fungicide you are selecting in store to make sure it contains an ingredient from this list. MSU Extension does not recommend any brand over any other brand, as a policy.

The frequency, method and time of application of the fungicide will also be listed on the label. Please follow the label directions exactly (it is especially important if you plan to harvest and consume the fruit of the tree you are treating.)

You can read more on black knot here: https://extension.umn.edu/plant-diseases/black-knot#using-fungicides-1170312





Thank you for your question!  Replied February 12, 2026, 8:37 AM EST

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