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Growth on plum tree #752894

Asked May 29, 2021, 7:52 PM EDT

We have a few plum trees that we planted about 4-5 years ago. Two of them are doing well but one has developed growths on trunk and branches. Is it possible to treat this or do we need to remove the tree?

Frederick County Maryland

Expert Response

Hi- this is black knot, a common fungal disease of plum, cherry, apricot, and some related species.

https://extension.umd.edu/resource/black-knot-disease-trees

https://extension.umn.edu/plant-diseases/black-knot#:~:text=Black%20knot%20is%20a%20common,branches%20and%20occasionally%20on%20trunks.&text=In%20these%20trees%2C%20leaves%20and,die%20on%20branches%20with%20galls.

The disease will continue to spread. Removing the infected wood (pruning cuts 4-8 inches below symptoms) is the only effective treatment. With such extensive trunk and branch infection the tree will go into a slow, steady decline.

Jon

Answered by the Home & Garden Information Center's Maryland Certified Professional Horticulturists Replied May 31, 2021, 10:26 AM EDT
Thanks Jon that’s bad news but appreciated

I’ll remove that tree and hopefully it hasn’t spread to any others. Is there anything I’ve done that could make it more prone to this fungus - like planting conditions?

We spray each spring with sulphur every other year and then something else in-between years. Does that help prevent this type of growth?

Sorry about all the questions!

Thanks

Alan

Sent from my mobile device

On May 31, 2021, at 10:26 AM, Ask Extension <<personal data hidden>> wrote:


The Question Asker Replied May 31, 2021, 3:08 PM EDT

Hi- yes, sulfur fungicide sprays at bud break and 2 weeks later can help slow infections. This is a common fungus on wild plum and cherry so spores may have spread to your tree from nearby wild trees.

Jon

Answered by the Home & Garden Information Center's Maryland Certified Professional Horticulturists Replied June 01, 2021, 10:59 AM EDT

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