Hello Becky,

Based on your images, this looks like a plum tree with a black knot infection. Wild cherries and some ornamental cherries can also get it.

Black knots primarily affect trees in the Prunus family in Michigan, with plums particularly vulnerable. Here's what you need to know:

Affected Trees:

Plum trees are the most commonly affected

Wild cherries and some ornamental cherries can get it

Sweet and sour cherry trees are rarely affected in Michigan

More information at this link:

Controlling black knot in Michigan - Fruit & Nuts

Treatment Options:

Winter Pruning (Most Important Step)

Prune infected areas during winter when trees are dormant

Cut at least 6 inches below each knot into healthy wood

Important: Burn or bury pruned material - don't leave it on the ground

More information at this link:

Your plum trees versus black knot - MSU Extension

Fungicide Treatment

Only recommended for severe cases or particularly valuable trees

Apply when trees are dormant in spring (before green buds appear)

The second application is when flower buds begin showing color

More information at this link:

Your plum trees versus black knot - MSU Extension

Can You Save the Tree? Yes, but it depends on the severity. You have two main options:

Remove the tree if the infection is too severe

Treat it through pruning and possible fungicide application

Early Detection: Look for these signs:

More information at this link:

Controlling black knot in Michigan - Fruit & Nuts

Initial symptoms: small, light brown swellings

Later stages: olive-green swellings that turn black and hard

The knots will expand over time and can attract wood-boring insects

Prevention is crucial - regular inspection and prompt removal of infected branches give your tree the best chance of survival.

Consider sending your images to the MSU Plant & Pest Diagnostics for precise diagnosis.

I highly recommend you send your images by e-mail to the MSU Plant & Pest Diagnostics Lab.

Their email is <personal data hidden> - Please include your first and last name.

The experts there can also provide you with the best treatment options.

The lab will let you know if they need a sample sent.

The lab may also ask for additional images. So be prepared.

Their website is at this link:

Plant & Pest Diagnostics (msu.edu)

Their Contact Information is at this link:

Contact Us - Plant & Pest Diagnostics (msu.edu)

This link will explain the details on submitting a sample to the MSU Plant & Pest Diagnostics Lab:

Submit Samples - Plant & Pest Diagnostics (msu.edu)

I hope this helps!