Hello,

The knot-type growths on your apple tree are likely burr knots or black knots.

Burr Knots

Burr knots are small, rough, and warty growths that can appear on the trunk and branches of apple trees. They are caused by the tree’s natural tendency to produce root initials above ground. These knots can become entry points for pests and diseases.

Treatment and Prevention:

Proper Planting: Ensure the graft union is just above the soil surface.

Pruning: Remove any burr knots during the dormant season to prevent pest infestations. More information is at this link:

Getting to the Root of Burr Knots on Apple Trees // Missouri Environment and Garden News Article // Integrated Pest Management, University of Missouri

Black Knots

Black knots are caused by the fungus Apiosporina morbosa. They appear as black, swollen galls on the branches and sometimes the trunk. This disease is more common in plums and cherries but can also affect apple trees.

Treatment and Prevention:

Pruning: Remove and destroy infected branches during the dormant season.

Fungicides: Apply fungicides containing chlorothalonil during the pre-bloom and bloom periods More information is at these links:

Controlling black knot in Michigan - Fruit & Nuts (msu.edu)

Black knot - Integrated Pest Management (msu.edu)

BEFORE YOU DO ANY TREATMENT AND PREVENTION – HIGHLY RECOMMEND YOU CONFIRMED THIS DIAGNOSIS!

I recommend that you send your image by e-mail to the MSU Plant & Pest Diagnostics Lab so that they can confirm and precisely identify the problem.

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

Their email is <personal data hidden> - Please include your name

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

FYI- The lab may also ask for additional images.

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 of submitting a sample to MSU Plant & Pest Diagnostics Lab:

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

I hope this helps!

Hello again,

These might also be Crown Galls – Check this out at this link:

Fact Sheet: Crown Gall – Database of Apple Diseases (cornell.edu)

Still, send your image to the MSU Plant and Pest Diagnostic lab for confirmation!