Hi Thomas,

Thank you for submitting your question to the UVM Extension Master Gardener Helpline.

The literature on black knot disease discusses susceptibility of plum trees and sweet cherries. Sour cherries are less susceptible than both of these. Interestingly, because sour cherries are less susceptible, I am not finding recommendations for specific resistant sour cherry varieties after looking at multiple extension websites. I would check with your local nursery for varieties that they favor for resistance.

If you have had black knot disease in your yard, you will want to make sure this is cleaned up so that it will not spread because the fungus can overwinter. As you may know, black knot is a fungal disease that leads to galls in the trees and affected tissue need to be pruned out in the winter season when the tree is dormant to keep the disease from spreading. The best references I found on the etiology of the disease and control are as follows:

https://extension.umn.edu/plant-diseases/black-knot#trees-affected-by-black-knot-in-minnesota-1171360

https://extension.wvu.edu/lawn-gardening-pests/plant-disease/tree-fruit-disease/an-introduction-to-black-knot

These references also mention the general increased resistance of sour cherries. I hope this was helpful.

Sincerely,