It looks a lot like what my family calls 'black knot'. I don't know what the normal name for it is.
We cut it off back to the trunk and dispose of the branches off-site as it's contagious. burning is a possible way to get rid of it, but it needs to be done right away. Clean the cutters with rubbing alcohol. After about three years of vigilant cutting out, it should be gone.
If you're pruning your trees, always leave the ones with a history of black knot to last to prevent spread.
I have the same thing!!! I have a bunch on my tree and not happy about it. This is the first year I am getting plums and have to cut off a bunch of them due to plum curculio. Anyone have any info on this or a name for it?
Black knot is endemic on our land and mostly grows on the pin cherry trees, which make up about 30% of the species mix in certain areas of the property, and nearly every one I've seen has black knot. In our clearing I have asked my husband to leave any trees that he sees that don't have black knot in case it's because they have developed resistance. I'm really worried about when we start bringing in other susceptible food forest species how we will ever prevent it because it is so prevalent. In choosing trees, we will have to look for strains that are listed as black knot resistant. My dad had a few fruit trees (plum, cherry, peach) and wasn't vigilant in removing the black knot and almost all stopped producing and died.
Wow! Those knots look scary!
Nice pics though...
I hope this one is the only one I ever see again. I cut back 8” so I hope that takes care of it: plus, I’m going to try a tea spray that fights this bacteria...
I would remove and dispose of it. Burning will work, but I personally would stay away from the smoke, and keep it from other plum trees. I think a hot compost would work, but it would have to be hot.
I think I would probably treat this like I would something like a cedar rust on apple.
I would remove the affected branches and dispose of them, and then mix up some aerated compost extract and douse the tree and all around it for as long as the extract held out.
Then I would mix up some more and get all the rest of the trees that could potentially harbour the contagion.
Then I would mix up some more and start from the beginning, all over again. At least twice in a season.
I know that some contagions, like mosaic virus, are easily spread downwind by the smoke of burning infected plants.
Glad to hear you've gotten ahead of it, Tim. Please keep us posted, and good luck in the future.
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein