found this for you....."The plum is a strikingly beautiful specimen tree, but it is notoriously short-lived (in some zones it won't exceed 10 years); it is susceptible to bark-cracking, diseases such as cankers on branches, leaf-shot on leaves (small holes caused by bacteria), pear saw-fly (larva of their eggs develop on leaves, resembling tiny slimy tadpoles, and they feed on the leaves). If your soil isn't perfect (rich in humus, or if it's a bit clay-heavy), this adds to the short lifespan. "
it got frost bite ---- you will have to prune it back
looks like Fire blight
I would agree from here it looks like fire blight :(
Well considering your location...I would attribute the damage to hurricane Irene....Most of the fruit trees here on Cape Cod suffered as well...and that looks exactly like my fig tree!! I would try pruning it way back...fertilize..and pray!
DOES NOT LOOK GOOD!
Looks to me like Black Knot...plums and some flowering/fruiting trees and shrubs are noted for this. I found this link for you so that you can treat it or decide what you need to do. I've seen this on flowering trees and shrubs before .
Ornamental plums are genetically susceptible to cankers and it looks like that's what you have. They can be difficult to treat. You may want to have a professional come out and take a look at it to determine how extensive the problem is.
I think you have a canker disease called black knot. It is common on plums but the bad news is that there is no cure for it other than a sharp pruner.
Cutting out all those diseased limbs will make the tree look pretty odd.
My advice is to enjoy it while you can and take it out when it becomes too ugly to bear.
The State of Michigan (I live in SW Michigan which is a fruit-belt) is having a lot of blight on fruit trees. The State Horticultural people come around every summer to check the ornamental fruit trees in our yard and if they find one infected we have to cut the tree down and destroy it immediately.
Black knot it is ! and so accurate a description I can't deny the sad truth. Oh well, landscaping for us has been trial and error all along, and so it goes. Thank you all for helpful hints.
Frances, if you choose to save the tree; you can cut the Black Knot out. Sterlize your cutting tools too to prevent the spread of the disease. Make sure the tree stays watered and fed (if it's competing for nutrients and as flowering trees and shrubs are heavy feeders). This just helps the tree to remain 'unstressed' and stay healthy.
How often is it cut back each year. Yes sterilized pruners is suggested. I have two in my front yard but they are only four years old and I keep them in check each year.
I had the same issue, my tree was 15+ years old tho, I pruned it drastically the last few years but finally just gave up.