When replying in Ask Extension, there should be a link to click that allows you to attach up to three image files per reply/submission, though you could also paste the images directly into the body of your reply, especially if you are replying via email instead. Some people send images to us pasted into a separate document, like a Word or PDF file, that is attached instead. As long as the photo files are at least 1MB in size, we should be able to see enough detail or enlarge them.

Does the symptom on the plum look like the photo on our Black Knot web page? If so, this fungus can be very common plum trees and their relatives, and needs to be pruned off when found. You can also explore our Growing Stone Fruits page if this plum is a fruiting type (not just a decorative flowering variety), since fruit trees can be vulnerable to a range of issues.

Dying leaves -- whether remaining attached and browning/drying or falling off -- suggest something is interrupting the water flow into the affected branches. This could be root damage, drought without irrigation, wood-boring insects somewhere in the trunk or the dying branch, or an infection in the wood. Aside from monitoring the tree for watering needs, there would be little that could be done to remedy those symptoms since pesticides would provide little or no benefit once symptoms appeared. If you are able to send photos, we'll see if we recognize the cause of the symptoms.

Miri

Thank you for the photos. This does indeed appear to be Black Knot fungal infection. The only recourse for post-infection treatment is to prune off all branches that have symptoms, since infected wood will not be curable.

Miri