My Santa Rosa plum has some disease that leaves a black covering on the leaves, fruit and stems, and covers everything under the t
ree. There is also sap oozing from the tree. What is this and how can I treat it and save this mature plum tree? All the fruit has now dropped, so is pruning appropriate now?
Certified GKH Gardening Expert
This sounds like black sooty mold! This can be caused by many things, but most usually from aphids or other insects. As far as pruning goes- I would wait until it is cooler. Spring or Autumn will be the appropriate time to prune.
These articles will help: https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm