Question: My plum tree’s trunk is covered with beads of dried sap, clear up into the limbs. What causes that, and what can be done to help the tree regain its vigor?

Answer: That’s the same bacterial stem canker that bothers peaches. Plums are often devastated by the disease. Use a labeled fungicide in November, after the tree has lost all its leaves. It’s much easier to prevent this particular disease than it is to cure it.