Question: Last week I noticed sap bubbles 6 to 8 inches off the ground on the trunk of my year-old Santa Rosa plum. I removed the bubbles and reapplied the whitewash. I checked again today, and they are back. I’ve had plums before, and the borers always win. I had hoped the Santa Rosa would do better. What can I do to save this tree?
Bubbles on plum trees don’t necessarily mean borers. They can do this with high temperatures. If you don’t see any other evidence of borers, such as bark coming off especially on the south or west sides, then I would leave it alone. Repainting is fine.
Try to keep as much shade on the trunk as you can from the canopy or even lean a board on that side of the trunk to shade it if you care to. But for now, just get some shade on it.
Bob Morris is a professor emeritus in horticulture with the University of Nevada and can be reached at email@example.com. Visit his blog at xtremehorticulture.blogspot.com.