Q: I was cutting my grass around my cherry tree, and noticed an oozing from a place at the bottom of the trunk.
Can I fill in the hole with anything to prevent disease from infecting the tree?
A: Gummy ooze from cherry trees is a common occurrence. Sometimes the oozing is caused by a borer but other times the tree does it in reaction to stress. In my experience the biggest stressor for a cherry is water around the roots and low soil pH. A wound from a mower bumping against the trunk will cause oozing too.
My advice is to examine the spot where the oozing originates. If the gum has specks of sawdust in it, a borer has been at work – but this is not likely. In any case, there is no spray that will kill borers in the trunk anyway.
The gum will probably be clear, in which case your job is to improve the growing conditions for the tree. Estimate the square foot area covered by the tree limbs and branches and increase it by 25%. (Example: if the tree covers 200 square feet, increase the number to 250 square feet.) For every 100 square feet scatter 4 pounds of garden lime under the tree. (For our example, you’d need 10 pounds.) This will gradually raise the soil pH.
If water accumulates over the root system after a rain, redirect the water to another spot. Remove thick mulch so the soil dries quickly.
Do not fill the hole with anything. Any material you might use will inevitably crack and make an excellent hiding place for insects and disease in the future. Your tree can do a fine job protecting itself if you make it healthy.
See Diagnosing Cherry Bleeding for more information.