The Q&A Archives: Sap Oozing on Ornamental Prunus

Question: In June we planted 3 Prunus cerasifera 'Krauter's Vesuvius' between our house and our neighbor's. I just noticed two sacks of a light brown substance that appears to be sap on one of the tree trunks about an inch up from the botton of the trunk. They are about an inch and a half in diameter and are about two inches apart. The sacks are firm, but somewhat flexible and have a shiney glass like appearance. The substance is a clear light brown. My neighbor had a similar looking hard

Answer: The oozing sap symptom is a general one, called "gummosis". Trees produce the gummy sap in response to diseases or insect invasion. Sometimes they produce excess sap for no reason at all. Wet spring weather can spread bacterial canker, but there are other symptoms associated with the disease. Bacterial canker also affects the rest of the tree, so if you aren't seeing gummy buds, twigs and damaged leaves as well, your tree may not be diseased but fighting the presence of a borer (trying to heal the wounds). Sometimes burls, which are benign growth abnormalities, form on trunks of trees for various reasons, and these can also ooze gum. To determine the cause of the trouble with your tree, consult with a local landscape professional, or see if a Master Gardener can offer you some on-site advice.

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