Globs of hardened sap form on cherry tree limbs
Q. "While putting up the Christmas lights in our front yard, we noticed strange, large blobs of what appears to be sap or something coming from numerous spots on the trunk and larger limbs of our Queen Anne cherry tree.
The tree is about 20 years old and has never done this before. It bloomed a prodigious amount last spring. We get little of its fruit, but we love to see the birds in it and would hate to lose the tree. What's causing this condition?"
A. From your photographs, it appears your cherry tree is suffering from one of three possible conditions. Either the bark has been damaged by woodpeckers, boring insects or a bacterial infection.
Damage from birds or borers seems unlikely here. Even the most industrious woodpeckers will seldom work the number of branches and trunk area as shown in the photographs. Also, woodpeckers tend to work methodically and will drill holes a series of holes at regular intervals. Your problem appears much more random and on branches that would be too small to hold any insects. We can discount bird damage.
Cherry trees are often attacked by borers - peach tree borers, oddly enough. But wait, you say: "This is a cherry tree." Yes, peach tree borers in North America ate wild cherry and plum trees until the peach was introduced from its native China to the Americas in the 16th century. Early American settlers bought large amounts of peach trees in Colonial times and took them along to settle the West. The borers found they liked peach trees better.
Peach borers attack trees around the soil line and lower parts of the trunk. As your damage is more widespread and high up on the tree, we can discount borers, as well.
Damage from bacterial infection. Probably the culprit here. Mildew, brown rot and cherry leaf spot generally exhibit symptoms on the leaves and fruit. You indicated a healthy tree until late summer. Bacterial infections, especially Leucostoma canker, result in lesions forming on the limbs and trunk. At the site of the lesion, sap/gum will exude and form the blobs you have. This problem is often found after a cool, wet spell after flowering and in trees that are stressed. In the Chicago area, we had two years of drought, followed by a hard winter, and then a cold, wet spring. Trees may not show signs of stress until months or years after the actual events.
What to do? The first line of treatment would be to prune out the diseased wood in late winter or early spring. Prune judiciously so not to stress the tree further, or make it so misshapen as to be counterproductive. Be sure to sterilize your pruning tools with a 10 percent bleach solution between cuts so as not to transmit the bacteria. A basic copper sulfate solution spray can be applied in the fall, but remember this type of chemical may damage stone fruits and impact next spring's crop of cherries, or other stone fruits nearby.
Ensure your tree is properly watered; that is, a deep, soaking watering during any dry periods. Mulch the roots to help the tree avoid root damage from frost heaving and drought. Apply a fertilizer with a slightly higher nitrogen ratio, 15-5-10 or so, in the fall after leaf drop. With luck, your Queen Anne cherry will recover.
- Matt Steichmann
• Provided by Master gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines. Call (847) 298-3502 or email northcookmg@gmail.com.