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Peach Tree Borer is the most destructive insect pest of peach, cherry, plum, nectarine, apricot and other stone fruits. It also attacks the flowering forms of these trees. It feeds under the bark at the base of the tree and eventually kills the tree.
Unlike exotic fruit pests, this is a native insect and prior to the time peaches were introduced, it lived on wild cherries and plums. It causes severe injury by feeding on the cambium and inner bark of the trunk close to the soil line.
This pest is no respecter of age. Young trees are often completely girdled in one year and subsequently die. Older trees may be severely injured and succumb to fatal damage from other insects or diseases.
Symptoms of borer damage are wet spots or oozing, gummy, sap. Sawdust-like excrement often mixes with the sap giving it a dark color. Damage occurs at the base of the tree beneath the soil line.
Adult borers are clear-winged moths that resemble wasps. They are active now and fly during the day. They begin laying their eggs about July 1 and continue for about two months. Each female lays up to 400 eggs at the base of the trunk. The eggs hatch in about 10 days and larvae burrow into the trunk through cracks in the bark and start to feed.
The insects feed under the bark through the fall and spend the winter under the bark, as partially grown larvae, a few inches below the ground. In the spring, they resume feeding and pupate in late spring. Adult moths emerge from the pupae and start the life cycle again.
Once inside the tree they are protected from most treatments. Treat before they tunnel under the bark. Apply preventive sprays the first week in July and the first week in August. Spray more frequently if sprinklers hit the trunks regularly.
Check with local nurseries for registered products. Spray the trunk and let the spray puddle around the base. Use the amount of spray recommended on the label. Keep the spray off the fruit and leaves.
Organic controls include parasitic nematodes. Release them at the base of the tree after the larvae become active. Other types of controls including companion planting are not effective and are not reliable to successfully control this pest.
There is strong evidence that trees showing signs of stress or other damage are more susceptible to borer attack. Keep trees healthy by avoiding over watering and damage to the trunk by string trimmers and lawn mowers. Inspect trees carefully and apply the preventive controls as needed
Larry A. Sagers
Horticulture Specialist
Utah State University Extension
Thanksgiving Point Office
