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This pest also attacks the flowering forms of these trees. It feeds under the bark and eventually kills the tree.
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. Oozing wounds higher in the tree are caused by other problems. The most common of these is cytospora, a fungal disease with symptoms that resemble borer damage.
Adult borers are clear-winged moths that resemble a wasp. 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 ten 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, as partially grown larvae, a few inches below the ground under the bark. In the spring they resume feeding and then 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. The time they are vulnerable is before they tunnel under the bark. Preventive sprays must be applied the first week in July and again the first week in August.
The most effective product is Dursban® if it is still available. otherwise use registered formulations of diazinon. Use the amount of spray recommended on the label. Keep the spray off the fruit and leaves.
Apply the first spray about July 1 and a second spray August 1. More frequent sprays are needed if sprinklers hit the trunks regularly.
Organic controls include parasitic nematodes. They are released at the base of the tree after the larvae become active. Other types of controls including companion planting are not effective and cannot be relied on 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.