The tunnels boring insects carve inside a tree provide a direct route for pathogens to enter. To protect trees susceptible to attack from boring insects, such as white birch, apply an insecticide when the pests are active. Insecticides with a residual effect, e.g., Lindane, control insects throughout the season. Only the bark of the tree should be sprayed. Insects such as peach-tree borers tunnel under the bark and can girdle a tree.
Borers enter dogwood trees through wounds in the bark.
To protect trees, keep them well watered so the sap runs freely, avoid damaging the bark with string trimmers and mowers, and make sure the area under the tree is free of debris. If you see signs of insect damage, begin a spray program.