Borer

Borers are a broad category of insects whose larvae feed within the woody tissues of trees. Common examples include the emerald ash borer, Asian longhorned beetle, bronze birch borer, and various clearwing moths. Adult borers lay eggs on bark surfaces, and the hatched larvae tunnel inward to feed on the nutrient-rich cambium, phloem, or xylem tissues.

The damage borers cause is often concealed beneath the bark, making early detection challenging. External signs include D-shaped or round exit holes in the bark, sawdust-like frass at the base of the tree or in bark crevices, bark splitting, canopy thinning, and branch dieback. By the time these symptoms are visible, the infestation may already be well established.

Prevention and early intervention are key to managing borers. Healthy, vigorous trees are more resistant to borer attack because they can produce resin or sap that drowns or repels larvae. Maintaining proper watering, mulching, and avoiding root damage keeps trees resilient. For high-value trees at risk, systemic insecticide treatments like trunk injections of emamectin benzoate or soil drenches of imidacloprid can provide effective preventive protection.