Wood boring insects feed on the inner wood (xylem) of roots, trunks, branches or shoots of a plant. While there are hundreds of wood boring species that are not considered pests, some species can cause branch dieback or even mortality. Recently transplanted young plants and stressed plants are most susceptible to attack from wood boring insects. Damage occurs when the larvae of wood boring insects chew through the nutrient and water transporting tubes of the plant.
This damage can be extremely devastating. In the early years of an infestation, there may be few signs as the pests bore inside the plant, creating irreversible internal injuries. As infestation progresses, exist holes where adults emerge may be visible in the trunk or branches. The plant may lose leaves and, in some cases, the beetles will leave a sawdust-like debris or frass nearby.
With the increase in international trade, many new invasive species have been introduced to North America over the past 20 years. One of them is the emerald ash borer—a metallic green beetle that kills ash trees. It is imperative to treat an ash tree or American fringe tree if the emerald ash borer is nearby. Otherwise, tree mortality will occur. Other wood boring insects such as the Asian longhorned beetle, the velvet longhorned beetle, and the spruce longhorn beetle have also been recently introduced to North America.