Key Features
- Many holes throughout trunk
- Holes are pencil sized
- Small beetles under bark
Symptoms
Limbs and entire trees turn brown, often from the top down. Large numbers of small holes (> 100 per 1 sq ft of bark) about as thick as a pencil lead are found along the main trunk and major limbs. Peel back bark to reveal engraved areas where larvae tunneled through cambium. Small, black beetles and white, legless larvae may be present. Although this beetle attacks only pines, it is representative of many other closely related bark beetles that attack conifers.
Biology
Beetles winter as white grubs under bark. Adults emerge in late April when redbuds are in bloom and attack nearby trees. Beetles often attack in large groups to overcome the ability of trees to defend themselves through the production of sap that can pitch out individual beetles from the trunk before they lay eggs. Many adults carry a blue staining fungus that attacks the plant's vascular system and further weakens trees. This fungus can be passed to new trees when attacked by the adult bark beetles. Although this species only attacks pines, it is representative of a wide variety of species that attack conifers. Can also occur on trees affected by sawyer beetle and pine wilt.
Management Recommendations
Borers tend to attack pine trees that are stressed due to lack of water. Be sure to water trees during a drought to keep trees strong. Sanitation, or the removal of heavily infested trees can greatly improve your ability to manage this pest. Be sure to destroy all wood prior to April 15 to reduce the number of beetles that may be available to attack nearby trees. Wood can be destroyed by burying at least a foot underground or by burning if allowed by local ordinances. Putting wood into local dumps away from your trees may be more practical. Apply insecticide to the trunk in mid April to kill beetles attempting to enter or leave remaining trees. Apply again late August. Soil applied systemic insecticides (imidacloprid) have been shown to reduce injury from this pest.
Effective Pesticides
Active Ingredients include: Bifenthrin, Imidacloprid, Permethrin
