Two-lined chestnut borer

The Two-lined chestnut borer (Agrilus bilineatus) is a member of the Buprestidae family of beetles. This wood-boring insect is primarily known for its devastating impact on oak trees, particularly those weakened by environmental stressors like drought, root diseases, or defoliation by other insects.

The life cycle of this beetle generally spans one year, although in northern parts of its range, it may take two years to complete. Adults emerge in late spring or early summer, feed on the foliage of the host tree for a brief period, and then mate. Females deposit eggs in bark crevices, where the larvae will eventually hatch and burrow inward.

Larval development is the most destructive phase of the insect's life. Larvae tunnel into the phloem and outer xylem, creating serpentine, frass-filled galleries. These galleries effectively girdle the tree, cutting off the flow of nutrients and water between the roots and the canopy, which leads to branch dieback and eventually tree death.

Economic and ecological damage caused by Agrilus bilineatus is significant in both forestry and urban landscapes. Symptoms of an infestation include leaf yellowing and browning in the upper crown, sparse canopy, and the presence of D-shaped exit holes on the bark of the trunk or larger branches when the adults emerge.

Protecting trees requires a multifaceted approach focused on increasing tree vigor. Management strategies include:

• Maintaining tree health through adequate irrigation and avoiding soil compaction near the root zone.
• Removing and destroying infested wood to reduce the population of emerging adults.
• Monitoring the population density using pheromone traps.
• Applying systemic insecticides on high-value specimen trees in urban environments to prevent larval survival.