Pacific flatheaded borer

The Pacific flatheaded borer (Chrysobothris mali) is a destructive wood-boring insect belonging to the Buprestidae family within the order Coleoptera. It is widely recognized as a significant pest in orchards, known for its ability to devastate both nursery stock and established fruit trees.

This pest has a broad host range, primarily attacking various fruit trees such as apple, pear, cherry, plum, and peach. It also targets several ornamental shrubs. The beetle prefers to lay eggs on trees that are stressed due to water deficiency, poor soil conditions, or physical damage, which makes maintaining tree vigor the first line of defense.

The life cycle involves four stages: egg, larva, pupa, and adult. Adult beetles appear in late spring and feed on foliage and bark. After mating, the female lays eggs in cracks or crevices of the bark. Upon hatching, the larvae burrow into the cambium layer, where they create flat, winding galleries that effectively girdle the tree and disrupt the flow of nutrients.

Damage caused by the larvae is often fatal to the affected branch or the entire tree. Symptoms include wilting foliage, branch dieback, and the presence of D-shaped or oval exit holes where adult beetles have emerged. Because the larvae feed deep inside the wood, they are often protected from conventional contact sprays once they have entered the tree.

Control strategies should be integrated into a comprehensive orchard management plan:

• Promoting optimal tree health through proper irrigation and balanced fertilization.
• Removing and destroying infested wood or heavily damaged trees to reduce the population.
• Applying whitewash to tree trunks to deter females from laying eggs.
• Using systemic or contact insecticides during the adult flight period to prevent new infestations.