Pacific Flatheaded Borer – Flatheaded Appletree Borer – Chrysobothris mali

Pacific Flatheaded Borer (Chrysobothris Mali) Latin Name: Chrysobothris Mali Common Name: Pacific Flatheaded Borer Appearance: Egg: The egg is pale yellow, disk-shaped, and wrinkled, with a diameter of around 1/20 inch (1 mm). Larva: The larva is a slender yellowish white grub that can grow up to 1 inch (25 mm) in length. The insect’s common name, flatheaded borer, comes from the broad and flat front section of its body. The larva is normally coiled up in a U shape on one side. Pupa: The pupa measures around 1/2 inch in length. It starts out light yellow but eventually turns brown. Adult: The mature beetle is a wide, flat beetle that is 1/4 to 1/2 inch (6 to 13 mm) in length. It is dark with irregular grey patterns and has a coppery sheen. It has a vivid green back beneath the wing coverings. Host plants: The borer attacks apple, pear, peach, apricot, plum, prune and cherry as well as many other trees and shrubs Territory: The Pacific flatheaded borer was once a major pest in the United States and southern Canada, but it is now uncommon in commercial orchards. Damage caused by Pacific Flatheaded Borer: Feeding by Pacific flatheaded borer larvae weakens the cane, resulting in stunted growth or death of the cane. Adult beetles are attracted to stressed or damaged blueberry canes, particularly areas with pruning scars or sunburn. Adult female beetles lay eggs on the injured area, and larvae excavate tunnels just beneath the bark and bore through the cane. Excavations are usually filled with tightly packed, finely powdered sawdust. Later, these areas may crack and expose the mines. Life history and Habits: Adults emerge shortly after the apple blossoms. Females lay eggs in fissures in the bark, generally on the sunny side of tree trunks below the lowest branches, from early June through July. Females prefer to lay eggs on trees that are diseased, dying, or have recently been transplanted. From mid-June until mid-August, the eggs hatch. Grubs that have just hatched burrow under the bark and eat between the bark and sapwood until they reach adulthood. When the grubs reach maturity, they dig a short distance into the wood and construct cells in which they overwinter and pupate in the spring. The emergence holes in the bark or exposed wood of the adults are oval, about 1/4 inch in diameter, and located towards the tree’s base.