Description of the Pest
The branch and twig borer is a slender brown beetle about 0.5 to 0.67 inch long. The body is cylindrical and the head and prothorax are narrower than the body proper. The beetle lays its eggs in the dead wood of a number of native and cultivated trees and shrubs outside the orchard or on dead plum limbs once an orchard becomes infested. Larvae bore into the heartwood of the host and feed within this area for a year or possibly longer. Pupation occurs within the wood, and adults emerge in early summer. They often fly from native vegetation to orchards where they bore into small branches on the trees. There is one generation per year.
The adults bore into small twigs and branches, making round holes, commonly at the axil of a bud or fruit spur or at the fork of two branches. One of the branches frequently dies. Branch and twig borers seldom cause economic injury and are found only rarely in plums.
These beetles do not prefer healthy, vigorous growing trees. Maintain a program of sunburn protection and proper irrigation and fertilization. Promptly destroy brush piles harboring these pests. Remove prunings and brush piles from orchard in early spring. Remove badly infested trees and branches from the orchard and destroy them by shredding or hauling them to the dump. There is no insecticide treatment currently recommended to control the larvae of these borers.