Dogwood Twig Borer

Plants Attacked

Dogwood, elm, azalea, viburnum, poplar, willow, and many fruit trees and bushes.

Description of Damage

The larvae tunnel down the center of live green twigs. They make a characteristic series of closely placed round holes in the bark through which they push frass out of their galleries (Fig. 1). Leaves above the tunneling wilt and die, followed by dieback of the mined twigs. Larvae periodically girdle twigs internally, causing the twigs to break off. Larvae plug these openings with frass and continue tunneling down the center of the green twig until they pupate.

Identification

Larvae are a creamy yellow-white with a brown head. The visibly segmented body measures about 0.75-1 inch (2-2.5 cm) long (Fig. 2). Adult beetles are slender and cylindrical, about 0.5 inches (1.3 cm) long. There can be much variability in the adult coloration. The antennae may be dark, or dark at the bases and more yellow-orange towards the tips. The head, legs, and thorax are usually yellow-orange.

There may be orange and black stripes on the wing covers, or the wing covers may be shaded to a dark grayish-brown or black. The underside of the body tends to be darker. There are three black spots on the orange thorax.

Coleoptera: Cerambycidae, Oberea tripunctata (Swederus)

Life History

Adult borers appear in early June. They girdle the tips of twigs and deposit eggs on twigs near the girdling. Eggs hatch and the larvae enter bore into and down the center of the twig. Feeding damage by the larvae usually causes death of the branches and ruins the appearance of shrubs or trees. The larvae overwinter in the hollowed stems. In spring, some of the larvae pupate while others continue to develop as larvae into the second year. Pupating larvae emerge as adults by mid-May or early June. There is one generation per year.

Control 

Pruning and burning infested twigs as soon as they are found is an effective control measure. Care should be taken to remove the larva or pupa at the base of each mined twig or branch. Spraying with recommended insecticides prior to budding will also kill adult beetles as they girdle the twigs as well as the newly hatched larvae boring into the twigs. This is a sporadic pest so chemical treatment will not be needed every year.

Revised 

Theresa A. Dellinger, February 11, 2020.