Published by Utah State University Extension and Utah Plant Pest Diagnostic Laboratory
ENT-243-23
August 2023
Poplar Borer Marion Murray, IPM Specialist and Ryan Davis, former USU Arthropod Diagnostician
Quick Facts • The poplar borer is an insect native to North America. The adult is a beetle and the young is a grub that bores into trees. • Hosts include aspens, poplars, and willows. • Infested trees become weak and less vigorous but are rarely killed. • Symptoms include wet spots on the bark and oozing sap mixed with fine frass. • Control includes cultural methods and insecticides.
The poplar borer is a common wood borer in quaking aspen and other poplars in Utah. While large trees are seldom killed by this pest, it can cause tree decline, weakened branches, and allow the introduction of pathogens.
Fig. 1. Poplar borer beetles (Saperda calcarata), with male on left and female on right.1 Larvae are legless, elongate, cylindrical, and yellow-white in color. Their full-grown length is about 1.5 inches (Fig 2). They feed in galleries which extend into the sapwood. Pupae are usually found near the entrance of frassplugged galleries. They are yellow-white and about 1 inch in length.
DESCRIPTION
LIFE CYCLE
The poplar borer, Saperda calcarata, is a member of the longhorned beetle family (Cermabycidae), so-named because of the adults’ long antennae. The larvae are known as roundheaded wood borers.
Depending on the location and climate, the poplar borer’s life cycle takes 2 to 5 years (Fig. 3). In Utah, larvae require about 3 years to develop to pupation.
Adults are 1- to 2-inch-long beetles with antennae that are about as long as the body. They are gray-blue with fine brown dots overlaying a faint yellow pattern on the wing covers (Figs. 1 and 2). The underside of the adult is somewhat hairy. Eggs are about 3-4 mm in length and creamy-white. Females chew slits into the bark and lay one to three eggs within each slit.
Poplar Borer (Saperda calcarata)
In the fall, larvae plug openings of their galleries with frass (sawdust-like excrement) and spend the winter in diapause. Young larvae continue feeding within the tree during the summer, diapause again in winter, and repeat until mature. Mature larvae may pupate at any time during the season. Larvae that pupate in the fall spend the winter in the tree and emerge the following spring. Most mature larvae pupate in mid to late spring, which takes a minimum of 2 weeks. Adult beetles emerge through the frass plugs at the lower end of the galleries.
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