Aspen Borer

Aspens are members of the willow family and in the genus

Populus (Populus tremuloides).  Most of the aspen you see  in the Utah / Intermountain West are  the quaking aspen, given its name because its leaves quake or tremble in the slightest breeze. This tree grows best above 5,000 feet elevation, where temperature and moisture are favorable. Aspens are usually found in groups of genetically identical individuals, called clones. Clones form because aspens reproduce by suckering (sprouting) from roots. As the stems age, they decline and eventually die, and they are replaced by suckers from their root systems. Aspens are short lived; even under optimal conditions, aspen trees rarely live longer than 100 years.

Aspen Borers.

Many species of boring beetles frequently attack aspen. The most important is Saperda calcarata, a round headed, long-horned beetle.  However, the damage is similar regardless of the boring insect involved.  These insects attack stressed trees, usually caused by the lack of water or planting to low in the Salt lake Valley ie below 5,000 feet, of varying size and age in an effort to lay their eggs. The damage is caused by developing larvae which feed in the trunk of the aspen for  several years. Their tunneling often weakens the wood of the trunk and allows invasion of insects, canker and decay fungi.

The tree may ultimately break in a wind or snow storm.  

Bleeding wound with frass (Saperda

Infected trees will  “bleed” from borer infection  sites.

                                                                      (Figure 2 ===>).

The most effective deterrent to borers is to maintain trees in a vigorous condition. Healthy trees can resist boring activity, preventing the insects from laying their eggs. Maintaining vigor may be difficult to do because ornamental aspens are subject to frequent stresses. Insecticides are of little benefit in controlling borers. Adult beetles do not feed on aspens, and thus do not ingest the insecticides. Insecticides, including systemics (those that move within the plant), are also ineffective because they do not reach the inner wood where the larvae are feeding. A good approach to dealing with borers in aspens is to remove the infested stem before it i dies and select one or several suckers as replacements.

The grayish-blue spotted female beetle lays eggs in late spring and early summer in slits chewed in the bark. Larvae bore into the stems or branches and make extensive galleries in the sapwood and heartwood. After 2 years' growth, the larvae pupate and adults exit through the former entrance hole.


 Aspen Borer larva in a chamber.