Aspen Tree Borers

Aspen trees (Populus tremuloides), also called mountain, golden and trembling aspen, are fast growing but short-lived trees with a wide distribution across North America. They reach reaches heights between 40 and 50 feet tall and have grayish-green bark with dark-green leaves. These trees have many serious disease and insect problems, including borer infestations.

Types of Borers

The poplar borer (Saperda calcarata) is the most damaging aspen tree borer, according to D.A. Perala from the U.S. Forest Service. Poplar borers are the larvae of inch-long, dark-gray, long-horned beetles. These yellowish-white, legless, wormlike insects grow to be around 1-1/4 inches long. Other types of beetle borers include Aspen root girdlers, bronze poplar borers, flatheaded apple tree borers, Aspen ambrosia beetles and Pacific flatheaded borers. The larvae of a clear-winged moth and a type of weevil called Cryptorhynchus lapathi also infest Aspen trees.

Feeding Damage

Borers usually attack weak or damaged Aspens. The adults lay eggs on the bark, and the emerging larvae chew small holes through the bark and enter the wood. Once inside, they create tunnel networks inside the tree. Some species feed on the sapwood inside the stems, twigs or branches, while others devour the xylem and phloem, which are the tissues between the bark and wood that carry water and nutrients from the roots to the branches.

Symptoms and Effects

A sawdustlike material often appears on the ground near Aspens infested with borers. You may see small holes in the bark. Some of the holes might ooze sap, while others contain sawdust. Infested Aspens show poor growth, and their limbs break easily during storms. Heavy or repeated infestations are often fatal. In addition to girdling the tree by cutting off its nutrients, borer infestations leave trees susceptible to attacks from fungi and other harmful pathogens.

Control

Controlling borers is difficult because insecticides do not penetrate the bark or enter the wood. Depending on the type borer and the extent of damage, severely infested trees may need to be removed to prevent other trees from attack. Prevent further infestation by spraying the bark once a month with chemical sprays such as permethrin or carbaryl that kill emerging larvae. When placed inside borer holes, some types of commercially available nematodes feed on the borers below the surface.

References

• University of Connecticut: Populus tremuloides
• Montana State University Integrated Pest Management; Tree Borers; Sherry Lajeunesse; 1997
• U.S. Forest Service;: Populus Tremuloides Michx. Quaking Aspen; D.A. Perala
• Colorado State University Cooperative Extension: The Poplar Borer -- Saperda calcarata; Judy Sedbrook