Balsam Woolly Adelgid: Appearance, Territory, Damage, and Life Cycle

Latin Name: Adelges Piceae

Appearance: Balsam woolly adelgids (Adelges piceae) are wingless insects that infest and kill fir trees, particularly balsam and Fraser fir. They are an invasive European species that was introduced to the United States around 1900. Female balsam woolly adelgids have soft bodies, are spherical, purplish-black, and lack wings. They are immobile and around 125 inches long. Immature nymphs can be spotted on bark in the winter. They have dark skin, and the margins of their bodies are surrounded by white, waxy rods.

By the time females are present, they may have developed a covering that may make them resemble tiny cotton balls as they continue to exude this waxy substance as they mature. Oblong eggs are laid in a group behind the female. The only stage with usable legs is the orange-brown crawlers. The crawlers also have red eye patches. To accurately locate each level, a hand lens is required.

Hosts Plants: Balsam woolly adelgid can infest true fir trees, including balsam, fraser, and concolor (white) fir.

Territory: It is indigenous to Central Europe. Balsam woolly adelgid first appeared in North America around 1900 in New England and Canada. It was discovered near San Francisco in 1928. Balsam woolly adelgid can now be found on the West Coast in California, Oregon, Washington, and Idaho, as well as in New England and parts of North Carolina, Virginia, West Virginia, Tennessee, and Michigan.

Damage Insect Cause: Damage from the balsam woolly adelgid comes in two forms. The presence of the insect covered in white fuzzy material in bark fissures, which results in swelling of the afflicted areas and an increase in stem diameter, marks affected trunks. As soon as the bug begins eating, the needles begin to fall, the crown turns brick red, and hard compression wood is formed, which degrades the quality of the wood fiber needed to make pulp and paper.

Insects attacking the shoots cause the second form of harm. This results in the illness known as “gout,” which results in swelling and deformation of the twigs. The long-term attack will impede bud and height growth and may eventually result in tree death, beginning at the top. The development of white woolly masses on the lower bole, and possibly on broad branches in the spring and summer, is the earliest indication that the bug is present. No matter what time of year it occurs, crown gout is another indication of an infestation.

Life History and Habits: Each year, the adelgid has two to four generations. The wingless female can lay over 200 amber-colored eggs. The eggs are placed beneath “cottony tufts” on the undersides of branches and on the trunk. Crawlers can be seen with a hand lens beginning around bud break. This is the most vulnerable stage to chemical control. Because there are no men, females give birth to more females.