Balsam Woolly Adelgid

An exotic pest that we do not want in Michigan

Introduced from Europe around 1900, the balsam woolly adelgid is considered a serious pest of forest, seed production, landscape, and Christmas trees. The balsam woolly adelgid attacks all true firs, Abies spp., including balsam and Fraser fir. However, while some species are very tolerant (Noble fir), other species are devastated by the pest (balsam, Fraser, and sub-alpine firs). Billions of feet of fir timber have been killed by balsam woolly adelgids in North America.

The adelgid is now distributed throughout eastern and western North America. It is apparently limited in its northern distribution in Canada by cold weather. Balsam woolly adelgids infest firs in southern Canada, the Pacific Northwest, and the northeastern United States. They also occur in the Appalachian Mountains as far south as North Carolina.

The adelgid feeds either on the outer portions of tree crowns or on the main stem and large branches. Main stem infestations are usually more serious, causing greater levels of damage and mortality.

Adelgids up close.

Identifying Injury

During the adelgid's feeding process, the host tree is stimulated to produce abnormal wood cells. This reduces the tree's ability to translocate food and water. Initial symptoms of adelgid attack may include gouting of buds or twig nodes and some twig and branch dieback. This is very evident on seedlings, young understory trees, and Christmas tree plantings. Other damage mav be stunted shoot and needle growth and loss of apical dominance in natural stands. A heavily infested tree may die within 2 to 7 years. As the tree, dies, portions of the crown or the entire crown will turn red.

Feeds on stem, branches and twigs. During feeding it injects a salivary substance into the tree causing gall-like formations on the twigs and branches (gouting). "Gouting" may progressively weaken a tree over a long period of time.

Adelgids are distributed by wind, birds and other animals in the crawler stage. Crawlers are tiny (1mm), immature adelgids that are mobile. When they establish on a host tree they become immobile adults. Adults form the diagnostic white waxy wool. Adelgids are also moved to new areas on infested nursery stock.

Economic Importance

The damage symptoms listed above render the wood brittle and with excessive resin content. This lowers its value as a lumber and pulping species. Mortality of stands causes early harvesting which disrupts planned harvesting schedules.

Feeding activity on the bole of the tree causes dense wood formation similar to compression wood.