Blog & News

The Balsam Woolly Adelgid (Adelges piceae) (archive)

Published on Wednesday January 6, 2016
Authored by PEIISC

Today we hear from David Carmichael, PEIISC member and Horticulturist with the provincial government, on the Balsam Woolly Adelgid (Adelges piceae).


The balsam woolly adelgid (Adelges piceae) (BWA) is a tiny, soft-bodied insect which appear, once matured, as white, woolly spots on true firs. The adelgid was introduced from central Europe where it feeds on silver fir. These firs have developed resistance to the pest and are not seriously harmed by it. All fir species can be seriously affected by BWA feeding and are often killed following several years of infestation. Balsam Woolly Adelgid is an introduced forest pest largely responsible for the decline of Balsam in Atlantic Canada and are of particular concern for Christmas tree growers. Adelgids are small and difficult to find on the tree. It takes several months before trees develop symptoms of insect damage. Because of this, BWA can increase unnoticed and can cause serious losses to unsuspecting Christmas tree growers.


All true Fir Species. Sites worth considering for Balsam Woolly Adelgid surveys include young to medium aged fir stands such as Christmas tree nurseries and plantations


The balsam woolly adelgid usually has two generations per year. During winter, the adelgid survives as a dormant nymph under bud scales, in crevices of the bark, at the bases of buds, and at the branch nodes. In the spring, the nymph resumes feeding and moults 3 times. After these three moults, it becomes an adult and begins to produce white, waxy wool on its body. The females begin laying approximately 30 – 80 eggs during the first part of May. The eggs hatch within 1-2 weeks and a mobile nymph emerges and searches for a suitable feeding site. This young nymph or “crawler” is the only mobile stage of this insect. After it inserts its mouthpart, called a stylet, into the tree it remains stationary until death. Feeding continues throughout the summer. By late summer, this generation of adelgids is laying eggs that will eventually become overwintering nymphs. (Source: Nova Scotia Department of Natural Resources)

The insects are dispersed by wind, birds, mammals, and the young crawlers moving around on the branches in the forest canopy.


Remove and destroy infested trees preferably during winter to reduce the spread.

See the gallery below for examples of common symptoms of a balsam woolly adelgid infestation.

Attached images:

Early symptoms of Balsam Wooly Adelgid include twisted needles. Image source: David Carmichael, PEIDAF.
An example of the “Gout” swelling to host as a result of significant Balsam Wooly Adelgid infestations. Image source: David Carmichael, PEIDAF.
“Gouting” (swelling) on old growth node. “Gouting” can also occur on current season twigs. Image source: David Carmichael, PEIDAF.
Balsam Wooly Adelgid . Image source: (Natural Resource Canada)
An example of Balsam Wooly Adelgid infestations on the trunk of a fir tree. Image source: NRCAN.
Example of “Low” Balsam Wooly Adelgid damage to host. The canopy of the tree may begin to thin, needles will start to twist and small amount of “Gouts” may have developed. Image source: David Carmichael, PEIDAF.
An example of “Moderate” Balsam Wooly Adelgid damage to host. Note the canopy is significantly thinning where lower branches are dying off, needles twisting with a moderate amount of “Gout” development throughout. The upper part of the tree is starting to take on a “Windswept Broom” effect. Image source: David Carmichael, PEIDAF.
An example of a “High or Severe” infestation of Balsam Wooly Adelgid to host. Note few living needles exist on the lateral side branches, and the “Windswept Broom” effect is very significant on the upper part of the tree. Image source: David Carmichael, PEIDAF.