Balsam Woolly Adelgid – Adelges piceae

Balsam Woolly Adelgid – Adelges piceae Description of Insect: The balsam woolly adelgid is a sap-sucking insect native to Europe that has become a destructive pest of fir trees in North America. Adult adelgids are wingless, pear-shaped, and measure less than 2 mm in length, making them difficult to spot with the naked eye. They are dark purple to black and secrete a white, woolly wax-like material that covers their bodies, hence called “woolly adelgid.” The nymphs also known as “crawlers” are reddish-brown, measuring almost 4 mm. They pierce the bark with their needle-like mouthparts and feed on sap, injecting saliva that disrupts the tree’s growth mechanisms. Life cycle of Balsam Woolly Adelgid The balsam woolly adelgid undergoes a simple life cycle consisting of egg, nymph, and adult stages. They complete their life cycle on a single fir tree, reproducing parthenogenetically. Adult females can produce more than 200 eggs during their lifetime, which are deposited in clusters beneath the protective woolly wax. Eggs hatch after a month into mobile nymphs, known as crawlers, which are the only stage capable of dispersal. However, the major dispersal to other trees occurs via animals, wind, and birds. After settling, the nymphs become immobile and begin feeding, eventually molting into adults. The life cycle is temperature-dependent, with two to four generations occurring per year. During the growing season, all stages of the balsam woolly adelgid may be present, making it hard to manage the infestation. Damage they cause: The balsam woolly adelgid is one of the most harmful pests affecting fir trees, with widespread ecological and economic impacts.

1. Ecological Impact: Balsam woolly adelgid causes an allergic reaction in the woods. This results in gouting of the twigs, swelling of the sapwood, and increased heartwood formation in the sapwood. The abnormal reaction wood, called “rotholz” or “redwood” limits normal movement of water and nutrients, distorting the tree’s growth. In heavily infested trees, crown dieback, stunted growth, needle dropping, and eventual tree death are common outcomes. Infested trees die within 2 to 3 years, leading to significant changes in forest structure and biodiversity.
2. Economic Impact: Fraser fir, a popular Christmas tree species, is particularly vulnerable to the balsam woolly adelgid infestations, rendering trees unsellable. The loss of needles and rigid branches renders the trees unsuitable for wreaths and roping. Additionally, the brittle, lignified wood also decreases the commercial value of the fiber. The costs of monitoring and removing infested trees add to the financial burden on landowners and forestry managers.

How Balsam Woolly Adelgid got into USA: The balsam woolly adelgid was accidentally introduced to North America from Europe in the 1900s. It was first discovered in New England and is believed to have arrived through imported nursery stock. Later it was recorded near San Francisco in 1928. The pest has since spread to the West Coast in California, Oregon, Washington, North Carolina, Virginia, Tennessee, and Michigan.   It has now also spread to British Columbia and Atlantic Canada. Human activities, such as the transport of infested nursery stock and Christmas trees, have played a significant role in its dispersal. Additionally, the adelgid’s ability to survive on a variety of fir species has allowed it to establish itself in diverse climates and regions.