Invasive Animal

Balsam woolly adelgid

Adelges piceae

About This Species

Adelgids are small, sap-sucking insects that feed on trees. The Balsam wooly adelgid is a European species that feeds on true firs (Abies spp.). It is an established invasive species throughout northwestern North America, including BC.

Balsam wooly adelgid is most widespread on the South Coast, the Lower Mainland, and along the East Coast of Vancouver Island. It was first reported in the Interior of BC in 2018, east to Nelson and north to Horsefly. It is expected to continue to spread throughout the Interior, especially in Subalpine fir (Abies lasiocarpa) forests, which are particularly susceptible to this pest.

Balsam wooly adelgids damage trees by feeding. As they drink sap through their straw-like mouthparts, they inject saliva which is toxic to the tree. The saliva causes swelling around the feeding area, which compressed the wood and kills terminal buds. This swelling, called tree gout, will hinder growth, cause needles to yellow and drop, and may kill the crown of a tree. It also reduces wood quality. By killing needles and preventing new growth, adelgid feeding can kill a tree within a few years.

How to Identify

Adult Balsam wooly adelgids resemble aphids. They are around 1 mm across and grey, with a white waxy sheen.

These insects have between 2-4 generations per year. Female adelgids lay up to 200 brown eggs under white woolly tufts of wax along tree trunks and branches, in a heavily infested tree the trunk may be covered with these tufts. The eggs hatch into an immature ‘crawler’ which disperses throughout the tree and to new host trees. These crawlers are about 1/3 the size of the adult with an amber coloured oval body.


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prevention tips


Do not move fir trees between regions. Prevent the spread of Balsam wooly adelgid by buying Christmas trees and firewood from local sources.

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