Balsam woolly adelgid

Adelges piceae (Ratz.)

The balsam woolly adelgid was accidentally introduced into North America from Europe. These aphid-like insects, though small, can damage or kill a tree.

On this page

• Description
• Host tree species
• Damage symptoms
• Management
• Identification images

Description

Balsam woolly adelgid is a significant pest of true firs in B.C., the Atlantic provinces, and the northeast and northwest United States. A provincial regulation has restricted the movement of true firs within B.C. with the intent of reducing the risk of balsam woolly adelgid spreading into the interior of the province.

However, recent surveys (as of 2018) have indicated that balsam woolly adelgid has spread into the interior of B.C.. The adelgid has been confirmed as far north as Horsefly and to the east as far as Nelson, B.C.

Balsam woolly adelgids have two to four generations per year. The wingless female can produce in excess of 200 amber colored eggs. The eggs are laid under the visible white, woolly tufts on the bark of the tree bole or on branches. Crawlers are visible with the aid of a hand lens beginning around bud break. There are no males, and females can lay female eggs without the presence of males.

Host tree species

The adelgid feeds on all true firs (Abies spp.) of which the most susceptible species in B.C. is subalpine fir (A. lasiocarpa).

Damage symptoms

These insects are inconspicuous, aphid-like pests that are approximately 1 mm long on the bark and can be easily overlooked in the early stages of infestation due to their size. However, despite their size, they can damage or kill a tree after several years of heavy feeding. To feed, the adelgids inject their mouthparts into the phloem of the tree causing abnormal cell development which restricts fluid transport in the tree and causes thickening of wood cells and inhibits bud formation.

Symptoms of balsam woolly adelgid infestations include:

• Yellowing and premature needle loss
• Swelling of branch nodes and terminal buds (gouting)
• Top deformation or top kill

Management

While there is no longer a provincial regulation or federal order restricting the movement of Abies in BC or across provincial and international borders (repealed in 2019), we encourage growers and silviculturists to take steps to prevent introductions to their fields and sites.  A basic best management program should include:

• Access Abies seedlings and trees from clean local sources where at all possible, so as not to introduce BWA into a new planting
• Discourage moving Abies trees from one region to another, to limit new introductions as much as possible 
• Cull and destroy any severely infested Abies trees when symptoms are first noticed.  Do not move infested or culled trees during the summer, as this can spread the BWA crawlers to new trees
• Insecticides used for aphid control and other pests may help decrease BWA levels and subsequent damage to the trees
• Contact your grower association, BC Ministry of Agriculture or BC Ministry of Forests Lands and Resource Operations and Rural Development for more information on pest biology and best management practices

Identification images

Balsam woolly adelgid white, woolly tufts that may be visible on the bole of infested fir trees.

Balsam woolly adelgid gouting symptoms on a fir branch.

Balsam woolly adelgid impacted fir tree with a characteristic flattened top and declining health.

Further reading

Read more about the balsam woolly adelgid in the Field Guide to Forest Damage in B.C. (PDF, 6.6MB)