Adelges piceae

Gouting caused by balsam woolly adelgid. Photo: Robert L. Anderson, USDA Forest Service, Bugwood.org.
Scientific Name: 
Adelges piceae
Common Name: 
Balsam Woolly Adelgid
Growing Degree Days (GDD's): 
Not available at this time.
Host Plant(s) Common Name (Scientific Name): 
Balsam fir (Abies balsamea) *Also seriously affected fir host.
Fir (Abies spp.)
Fraser fir (Abies fraseri) *Most seriously affected fir host; death can occur.
Subalpine fir (Abies lasiocarpa)
Insect Description: 

This non-native, aphid-like insect was introduced into the United States around 1900. In the USA, the entire population consists of females. Adults are less than 0.04 inch long and are purple-black in color if the white-woolly material they surround themselves with is removed. These insects are wingless and legs can only be seen with magnification. The crawler or immature stage is the only mobile form of this insect as the adults are attached to the host by their mouthparts for their entire lifespan. Crawlers move actively to disperse, or may be blown to new hosts by the wind (and are thought to be carried large distances by the wind). Once a host has been located, the immature insect will insert a long, piercing-sucking mouthpart to feed. It will secrete a white, waxy wool which eventually covers the insect. Eggs are attached to the bark behind the body of the female. Approximately 2 generations occur in NE, but 2-4 per year are possible in warmer regions.

Damage to Host: 

Creates woolly masses along twigs as well as gouting (swelling) of twig ends. Can greatly weaken, disfigure, and even kill the host plant. Usually found on mature trees first, then moves to younger trees. In heavy infestations, the entire trunk of the host may be covered in the white waxy material created by this insect. Heavily infested firs may be unable to create new growth. Balsam and subalpine firs are considered more susceptible to this insect, and may be killed by it before the terminal twig swell (or show signs of gouting). This insect can be a serious pest on both forest and landscape trees, and has killed millions of feet of fir timber in North America.

Monitoring: 

Scout susceptible hosts monthly from spring to fall for white, cottony masses on the bark of twigs, larger branches, and the main trunk. Focus on large, older trees in the landscape first, as they may be the first to be attacked. Manage before symptoms are apparent. Additional signs and symptoms of this insect include: a flat top to the tree or weak, slanted terminal, swollen (gouted) twigs losing needles, dead shoots/branches, wilted shoots, or the white woolly material produced by the insects themselves. 

Cultural Management: 

Remove heavily infested plants. Silver fir (Abies alba; European silver fir) is considered to be relatively resistant to this insect. Douglas-fir (Pseudotsuga menziesii; not a true fir) is not a host for this insect. Minimal damage is done to Abies procera, the noble fir (Johnson and Lyon, 1991). Consider planting non-hosts or resistant species in areas where this insect is known to be a problem. Do not transport wild trees from infested areas. 

Natural Enemies & Biological Control: 

Natural enemies may not always provide enough control to keep this insect below damaging levels. Native and imported predators, such as lady beetles and certain flies, including the larvae of syrphid flies, can be important. The lady beetle Aphidecta obliterata and an aphid fly (Leucopis obscura) are thought to be important in the natural management of this insect (Johnson and Lyon, 1991). 

Chemical Management: 

Abamectin (NL)

Acephate (NL)

Acetamiprid (L)

Bifenthrin (NL)

Chlorpyrifos (N)

Chromobacterium subtsugae (NL)

Clothianidin (NL)

Cyantraniliprole (NL)

Dinotefuran (NL)

Flonicamid+cyclaniliprole (N)

Horticultural oil (L)

Imidacloprid (L)

Insecticidal soap (NL)

Pyrethrin+sulfur (NL)

Tau-Fluvalinate (NL)

Notes: 

Sprays should be timed with budbreak and thorough coverage is, as always, important. 2-3 additional applications of contact insecticides at weekly intervals may be needed in the summer months, according to label instructions. Christmas tree growers in areas where this insect is a significant problem may need to consider growing non-hosts.

Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), acetamiprid (injection), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), and imidacloprid (soil drench).

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022 neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program. 

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: January 2024. To check current product registrations in Massachusetts, please visit: https://www.mass.gov/pesticide-product-registration .