Adelges cooleyi

Cooley spruce gall adelgid gall. Photo: Pennsylvania Department of Conservation and Natural Resources, Bugwood.
Scientific Name: 
Adelges cooleyi
Common Name: 
Cooley Spruce Gall Adelgid
Growing Degree Days (GDD's): 
Spruce: 22–81 GDD's (Mid-late April), 1850–1950 GDD's (Mid-September); Douglas-fir:120-190 GDD's (early-May) and again at 1500-1775 GDD's (late July to early August); Base 50F, March 1st Start Date. (Source: Cornell Cooperative Extension)
Host Plant(s) Common Name (Scientific Name): 
Colorado blue spruce (Picea pungens) *Gall formed.
Douglas-fir (Pseudotsuga menziesii) *Causes needle injury.
Engelmann spruce (Picea engelmannii) *Gall formed.
Oriental spruce (Picea orientalis) *Gall formed.
Sitka spruce (Picea sitchensis) *Gall formed.
Insect Description: 

The life cycle of the Cooley spruce gall adelgid is incredibly complex. It requires a period of two years and two different hosts to complete. Normally, the Cooley spruce gall adelgid overwinters as an immature female on spruce near the twig terminals. The female will mature in the early spring into a stem mother and will lay hundreds of eggs on lateral terminals. These eggs hatch on spruce and nymphs migrate to the new growth where their feeding induces the development of a pineapple-like gall on the spruce host. These galls can be up to 2.5 inches in length and will be found at the very tips of the twigs (no growth beyond the gall). By mid-summer, the gall becomes woody and will crack open, allowing the newest generation of adelgids to migrate to the tips of the needles where they form wings and disperse to Douglas-fir or another spruce host. On Douglas-fir, the adelgids will lay eggs on the needles which hatch into a woolly adelgid whose feeding can lead to distorted, bent, and yellowing needles - but no gall is formed by this insect on Douglas-fir. Two or more generations of these adelgids can occur per year on Douglas-fir. This insect can reproduce through parthenogenesis.

Damage to Host: 

This pest makes galls on spruce and can cause twig die-back. The galls on spruce will be pineapple shaped and found at the tip of the shoot (no growth beyond the gall). On Douglas fir, it not only produces woolly masses but can cause distorted foliage (crooked needles).

Monitoring: 

Look for green galls on spruce in the spring and wool-covered adelgids on Douglas-fir needles in the spring and late summer. Douglas-fir needles may appear bent or distorted with yellowish spots due to feeding. 

Cultural Management: 

Do not plant both hosts (spruces and Douglas-fir) close together. Some trees are resistant to adelgids. (Ex. the green forms of Colorado blue spruce are more susceptible to galls from this insect than the blue forms (Davidson and Raupp, 2014).) On smaller spruce where galls can be reached, prune out the galls and bury or otherwise destroy them prior to July. Do not fertilize either host plant if it is infested with this insect, as fertilizers may help increase adelgid populations on individual trees.

Natural Enemies & Biological Control: 

This insect has no effective parasites.

Chemical Management: 

Abamectin (NL)

Acephate (NL)

Acetamiprid (L)

Bifenthrin (NL)

Carbaryl (L)

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: 

Oil sprays may temporarily discolor Colorado blue spruce. Consult label instructions concerning oil on Douglas-fir and blue spruce. Imidacloprid soil application late fall or early spring. Manage overwintering nymphs in early spring prior to gall formation on spruce.

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 .