Cooley Spruce Gall
Cooley spruce gall adelgid, Adelges cooleyi, commonly causes abnormal growths called galls and distortion to the new needles of Colorado spruce and Douglas fir trees. Galls appear as small pineapple shaped growths early in the season. They brown out in the summer and can be confused with seed cones. The galls rarely cause serious harm and can be covered by new growth the following season.
Trees at Risk
Colorado spruce, Douglas fir, and many other spruce species are susceptible.
Signs of Damage
- On spruces, pineapple-like formations (galls) are present on the tips of new growth. Galls turn brown during the summer months.
- Galls are not formed on Douglas fir, but needles may become discolored, distorted, and prematurely drop from the tree.
- Similar to aphids in appearance.
- Both winged and wingless adult females are approximately 1 mm long and dark brown to black.
- Adults on Douglas fir secrete white strands of wax that cover their bodies.
Cooley spruce gall’s life cycle is fairly complex, as it involves multiple biological forms. Three of these biological forms take place on spruce and two on Douglas fir. The complete life cycle through all five of these forms takes at least two years to complete. The pest’s life cycle can be completed on Douglas fir alone, but the forms that take place on spruce have to find Douglas fir as the second host to complete the entire life cycle.
- Females feed in the spring and lay several hundred eggs.
- Eggs hatch in 10-14 days.
- Young nymphs move to new growth to feed at the base of the needles.
- Feeding causes distorted gall formations that soon surround the young nymphs.
- Galls dry out and brown by mid-summer.
- Adelgids emerge from galls and move to Douglas fir or stay on the spruce.
- Immature females overwinter at the base of terminal buds.
On Douglas fir:
- Females that have migrated from spruce lay eggs on needles.
- The following spring, winged females are produced and they return to the spruce to start the life cycle over again.
- Wingless females stay on the Douglas fir and reproduce.
Cooley spruce gall adelgid can be tough to manage. Once the galls begin to form, contact insecticides usually are ineffective because the insects are protected within galls. Galls can be pruned-out by hand in small trees. If galls are seen during the season, systemic soil application of Xytect™ should be made in late summer/fall because of the early spring activity of adults the following year. Apply Transtect™ in early spring to spruce.