Adelgids are soft-bodied insects which feed by sucking plant juices. They are so small they are not readily seen. The nymphs of this species cause long curved persistent galls to form on the new shoot tip of blue spruce. These attacks may kill shoots and deform the tree.

If given the opportunity, the nymphs will spend a portion of their life cycle on Douglas fir. On Douglas fir, nymph feeding discolors and distorts needles, but does not produce galls

Hosts: Colorado blue spruce and Douglas fir.

Look For (on spruce):
* Galls - conelike, green, purple or brown swellings, 2 - 2 ‡ inches long on the tips of new shoots. Galls turn brown in August.

Look For (on Douglas fir):
* Small cottony balls dotting the undersides of needles.
* Yellow spots on bent or curled needles, caused by nymph feeding

Biology: On spruce, young females lay eggs in the spring under a mass of white, cottony wax near the terminal (end) bud. Nymphs hatch and feed at the needle bases of expanding buds, producing galls that enclose and protect them. After galls dry up in midsummer, the exposed nymphs will either continue their life cycles on blue spruce or fly to Douglas fir to lay eggs. Feeding on Douglas fir does not cause galls to form. The nymphs overwinter, and the next spring the winged forms may fly back to spruce, where they reproduce gall-forming adelgids and thus complete the life cycle on 1 or 2 hosts; however, injury tends to be more serious when they move between two hosts.

Monitoring & Control:
On blue spruce: Look for brown galls on trees of all ages in August.
* Clip and destroy scattered green galls before they open in July. Removing brown galls will improve the tree aesthetically, but will have no impact on controlling the insect.
* If needed, treat trees with a registered insecticide (Sevin 4 SL, XLR Plus, or 4F). Apply it in the spring as the buds are swelling, but before the bud cap breaks loose. Treat again in early fall if necessary.

On Douglas fir: Look for small cottony balls on the undersides of needles
* To control overwintering aphids, apply a registered insecticide to trees in early October or just before Douglas fir buds open in April or early May. Spray trees when the temperature is above 60 degrees F.
* An application in late June to mid July may be needed to control later stages.
* Or, apply dormant oil in early spring or late fall when the trees are dormant.

Do not plant Colorado blue spruce and Douglas fir in close approximation of each other!

Source: USDA Forest Service, Christmas Tree Pest Manual, 1998

McCullough, Deb and Ellis, Tom, Control & Management of Christmas Tree Insect Pests in Michigan 1995, Michigan State University Extension

more info: http://ohioline.osu.edu/hyg-fact/2000/2552.html