EASTERN SPRUCE GALL ADELGID ( Adelges abietis )
The Eastern spruce gall adelgid, mainly attacks white and Norway spruce and causes the formation of unattractive galls to develop on the shoots. In the spring, the overwintering females may be found on the underside of the shoots, usually tucked right in next to a bud. In the spring these stem mothers, which appear as tiny black specks, each one smaller than the head of a pin, begin to feed, grow, produce cottony wax, and eventually lay up to 100 eggs beneath that wax. When the eggs are close to hatching and budbreak is just beginning, these females initiate gall formation. Then, as the eggs hatch, the young nymphs can crawl right in to the tiny chambers of the gall as they are forming, and are enclosed witin them. The gall which forms is small, usually no more than an inch long, and the shoot continues to grow so that the gall is left behind at the base of the shoot. This makes the gall particularly destructive, because the entire shoot must be removed in order to remove the gall.
When using an insecticide to control these insects, begin scouting in late March to early April. The adelgids will usually become active before the trees begin to show evidence of breaking dormancy, so it is important to scout early. As soon as you see the adelgids begin to enlarge, it is time to spray. If you wait too long, they will be covered with cottony wax, and the spray may not be able to penetrate that and reach the insects. A dormant treatment may be more successful, although success here depends upon many factors such as: what chemical is used, how it is applied, what type of equipment it is applied with, how large is the population, and even, will the weather cooperate so you can get out into the field? Spring or fall dormant treatments should work equally well if adequate coverage is obtained.
Fig. 1. New galls of the Eastern spruce gall adelgid on white spruce
Fig. 2. Part of this gall, caused by the Eastern spruce gall adelgid, has been cut away to show the tiny adelgids living within the chambers.
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