Cooley Spruce Galls Description

The Cooley spruce gall adelgid is a species that produces galls in the spruce trees. The Cooley spruce gall interferes with the growth of the spruce, which is why it is said to have an abnormal growth or ‘gall’. Plus, it appears to have the shape of a cone and is light brown in color, after weathering.
However, the Adelges cooleyi, which is also known as Gillete, is the most common host of the Cooley spruce gall adelgid. The galls are basically found in huge numbers on the northern and the eastern sides of the trees. The significant incidence of galling has been increasing abundantly over the past few years, and most of them are on the Front Range.

Cooley Spruce Galls Description & Life Cycle:

This unusual species has a complicated life cycle, which is ultimately alternative between the two plants; i.e. Douglas-fir and spruce. The five biological forms of this insect occur on each side of these plants, as three of the insects occur on the spruce and the other two occur on Douglas-fir. The species require at least two years for performing the complete five forms on both of the host plants. On the other hand, the insect is said to be a type of ‘woolly aphid’, as it covers itself with the waxy threads.
During the winter season or during the early spring season, it is found on the underside of the twigs, within a few inches of the buds of the spruce. It does not arise on the outer side of the spruce due to the weather but in the mid-spring season, in late April and May, it feeds itself hastily and swells. In addition to that, the young aphids move towards the emerging needles to feed themselves, and thus, to do that, they have to suck a bit of the spa in order to inject substances in their saliva. The saliva ultimately induces the new procedure of growth of the insect, as it swells and overgrows them.
However, they are protected by the plant, which allows them to grow inside the cells of the gall. During the late spring season, when it starts emerging outside, the female then produces a large mass of eggs that hatch in synchrony with the bud break. The eggs hatch within 10 to 14 days into young nymphs. Eventually, the Cooley spruce galls emerge from the needles by crawling its way outside. Later on, it transforms itself into a winged state in order to leave the tree on a permanent basis. The feeding of the insect causes an irregular plant cell development.
Throughout their life stages, they stay inside the chambers of the gall tissue, mostly throughout the summer season. Around the mid-summer season, the galls dry out and appear from the opened chambers in order to shift to Douglas-fir or to stay on the spruce.