Today's forests are under a continuous compound of physical stresses. In North America examples of this are evident in all regions, whether it be the subjection of Great Lakes woodland's to acid precipitation, the submission of hundreds of thousands of forested acres out west to fire of the catastrophic level, or annual gypsy moth defoliation of entire mountain sides in north central Pennsylvania. These dangers are out there and they are only a handful of the prospective damaging agents that exist in forested areas.
The focus of this term paper will be on the nature and characteristics of an insect that inhabits a coniferous species of North America. Adelges piceae, commonly known as the balsam woolly adelgid/aphid, exists by means of a parasitic relationship with specific trees native to the United States and Canada. The insect is a damaging factor that must be dealt with before it claims victims our coniferous forests and ecosystems can't live without.
Adelgis piceae was accidentally introduced to North America from Europe and has become an important pest of true firs (Abies sp.). The range of the adelgid includes all of the Maritime Provinces, New England, down through the Appalachians, and is found throughout the Pacific Northwest. Currently it devastates stands of subalpine fir (Abies lasiocarpa) and severely affects growth of silver fir (Abies amabilis) in many areas. This insect is now an urban pest of ornamental firs and a major Christmas-tree plantation problem, especially with Fraser fir (Abies fraseri) growing in the Appalachians (Edmonds, 2000). Presumably it is capable of spreading over much of the range of its host. Although, the aphid generally does not survive temperatures below -34 degrees C, but may persist at lower temperatures on the lower parts of tree boles protected by snow (Harris, 1978).
A summarized life history of Adelgis piceae would read as follows. The immature adelgid (nymph) over-winters on the bark of trees. Depending on climatic conditions, the nymph will come out of hibernation in late April to early May. By July the nymph reaches adulthood and begins laying eggs. Females, there are no males, may lay over 200 eggs throughout a six week period (Harris, 78). The adelgid that hatches is called a crawler and represents the only mobile stage of the insect's life. The dark purple to black nymph is very small and is blown about the wind as it moves around on the tree. This is how the insect spreads to other trees.
While in the crawler stage, the nymph searches for a desirable location to settle down and feed. When a favorable location is found, the adelgid attaches itself to the tree by inserting its long mouthparts into the living bark. Once it is attached and begins feeding, it becomes sedentary and starts secreting the white waxy material that covers it's body.
In late September and early October the second generation matures and begins laying eggs. It is the nymphs that hatch from these...