Relationship between total and amino nitrogen in HWA (Adelges tsugae) and the health of its host tree

Nitrogen content between phytophagous insects and their host plants can determine the insect’s success. The hemlock woolly adelgid (HWA) is a small invasive insect that settles at the base of hemlock needles (Tsugae spp.). While infested eastern hemlock (T. canadensis Carriere) can die within as little as four years, many hemlocks survive for ten years or more in poor health. Healthy trees that become infested by the adelgid are depleted of nutrients, leading to a reduction of the adelgid population. It has been observed that hemlocks will make a partial health recovery, only to undergo re-colonization of the adelgid the following season. Since the adelgid is dependent on hemlock for nutrients, feeding on trees in poor health may affect the insect’s ability to obtain necessary nutrients. We examine the adelgid’s physiological state based on comparisons of total and amino nitrogen content in relation to the relative health of their host.