Fitness and fecundity of hemlock woolly adelgid in relation to the health of the eastern hemlock

The hemlock woolly adelgid is a small invasive insect (1.3-1.5 mm long) 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 A. tsugae is dependent on hemlock for nutrients, feeding on trees in poor health may affect the insect’s ability to obtain necessary nutrients. We predict that adelgid fitness and physiological state can be correlated with the health of their host. A. tsugae are being studied on both heavily and lightly impacted hemlock trees. A preliminary report of these data will be presented.