Balsam woolly adelgid
Balsam woolly adelgids (Adelges piceae) are small wingless insects that infest and kill firs. In their native Europe they are a minor parasite on silver fir and sicilian fir, but they have become a threat especially to balsam fir and Fraser fir after they were introduced to the United States around 1900. Because this species is not native to the United States, the Fraser fir has not evolved any type of defense against it. Reproduction These insects typically lay about one hundred eggs and have three generations per year. The adelgid attacks the tree by feeding in fissures within the bark of trees larger than about four centimeters in diameter at breast height. As it feeds, it releases toxins contained within its saliva. These toxins reduce the conductance of sapwood being built, which causes water stress and kills the trees. Impact The Great Smoky Mountains National Park, straddling North Carolina and Tennessee in the Southeastern United States, contains about 75% of all southern spruce-fir ecosystems. These ecosystems covered vast portions of the Southeast during the last ice age, when the climate was cool and moist. Since the retreat of the glaciers, this ecosystem has been confined to the higher elevations