The hemlock woolly adelgid is a small, sap-sucking insect that primarily affects hemlock trees. Native to Asia, it was first discovered in the United States in the 1950s. The adelgid feeds on the tree's sap, weakening it and potentially leading to its death. These pests are identifiable by the white, woolly masses they produce on the underside of tree branches. Infestations can spread rapidly, posing a significant threat to hemlock populations, which are vital to forest ecosystems. Efforts to manage and control the adelgid include biological control and chemical treatments.