Important dosage information when treating for hemlock woolly adelgid.

Hemlock trees in eastern forests are late successional tree species that provide shade for the forest understory. Globally, there are ten hemlock species, with populations located in Asia and eastern and western North America12. Eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) grow in the eastern U.S. These trees have great ecological and cultural value in forests. However, the invasive hemlock woolly adelgid (Adelges tsugae or HWA) is decimating hemlock populations throughout much of the trees’ native range, altering landscapes, and threatening these iconic tree species in both rural and urban areas.

Managing hemlock woolly adelgid (HWA) can involve use of insecticides. When it does, the non-target impacts (negative effects to other organisms) need to be thoroughly considered
and weighed against the environmental cost of inaction or alternative management approaches. Insecticides applied for HWA management are used for conservation purposes, which may seem counterintuitive. However, hemlocks are a key forest species, and so their loss can result in severe ecological consequences. To justify insecticide use against HWA, we have to ask: What are the possible negative consequences of using insecticides in the forest? We must consider these trade-offs in hemlock management. It is important to remember that there will be trade-offs in any kind of resource management discussion, even if it may not initially seem apparent. The negative environmental consequences of hemlock mortality must be weighed against the known consequences of insecticide use to preserve hemlocks.