The Hemlock Wooly Adelgid is an invasive species that has been killing Hemlocks throughout the Eastern US. Hemlocks are long lived trees that can dominate with their height and shade. Their loss can alter forest ecosystems. Efforts to save Hemlocks include aerial sprays that are marginally effective and injecting trees with insecticide, a laborious, time consuming process that must be repeated. A longer term solution would be effective biological control.
Laricobius nigrinus is a specialist feeding on Hemlock adegid species native to the Northwest US. However, Laricobius nigrinus is not adapted to cold winter temperatures. The polar vortex in the winter of 2014 killed both adenoids and Laricobius nigrinus. A related species from Japan that feeds on Hemlock Wooly Adelgid in its native range, Laricobius osakensis has been approved for release in the US by the USDA for control of Hemlock Wooly Adelgid . Unfortunately, propagating these beetles in laboratories has proved difficult, slowed their release and delayed their study under natural conditions. Laricobius osakensis
Biological control solutions that require insect importation require time. The insect must be evaluated to ensure it will not become a pest. Populations require time to increase to potentially effective levels. Even then, it is uncertain how the insect will respond to local environmental conditions. Breeding programs that would select for useful traits in biological control agents in laboratories have been discussed, but would require far more knowledge than we currently posses. Meanwhile we can only hope that one of the naturally occurring predators will be able to stabilize the hemlock population.