Integrating chemical and biological control of the hemlock woolly adelgid: a resource manager’s guide
A non-native invasive insect, the hemlock woolly adelgid (HWA), threatens the ability of natural resource managers to maintain eastern and Carolina hemlocks as critical components of unique forest ecosystems in eastern North America. Although substantial progress has been made in both chemical and biological control of HWA, neither of these tactics applied alone are expected to provide adequate control of HWA throughout its introduced range. This guide presents a methodological strategy for integrating biological and chemical control together in the same forest stands. The goal of the strategy is to prolong hemlock health on certain hemlock trees through temporary insecticide protection, while simultaneously establishing predators on nearby untreated trees. Temporarily-protected hemlocks are expected to eventually support predators after their chemical treatment wears off. Guidelines for site selection, treatment timing, spatial considerations, monitoring, and assessment are included. The guide is intended as a starting point for a more sustainable approach to HWA management that reduces the amount of insecticide applied, and that can be integrated with additional management tools as they are developed.