Integrating chemical and biological control
Research and management efforts to establish an effective biological control program against HWA has received significant support by the U.S. Forest Service over the past 17 years. Other federal and state agencies, universities, and private entities have also contributed to this overall research and management effort. Although a number of HWA-specific predator species from Asia and western North America have been studied in quarantine, mass reared, and released, the work discussed here will focus on Laricobius nigrinus (Coleoptera: Derodontidae). This predator, from western North American hemlock forests, has become established throughout the mid-Atlantic region (Mausel et al. 2010). Also current studies by G. Davis (Ph.D student at Virginia Tech) show that the beetle does not disperse very far the year they are released and only about 300 m 5 years after release. Long-term impact studies of the predator are ongoing, but it is apparent that at many of the release locations where L. nigrinus has established, older mature trees have succumbed to HWA. The younger, more vigorous understory trees do not decline as quickly, and appear to sustain growing populations of L. nigrinus.