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The Pest and the Problem. The hemlock woolly adelgid (HWA), Adelges tsugae, is an invasive species causing widespread mortality of eastern and Carolina hemlocks in the eastern United States. This tiny pest, distantly related to aphids, was first discovered in the eastern U.S. in Richmond, Virginia in 1951 and is believed to have been accidentally imported on exotic ornamental hemlocks. Extensive damage to hemlocks in a forest setting, however, was not reported until the 1980s in the northeastern U.S. including New England. The pest now occurs in 18 states from Maine south to Georgia and South Carolina. It was first discovered in Tennessee in 2002.
In the southern Appalachians trees are irreparably damaged in as little as four years after initial infestation. Other stress factors such as drought only exacerbate the problem. Unlike a similar introduced species, the balsam woolly adelgid that attacks and kills only mature fir trees, HWA kills eastern and Carolina hemlocks of all age classes. Greater than 90% of hemlocks in the Shenandoah National Park in Virginia have succumbed to the pest; and mortality of hemlocks in areas south may approach this level.
Hemlocks provide critical habitat for many forest species. They also moderate temperatures locally such as in streams where trout and other aquatic organisms require specific conditions to survive. Because of these and other unique properties, the loss of hemlocks would be devastating to forest ecosystems.
Although chemical treatments provide control, treating trees over vast areas, such as in forests, is not feasible. Presently, biological control using predatory beetles is recognized as the only viable option for suppressing HWA populations on a large scale. Biocontrol also has the potential to permanently reduce HWA numbers. Several beetle species have been identified as HWA predators, but only a few are mass-reared for release. The Lindsay Young Beneficial Insects Laboratory (LYBIL), part of the Department of Entomology and Plant Pathology at the University of Tennessee-Knoxville, rears these predators for release on public lands in Tennessee. Of these, the two reared and released in the greatest numbers are the coccinellid Sasajiscymnus tsugae and the derodontid Laricobius nigrinus.
History of the Beneficial Insects Lab. After HWA was discovered in the Great Smoky Mountains National Park (GRSM) in 2002, the U.S. Forest Service (USFS) and National Park Service (NPS) approached the University of Tennessee Entomology and Plant Pathology Department (EPP) about cooperation in a management plan for HWA in which EPP would develop a biocontrol facility for production of predatory beetles. Initial funding from Friends of the Smokies and USFS enabled the Tennessee Agricultural Experiment Station to designate temporary lab space to begin beetle production. Laboratory personnel were hired and the necessary equipment was purchased or built. Lab personnel visited the Philip Alampi Beneficial Insects Laboratory in Trenton, New Jersey for training in production of the coccinellid beetle Sasajiscymnus tsugae.
The beetle-rearing laboratory became operational in fall 2003. Sasajiscymnus tsugae, obtained from the New Jersey lab, was used as the starter colony for the Tennessee lab which produced more than 25,000 beetles the first season (January-June, 2004). These beetles were released primarily in GRSM, with one release in Martha Sundquist State Forest. The Friends of the Smokies, NPS, USFS, and the State of Tennessee all provided funds that enabled the laboratory to plan for at least three additional years of operation. In the second season (November 2004-June 2005), the lab produced nearly 100,000 S. tsugae. Nearly all of these beetles were released into GRSM with one release made in Cherokee National Forest.
During the second season of operation, the UT lab began pilot production of Laricobius nigrinus, a second predator beetle of the adelgid which has a different rearing regimen than that for S. tsugae. The Tennessee Agricultural Experiment Station provided the necessary growth chambers and cold rooms for rearing L. nigrinus.
In spring of 2005, the University of Tennessee used funding from the Aslan Foundation, Friends of the Smokies, the State of Tennessee, and the USFS to begin renovation of buildings on University property that allowed for greatly increased production of biocontrol agents. This building complex was officially dedicated the Lindsay Young Beneficial Insects Laboratory (LYBIL), in honor of the founder of the Aslan Foundation. The first two buildings renovated for permanent occupancy by LYBIL were fully operational in October 2005. A third facility to house walk-in growth chambers and storage space was completed in summer 2006. The chambers provide precise temperature control that will lengthen the production seasons for both beetles, and allow for more controlled experimentation.
Dr. Ernie Bernard, professor in EPP, oversaw the development of the lab that was to become LYBIL with able assistance from the Lab's first manager Veronica Gibson. Dr. Pat Parkman, hired as the full time director of LYBIL in November 2006, currently (summer 2010) supervises three full-time technicians.
- Thanks to Ernie Bernard who wrote most of this history.