Rearing Predators for Suppression of Hemlock Woolly Adelgid

 About the Research Project:
         Project Investigators: James P. Parkman; Director, Lindsay Young Beneficial Insects Laboratory
         Project Funded by: USDA Forest Service
            Project Monetary Funding: $380, 000
Jennifer Chandler making bouquets of hemlock woolly adelgid-infested foliage
used to rear predaceous beetles at the Beneficial Insects Lab.


This project will provide support to the Lindsay Young Beneficial Insects Laboratory (LYBIL) at the University of Tennessee for the mass production of predators of the hemlock woolly adelgid (HWA), Adelges tsugae, to release in Tennessee. From late 2003 to 2011, LYBIL has produced more than 915,000 adults of the predator Sasajiscymnus tsugae, with approximately 745,000 released on federal and state lands in the southern Appalachians. Also, over 161,000 S. tsugae eggs have been released or provided for research. Since late 2004 we have also reared the derodontid beetle Laricobius nigrinus. Almost 36,000 adult L. nigrinus have been produced since then with over 26,000 released on federal and state lands in Tennessee. Since 2009 we also reared, either experimentally or in limited numbers, the predators Scymnus sinuanodulus, S. coniferarum, and Laricobius osakensis. This was the first attempt, anywhere, at mass rearing S. coniferarum.  
The HWA is an introduced, invasive species that causes damage to both eastern (Tsuga canadensis) and Carolina (T. caroliniana) hemlocks in both natural and ornamental settings. Other hemlock species such as the western and those in Asia are not seriously affected by the pest. Hemlock forests play major roles in the stability of ecosystems in the southeastern United States, and are a major component of the Great Smoky Mountains National Park (GRSM). Living as long as 500 years, these trees serve to stabilize the soil throughout their range, provide dense shade that lowers water temperatures in streams as much as six to eight degrees Fahrenheit, and serve as cover and forage for many species of birds and wildlife. Hemlocks are among the few truly irreplaceable parts of their ecosyjdee harvesting.jpgstem and people respond to the stately trees with feelings of tranquility and awe. A minor pest of Asian hemlock species, HWA has been in the eastern U.S. (Virginia) since at least 1951. The adelgid is a relative of scale insects. It preferentially feeds on storage cells in young, soft tissue near the ends of branches and twigs. A heavy infestation of only two or three years' duration can cause irreversible damage, and, in the southeastern U.S., trees may die within four years of the original infestation. The insect-plant interactions that result in serious damage on eastern hemlocks, as opposed to innocuous infestations on Asian and western U.S. species, are not understood. The adelgid has been recognized as a serious pest since 1985, when it first caused major damage in Connecticut. Its range has grown steadily until today it is found in at least one-third of the range of hemlock in the eastern U.S. The mid-Atlantic states have been particularly devastated. Hemlocks are found in much of the forested eastern half of Tennessee. Adelgid populations were first identified on federal land within state boundaries in 2002. Although individual trees in ornamental settings or close to roadways can be treated with pesticides on a regular basis, long-term and environmentally sound solutions currently revolve around biological control.                                                                                                    Jim Dee harvesting newly-emerged Sasajiscymnus tsugae beetles at the Beneficial Insects Lab.
Predatory beetles that attack only HWA and a few closely related pest species (e.g., balsam woolly adelgid) are
the major management tool for combating HWA in most of the hemlock stands in the eastern U.S. Currently, four laboratories are producing beetles for release specifically in the southern range of hemlock. These facilities are the laboratories at Clemson University and the University of Georgia, the North Carolina Department of Agriculture lab at Cary, North Carolina, and the LYBIL at the University of Tennessee, Knoxville. Beetle production, of necessity, must be a regional operation since production is dependent on a high-quality supply of adelgids for food. The beetles require living prey for egg production and development; therefore, periodic (weekly or biweekly) collection of massive quantities of infested branches is a necessity. Fortunately, the Tennessee laboratory is ideally situated for mass rearing of these beneficial predators, since the laboratory is within practical driving distance of many of the current and projected HWA foci in Eastern Tennessee.
The current funding is to support labor and supplies for the continued production of S. tsugae, L. nigrinus, and renewed rearing of S. coniferarum and L. osankensis at the University of Tennessee's Lindsay Young Beneficial Insects Laboratory and travel (to collect adelgids for rearing and to HWA-related conferences). The initial goal of this facility is to produce sufficient quantities of for management of HWA on Federal lands in the southern Appalachian region or at other sites as designated by the U.S. Forest Service. Research and monitoring efforts funded by the Forest Service in the Northeast have demonstrated that S. tsugae can reduce HWA populations by 47-87%. This beetle and others thus must be considered a worthwhile investment for the protection of eastern and Carolina hemlocks.

Publications based on Research:

Parkman, J.P. Evaluation of rearing techniques for predators of hemlock woolly adelgid. 2011. pp. 177-179 in Proc. 5th Hemlock Woolly Adelgid Symposium.
Photos and information provided from James P. Parkman (UTK-EPP)


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