Hemlocks in Peril

The hemlock woolly adelgid (HWA), an invasive insect, poses the single greatest threat to the health, sustainability, and future of Eastern and Carolina hemlocks. In the absence of natural control elements in eastern North America, this introduced insect pest attacks hemlock which are often damaged and killed within a few years of becoming infested. Hemlock is an ecologically important species in many habitats and irreplaceable for its biodiversity value and as an old growth species  

Hemlock with HWA

Hemlocks of Georgia are plagued by hemlock woolly adelgid (HWA)
 – a tiny non-native insect that quickly kills trees once they become infested.
 Healthy trees can succumb to adelgid infestations in less than 5 years.


Hemlocks in Georgia

Hemlock treatments with USFS volunteers at Sosebee Cove April 14, 2012

HWA is now established from northern Georgia to southeastern Maine and as far west as eastern Kentucky and Tennessee.  In a cooperative effort with states, conservation organizations, national forests and other federal agencies, the Forest Service is working to mitigate the impacts of the HWA within the 17 affected states.

HWA first arrived in Georgia in the Chattooga River gorge along the South Carolina - Georgia border in 2002. Within ten years, infestations had been confirmed in 19 Georgia counties, encompassing the entire native hemlock range in Georgia. 

Standing dead hemlocks present a challenge to wildland firefighters. Not only do dead hemlocks exhibit torching fire behavior, but they present a very dangerous situation for firefighters with the hazard of falling snags. While wildfire can create a lot of natural benefits here in the Southern Appalachians, hemlocks are not a very fire adapted species, and natural rhythm fires would have historically burned themselves out when reaching hemlock coves along streams and rivers. That's no longer the case where HWA has devastated hemlock populations.

Rabun County was the first place in Georgia to see the arrival of HWA. More than a decade later, HWA elevates the danger of increased wildfire intensity. This is one more important reason to protect our hemlock populations on the national forest in Georgia.

Hope for Hemlocks

The Forest Service is working with partners and volunteers, including Save Georgia’s Hemlocks, area colleges and universities, and the Georgia Forestry Commission, to monitor and treat hemlocks and release and monitor predator beetles as part of an active maintenance and restoration program.

Hemlock at Tallulah riverOur forest established 144 Hemlock Conservation Areas (HCA) in response to the devastating mortality created by the HWA. We have been successfully treating these HCAs as well as key recreation areas both biologically and chemically for 10 years.  Predator beetles are being released in addition to targeted root injections of insecticide across nearly 1000 acres of national forest lands. Volunteers with Save Georgia's Hemlocks have been working with Forest Service employees in retreating hemlock trees since 2012. The volunteer effort is the first of its kind on a national forest, and has helped us make huge strides in achieving our targets and preserving the species.

Thousands of hemlocks have been lost in Georgia, as research into the establishment and effectiveness of treatment options continues. Currently, insecticides and biocontrol with predator beetles are the tools being used to protect the trees on the national forest. Care is taken to protect streams and waterways when making soil injections of insecticides at the base of infested hemlock trees.

The Forest Service is working with others to investigate alternative treatment methods, such as thinning around hemlocks to increase sunlight that strengthens the trees while fighting the invasive wooly adelgid pest.

Hemlock Conservation Areas

Hemlock Conservation Area map

In 2005, a decision was signed to create designated areas of hemlock stands across the Chattahoochee National Forest that would receive treatment and further efforts to reduce mortality and explore methods of conserving hemlocks from complete loss. Read more about these efforts:

Tallulah River Kids Fishing Rodeo 2011_14

Hemlock in the Foothill Landscape Project

The Foothills Landscape is made up of 143,419 acres where the mountains are visibly reduced. The Foothills project proposes to create, restore and maintain ecosystems that are more resilient to natural disturbances.

The collaborative process leading to the Foothills Landscape Project proposal  identified a need to continue to conserve our hemlock forests, including locating additional areas for hemlock conservation. Early discussions also brought forward the idea for restoring hemlock to areas where hemlock woolly adelgid has caused significant mortality to the previous hemlock canopy. A preliminary analysis indicates that an additional 1,400 acres of hemlock associated forest types are present immediately adjacent to the existing Hemlock Conservation Areas. (map)

The Foothills Landscape Project will plant hemlock seedlings throughout these treated locations to add structural and age diversity where needed. Efforts to control non-native invasive species or vegetative competition will also occur in treatment areas. Finally, sustainable predator beetle populations require insectaries are strategically placed in locations with healthy hemlock trees.

Treatment would include soil injections of imidacloprid or other approved insecticides at the base of infested but responsive hemlock trees in neighboring areas to existing conservation areas or in other areas where hemlock survival is still fairly adequate accessible. Hemlock seedlings would be planted on a wide and variable spacing beneath natural openings in the canopy. Planted seedlings would be treated with soil injection with imidacloprid.

Considering hemlock, the forest is looking to pursue many alternatives to their conservation.  This includes incorporating the work of Southern Research Station (SRS), University of North Georgia (UNG), Georgia Forestry Commission (GFC), and other cooperators or organizations with working backgrounds in Hemlock Conservation.  The forest is working with these organizations to develop design criteria that can be researched, potentially duplicated if successful, and presented/shared with any individuals interested in the conservation of hemlock.

Preliminary discussions have developed multiple options for various treatments.  Potential treatments could include applications of insecticide, day lighting of individual trees, expanding gap, underplanting (translocation of seedlings from within the forest), predator beetles and development of insectaries.  Any combination of these treatments may be used throughout the foothills landscape.

To learn more about the proposal, visit www.tinyurl.com/FoothillsLandscapeCollaborate

Research by the USDA Forest Service - Research and Development

Find below a series of articles and science research about hemlock conservation.

Find even more on the Southern Research Station website.

A Hemlock in the Town Square

by Remi Shaull-Thompson, SRS Science Communications Intern  •  

This summer, I joined USDA Forest Service scientist Andy Whittier for a day of field work as a part of my internship with SRS Public Affairs and Science Communications. We traveled to Green Mountain, NC to check up on an experiment led by research entomologist Bud Mayfield on hemlock trees. Throughout the eastern U.S., the invasive…  MORE 

Conserving Eastern Hemlock

by Sarah Farmer, SRS Science Communications  •  

Where can you go to find an eastern hemlock tree? Although threatened by the hemlock woolly adelgid, eastern hemlock has an extensive range. “Eastern hemlock grows throughout the southern Appalachians,” says U.S. Forest Service collaborator and ecologist Kevin Potter. Potter is also a forestry faculty member at North Carolina State University. “Hemlock grows in the…  MORE 

Carolina Hemlock Populations: Isolated and Imperiled

by Jennifer Moore Myers, SRS Science Communications  •  

Hemlocks are under attack. U.S. Forest Service scientists and their partners are working to save the native conifers from the hemlock woolly adelgid (HWA), an invasive insect from Japan. Carolina hemlock (Tsuga caroliniana) trees can survive HWA infestation for a decade or more but often die within four years. Carolina hemlocks grow in tiny, isolated…  MORE 

Hemlock Seed Banking

by Stephanie Worley Firley, Eastern Threat Center  •  

Eastern and Carolina hemlock trees in more than 400 counties across 19 states are dead, dying, or threatened by infestation of the invasive hemlock woolly adelgid. As the aphid-like pest continues to spread throughout the ranges of these economically and ecologically important trees, scientists, managers, and other specialists from North Carolina State University’s (NCSU) Camcore…  MORE 

Sunlight vs. Hemlock Woolly Adelgids

by Sarah Farmer, SRS Science Communications  •  

Scientists have identified a potential new strategy for protecting hemlocks from the miniscule insect that plagues them. “High levels of sunlight help reduce hemlock woolly adelgid abundance on young seedlings,” says U.S. Forest Service project leader Bud Mayfield. “Follow-up experiments in the field are still needed, but the results suggest thinning or strategically creating gaps…  MORE 

Sap-sucking Bugs Threaten Hemlock Forests

by Adam Voiland, Science Writer, NASA Earth Observatory  •  

Sap-sucking insects called hemlock woolly adelgids are draining the life from a common evergreen tree in the eastern United States. Since arriving from Japan in the 1950s, the tiny bugs have spread from Georgia to Maine—about half of the Eastern hemlock’s range. Once the bugs become well-established, the consequences can be grave. Areas with severe…  MORE 

White Pines, Hemlocks, and Sunlight

by Zoё Hoyle, SRS Science Communications  •  

The Blue Valley Experimental Forest (Blue Valley) lies in southwest North Carolina in the Nantahala National Forest. Located in Macon County, near the point where North Carolina meets Georgia and South Carolina, the experimental forest was established in 1964. At 1,300 acres, it is the smallest of the three experimental forests in North Carolina and the second smallest…  MORE 



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