Biological Controls

 The Challenge        The Hope        Advice        How to Help on Public Lands        Supporting the Beetle Labs        Publications  

Biological controls are the third part of the three-pronged attack for fighting the hemlock woolly adelgid, along with cultural and chemical controls.  Biological controls refer to beneficial living organisms that can kill, disable, or otherwise hinder harmful living organisms.  In the case of hemlocks, the biological controls currently receiving the most attention are other insects -- several species of predatory beetles -- that prey specifically and solely on adelgids.  Three research labs in the southeast, in partnership with the U. S. Forest Service, are rearing these beetles for release on public lands in Georgia with the hope that a predator-prey balance can be established to control adelgid populations to such a degree that the hemlocks can survive and even thrive again.

A promising biological control is joining the frontlines of the fight against hemlock woolly adelgid. Two species of silver flies native to the pacific northwest — Leucotaraxis piniperda and Leucotaraxis argenticollis — are showing promise as an HWA predator during research efforts conducted through state and university partnerships with the U. S. Forest Service.   Please see the article below.

The Challenge The valiant efforts of researchers face serious challenges.  Because of the adelgids' incredibly prolific reproductive rate, many beetles are needed, yet supplies are extremely limited.  Rearing beetles in a laboratory or field setting is scientifically demanding, labor-intensive, and very expensive.  The picture is further complicated by the fact that, as most experts agree, the biological solution involves developing a complex of predators rather than relying on a single species, a process that requires careful work, much testing, and time.  And as time marches on, hemlocks continue to decline.

The Hope

But there is also cause for hope.  The U.S. Forest Service has designated 144 Hemlock Conservation Areas in the Chattahoochee-Oconee National Forest in Georgia for treatment with biological or chemical controls or both (separated by a buffer of space and/or time).  About 800,000 beetles have been released in the designated insect areas so far, and researchers have recently documented solid evidence of beetle survival and reproduction in the wild.  The chemicals being used to treat hemlocks in the designated insecticide areas are proving to be quite effective, and while it is recognized that chemicals are a "band aid," they are working very well and buying valuable time in which long-term, natural solutions can be developed.  Click here for a map of the Hemlock Conservation Areas in Georgia, some explanatory information on how the priorities were established, and a chart indicating the location name, treatment method(s), and number of acres for each area.

Advice

So what does all this mean for private property owners who want to help their hemlocks?  For now, property owners should continue to treat their trees with a combination of cultural and chemical controls; these are the best solutions from the standpoint of both cost and effectiveness.  Beetles are not yet an advisable option for private property because of the as-yet unproven performance of the single-species approach, the unavailability of the multi-species complex, and the extreme expense.

How to Help on Public Lands

Treating Hemlocks on Public Lands -- Save Georgia’s Hemlocks and the U. S. Forest Service have established an agreement under which SGH Facilitators and other volunteers can chemically treat hemlocks in designated Hemlock Conservation Areas (HCAs) of the Chattahoochee-Oconee National Forest.  We have a similar agreement with the Georgia Department of Natural Resources to treat hemlocks in wildlife management areas and state parks on a project-by-project basis.  Anyone interested in treating hemlocks on a public lands project may call the Hemlock Help Line 706-429-8010.

Helping Hemlocks in Other Ways -- If you would like to help the hemlocks on public lands in Georgia in ways other than actually treating trees, you can volunteer with the U. S. Forest Service, the GA Forestry Commission, the Georgia Department of Natural Resources, or any of the Friends of the Parks organizations in Georgia.  Then, when volunteer opportunities arise, they can contact you to see if you’re available to help.  The nature of the activities will vary widely but might include measuring and tagging trees that will be or are being treated or monitoring sites that have been treated with beetles or chemicals.

Supporting the Beetle Labs

Please consider making a donation to support the beetle labs.  Sources of funding that are independent of large granting agencies are vitally important to continue the struggle to save the hemlocks here in the Southern Appalachians.  You can send a donation directly to any of the labs in the Southern Consortium that rear beetles for release in Georgia listed below.  Make your check payable to the particular beetle lab you want to support and mark it "For Hemlock-HWA Project." 

The labs are also in need of volunteers to help gather infested hemlock branches that the beetles feed on, perform other tasks in the lab, monitor beetle release sites, and possibly participate in beetle releases.  If you'd like to volunteer, please contact the lab manager.

Research labs rearing beetles for release in Georgia are:

Other beetle-rearing research labs in the south include the University of Tennessee at Knoxville, State of North Carolina Agriculture Department, and Virginia Tech.  In the northeast, there are beetle-rearing research labs in New Jersey, Connecticut, and Massachusetts.

Publications Addressing Biological Controls

•   Silver Flies for Control of HWA -- NEW  Article prepared by Brianna Ross, 2023

•   Environmental Assessment 2005: Conservation of the Eastern Hemlock by Suppression of Hemlock Woolly Adelgid Infestations in the Chattahoochee-Oconee National Forests

•   Environmental Assessment for 2010 Suppression of Hemlock Woolly Adelgid Infestations in the Pisgah National Forest and the Nantahala National Forest

•   Developing Hemlocks Resistant to HWA -- PowerPoint presentation prepared by K. L. F. Oten, L. N. Walker-Lane, R. M. Jetton, N. Kaur, B. Smith, J. Frampton, A. C. Cohen and F. P. Hain to provide an update on the progress made to develop a HWA-resistant hybrid hemlocks. 2011.  See "Development of Resistant Hybrid Hemlocks" from 2010 and "New Hemlock Hybrid Withstands Killing Insect" from 2020.

•    Development of Resistant Hybrid Hemlocks -- Research summary by Michael Montgomery, Susan Bentz, and Richard Olsen, July 2010

•   Fungi Associated with HWA and Assessment of Entomopathogenic Isolates for Management -- This research paper by W.R. Reid, B.L. Parkerb, S.Y. Gouli, M. Skinner, V.V. Gouli, and H.B. Teillon, describes research on fungal pathogens associated with the hemlock woolly adelgid and their ability to cause mortality in low-density populations of aestivating sistens.

•   Gene Conservation of Carolina and Eastern Hemlocks -- Camcore (Department of Forestry & Environmental Resources at North Carolina State University) and the USDA Forest Service are collaborating to collect seeds from populations of both Carolina and eastern hemlock throughout the southern U.S.  These seeds have been placed in cold storage or have been germinated to establish ex situ conservation plantings in Latin America and the Ozark Mountains of Arkansas.

•   New Hemlock Hybrid Withstands Killing Insect -- Exciting announcement from the USDA about "Traveler," the new hemlock hybrid that is resistant to HWA. 2020

•   Young Harris College Hemlock Project -- article about The YHC Hemlock Project published on YHC's web site, 2010

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