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Ecological Protection Lab FAQs

Hemlock Woolly Adelgids

What are the adelgids like, what do they do, and how do they do it?
The Hemlock Woolly Adelgid (HWA) is a small aphid-like insect (NOT a beetle) that feeds by inserting its stylet (straw-like mouthpart) into the tree and sucking out the nutrients. This then creates tiny holes in the tree which limits its ability to uptake nutrients (This can be comparable to trying to drink from a broken straw). On the east coast this invasive insect is devastating the Eastern and Carolina Hemlocks. HWA can also be found throughout Asia and the Pacific Northwest. However due to natural predators and tree resistance, HWA is not seem as a threat in these areas.
When and how did it start?
The hemlock woolly adelgid was first noticed on the east coast in 1951 in Virginia. It has since spread north to Maine, south to Georgia and is continually spreading west. HWA first documented in Rabun County, GA in 2003 and has since spread west into Murray, Gilmer, and Dawson Counties.
How do these little varmints spread?
During the “crawler” lifestage, HWA can be spread by crawling, being blown by the wind, or hitchhiking a ride on humans, deer, birds, etc. that brush up against an infested hemlock tree.
HWA is parthenogenetic, it reproduces asexually and basically clones itself, and goes through two developmental stages every year. The progredien, or the first generation, develops from February to May in Georgia. During this cycle over-wintering adults lay eggs, which develop into two forms - sexual winged forms and asexual wingless forms. The winged forms require spruce trees to complete their life-cycle which fortunately we lack an adequate spruce in eastern United States. The winged forms die due to lack of suitable hosts. The wingless forms continue feeding and developing on hemlocks. The spring generation reaches maturity by mid-May in GA, when they are ready to lay eggs. The sisten, second generation, "crawlers" that hatch from these eggs in early June, find new needles to settle on and become dormant until October. They feed and continue to develop during the winter and by February of the next year are ready to lay eggs again.
How can I tell if my trees have HWA?
HWA is active during the cooler months of the year. At this time the adelgid will produce a waxy substance that makes it resemble small cotton balls. There are also two crawler stages during March through July. If you get them on your skin they resemble tiny freckles and smear brown when brushed off. HWA aestivates (dormant during the summer) and during that time can been seen (a hand lens will help) as a tiny dot usually at the base of the needles.
How often should I inspect my trees?
It is easiest to see the adelgid once it breaks aestivation (summer dormancy) in October-November. They will produce a waxy cotton ball coating that is fairly easy to see. However it would be a good idea to continually check your hemlocks for signs of infestation.

Hemlock Trees

What is happening to the hemlock trees?
The Eastern and Carolina Hemlock trees are being devastated by an invasive insect called the hemlock woolly adelgid (pronounced ah-dell-jid).
Why do hemlock trees matter? What other plants and animals depend on them? What good do hemlocks do?
Eastern hemlocks are an evergreen tree, found primarily in riparian zones, which can live up to 800+ years. They are very shade tolerant and provide a dense canopy that helps maintain moisture and moderate forest floor and streams temperatures. Cool mountain streams are needed for trout and other native fish, along with aquatic insects, salamanders, and crawfish. Moderate forest floor temperatures and thick boughs provide shelter during the winter for many birds and mammals, some that nest solely in hemlock trees. There is also the economical importance of hemlocks for timber along with the pure aesthetic value that a hemlock forest provides.
What would happen if they all died?
The devastation caused by the hemlock woolly adelgid is most likely comparable to the chestnut blight, which radically changed forest composition.
What is being done to try to save the hemlocks?
  • Predator Beetles are being mass reared by multiple universities and government organizations. The Georgia forests are being supplied by UNG, UGA, Young Harris, and Clemson
  • Chemical Controls are widely used throughout the eastern U.S.
  • Genetic Engineering is being researched to try and create a HWA resistant strain of Eastern and Carolina Hemlocks.
  • Seed Banks and Nurseries have been established. The nurseries are in central U.S., South America, and Australia.
  • A strain of Fungus is being researched to control HWA.

Treatment: Biological Controls

What are the beetles like, what do they do, and how do they do it?
  • Sasajiscymnus tsugae(St): Imported from Japan it belongs to the Coccinellid family and is a small black beetle about 2mm long. It feeds primarily on adelgids and both larvae and adults feed on all stages of HWA. St is active during the summer and hibernates in the winter. They have two generations a year, just like HWA, and can produce up to 500 eggs in their lifetime. This type of beetle has been released since 1995.
  • Scymnus sp: Imported from China it belongs to the Coccinellid family and is a small black beetle, with coppery colored elytra (hard wings). Some species have two black dots on their elytra as well. They prefer to feed on adelgids, but will feeds on aphids to a certain degree. Scymnus adults feed on all life stages of the adelgid, but the larvae need HWA eggs. They are active during the summer and hibernate in the winter. Scymnus produce one generation a year and can lay up to 200 eggs.
  • Laricobius nigrinus: A Derodontidae beetle from British Columbia, Oregon, and Washington, who voraciously feeds on HWA on western hemlocks. Laricobius need HWA to develop into adults and will feed on all life stage, though larvae feed exclusively on HWA eggs. These beetles have one generation a year, however, just like HWA they are active during the winter months and aestivate in the summer.
How are the beetles raised, and where are they released?
Currently in the GA area, UNG, Young Harris, UGA, and Clemson rear 1-3 of these species. There are multiple facilities throughout the east coast, Pacific Northwest, and Asia that work with these beetles and HWA. In GA there are over 100 Hemlock Conservation Areas (HCAs) in which the predator beetles are released into.
Why can't we just raise a bazillion of them and turn them loose in the forest?
There is a lot of work that goes into the rearing process and what it typically comes down to is size of lab, amount of workers, funding, quality of food, etc. Each lab is dedicated into rearing as many beetles as possible in order to combat against the hemlock woolly adelgid.
How do you know the beetles won't eat anything but the adelgids?
Every imported species is held in quarantine and numerous tests are run to ensure that this species won’t get out of control. Only after it has been approved can these species then be released.

Treatment: Chemical

What kinds of chemical treatments are being used, who can use them, and how do they work?
  • Merit: (Active Ingredient: Imidicloprid) Can be used by anyone, with caution, and is best applied through soil injections.This product takes longer to kill HWA but typically stays in the tree longer
  • Safari: (Active ingredient: Dinotefuran) Can be used by anyone, with caution. This product quickly kills HWA, but will need retreating more often.
How sick should a tree be before chemical treatment is done? Can a tree be saved if the early stages of its death are noticed?
Here is a passage taken from a publication from Webb et al.

“Trees with the healthiest, most foliated canopy improved the least following the reduction in adelgid populations. Trees with little new growth but no dieback recovered the quickest and most densely. Trees in the poorest condition at the onset recovered impressively but more slowly. Trees left untreated remained sparsely foliated, with dieback”.

Can chemical treatment be done more than once in the life of a tree?
Yes, while there is varying evidence on how long treatments can work, 1-10 years depending on the product, the trees will have to be retreated if the chemical doesn’t initially take, or when the chemical losses potency.
Why can't we just fly a plane over the forest and spray all the trees?
The chemicals used for killing HWA are insecticides and do not discriminate on which insect it kills. Therefore, spraying an entire forest would devastate the insect population, have adverse effects on most likely all living things that are over exposed to it, contaminate water ways, and overall just be a really really bad idea.
How often should trees be treated after the initial treatment is done?
Depending on the product used it could take up to 18 months for the chemical to move throughout the tree. Soil conditions and moisture levels also play a role in this. It could possible be that the chemical wasn’t taken up by the tree. Monitor the trees after treatment to determine if the chemical was taken up. You would want to look for presence of new wool (nice white cottonball) as the old wool (dingy, possibly torn up cottonball) does remain on the tree as well. If you do find that your tree is becoming adelgid free then occasionally monitor your trees for any signs of re-infestation and take action again.


What are the roles of the state and federal government in helping the hemlocks? Who is responsible for what?

The state and federal governments are not only doing their best to control the spread of HWA and save the hemlocks, but are also working with multiple universities and organizations on research, beetle releases, and chemical treatments.

  • National Forests: USDA Forest Service
    - HWA Management Plan
  • State Properties: GA Forestry Commission
  • State Campgrounds: GA DNR
  • Private Property: Home Owner
And what can the general public do to help save hemlocks on national forest or other public land? Who can I contact?

There are multiple options for the public in order to help save hemlocks on public lands:

  • Visit the Parks. Park fees are used to maintain the parks including treating hemlock trees.
  • Georgia Department of Natural Resources has played a huge role in treating hemlock trees and spreading information.
  • Become a Friends of GA's State Parks and Historic Sites
  • Donations to the Ecological Protection Lab
    - UNG and Young Harris
  •  Attend Hemlockfest where all proceeds go towards saving the hemlock trees.
  • Contact other organizations such as Lumpkin Coalition, Trout Unlimited, Sierra Club, Georgia Forest Watch, etc. and see what their efforts are in saving the hemlocks.
What can businesses and homeowners do to save hemlocks on their own property?
Please see Home Owner Options
Is there any help available to private property owners?
  • Consultations:
    - Feel free to contact me and I will provide any info I can
    - Lumpkin Coalition: PLATT
    - Save Georgia Hemlocks:
    - AdelRid:
  • Purchase Beetles:
    - Jayme Lynne Longo
      Owner and Environmental Scientist
      Forever Green Environmental Services
      P.O. BOX 270
      Scranton, PA 18504
I wonder if there is any evidence that there may be an HWA-resistant strain of Hemlocks developing?
Samples have been taken from hemlocks all over the eastern U.S. from possible HWA resistance trees.
What else is being done to breed trees that are resistant to the woolly adelgid?
There are current studies looking at a hybrid from a Carolina Hemlock and the Chinese Hemlock were viable offspring were produced. I have not found any information of viable offspring with the Eastern Hemlock.
Will the HWA beetle ever be gone?
Well first off HWA is NOT a beetle, but an adelgid, a small aphid like insect. It is highly unlikely that HWA will ever be eradicated from the eastern forests. Therefore it is important to create a predator-prey balance by releasing predator beetles in order to control HWA populations.
What are the best web sites for tracking HWA issues?
What is the best scientifically based evidence that the "beetle solution" is working?

“Results have been encouraging when HWA densities on hemlock trees in release areas were compared with those in similar control areas (beetles absent in the area)at least half a mile away. In 1996, adelgid densities on monitored branches in release areas were reduced by 47%-87% in just five months by a starting population of only 2,400 to 3,600 adult beetles, indicating a remarkable shortterm impact of P. tsugae on HWA”

“Other field studies have shown that S. tsugae can reproduce after release, disperse locally, survive heat waves, overwinter, and establish in a variety of different hemlock habitats in Connecticut and other states (Cheah and McClure 2000).”

“Biff Thompson, a forest health inspector from the Maryland Department of Agriculture (MDA) and Brad Onken, a forest entomologist from the U.S. Department of Agriculture (USDA) Forest Service recovered first generation adults of two species of tiny “lady bug” beetles. These insects, about the size of a poppy seed, were released in an effort to control the Adelges tsugae or hemlock woolly adelgid (HWA), a serious pest of hemlock trees. MDA has released three different species of insect predators against the HWA since 1999 and recovered two of them on Oct. 18, 2005. Recovery of the other species, Laricobius nigrinus, was even more encouraging. In May of this year, MDA entomologists, Onken, and Dave Mausel, a graduate student at Virginia Tech, recovered several larvae of this species following a release of approximately 1,200 of the beetles at Rocky Gap last fall.”

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