Biological Control 
 
insecticidal soaps, and dormant oils can be used. This type of treatment is most practical on small trees or hemlock hedges. Avoid making foliar applications in late February/ early March and late May when adults and eggs have their heaviest wool coverings. Be sure to spray in an upward fashion to thoroughly coat the underside of the branches. The key to success with soaps and oils is thoroughly coating the adelgid with the solution. Insecticidal soaps and dormant oils pose little risk to the applicator, children, or pets, but offer no residual control. 
Stem injections: In this systemic treatment, imidacloprid is injected into the trunk of the tree. This application is normally recommended for trees growing in very rocky soils where soil treatments can not be made. Stem injection treatments require specialized equipment and are usually made by professional arborists. The higher cost and tree wounding associated with stem injections should be considered before using this method. 
Because HWA is not native to the eastern U.S., few predators exist to limit its population growth. Survival of the hemlock species is dependent on the establishment of biological agents to keep the HWA population in check. Researchers are now using three kinds of predacious beetles to fight HWA. Two species of beetles native to Asia, Scymnus sinuanodulus and Sasajiscymnus tsugae, and one species native to the Pacific NW, Laricobious nigrinus, are currently being released in Georgia (Figures 6, 7, & 8). These beetles are mass reared in labs in Georgia and surrounding states. 
Research is ongoing into other predatory insects and diseases that can control HWA. 
Fig. 6, 7, & 8 - Predator beetles being used to control HWA. From top: Sasajiscymnus tsugae, Laricobious nigrinus, and Scymnus sinuanodulus. 
 
Photo Credits Cover - Deborah Breedlove, Georgia Forestry Commission 
Figure 1 - Scott Griffin, Georgia Forestry Commission Figure 2 - Mike Montgomery, U. S. Forest Service 
Figure 3 - James Johnson, Georgia Forestry Commission Figures 4 & 5 - Scott Griffin, Georgia Forestry Commission Figure 6 - Carole Cheah, Connecticut Agricultural Experiment Station 
Figure 7 - Ashley Lamb, Virginia Tech Figure 8 - Guangwu Li, Chinese Academy of Forestry 
References: Jefferey S. Ward, Michael E. Montgomery, Carole A.S.J. Cheah, Brad P. Onken, and Richard S. Cowles 2004. Eastern Hemlock Forests: Guidelines to Minimize the Impacts of Hemlock Woolly Adelgid. 
Funds for this publication are provided by the USDA Forest Service. 
Thanks to Dr. Tom Coleman and UGA for review of this publication. 
 
The Hemlock Woolly Adelgid in Georgia 
 
 What is the Hemlock Woolly Adelgid? 
 
The hemlock woolly adelgid (HWA) is a tiny pest posing a giant threat to hemlock trees in Georgia. It is an aphid-like insect that feeds on the sap of eastern and carolina hemlock trees and is capable of causing tree death within four short years of infestation. 
 
History of Spread 
 
HWA was accidentally introduced into Virginia in the 1950s. The insect is native to Japan, China, and the United States' Pacific Northwest region. HWA was first discovered in Georgia in 2003 near the Ellicott Rock area of Rabun County and can now be found in almost all Georgia counties where native hemlock occurs. The Georgia Forestry Commission conducts annual surveys to find newly infested areas. The adelgid is dispersed by wind, birds, and human activity. It is spreading at an alarming rate. 
 
Identification 
 
The hemlock woolly adelgid is a tiny 
 
insect measuring approximately 1/16th 
 
of an inch long. As the adelgid matures, 
 
it produces and covers itself 
 
and its eggs with a white, 
 
waxy filament (Figure 1). 
 
This waxy covering provides 
 
protection from predators and 
 
from drying out. The adelgid 
 
is most conspicuous from late 
 
fall to early summer when the 
 
Fig. 1 - Mature HWA "woolly" covering is present. Adelgids 
 
and ovisacs in late winter. 
 
are found primarily on the underside of branches at the base of needles on the 
 
newest growth. 
 
Life Cycle in Georgia 
 
HWA completes two generations a year, a winter and spring generation, which are both all-female and wingless. Adults of the winter generation are capable of laying up to 300 eggs. These eggs, which are the beginning of the spring generation, will begin to hatch during the month of April. Crawlers, the first nymphal stage and dispersal phase, move out in search of suitable feeding locations. The crawler 
 
settles at the base of a needle, then inserts a long feeding tube called a stylet. The nymph will remain here until reaching maturity in late May to early June. If tree health is very poor, a portion of the spring generation will form into winged adults that fly off in search of a spruce tree. However, no suitable species of spruce is found in North America, resulting in the death of the winged adelgids. The spring generation adults that remain on the tree lay 20-75 eggs each, beginning the winter 
generation. Crawlers hatch from the eggs in late June to early July and disperse to settle on the newest hemlock growth. Once attached, the nymphs go dormant for the summer and no wool is produced during Fig. 2 - HWA nymphs this time (Figure 2). In early October the in summer dormancy. nymphs break dormancy and begin to feed and produce their woolly covering. The nymphs become mature adults by mid February to mid March. 
 
Damage 
 
All ages and sizes of hemlocks can be 
 
attacked by the HWA. The pest causes 
 
damage to the tree by feeding 
 
on the starch it produces. This 
 
inhibits the tree's ability to 
 
produce new growth. Trees that 
 
have been infested for a couple 
 
of years will show visible signs 
 
of decline. Unhealthy hemlocks 
 
will appear a dull green to gray 
 
color, possess premature needle 
 
loss, and exhibit branch die- 
 
Fig. 3 - Hemlock tree in 
 
back (Figure 3). Tree mortality 
 
serious decline due to usually occurs after 4-10 years of 
 
HWA infestation. 
 
infestation. 
 
Chemical Control Several options are available for chemiRecommendations cal control of HWA. Because tree death 
from HWA is not sudden, it is recommended that treatment options only be used when HWA is present on the tree or is known to be in your immediate area. Always follow the product label 
 
when applying chemicals. The following describes three basic treatments for controlling the hemlock woolly adelgid. More detailed information on HWA control can be found at www.gatrees.org. 
 
Soil Treatments: In this systemic treat- 
 
ment, an approved insecticide is applied 
 
to the soil around the base of the tree 
 
and is taken up by the root system. There 
 
are several products that are labeled for 
 
this type of application. This includes 
 
products that contain the ac- 
 
tive ingredient, imidacloprid, 
 
such as Bayer Advanced Tree 
 
& Shrub Insect Control, 
 
Merit, Imidipro, Touch- 
 
stone, Zenith, Quali- 
 
Pro, and Lesco. A prod- 
 
uct called Safari 20 SG, 
 
Fig. 4 - Insecticide being applied by using a soil injector to inject the chemical into the ground. 
 
containing the active ingredient dinotefuran, is also effective. Bayer Advanced Tree & Shrub Insect Control can be purchased at most hardware stores and the other 
 
products can be purchased 
 
from pesticide distributors or 
 
some farm supply stores. The 
 
application is made by mixing 
 
the chemical with water and 
 
injecting or pouring it into 
 
the soil around the base of 
 
the tree (Figures 4 & 5). Soil 
 
Fig. 5 - Insecticide being applications are best made in the spring 
 
applied to the soil by (March to early June) or fall (mid-Septem- 
 
mixing the chemical ber to mid-November) when adequate soil 
 
with water and pouring around the tree. 
 
moisture is present. Avoid applications to frozen or waterlogged soil. One applica- 
 
tion can provide protection for 2-3 years. 
 
Soil injection is currently the most effective 
 
approach for treating HWA. 
 
Foliar Treatments: This refers to treatments that kill adelgids by spraying a product on the adelgid, foliage and/or stem of the tree. Imidacloprid products, Talstar (bifenthrin), Safari 20 SG (dinotefuran),