Hemlock Woolly Adelgid (HWA)
An exotic insect pest that was found infesting trees in Ohio for the first time in August, 2002.
Hemlock Woolly Adelgid, Adelges tsugae is an introduced pest from Asia that is a threat to Eastern Hemlock, Tsuga canadensis and Carolina Hemlock, Tsuga caroliniana in eastern North America. White cottony sacs found at the base of the needles are good evidence of the Hemlock Woolly Adelgid. The Adelgid uses these sacs to protect itself and its eggs. These sacs, resembling the tips of a cotton swab can be seen from early winter till early summer but are most prominent in early spring. This small, less than 1/16” insect, sucks sap from young twigs which retards or prevents tree growth causing needles to discolor and drop prematurely which severely affects plant health. Defoliation and tree death can occur within 4 to 10 years of infestation.
Hemlock Woolly Adelgid has infested eastern states and threatens the ecological balance that exists in the Eastern Hemlock forest.
The first discovery involved 15 hemlock trees grown at a nursery in a state east of Ohio and purchased in Ohio as balled & burlap stock. The hemlock trees were planted in a home landscape near Painesville (Lake County) three years prior to discovery of the insect.
Of the 15 trees planted, 8 were infested with HWA. Other hemlock trees growing in the surrounding area were inspected, but none were infested. The Ohio Department of Agriculture (ODA) destroyed the 15 trees on August 28, 2002 to ensure that the insect did not spread to other trees.
A second HWA infestation was subsequently discovered in November, 2002. This infestation involved 5 hemlock trees growing in a home landscape near Stow (Summit County).
All 5 trees harbored HWA and had been planted about 6 years prior to discovery of the insect. These trees also originated in a state east of Ohio, but were purchased here in our state. Again, surrounding trees were inspected but were not infested. ODA destroyed the 5 hemlocks on November 19, 2002.
In 2004, HWA was discovered at two additional locations in NE Ohio. Both cases involved infested landscape trees that were planted within the past 3-5 years.
The infested hemlock trees were found near Bainbridge (Geauga County) and in Hudson (Summit County). A detection survey was performed and the insect could not be found on trees away from the infested sites. On August 9, 2004, ODA destroyed the infested trees (9 trees in Summit County and 2 trees in Geauga County) in an effort to eradicate the pest from these sites.
During 2006, about 10 infested landscape trees were destroyed by ODA in Lorain, Cuyahoga and Geauga counties. For 2007, a few trees in Lake County were found to be infested with HWA. HWA was then found in 2008 in a Summit county landscape. The infested trees discovered in 2007 and 2008 were destroyed by the Ohio Department of Agriculture (ODA).
HWA was found in two counties in 2009, Cuyahoga and Clermont County. The Cuyahoga find was on a landscape tree which was removed and burned. Several lightly infested hemlock trees were discovered during a routine inspection by ODA inspectors at a nursery in Clermont County. The entire shipment associated with these trees were seized and rejected back to the shipper in Tennessee.
Follow up inspections will be done at these locations to ensure no HWA is present.
No infestations were found during a survey by the Ohio Division of Forestry staff during a 2007, 2008 or 2009 survey of the Clearfork Gorge area in Ashland County and the Hocking Hills region.
 Additional Information
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| Infested Hemlocks were cut down and prepared for bagging. |
Hemlock branch infested with HWA. |
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| Bagged trees were transported in closed vehicles |
Infested trees were burned to destroy insects. |
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