Hemlock Woolly Adelgid (Adelges tsugae)
Hemlock Woolly Adelgid (Adelges tsugae) was first reported on western hemlock (Tsuga heterophylla) in the Pacific
Northwest in the 1920's, and a separate introduction in Virginia in 1950 established the pest on the east coast on
eastern and Carolina hemlocks (T. canadensis and T. caroliniana). The insect feeds on xylem ray parenchyma cells
which causes premature needle drop. Extensive decline and mortality has occurred in Virginia, Pennsylvania, New
Jersey, and Connecticut within ten years of the first detection. The native range of eastern hemlock includes the
eastern half of Ohio, which is at risk for infestation as at least half of the eastern range of hemlock is already
infested. The role of hemlock in many specialized ecological niches, such as those of birds, small mammals, amphibians
and invertebrates, makes excluding this pest a priority. Interceptions have been made in Lake and Summit counties
and the pest was eradicated. Two additional interceptions occurred in 2007, and nursery stock from both infested
shipments was sold prior to the detection. Ohio's shipping nurseries are only able to ship to Canada if the pest
is not known to occur in the county where the nursery is located. Thus it is important to demonstrate by survey
that the pest does not occur in Ohio. These factors make this pest suitable for continued survey to be sure it
doesn't become established in the state.
The woolly egg sacs of hemlock woolly adelgid will be found at the base of newly formed needles.
They should not be confused with elongate hemlock scale which can also appear whitish and can be
found anywhere on the needles. If you suspect you have found a hemlock woolly adelgid infestation
contact the Ohio Department of Agriculture Plant Pest Control Section.
Fact Sheet
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