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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.
Update on HWA: in the fall of 2008 a HWA infestation was detected in a planting at a botanical garden in Summit county. The infested plant material was traced back to a local nursery that received it from a southern state. Two heavily infested trees were cut and burned and adjacent trees were treated with dormant oil and insecticide. The infestation has been declared eradicated by ODA. In a separate incident in 2009 a HWA infestation was detected in a residential planting in Cuyahoga county. One heavily infested tree was cut and burned and adjacent trees were treated with insecticide. The source of the plant material could not be traced back. The infestation has been declared eradicated by ODA. The two sites will remain under surveillance for the foreseeable future.