Chinese hemlock (Tsuga chinensis) susceptibility to hemlock woolly adelgid (Adelges tsugae) [2006]
In 2006 I conducted a study to test eastern hemlock (Tsuga canadensis) and Chinese hemlock (T. chinensis) susceptibility to hemlock woolly adelgid (Adelges tsugae) (HWA). The study involved collecting HWA ovisacs from infested eastern hemlocks in Centre County, Pennsylvania and inoculating non-infested eastern and Chinese hemlocks at three Pennsylvania experiment sites (Berks County, Centre County, Lackawanna County) in the month of May.
The counties where the experiments were conducted in Pennsylvania.
Counting ovisacs during inoculum collection.
Hemlock woolly adelgid inoculum.
Treatments included rate of HWA inoculum (high = 25-40 ovisacs and low = 10-20 ovisacs) and mesh sleeves (mesh aperture sizes = 100 μm and 1000 μm, control = sleeveless). The sleeves were 38 cm long, with a 9 cm diameter.
An inoculated hemlock.
In November HWA nymphs were counted on the experiment plants.
Hemlock woolly adelgid nymphs on an eastern hemlock.
Counting hemlock woolly adelgid nymphs.
The Chinese hemlocks in this experiment remained free of HWA infestation. Use of sleeves increased HWA infestation on eastern hemlocks. Both inoculum densities resulted in the same level of infestation on eastern hemlock.
Results from this study were presented at the International Society of Arboriculture 83rd Annual Conference and Trade Show (Honolulu, HI) and 4th Hemlock Woolly Adelgid Symposium (Hartford, CT), and an article was published in Arboriculture and Urban Forestry .[1]
[1] Hoover, B.K, R.M. Bates, J.C. Sellmer, and G.A. Hoover. 2009. Challenging Chinese hemlock (Tsuga chinensis) with hemlock woolly adelgid (Adelges tsugae) ovisacs. Arboriculture and Urban Forestry. 35(1): 1-4
