Few options to manage HWA in forests exist at this time, although chemical and cultural management practices and biological controls are being developed. There are few natural predators of the HWA in North America, and these have little to no effect on populations of this pest. Hybridization of Eastern Hemlock species with Asian and western species of hemlocks (T. heterophylla and T. mertensiana) may improve resistance of eastern hemlocks to HWA. Research is also being carried out to evaluate the potential for biological control of American HWA populations by importing two very effective asian predators; these are an oribatid mite (Diapterobates humeralis) and a ladybird beetle (Pseudoscymnus tsugae).
HWA can damage trees very quickly, and usually kills the tree within three to five years of infesting it. Using piercing and sucking mouthparts, the Hemlock Wooley Adgeid feeds on plant juices at the base of the needles, and while doing so, also injects toxic saliva that causes the death of the needles. HWA is can be recognized by the white protective wax it secretes as protection, which looks like a woolly ball at the base of hemlock needles. HWA is frequently dispersed by birds, animals and wind, as well as by hitch-hiking to new locations on contaminated branches.
(McClure, 2007; National Park Service 2011; Wikipedia 2011; United States Department of Agriculture, 2011)
- McClure, M.S. 2007. Hemlock Woolly Adelgid, Adelges tsugae (Annand). Connecticut Agricultural Research Station. Retrieved September 26, 2011 from http://www.ct.gov/caes/cwp/view.asp?a=2815&q=376706
- National Park Service, 2011. Hemlock Woolley adelgid. Great Smoky Mountains National Park. Retrieved September 26, 2011 from http://www.nps.gov/grsm/naturescience/hemlock-woolly-adelgid.htm
- United States Department of Agriculture, September 22, 2011 National Invasive Species Information Center. Species Profiles, Hemlock woolly adelgid. Retrieved September 26, 2011 from http://www.invasivespeciesinfo.gov/animals/hwa.shtml
- Wikipedia, The Free Encyclopedia. 22 May, 2011. “Hemlock woolly adelgid”. Retrieved September 26, 2011 from http://en.wikipedia.org/w/index.php?title=Hemlock_woolly_adelgid&oldid=430297902
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