Canadian Forest Service Publications
Use of ultraviolet light to assess hemlock woolly adelgid populations. 2018. Fidgen, J.G.; MacQuarrie, C.J.K.; Turgeon, J.J. Natural Resources Canada, Canadian Forest Service, Great Lakes Forestry Centre, Sault Ste. Marie, Ontario. Frontline Technical Note 117. 4p.
Available from: Great Lakes Forestry Centre
Catalog ID: 39405
CFS Availability: PDF (download)
Plain Language Summary
This note describes a procedure for collecting and processing twig samples infested with the hemlock woolly adelgid under black light. Researchers found that this technique is 10 times faster than pulling apart ovisacs in determining the size of a population. Estimates of the density of the invasive, non-native hemlock woolly adelgid are needed when deciding if control treatments are required or have been successful. Typically, the number of ovisacs (structure within which adelgids live) are counted on twigs to estimate population levels. To obtain accurate estimates of populations, the ovisacs must be pulled apart to see if the nymph or adult within is still alive. This takes time. Adelgids produce a waste product similar to aphids, called honeydew. If honeydew is present on the surface of an ovisac, it will glow when exposed to ultraviolet light which can be then used to count the number of live insects. When used under the prescribed conditions this technique can provide the most accurate estimates of adelgid survival.
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