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Outbreaks of the western hemlock looper (WHL) are characterized by rapid increase, patchy distribution, and significant and extensive tree mortality over large areas in mature cedar-hemlock-spruce forests of BC. Outbreaks occur approximately every 10 years, and last about 4 years. There is currently an outbreak in BC. It is known that looper egg counts and the percentage of parasitized eggs provide a localised estimate of population trends and expected defoliation during outbreaks. With this information management activities such as targeted harvesting or organic insecticide sprays can be planned to mitigate losses. Current egg sampling technology is arduous, time-consuming, and expensive, and requires a specialised extraction process. It involves collecting lichen (a preferred egg-laying substrate) from trees in infested areas, and then processing the lichen in a hot water or bleach bath to separate the eggs from the lichen. Viable overwintering eggs are then counted per 100 g of lichen. Other disadvantages of this sampling system are that lichen is not always abundant at preferred sample sites, and old eggs left on the lichen need to be separated out before viable eggs can be counted. Project objectives are to 1: Test the effectiveness of a new artificial substrate egg sampling technology for predicting localised western hemlock looper population trends and defoliation severity during outbreaks; and, 2: Compare the efficacy and cost-effectiveness of the new sampling technology against current sampling technologies for WHL. If the new oviposition sampling system proves efficacious, then BC will have a standardised, cheaper, easier, and more robust method that can be installed and collected by non-specialists, and rapidly and easily assessed. The technique will fit smoothly into, and add to the accuracy of, the current monitoring system for WHL.
Arthur J. Stock, Marnie Duthie-Holt.
Stock, Arthur J., Duthie-Holt, Marnie; Otvos, Imre S.; Maclauchlan, Lorraine E.. 2006. Oviposition traps to survey for population trends and defoliation prediction of the western hemlock looper (Lambdina fiscellaria lugubrosa) (Lepidoptera: Geometridae) in British Columbia. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), Lambdina, Fiscellaria, Lugubrosa, Control
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