Canadian Forest Service Publications
Spruce budworm impact, abundance and parasitism rate in a patchy landscape. 1998. Cappuccino, N.; Lavertu, D.; Bergeron, Y.; Régnière, J. Oecologia 114: 236-242.
Available from: Laurentian Forestry Centre
Catalog ID: 39533
CFS Availability: PDF (request by e-mail)
The hypothesis that vegetational diversity may lessen the impact of forest insect pests by favoring natural enemies is appealing to those who seek ecologically sound solutions to pest problems. We investigated the effect of forest diversity on the impact of the spruce budworm Choristoneura fumiferana following the last outbreak, as well as the budworm's current abundance and parasitism rate, in the boreal forest of northwestern Québec. Mortality of balsam fir caused by the budworm was greater in extensive conifer stands than either in “habitat islands” of fir surrounded by deciduous forest or on true islands in the middle of a lake. Adult spruce budworm abundance, assessed by pheromone traps, did not differ significantly between the three types of sites. Larval and pupal parasitism rates were examined by transferring cohorts of laboratory-reared larvae and pupae to trees in the three site types and later collecting and rearing them. The tachinid Actia interrupta, a parasitoid of fifth and sixth instar larvae, as well as the ichneumonid pupal parasitoids Itoplectes conquisitor, Ephialtes Ontario and Phaeogenes maculicornis, caused higher mortality in the habitat islands than on true islands or in extensive stands. Exochus nigripalpis tectulum, an ichneumonid that attacks the larvae and emerges from the pupae, caused greater mortality in the extensive stands of conifers.
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