title: Spruce budworm impact, abundance and parasitism rate in a patchy landscape.
abstract: 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 Choristoneurafumiferana 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 Actiainterrupta, a parasitoid of fifth and sixth instar larvae, as well as the ichneumonid pupal parasitoids Itoplectesconquisitor, Ephialtesontario and Phaeogenesmaculicornis, caused higher mortality in the habitat islands than on true islands or in extensive stands. Exochusnigripalpistectulum, an ichneumonid that attacks the larvae and emerges from the pupae, caused greater mortality in the extensive stands of conifers.
authors.affiliation: Department of Zoology, University of Texas at Austin, Austin, TX 78712, USA, , , , , , US.
authors.forename: Naomi
authors.initials: N
authors.lastname: Cappuccino
authors.affiliation: Groupe de Recherche en Écologie forestière, Université du Québec à Montréal, CP 8888, succ. Centre-ville, Montréal (Québec) H3C 3P8, Canada, , , , , , CA.
authors.forename: Denis
authors.initials: D
authors.lastname: Lavertu
authors.affiliation: Groupe de Recherche en Écologie forestière, Université du Québec à Montréal, CP 8888, succ. Centre-ville, Montréal (Québec) H3C 3P8, Canada, , , , , , CA.
authors.forename: Yves
authors.initials: Y
authors.lastname: Bergeron
authors.affiliation: Canadian Forest Service, P.O. Box 3800, Ste-Foy (Québec) G1V 4C7, Canada, , , , , , CA.
authors.forename: Jacques
authors.initials: J
authors.lastname: Régnière
keywords: Boreal forest; Choristoneura fumiferana; Enemies hypothesis; Key wordsAbiesbalsamea; Landscape diversity