Role of Parasites in the Population Dynamics of the Western Spruce Budworm (Lepidoptera: Tortricidae) in the Northwest

Torgersen, Torolf R.; Campbell, Robert W.; Srivastava, Nilima; Beckwith, Roy C.

doi:10.1093/ee/13.2.568

Cited by 8 publications

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“…Attempts to find ways to control or minimize losses from these and other Choristoneura species in North America and Europe have involved many studies of their primary parasitoids (e.g. Dowden et al 1948;Wilkes et al 1948;Drooz and Benjamin 1956;Coppel and Smith 1957;Carolin and Coulter 1959;McGugan and Blais 1959;Blais 1960;Kulman and Hodson 1961;Miller 1963;Dixon and Benjamin 1963;McKnight 1974;Harris and Dawson 1979;Dearbom 1980;Torgersen et al 1984;Tilles and Woodley 1984;Pogue 1985;Elliott et al 1986aElliott et al ,1986bMaltais et al 1989;Ennis and Caldwell 199 1;Mills and Kennis 199 1;Nealis 199 1;Schaupp et al 1991;Williams 1994). In contrast, there are relatively few studies of the impact of hyperparasitoids on the primary parasitoids of Choristoneura (e.g.…”

Section: Introductionmentioning

confidence: 99%

THE CHALCIDOID PARASITOIDS AND HYPERPARASITOIDS (HYMENOPTERA: CHALCIDOIDEA) OFCHORISTONEURASPECIES (LEPIDOPTERA: TORTRICIDAE) IN AMERICA NORTH OF MEXICO

et al. 1996

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An illustrated key is given to 28 genera, representing 10 families of at least 50 chalcidoid parasitoids and hyperparasitoids recorded from Choristoneura species (Tortricidae), or their primary parasitoids, in America north of Mexico. We include species reared throughout a 12-year study of the parasitoids and hyperparasitoids associated with the spruce budworm, Choristoneura fumiferana (Clemens), in New Brunswick, Canada, as well as those listed in various catalogs. Notes are provided for all the chalcidoid species, whether or not they are recorded in the literature. Nine species doubtfully or incorrectly recorded from Choristoneura species are also discussed.Primary parasitoids belonging to the Ichneumonidae, Braconidae, and Tachinidae have been recorded from 10 of the 16 Nearctic Choristoneura species but chalcidoid parasitoids are recorded, usually as hyperparasitoids, from only four of the 16 species. The species of primary parasitoids of Choristoneura checked for records of parasitism by Chalcidoidea are tabulated by host species. Also listed are species of primary parasitoids serving as hosts for each of the chalcidoid species. We report 51 new host records of primary parasitoids and hyperparasitoids from C. fumiferana and its parasitoids collected in New Brunswick.A new generic combination is given: Mesopolobus tortricis (Brues) comb.nov. from Psychophagus (proposed by Z. Boucek).

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Section: Introductionmentioning

confidence: 99%

THE CHALCIDOID PARASITOIDS AND HYPERPARASITOIDS (HYMENOPTERA: CHALCIDOIDEA) OFCHORISTONEURASPECIES (LEPIDOPTERA: TORTRICIDAE) IN AMERICA NORTH OF MEXICO

et al. 1996

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“…Higher parasitism in declining epidemic populations is consistent with the very high mortality that characterizes collapsing outbreaks. Lower parasitism rates in sparse versus declining outbreak populations also were found by Torgersen et al (1984). Overall parasitism calculated from their data for sparse populations was 13, 16, and 38% for the three plot-years.…”

Section: Methodsmentioning

confidence: 85%

“…For five declining outbreak populations parasitism averaged 54% (range 38-7 1 %). Torgersen et al (1984) likely underestimated apparent parasitism, because samples of late larvaeearly pupae were not taken. Species active during this period of rapid change in the host population would be either underestimated or missed (McKnight 1974; Carolin and Couiter 1972).…”

Section: Methodsmentioning

confidence: 99%

“…The incidence of Mesochorus tachypus Holmgren, a secondary parasitoid reported to attack A. fumiferanae (Harris and Dawson 1979), was high (Table 3). Carolin and Coulter (1959) and Torgersen et al (1984) consistently reared this species. Parasitoids attacking budworm pupae reared from epidemic populations include, in order of abundance, P. maculicornis hariolus, Brachymeria ovata ovata Say (plot 38 only), I. quadricingulata, E. ontario, and Coccygomimus varians Townes (Ichneumonidae).…”

Section: Methodsmentioning

confidence: 99%

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PARASITOIDS OF ENDEMIC AND EPIDEMIC POPULATIONS OF CHORISTONEURA OCCIDENTALIS FREEMAN AND CHORISTONEURA RETINIANA (WALSINGHAM) (LEPIDOPTERA: TORTRICIDAE) IN SOUTHERN OREGON

1991

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Parasitoid species attacking sparse, endemic populations of Choristoneura occidentalis Freeman and C. retiniana (Walsingham) are reported from 2 years of host collections at seven sites across southern Oregon. Results are compared with rearings from epidemic populations either from the same region or the same plot. Collections were designed to allow quantitative estimation of host density. Most of the parasitoid species present during epidemics across North America were recovered from the endemic and epidemic populations studied. The major difference is that at endemic host densities Glypta fumiferanae (Viereck) (Ichneumonidae) is rare to absent, whereas ichneumonids of the tribe Campoplegini, especially Tranosema (= Diadegma) interruptum (Ashmead), are common. This is the reverse of the situation at epidemic densities and consistent with results reported from eastern North America. It is suggested that the observed shift in the parasite complex with budworm density has the potential for predicting population trends.

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Ecology of outbreak populations of the western spruce budworm

Nealis

Régnière

2021

Ecosphere

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We sampled outbreak populations of western spruce budworm, Choristoneura occidentalis (Lepidoptera: Tortricidae), between 1997 and 2016 in Douglas-fir forests in the interior of British Columbia, Canada. Annual rates of change in population densities were correlated with generation survival, modulated by egg recruitment via dispersal of moths. Most temporal variation in generation survival was the result of variation in survival of small, non-feeding larval stages. Survival rates of feeding larval and pupal stages determined the magnitude of generation survival but contributed little to temporal trend. Survival of small larvae was the product of density-related losses of larvae dispersing to and from hibernation sites and weather-related stress caused by warm temperatures in late summer and early spring. Overwinter survival improved in cooler years and at higher elevations. Survival of feeding larvae and pupae was associated with mortality by natural enemies, in particular a few species of dominant, ubiquitous endoparasitoids, and an episodic, virulent baculovirus. Recruitment of eggs indicated emigration of gravid moths independent of defoliation but proportional to density of local moths. During periods of increasing and decreasing population densities over a large outbreak area, a marked differential in adult densities among locations resulted in greater than expected per-capita egg recruitment to areas of relatively low density and vice versa, indicative of net exchange of gravid moths from high-to low-density populations. The result was homogenization of egg densities among locations, apparent synchrony of the outbreak at the large scale, and extended duration of the outbreak at some locations, despite declining generation survival. These results are compared with field studies of the closely related spruce budworm, Choristoneura fumiferana. We suggest our interpretation applies more generally and outbreaks of conifer-feeding budworms are maintained for several years by compensatory survival of sequential life-history stages and spatio-temporal smoothing of densities via dispersal of gravid moths. Parasitoids and pathogens can cause sudden declines in densities, but populations inevitably wane as a result of cumulative degradation of their resource. The interaction and temporal sequence of bottom-up and top-down factors explain the similarities and differences in outbreak characteristics within-and among-budworm species.

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Role of Parasites in the Population Dynamics of the Western Spruce Budworm (Lepidoptera: Tortricidae) in the Northwest

Cited by 8 publications

References 0 publications

THE CHALCIDOID PARASITOIDS AND HYPERPARASITOIDS (HYMENOPTERA: CHALCIDOIDEA) OFCHORISTONEURASPECIES (LEPIDOPTERA: TORTRICIDAE) IN AMERICA NORTH OF MEXICO

THE CHALCIDOID PARASITOIDS AND HYPERPARASITOIDS (HYMENOPTERA: CHALCIDOIDEA) OFCHORISTONEURASPECIES (LEPIDOPTERA: TORTRICIDAE) IN AMERICA NORTH OF MEXICO

PARASITOIDS OF ENDEMIC AND EPIDEMIC POPULATIONS OF CHORISTONEURA OCCIDENTALIS FREEMAN AND CHORISTONEURA RETINIANA (WALSINGHAM) (LEPIDOPTERA: TORTRICIDAE) IN SOUTHERN OREGON

Ecology of outbreak populations of the western spruce budworm

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