Journal of Economic Entomology (1995) 88, 97-105

Kees van Frankenhuyzen, Carl W. Nystrom and Bruce E. Tabashnik (1995)
Variation in tolerance to Bacillus thuringiensis among and within populations of the spruce budworm (Lepidoptera: Tortricidae) in Ontario
Journal of Economic Entomology 88 (1), 97-105
Abstract: Variation in tolerance to Bacillus thuringiensis Berliner subsp. kurstaki (strain HD-1-S-1980) among and within populations of the spruce Budworm, Choristoneura fumiferana (Clemens), was assessed in the laboratory. Force-feeding assays using offspring of females collected as pupae from nine locations throughout Ontario and from a laboratory colony (DCF) demonstrated limited variation in tolerance among populations. Variation among populations was comparable with the variation observed among repeated assays with different batches of larvae from the DCF colony. Population LC₅₀s were not significantly associated with age of the outbreak, host-plant species, incidence of the microsporidian Nosema fumiferanae (Thomson), or size of the-female parent. Upper limits for genetic variation in tolerance were estimated by examining variation among full-sibling families within same populations. Mortality of individual families ranged from 6.5 to 70.9% within five field populations and from 2.7 to 93.3% within two laboratory colonies in response to a dose that caused a mean mortality of 40%. Familial factors accounted for 32.8% of the phenotypic variation in response across field populations, as compared with 3% for population factors. These data suggest that the phenotypic variation in tolerance to B. thuringiensis has a substantial genetic component and may provide a basis for evolution of resistance given sufficient selection pressure.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Kees van Frankenhuyzen, Bruce E. Tabashnik

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Choristoneura fumiferana		Canada (east)
Bacillus thuringiensis var. kurstaki (entomopathogen)	Choristoneura fumiferana		Canada (east)