Agricultural and Forest Entomology (2002) 4, 57-70

Éric Bauce, Yannick Bidon and Richard Berthiaume (2002)
Effects of food nutritive quality and Bacillus thuringiensis on feeding behaviour, food utilization and larval growth of spruce budworm Choristoneura fumiferana (Clem.) when exposed as fourth- and sixth-instar larvae
Agricultural and Forest Entomology 4 (1), 57-70
Abstract: 1. Feeding behaviours, and lethal and sublethal (growth, development and food utilization) effects of Foray 48B, a commercial formulation of Bacillus thuringiensis (kurstaki), were investigated on fourth- and sixth-instar spruce budworm larvae according to food nutritive quality. Nitrogen and soluble sugar content of artificial diets were modified to obtain three different qualities of food, simulating variations in nutritive quality of host tree.
2. Larval development times were longer for Bt-treated larvae and pupal weights were reduced for sixth-instar larvae only. Bt-induced mortality levels were influenced by food quality. Ingested dose of Bt and feeding inhibition times were strongly affected by the Bt treatment, but food quality affected only fourth-instar larvae. Except for food digestibility, nutritional indices were negatively affected by the Bt treatment and by the reduction in food quality.
3. Contrary to early treated larvae (fourth instar), larvae treated at the beginning of the sixth instar were not able to compensate for Bt injury and were consequently more affected by the Bt-treatment both in terms of lethal and sublethal effects.
4. Bt efficacy was not directly related to the ingested dose.
5. Increase in larval vulnerability to Bt was more likely a consequence of a general stress induced by a less suitable food than a direct interaction between Bt and food nitrogen or sugar compounds.
6. The application of Bt on late-instar larvae could be a successful operational strategy at low population levels when field sprays target the insect instead of foliage protection.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Eric Bauce

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution
application technology

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Pest and/or beneficial records:

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