Stress response of sixth instar spruce budworm [Choristoneura fumiferana (Clem.)] larvae surviving application of sublethal doses of fenitrothion or Bacillus thuringiensis var. alesti. as exhibited by two developmental stages.

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University of New Brunswick


Sixth instar spruce budworm Choristoneura fumiferana (Clem.) larvae were treated with sub-lethal doses of fenitrothion a chemical insecticide and Bacillus thuringiensis van alesti a biological insecticide. The effects of each insecticide on the surviving larvae were monitored. Larvae treated with, but not killed by the insecticides, required less time to complete pupation. Larvae treat ed with fenitrothion, appeared to pupate within a shorter time interval, than larvae treated with Bt. var. alesti, however the difference was not statistically different. A given treatment appeared to be effective in reducing pupal mass relative to its control, however significant interaction prevented further statistical analysis from being undertaken. I t was not possible to clearly indicate from the results of this experiment which of the two insecticides is more effective in controlling spruce budworm. However, a literature survey revealed that fenitrothion causes more disturbance in the forest ecosystem than Bt. var. alesti and from this point of view Bt. var. alesti may be considered more desirable of the two insecticides.