Bacillus thuringiensis var. kurstaki affects a beneficial insect, the cinnabar moth (Lepidoptera: Arctidae)
Authors: James, R.R., Miller, J.C., Lighthart, B.
Journal, Volume, Year: Journal of Economic Entomology, volume 86:334-339, 1993
Laboratory feeding studies, using foliage dipped in Btk solutions, were conducted to evaluate the effects of Btk on first through fifth instars of the cinnabar moth. Survival of first through third instars was unaffected, but fourth and fifth instars were susceptible. Field tests were also conducted to evaluate the effects of Btk on larval defoliation of potted tansy ragwort plants. Five application rates of Btk were used, and application rate was found to significantly affect percentage of leaves defoliated and mean number of cinnabar moth-days per plant.
The authors suggest that Btk may interfere with the biological control of tansy ragwort, however, most applications for western spruce budworm and gypsy moth occur when early instars of cinnabar moths are present. Therefore, it does not appear that transgenic plants expressing Bt toxins are likely to interfere with the cinnabar moths biological control of tansy ragwort.