Abstract
Sub-lethal effects of commercially formulated Bacillus thuringiensis Berliner var. tenebrionis and B. thuringiensis var. kurst were investigated on second instar larvae of Colorado potato beetle, Leptinotarsa decemlineata (Say). Feeding, development and survival to adulthood were examined after exposing larvae to B. thuringiensis (400 ppm) treated potato foliage. Significant difference was observed between the treatments for all of the studied traits at p = 0.01%. Eight days after the release of the larvae, larvae weights on B. thuringiensis var. kurstaki (400 ppm)-treated foliage and control foliage were 18.30 ± 1.01 and 158.00 ± 3.36 mg, respectively. Mortality rates during developmental stages (larvae and pupae) on B. thuringiensis var. kurstaki (400 ppm)-treated foliage and control foliage were 86.00 ± 2.45 and 26.00 ± 4.00%, respectively. The longest developmental time (larvae and pupae) was observed on B. thuringiensis var. kurstaki (400 ppm)-treated foliage with means of 30.18 ± 2.18 days and the least developmental time was observed on control with means of 19.44 ± 1.00 days. The results from this study indicate that the overall mortality caused by the application of B. thuringiensis-based insecticides will be higher than the estimated amounts, because high levels of mortality occurring during the later larval stage and the pupae stage in the B. thuringiensis-contaminated groups are often neglected.
Published Version
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