Abstract
This research examined the effects of the Cry1Ac toxin on the chrysopid predator Chrysoperla externa, fedAshbya gossypii-aphids reared on cotton (Bt) NuOPAL and non-Bt DeltaOPAL (BollgardTM) for two generations. Individual eggs from the predator were placed in glass containers, and hatched. Each treatment consisted of 20 replicates, each containing one insect. Larvae in treatment 1 were fed A. gossypii individuals reared on a diet of NuOPAL (Bt) cotton leaves. Larvae in treatment 2 were given aphids of the same species previously fed leaves of conventional DeltaOPAL cotton. The average duration of larval instars, pre-pupal and pupal phases from both treatments (Bt and non-Bt) and between generations were evaluated using the t test at 5% probability. The duration of the larval instars in treatment 2 was longer than in treatment 1, but these differences were significant only for the second and third instars. In the second generation, a significant difference in the duration of the first instar and the larval phase were observed. However, when comparing the data on the duration of the second instar, the first generation predators in treatment 1 had a shorter lifespan. The average viability was 96.29% for non-Bt treatment against 91.07% for individuals in the Bt treatment. The results of this study suggests that the biology and development of C. externa larvae fed aphids reared on Bt cotton leaves were not affected by the Bt-toxin, possibly because these aphids do not accumulate the Bt-toxin. Key words: Chrysopidae, biological control, genetically modified plant.
Highlights
The cotton aphid, Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) is found in all continents, and is abundant in the tropics, where it attacks many crops
We compared the lifespan of two generations of predators given a diet of aphids reared on cotton (Bt) NuOPAL and non-Bt DeltaOPAL
In Treatment 1, predators were offered A. gossypii cotton aphids reared on NuOPAL (Bt) cotton leaves
Summary
The cotton aphid, Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) is found in all continents, and is abundant in the tropics, where it attacks many crops. Studies on the tritrophic interactions between the predator C. carnea (Stephens) and the prey Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) found that predators consuming caterpillars contaminated with the Bt toxin had a reduced longevity when compared with predators eating caterpillars reared on a diet free from the toxin (Hilbeck et al, 1999; Dutton et al, 2002). In those studies, predators maintained on an artificial diet containing the Bt-toxin lived longer than their counterparts preying on items reared on Btcrop (Hilbeck et al, 1998b). We compared the lifespan of two generations of predators given a diet of aphids reared on cotton (Bt) NuOPAL and non-Bt DeltaOPAL
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