Prey‐mediated effects of Cry1Ab toxin and protoxin and Cry2A protoxin on the predator Chrysoperla carnea

Journal or Publishing Institution: Entomologia Experimentalis et Applicata

Study: https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1570-7458.1999.00497.x

Author(s): Hilbeck, A., Moar, W.J., Pusztai‐Carey, M., Filippini, A. and Bigler, F.

Article Type: Peer Reviewed Study

Record ID: 1004

Abstract: Laboratory feeding experiments were carried out to study prey-mediated effects of artificial diet containing Bacillus thuringiensis proteins on immature Chrysoperla carnea. Activated Cry1Ab toxin and the protoxins of Cry1Ab and Cry2A were mixed into standard meridic diet for Spodoptera littoralis (Boisduval) larvae at the following concentrations; for Cry1Ab toxin, 25, 50, 100 µg g−1 diet were used; for Cry1Ab protoxin, the concentration was doubled (50 µg g−1 diet, 100 µg g−1 diet and 200 µg g−1 diet) to give relative comparable levels of toxin concentration. Cry2A protoxin was incorporated into the meridic diet at one concentration only (100 µg g−1 diet). For the untreated control, the equivalent amount of double distilled water was added to the meridic diet. Individual C. carnea larvae were raised on S. littoralis larvae fed with one of the respective treated meridic diets described above. The objectives were to quantify and compare the resulting effects on mortality and development time of C. carnea with those observed in two previous studies investigating prey-mediated effects of transgenic Cry1Ab toxin-producing corn plants and the other studying effects of Cry1Ab toxin fed directly to C. carnea larvae. Mean total immature mortality for chrysopid larvae reared on B. thuringiensis-fed prey was always significantly higher than in the control (26%). Total immature mortality of C. carnea reared on Cry1Ab toxin 100 µg g−1 diet-fed prey was highest (78%) and declined with decreasing toxin concentration. Cry1Ab protoxin-exposed C. carnea larvae did not exhibit a dose response. Prey-mediated total mortality of Cry1Ab protoxin-exposed chrysopid larvae was intermediate (46–62%) to Cry1Ab toxin exposed (55–78%) and Cry2A protoxin (47%) exposed C. carnea. In agreement with the previous studies, total development time of C. carnea was not consistently, significantly affected by the Bt-treatments except at the highest Cry1Ab toxin concentration. However, both highest mortality and delayed development of immature C. carnea raised on Cry1Ab toxin 100 µg g−1 diet – fed prey may have been confounded with an increased intoxication of S. littoralis larvae that was observed at that concentration. At all other B. thuringiensis protein concentrations S. littoralis was not lethally affected. Comparative analysis of the results of this study with those of the two previous studies revealed that in addition to prey/herbivore by B. thuringiensis interactions, also prey/herbivore by plant interactions exist that contribute to the observed toxicity of B. thuringiensis – fed S. littoralis larvae for C. carnea. These findings demonstrate that tritrophic level studies are necessary to assess the long-term compatibility of insecticidal plants with important natural enemies.

Keywords: Bacillus thuringiensis, Cry1Ab, Cry2A, Chrysoperla carnea, Spodoptera littoralis, Ostrinia nubilalis, natural enemies, transgenic plants, tritrophic level experiments, arthropods, Bacillus thuringiensis, Chrysoperla carnea, insects, Spodoptera littoralis, agricultural entomology, arthropod pests, bacterial insecticides, bacterial toxins, beneficial arthropods, beneficial insects, beneficial organisms, biological control, biological control agents, diets, entomopathogens, insect pests, insecticides, natural enemies, nontarget effects, pathogens, pests, plant pests, predators, predatory insects, prey, toxins, bacterium, beneficial species, biocontrol, biocontrol agents, biological control organisms, pest arthropods, pest insects, predaceous insects, predacious insects, invertebrates, animals, eukaryotes, Bacillus (Bacteria), Bacillaceae, Bacillales, Bacilli, Firmicutes, Bacteria, prokaryotes, Chrysoperla, Chrysopidae, Neuroptera, insects, Hexapoda, arthropods, Spodoptera, Noctuidae, Lepidoptera, Chrysoperla carnea, toxin, toxins, predator, diet, predators, Spodoptera littoralis, meridic diets, larva, larvae, Bacillus thuringiensis, immatures, mortality, herbivores, herbivore, pesticidal plants, effect, artificial diet, protein, artificial diets

Citation: Hilbeck, A., Moar, W.J., Pusztai‐Carey, M., Filippini, A. and Bigler, F., 1999. Prey‐mediated effects of Cry1Ab toxin and protoxin and Cry2A protoxin on the predator Chrysoperla carnea. Entomologia Experimentalis et Applicata, 91(2), pp.305-316.