Evaluation of the insecticidal activity of the spider-venom peptides Dc1a and Ta1a against economically important lepidopteran pests

Lepidopterans are the most economically significant crop pests. They are mainly controlled with chemical insecticides that often suffer from insect resistance and adverse effects on the environment and human health. Insect-specific spider-venom peptides are considered safer, eco-friendly alternatives to chemical insecticides, and two insecticidal spider-venom derived peptides have already been commercialised by Vestaron Corporation, while more candidates are being progressed in global discovery pipelines. This study focusses on two insecticidal spider-venom peptides-Dc1a and Ta1a- and assesses their suitability in targeting five species of lepidopteran pests by injection and oral application, using Vestaron's commercial ω/κ-Hv1a as a reference. In addition, the potential of bacterial Bt Cry toxins in providing synergistic insecticidal activities with these spider-venom peptides is evaluated. We found that when applied by injection, all peptides caused paralysis and mortality against all tested lepidopteran species within a narrow dose range. In contrast, the differences in insecticidal activity were more pronounced when orally applied. Helicoverpa consistently was the genus most susceptible to the spider-venom peptides, independent of the route of application, which we presume being related to its particular food preferences. Furthermore, we found synergistic activities for co-application of each of the spider-venom peptides with sublethal amounts of Bt Cry toxins in H. armigera. Overall, our results indicate that Dc1a and Ta1a are suitable bioinsecticide candidates for targeting certain lepidopteran pests, with co-application of Bt Cry toxins considered a viable strategy for increasing their efficacy as foliar sprays.