Cyclosporin A as a Potential Insecticide to Control the Asian Corn Borer Ostrinia furnacalis Guenée (Lepidoptera: Pyralidae)

Abstract

The long-term use of chemical insecticides has caused serious problems of insect resistance and environmental pollution; new insecticides are needed to solve this problem. Cyclosporin A (CsA) is a polypeptide produced by many fungi, which is used to prevent or treat immune rejection during organ transplantation. However, little is known about the utility of CsA as an insecticide. Therefore, this study evaluated the insecticidal activity of CsA using Ostrinia furnacalis as a model. The results demonstrated that CsA was toxic to O. furnacalis with LC₅₀ values of 113.02 μg/g and 198.70 μg/g for newly hatched neonates and newly molted third-instar larvae, respectively. Furthermore, CsA treatment had sublethal effects on the development of O. furnacalis, and significantly reduced the fecundity of adults; this suggests that CsA has great potential to suppress O. furnacalis populations. Further analysis revealed that CsA suppressed calcineurin activity in larvae. CsA had independent or synergistic toxic effects on O. furnacalis when combined with β-cypermethrin, indoxacarb, emamectin benzoate, azadirachtin, and the Bacillus thuringiensis toxin Cry1Ac, which suggests that CsA can help prevent or manage resistance. Our study provides detailed information on the potential of CsA as an insecticide for controlling lepidopterans.

Keywords: Ostrinia furnacalis; cyclosporin A; insecticidal activity; sublethal dose.

Figure 1

Sublethal effects of CsA on O. furnacalis larvae, pupae, and adults. (A–C) The body size (A), weight (B), and larval period (C) of the larvae after treatment with 0, 24, and 48 μg/g of CsA for 8 days. (D) Pupation rate under the different treatments of CsA. (E–G) Effects of CsA on the body size (E), weight (F), and period (G) of the pupae. (H) Emergence rate under the different treatments of CsA. (I) Phenotype of adults under each treatment. Data are means ± SE of more than three biological replicates. The significant differences were analyzed using ANOVA followed by Tukey’s (equal variances assumed) or Dunnett’s T3 (equal variances not assumed) HSD test on SPSS Statistics 20. Different lowercase letters indicate significant differences at the level of p < 0.05.

Figure 2

Post-exposure effects of CsA on reproduction of O. furnacalis. (A) Ovaries under the different treatments of CsA. (B) Ovary length under the different treatments of CsA. (C) Number of mature eggs in ovaries under each treatment. (D) Effects of CsA on mating rate. (E) Eggs laid by adults each day under different treatments of CsA. (F) Eggs laid per female under different treatments of CsA. (G) Hatching rate of eggs under different treatments of CsA. Data are means ± SE of more than three biological replicates. Significant differences were analyzed using ANOVA followed by Tukey’s (equal variances assumed) or Dunnett’s T3 (equal variances not assumed) HSD test on SPSS Statistics 20. Different lowercase letters indicate significant differences at level of p < 0.05.

Figure 3

CaN activity of the larval midgut after treatment with CsA for 1, 3, 5, and 7 days. Data are means ± SE of three biological replicates. Different lowercase letters upon error bars indicate significant differences analyzed using ANOVA followed by Tukey’s (equal variances assumed) or Dunnett’s T3 (equal variances not assumed) HSD test on SPSS Statistics 20 at level of p < 0.05.

Figure 4

Combined toxicity of CsA and five toxins against 3rd-instar larvae of O. furnacalis. (A) Significant synergistic effects of the combinations of 5 μg/g of β-cypermethrin + 24/48/96 μg/g of CsA against 3rd-instar larvae for 2 days. (B) Significant synergistic combined toxicities of 10 μg/g of indoxacarb + 24/48/96 μg/g of CsA against 3rd-instar larvae for 3 days. (C) Expected and observed mortality under the combinations of 10 ng/g of emamectin benzoate + 24/48/96 μg/g of CsA for 3 days. (D) Expected and observed mortality caused by the combinations of 5 μg/g of azadirachtin + 24/48/96 μg/g of CsA against 3rd-instar larvae for 5 days. (E) Expected and observed mortality of larvae fed 10 μg/g of Cry1Ac + 24/48/96 μg/g of CsA for 5 days. Data are shown as means ± SE of three biological replicates, and the significant differences were analyzed using independent samples t-test on SPSS Statistics 20; “*” indicates p < 0.05, “N.S.” indicates no significant difference.