Sublethal effects of spinosad on survival, growth and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae).

BACKGROUND

Helicoverpa armigera (Hübner) is one of the most important pests in many countries. Spinosad is used widely for the control of pests, but there is sparse information available regarding its sublethal effects on H. armigera. Here, the authors attempt to investigate the sublethal effects of spinosad on H. armigera in order to reveal the negative, non-lethal impact of insecticides on this pest.

RESULTS

The toxicity of spinosad against H. armigera was determined under laboratory conditions by oral exposure of late second-instar larvae to the compound. The 48 h LC(50) and 72 h LC(50) values of spinosad to this pest were found to be 0.41 mg kg(-1) and 0.35 mg kg(-1) respectively. Spinosad at sublethal concentrations significantly extended the developmental time of survivor larvae, and reduced larval wet weight. Post-exposure effects were indicated by decreased pupation ratio and pupal weight, by prolonged prepupal and pupal periods and by decreased emergence ratio, fecundity and longevity of adults.

CONCLUSION

These results suggest that the combination of lethal and sublethal effects of spinosad might affect pest population dynamics significantly by decreasing its survival and reproduction, and by delaying its development.