LC of lambda-cyhalothrin stimulates reproduction on the moth Mythimna separata (Walker).

Lambda-cyhalothrin has long been recommended as an effective insecticide to control the oriental armyworm, Mythimna separata (Walker), a notorious migratory pest of agricultural plants. Previous researches have suggested that survival, development, and reproduction of insects are influenced by sublethal concentrations of insecticides. However, the effects of sublethal concentrations of lambda-cyhalothrin on M. separata are less known. In this study, we determined the toxicity and effects of LC and LC concentration of lambda-cyhalothrin on development and reproduction of M. separata. Results indicate that LC of lambda-cyhalothrin tends to decrease the life traits of M. separate, with a shortening larvae period of offspring and oviposition period, whereas LC of lambda-cyhalothrin stimulates daily maximal fecundity and forwards the oviposition peak, suggesting a stimulation of reproduction by LC of lambda-cyhalothrin. The M. separata population was increased by an LC concentration of lambda-cyhalothrin, resulting in a net reproductive rate (R) and intrinsic rate of increase (r) significantly higher than that of the control. Transcripts of vitellogenin (MsVg) and vitellogenin receptor (MsVgR) genes were suppressed at day 1 after emergence of moth which developed from the larvae exposed to LC and LC of lambda-cyhalothrin, but were significant induced when the moth begin to lay eggs (day 4), with a more remarkable induction by LC of lambda-cyhalothrin than those of LC of lambda-cyhalothrin. Our results indicate that the observed stimulation of reproduction is therefore the results of up-regulation of MsVg and MsVgR by LC of lambda-cyhalothrin.