Effects of sublethal concentrations of abamectin on development of Oligonychus litchii

In order to investigate the sublethal effects of abamectin on the development of Oligonychus litchii, Potter-spraying method was employed to test the sublethal concentrations (LC10 and LC30) of abamectin to adults of O. litchii, and analyzed the effects of sublethal concentrations (LC10 and LC30) of abamectin on the growth and reproduction of O. litchii by means of lifetables in laboratory. The results showed that the fecundity of female adults treated with abamectin at concentrations of LC10 and LC30 were reduced by 79.16% and 71.83%, respectively, and their longevities were also reduced significantly. The duration of larval and preoviposition stages of F1 generation were not significantly different from that of the control. But the duration of egg, proto-nymph, deuto-nymph of F1 generation were longer than that of the control, Which of the LC30 treatment samples were increased by 41.4%, 39.4%, 36.1%, respectively. In addition, both the fecundity and egg laying period of female adults decreased,and the sex ratio of progeny of O. litchii was improved. After treated by sublethal concentrations (LC10 and LC30) of abamectin, the intrinsic rates of increase were decreased from 0.132 3 to 0.127 3 and then to 0.0758. The mean generation time was shorter than that of the control and the population doubling time was longer than that of the control. The net reproductive rate and finite rate increase were both decreased compared to the control. These results indicated that abamectin at sublethal concentrations had a negative effect on the population development of O. litchii.