ZHANG Xiaoyue, MENG Fengxia, LIU Qiyong, REN Dongsheng, LIU Xiaobo, LI Guichang, LI Yuansa, WANG Jun, ZHAO Wei, WANG Xiaohua, HE Changhua, WANG Yanbo, ZHONG Wenbing, CAI Fang, OU Tingting, SUN Dingwei, ZENG Linhai, LI Shangan, LI Changqing
Objective The efficacy of spinosad Natular G30 against Culex pipiens quinquefasciatus was evaluated at different doses with comparing sewage habitat and small body of water with waste plants habitat, so as to provide evidence for mosquito control. Methods Using wild Cx. pipiens quinquefasciatus larvae and water in sewage and small body of water in Haikou, Hainan province, the efficacy of Natular G30 at 10, 20, 40, 80 mg/L was tested, percentage reduction was taken as efficacy index. The pH, temperature, total solids, salinity, dissolved oxygen of habitat water were determined at any two points of time during the trial period. Results There were significant differences (P＜0.05) between pH and dissolved oxygen in the two habitats, while no differences between temperature, total solids, salinity. The pH and dissolved oxygen of sewage water were (9.62±0.43) and (12.79±3.01) mg/L, and those in small body of water with wasted plants were (8.91±0.39) and (7.77±3.46) mg/L. The residual efficacy of Natular G30 at 10 mg/m2 and 20 mg/m2 against Cx. pipiens quinquefasciatus in sewage breeding site lasted for 12 days, while 40 mg/m2 and 80 mg/m2 in both habitats was more than 30 days. In two tested habitats, after one day of Natular G30 using, the first and second instar mosquito reduction was nearly 100%, but for the third and forth instar larvae, 100% reduction date was at three to seven days. To our surprise, the reduction of pupae was negative after one day insecticide applied. Conclusion Spinosad has high and long-lasting efficiency against Cx. pipiens quinquefasciatus larvae. Its effectiveness is better when applied in the habitats of small body of water with wasted plants than that of sewage. Spinosad has a very higher efficacy to control the first and second instar young larvae than the third and forth instars larvae, but no noticeable effect on pupae. To control Cx. pipiens quinquefasciatus, the spinosad rate should be adjusted based on the characteristics of habitat water.
