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Objective: To investigate the relationship between Wolbachia and deltamethrin resistance in Culex pipiens pallens., Methods: PCR was used to detect Wolbachia in Culex pipiens pallens and qRT-PCR was performed to determine and compare the expression of Wolbachia between deltamethrin- resistant and - susceptible strains of Culex pipiens pallens., Results: Wolbachia was detected in Culex pipiens pallens in the laboratory. The expression of Wolbachia was 18.42, 3.69, 4.43, 3.96, 6.31, 1.55 and 3.76 folds higher in the deltamethrin-resistant strain than in susceptible strain in the egg, 1st, 2nd, 3rd, 4th stages, and male and female adults, but there was no statistical difference in the pupae stage. The expression of Wolbachia was 2.64 folds higher in deltamethrin-resistant females than in susceptible females which were caught in Jiangxinzhou of Nanjing., Conclusion: Wolbachia is associated with deltamethrin resistance in Culex pipines pallens.

Objective: To understand the cross-resistance of Culex pipiens pallens to common pesticides, so as to provide the evidence for improving the application of chemical pesticides., Methods: The IV instar larvae of DDVP-resistant, propoxur-resistant and cypermethrin-resistant strains as well as the sensitive strain of Culex pipiens pallens were collected to detect the resistance to DDVP, propoxur and cypermethrin based on the WHO bioassay method., Results: The resistance coefficients of DDVP-resistant strain to DDVP, propoxur and cypermethrin were 14.47, 8.96 and 207.27 respectively. The resistance coefficients of propoxur-resistant strain to DDVP, propoxur and cypermethrin were 3.27, 6.93 and 8.65 respectively. The resistance coefficients of cypermethrin-resistant strain to DDVP, propoxur and cypermethrin were 2.93, 1.61 and 501.11 respectively., Conclusion: The resistance and cross-resistance could be generated during the long-term application of a single kind of chemical pesticide, and we should pay more attention to the varieties and dosages of them.

Objective: To evaluate the toxic effect of Bacillus thuringiensis var. israelensis (Bti) wettable powder against Aedes, Culex and Anopheles larvae., Methods: The biological assay was applied to test the lethal concentration of 50% (LC50) of Bti wettable powder against Aedes, Culex and Anopheles larvae., Results: The LC50(s) of Bti wettable powder against Aedes albopictus, Culex pipiens pallens and Anopheles sinensis larvae were 0.104, 0.160 microg/ml and 0.324 microg/ml, respectively; its biological potencies against them were 0.125, 0.192 IU/ml and 0.389 IU/ml, respectively. The LC50(s) of continuous contact of Bti wettable powder with An. sinensis stage III larvae for 1, 2 d and 3 d were 0.324, 0.092 microg/ml and 0.032 microg/ml, respectively, and its biological potencies were 0.389, 0.110 IU/ml and 0.038 IU/ml, respectively. The LC50(s) of the bacteria against An. sinensis stage I , II, III, IV were 0.024, 0.137, 0.324 microg/ml and 0.450 microg/ml, respectively, and the biological potencies were 0.029, 0.164, 0.389 IU/ml and 0.540 IU/ml, respectively., Conclusion: Bti wettable powder has a good toxicity to Aedes, Culex and Anopheles larvae, especially for the latter two. It is better to apply the bacteria at the early stage of mosquito larvae.

Objective: To compare the biological characteristics of Culex pipiens pallens between permethrin-resistant strain and the susceptible strain., Methods: In laboratory, the biological characteristics about bloodsucking, reproduction and development of permethrin-resistant and susceptible strains were observed and recorded. Life table of the experimental populations was constituted., Results: The bloodsucking rate of resistant strain was lower than susceptible strain and the difference was significant. The life-span of adults of resistant strain and the developmental duration of eggs, larvae and pupae were longer than susceptible strain and the difference was significant. The death rate of eggs of resistant strain was higher than that of susceptible strain and the difference was significant. The permethrin-resistant strain showed a fitness value of 0.58 relative to the susceptible strain., Conclusion: The permethrin resistance of Culex pipiens pallens may result in a disadvantage to its reproduction and development.