Study on the Resistance of Culex tritaeniorhynchus to DDT and Deltamethrin in Yunnan Province

Objective To investigate the resistance level of Culex tritaeniorhynchus to DDT and deltamethrin in Yunnan Province. Methods Adult Culex tritaeniorhynchus samples were collected in Zhaoyang District of Zhaotong City, Mangshi County of Dehong Prefecture, Yuanjiang County of Yuxi City, Jiangcheng and Menglian County of Puer City. The susceptibility of Cx. tritaeniorhynchus to DDT and deltamethrin were tested by bioassay method. The resistance level was judged by adjusted mortality. Results Culex tritaeniorhynchus collected from Zhaoyang, Mangshi, Jiangcheng,Menglian, and Yuanjiang, and exposed to DDT for 1 h, the mortality after 24 hours was 51.1%, 86.8%, 35.4%, 21.0%,and 4.6%, respectively; the resistant grade in Mangshi was maybe resistance(M), and the others 4 sites were resistance(R). The range of KT50 to DDT was from 18.76 min to 395.65 min. The mortality of the mosquitoes from the five sites to deltamethrin was 36.9%, 59.2%, 43.1%, 34.1%, and 3.3%, respectively; the resistant grade was R in all sites, and the range of KT50 was 8.69-715.37 min. Conclusion Culex tritaeniorhynchus in Yunnan Province shows simultaneously resistant to DDT and deltamethrin, and therefore the insecticiding strategy should be adjusted.