Laboratory efficacy of polydimethylsiloxane liquid film against three mosquito species
Objective To evaluate and compare the efficacy of polydimethylsiloxane liquid film against the larvae and pupae of Culex pipiens quinquefasciatus,Aedes albopictus,and Ae.aegypti at different instars under laboratory conditions.Methods Thirty samples each of larvae of different instars and pupae were selected and placed in water containing the liquid film(1 ml/m2).The growth,development,and death of the larvae or pupae were observed in a laboratory environment or in an artificial incubator at different temperatures.The data were organized and analyzed using Excel 2016 and SPSS 27.0 softwares.The survival curves of larvae or pupae exposed to the liquid film between different groups were compared using the log-rank test.The length of larvae was compared using the independent samples t-test.Results After exposure to the 1 ml/m2 liquid film,the median lethal times for the larvae at Ⅰ-Ⅱ instars of Cx.pipiens quinquefasciatus,Ae.albopictus,and Ae.aegypti were 2.67,7.04,and 6.45 d,respectively;for the larvae at Ⅲ-Ⅳ instars,the values were 0.53,1.64,and 1.71 d,respectively;and for the pupae,the values were 96.68,115.54,and 109.77 min,respectively.After 7 days of rearing,the mean larval lengths for Cx.pipiens quinquefasciatus,Ae.albopictus,and Ae.aegypti exposed to the liquid film were(3.28±0.40),(3.17±0.61),and(3.21±0.47)mm,respectively,which were significantly shorter than their respective control groups(all P＜0.001).Across the temperatures of 20,25,30,and 35 ℃,the mortality rates of larvae in the liquid film groups increased with rising temperatures:the mortality rates on the first day were 66.67％,71.11％,91.11％,and 100％for Cx.pipiens quinquefasciatus,respectively;8.89％,30.00％,55.56％,and 81.11％for Ae.albopictus,respectively;and 14.44％,25.56％,56.67％,and 75.56％for Ae.aegypti,respectively.Conclusions The polydimethylsiloxane liquid film can well control the larvae and pupae of the three mosquito species and impede larval growth and development,and high temperatures can enhance the effectiveness.The polydimethylsiloxane liquid film is suitable for controlling various types of mosquitoes.
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