Influence of Aquatain™, a monomolecular surface film on surface tension for controlling the filarial vector Culex pipiens (Diptera: Culicidae)

Surface tension is a phenomenon in the liquid media and plays an important part in the development and survival of aquatic animals. Influence of Aquatain™ monomolecular film on surface tension was determined against mosquito larvae and pupae at different temperatures (10, 15, 20, 25, 30 and 35 °C) and Aquatain™ doses (0.5, 1.0 and 2.0 ml/m(2)). In the laboratory, Aquatain™ showed larvicidal and pupicidal effects against the filarial vector Culex pipiens. Higher mortality was observed in late and more weighted instars/stages than young ones as well as in the pupal stage. The pupal mortality reached 76.2%, 86% and 93.3% after 12 h post-treatment at 0.5, 1.0 and 2.0 ml/m(2), respectively, and it was completely eliminated (100%) within 24 h compared to 15.1%, 26.9% and 38.2% for 1(st) larval instar, respectively. Also, results showed at 0.5 ml/m(2) with temperature range: 10, 15, 20, 25, 30 and 35 °C, the mortality reached 4.0, 6.7, 10.8, 17.3, 22.7, 29.3% and 32, 44, 54, 72, 84, 97.3% for 1(st) and 4(th) larval instar, respectively, where the surface tension (γ) was 65.6, 62.4, 58.0, 57.0, 54.2 and, 49.6 dyn/cm, while the Aquatain™ was more effective on mosquito larvae and pupae at high doses with the temperature range. On the other hand, without Aquatain™ dose, the mortality value ranged between 0.0 - 1.2%, and the surface tension (γ) was 74.5 dyne/cm, which is considered as an accidental death. Aquatain™ was effective against all aquatic phases of mosquitoes, especially against the last and weighted ones. Not only was the efficacy of Aquatain™ increased by increasing the dose, but it also increased with the increased temperature of the environment. This efficiency of Aquatain™ is due to its ability to reduce the surface tension of the water medium, preventing different stages of mosquitoes from reaching the surface for breathing thereby leading to suffocation and death. Therefore, we recommended Aquatain™ in programmes for mosquito control and other aquatic insects as a safe, cost-effective control agent.