Biological and Biochemical Studies on Culex pipiens L. (Diptera:Culicidae) Exposed to Allium sativum,Nigella sativa Oil Extractsand Bacillus sphaericus(Neid)

Abstract

Bacillus sphaericus has a larvicidal activity towards Culex pipiens larvae.Development of resistance in certain populations of Culex sp. is the most common disadvantage of B. sphaericus application. During application, pesticide, B. sphaericus formulations suffering from long exposure to sun light and UV which turned them impotent. So, the present study was designed to evaluate the larvicidal activity of Bacillus sphaericus toxin, Allium sativum and Nigella sativa oil extracts solitary and in combination against Culex pipiens 3rd larval instar. Data revealed that, Bacillus sphaericus was the most potent insecticide recording LC50 value as (0.25ppm.) followed by Allium sativum and Nigella sativa recording (0.45 and 2.46 ppm.), respectively. Addition of Allium sativum generally increased the toxic effect of Bacillus sphaericus, where LC50 decreased from (0.25 ppm to 0.12 ppm). Addition of Nigella sativa to Bacillus sphaericus decreased the toxicity of Bacillus sphaericus by increasing its LC50 from (0.25 ppm to 0.39 ppm) .The biochemical studies using (SDS-PAGE), revealed that there was an increase in number of protein bands due to treatment with (Bacillus sphaericus combined with Allium sativumandBacillus sphaericus with Nigella sativa). Theseimpressive results from combinations proved that when joint-action is considered, the application possibilities for vector control increase significantly.

Keywords: Bacillus sphaericus, Plant oil extracts, Allium sativum, Nigella sativa, Culex pipiens, Bioassay test, protein electrophoresis.