Effect of Bacillus thuringiensis var krustaki on the mortality and development of Culex pipiens (Diptera; Cullicidae)

The bacterium Bacillus thuringiensis, is one of the insecticides mostly used at the moment as agent of biological control to suppressing the populations of diverse insect pests. The present study tested the strain Bacillus thuringiensis var krustaki against fourth stage larvae of Culex pipiens where they were exposed to different concentrations of Btk (25mg/l, 50mg/l et 83mg/l) for 48h, 120h, 240h and 360 hours. High larval mortality was recorded; this toxicity is expressed in terms of dose and time. Lethal concentrations LC50 calculated after 48 hours is 380.19 mg/l and the LC90 was 8912.51 mg/l. However, at 360 hours of the treatment, the CL50 % and the CL90 % does not exceed the 52.48 mg/l and 107.15 mg/l. Btk disrupts fecundity and fertility of adults issued from treated larvae, with an average low eggs of 33.20 ± 5.116 induced by the dose of 25 mg/l and low hatching duration of eggs with 2.30 ± 0.48 %.