Efficacy of Bacillus thuringiensis israelensis (Bti) and four plant extracts on the mortality and development of Culex quinquefasciatus Say (Diptera: Cullicidae)

The efficacy of the bio-insecticide, Bacillus thuringiensis var. israelensis ( Bti ), and four plant-ethanol extracts Cinnamomum osmophloeum , Matricaria chamomilla , Seasamum indicum , and Nigella sativa was tested against larvae of filarial vector, Culex quinquefasciatus , under laboratory conditions. The Bti and extracts of N . sativa and C . osmophloeum showed the highest insecticidal activity, with LC 50 values of 7.18, 14.59, and 28.87 mg/l 24 and 48 h post treatments, respectively. The extracts of M . chamomilla and S . indicum were effective. The tested extracts altered some biological aspects of Cx . quinquefasciatus , i.e., developmental periods, pupation rate, and adult emergence. Pupation rate was suppressed by Bti at 7.5 mg/l and by C . osmophloeum at 75 mg/l. In addition, the tested plant extracts exhibited various morphological abnormalities of larvae, pupae, and adults.