Response and effect of two plant crude extracts on mosquito larvae Culex pipiens

The response and effect of two plant crude extract from dry Damsissa (Ambrosia maritima) and Neem seeds (Azadirachta indica) were tested against the first and third instar larvae of mosquito (Culex pipiens). The results showed that both extracts had a larvicidal effect. Neem seed extract was more toxic than Damsissa extract against both the first and third instar larvae. In addition, the young larvae (first instar) were more susceptible to Neem seeds than the old ones (third instar) as revealed from the LC50 values, while Damsissa showed nearly the same effect against both stages. Meanwhile, treatment of Neem seed extracts resulted in prolongation of the larval period accompanied with a decrease in larval activity. Moreover, the effect of the two extracts on larval total esterase isozymes was examined. Neem extract showed an adverse effect on the third instar larvae, since only one band (E1) was observed and the other 4 bands disappeared at all concentrations used, as compared with untreated control larvae (El, E2, E3, E4, and E5). Meanwhile, Damsissa extract treatment of the third instar larvae showed an additional band located between E3 and E4, and the absence of two bands (E2 and E3) after treatment with 0.5x10(4), 1x10(4) and 1.5x10(4) ppm, while treatment with 0.25x10(4) ppm did not result in any changes in larval total esterase.