Susceptibility of laboratory-reared anopheles stephensi (Diptera: Culicidae) and field-collected culex quinquefasciatus larvae to Bacillus thuringiensis serovar. Israelensis and Bacillus sphaericus in Lahore,Pakistan

Susceptibility of late 3 rd instars laboratory-reared anopheles stephensi and field-collected culex quinquefasciatus in lahore,pakistan to a technical powder of bacillus thuringiensis serovar. israelensis (bti) and a technical powder of bacillus sphaericus (bsph) were studied in the laboratory. at 24 h post-treatment the lc 50 and lc 95 values for an. stephensi amounted to 0.041 and 0.11 ppm,respectively. at 48 h post-treatment,these values were reduced to 0.025 ppm (lc 50) and 0.083 ppm (lc 95). in comparison,cx. quinquefasciatus larvae at 24 h post-treatment required 0.048 ppm bti to achieve lc 50 level and 0.128 ppm to achieve lc 95 level; the 48 h lc 50 for this species was exceptionally low (0.002 ppm). in general,both species exhibited somewhat similar levels of larval susceptibility to the technical powder of bti. the lc 50 and lc 95 values of bsph against an. stephensi at 24 as well as 48 h post-treatment were rather high,exceeding 1 ppm at the lc 95 level. however,cx. quinquefasciatus larvae were highly susceptible to bsph with lc 50 and lc 95 values of 0.043 and 0.12 ppm,respectively at 24 h,and at 48 h posttreatment,0.008 ppm (lc 50) and 0.11 ppm (lc 95). copyright 2011 zoological society of pakistan.