COMPARABILITY OF TWO COMMERCIAL FORMULATIONS OF BACILLUS THURINGIENSIS VAR ISRAELENSIS AND B. SPHAERICUS AGAINST LARVAE OF CULEX QUINQUEFASCIATUS (D1PTERA:CULICIDAE) IN VARIOUS ECOLOGICAL NICHES

Abstract-A study was initiated in the laboratory to compare the effects of spore dust and sawdust formulations of Bacillus thuringiensis var israeler~sis and B.sphaericus on immatures of laboratory and field samples of C.quinquefasciatus. Various types of ecological niches including cess pits, cement tanks and 'U' drain which form the habitats of the mosquitoes, were selected for this study. Bacilli formulations were tested against 2nd, 3rd and 4th instar larvae of laboratory and field collected samples as mentioned above and the LC50 values were determined by computer analyses. The LCsos of B.t/luringiensis were compared with those of B.sphaericus and it was concluded from this study that B.rhuringiensis is highly toxic to all stages of larvae in laboratory and field habitats. Both sawdust formulations produced 80-100 % mortality after 24 hrs. in all stages of larvae from three habitats and in laboratory samples at 0.005 % concentration. It was concluded from these results that B.rhuringiensis is a more effective biocide than B.spkuericus in moderate and tropical conditions