Delayed mortality and morphogenetic anomalies induced by the microbial control agent Bacillus thuringiensis ser....

Sublethal concentrations of Bacillus thuringiensis ser. H-14 were applied to early 4th-instar larvae of Culex quinquefasciatus to assess mortality and morphogenetic aberrations in larvae, pupae and adults. At the 24 h LC10, LC25, LC50 and LC80, additional mortality occurred in surviving larvae beyond a 24 h exposure period. The cumulative mortalities increased daily and the overall mortality of larvae up to 7 days posttreatment were 12, 73, 82 and 96% at the indicated concentrations, respectively. Delayed mortality also occurred in the pupal and adult stages. Morphogenetic aberrations were noted in dead larvae and pupae but were rare in the adults. These aberrations are categorized and described. There was little or no delayed effect on the survivorship or fecundity of adults, but in all the treatments the number of emerging males was higher than females. The sex ratio in check adults was 1:1.