Bacillus velezensis as an active ingredient in toxic sugar baits against adult Culex quinquefasciatus (Diptera: Culicidae)

Abstract Toxic sugar baits (TSBs) exploit mosquito sugar-feeding behavior to deliver orally ingested lethal toxins. Most existing TSB formulations rely on synthetic chemical insecticides, highlighting the need to evaluate alternative active ingredients compatible with TSB delivery systems. Bacillus velezensis (Bv), a bacterium with demonstrated mosquitocidal activity, represents a promising microbial active ingredient but has not previously been evaluated as the active ingredient in TSBs. We evaluated the oral toxicity effects of Bv crude toxin-containing sugar bait (BvTSB) against adult Cx. quinquefasciatus, quantifying acute mortality, longevity, and reproductive outcomes. Ingestion of BvTSB caused significant lethal mortality in both sexes compared to sugar-fed controls, with males exhibiting greater susceptibility than females. Sublethal exposure reduced adult longevity, decreased egg production, and lowered fertility. These results demonstrate that Bv adversely affects multiple life history traits relevant to mosquito population dynamics and impairs traits related to vectorial capacity. Collectively, our findings show that Bv, when used as the active ingredient in toxic sugar baits, exhibits substantial mosquitocidal activity against adult Cx. quinquefasciatus and may serve as an alternative active ingredient to conventional chemical insecticides in TSB-based vector control.