Multi-stage bioefficacy of Bacillus thuringiensis extract against Culex quinquefasciatus: effects on mortality, egg hatching and adult emergence

Tara Aso Taher, Sahar Abd Kathier

Abstract


Mosquito control requires effective alternatives to conventional insecticides. This study evaluated the insecticidal activity of Bacillus thuringiensis extract against different developmental stages of Culex quinquefasciatus. The extract exhibited significant, concentration-dependent ovicidal, larvicidal, and pupicidal activities. The highest concentration (10-1) caused 100% egg mortality and completely inhibited hatching, while the 10-2 and 10-3 concentrations resulted in 97.67% and 91.33% mortality, respectively. Against fourth-instar larvae, mortality reached 70.00% at the highest concentration, compared with 56.67% and 43.33% at the 10-2 and 10-3 concentrations, respectively. Exposure also caused substantial delayed mortality during pupation (62.33–68.33%) and markedly reduced adult emergence to 10.00–23.33%, compared with 100% in the untreated control. Direct pupal treatment resulted in 60.00–80.00% mortality, with adult emergence decreasing to 20.00% at the highest concentration. Probit analysis further demonstrated high toxicity, with LC50 values of 3.13 × 10-3 for fourth-instar larvae and 1.44 × 10-4 for pupae. The models showed satisfactory goodness of fit (P > 0.05). Overall, the B. thuringiensis extract demonstrated substantial toxicity across multiple developmental stages and disrupted mosquito development and adult emergence. These findings support its potential as a biological tool for managing C. quinquefasciatus, although further studies are needed to establish field efficacy, environmental safety, and practical application.

Keywords


Bacillus thuringiensis, Culex quinquefasciatus, Ovicidal activity, Larvicidal activity, Mosquito control

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References


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DOI: https://doi.org/10.33804/pp.010.05.6268

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