Malaria vector control in Ethiopia faces growing challenges due to widespread insecticide resistance and environmental concerns associated with synthetic chemicals. Botanical insecticides offer a promising alternative; however, systematic evaluations of locally available plants and their combinations remain limited. This study investigated the larvicidal efficacy of selected single and combined plant extracts against 4th instar Anopheles arabiensis larvae. Larvicidal activity of Allium sativum (garlic bulbs), Zingiber officinale (ginger rhizomes), Eucalyptus globulus (leaves), Nicotiana tabacum (leaves), and Phytolacca dodecandra (leaves) extracts were evaluated against 4th instar larvae of Anopheles arabiensis under laboratory conditions. Crude extracts were prepared using aqueous and ethanol solvents from each plant species. Individual (single) treatments were tested separately for each extract, while combined treatments were formulated by mixing extracts in equal proportions to generate two, three, and five-component combinations. The concentrations of 0.05, 0.1 and 0.15 mg/mL with three replications for each was prepared for both single and combined extracts, and standard larval bioassays were conducted following WHO guidelines. Larval mortality was recorded after 24, 48, and 72 h of exposure, and all treatments were replicated. Control groups containing solvent only were included for comparison. Data were analyzed using one-way ANOVA followed by Tukey’s HSD for mean separation, and probit analysis was conducted to determine LC50 and LC90 values. Larval mortality increased with concentration and exposure time. Among single extracts, at 72 h, P. dodecandra aqueous extract at 0.15 (mg/mL) resulted in complete larval mortality, whereas the ethanol extract at the same concentration caused 93.33% mortality. The maximum mortality for three-plant aqueous combinations at 72 h was 88.68%, observed for Z. officinale + P. dodecandra + N. tabacum, followed closely by 88.33% for A. sativum + P. dodecandra + N. tabacum, both at 0.15 mg/mL. Probit analysis revealed substantially lower LC50 values for ethanol extracts compared to aqueous extracts, indicating higher potency. Significant differences (p < 0.05) were observed among treatments and concentrations. Both single and combined plant extracts particularly ethanol-based formulations exhibited strong larvicidal activity against An. arabiensis. These findings highlight the potential role of locally sourced botanical insecticides in enhancing sustainable malaria vector control strategies. Further field validation and formulation refinement are recommended.

Larvicidal efficacy of selected botanical extracts applied singly and in combination against Anopheles arabiensis in Ethiopia: laboratory study results

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发表日期：

2026年5月2日

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Getnet Atenafu

摘要

Malaria vector control in Ethiopia faces growing challenges due to widespread insecticide resistance and environmental concerns associated with synthetic chemicals. Botanical insecticides offer a promising alternative; however, systematic evaluations of locally available plants and their combinations remain limited. This study investigated the larvicidal efficacy of selected single and combined plant extracts against 4th instar Anopheles arabiensis larvae. Larvicidal activity of Allium sativum (garlic bulbs), Zingiber officinale (ginger rhizomes), Eucalyptus globulus (leaves), Nicotiana tabacum (leaves), and Phytolacca dodecandra (leaves) extracts were evaluated against 4th instar larvae of Anopheles arabiensis under laboratory conditions. Crude extracts were prepared using aqueous and ethanol solvents from each plant species. Individual (single) treatments were tested separately for each extract, while combined treatments were formulated by mixing extracts in equal proportions to generate two, three, and five-component combinations. The concentrations of 0.05, 0.1 and 0.15 mg/mL with three replications for each was prepared for both single and combined extracts, and standard larval bioassays were conducted following WHO guidelines. Larval mortality was recorded after 24, 48, and 72 h of exposure, and all treatments were replicated. Control groups containing solvent only were included for comparison. Data were analyzed using one-way ANOVA followed by Tukey’s HSD for mean separation, and probit analysis was conducted to determine LC₅₀ and LC₉₀ values. Larval mortality increased with concentration and exposure time. Among single extracts, at 72 h, P. dodecandra aqueous extract at 0.15 (mg/mL) resulted in complete larval mortality, whereas the ethanol extract at the same concentration caused 93.33% mortality. The maximum mortality for three-plant aqueous combinations at 72 h was 88.68%, observed for Z. officinale + P. dodecandra + N. tabacum, followed closely by 88.33% for A. sativum + P. dodecandra + N. tabacum, both at 0.15 mg/mL. Probit analysis revealed substantially lower LC₅₀ values for ethanol extracts compared to aqueous extracts, indicating higher potency. Significant differences (p < 0.05) were observed among treatments and concentrations. Both single and combined plant extracts particularly ethanol-based formulations exhibited strong larvicidal activity against An. arabiensis. These findings highlight the potential role of locally sourced botanical insecticides in enhancing sustainable malaria vector control strategies. Further field validation and formulation refinement are recommended.