Larvicidal and Antifeedant Activities of Garlic (Allium sativum) Extract against the Larvae of Army Worm (Spodoptera frugiperda) on Maize Farm in Lapai Town Niger State, Nigeria

Abstract

This study evaluated the larvicidal and antifeedant efficacy of Allium sativum (garlic) extracts against S. frugiperda under laboratory conditions. Fresh garlic cloves were extracted using n-hexane, methanol, and aqueous solvents and screened for qualitative and quantitative phytochemical constituents. Larvicidal bioassays were conducted at concentrations of 5, 10, and 15 mg/mL, while antifeedant activity was assessed using treated maize leaf discs. Mortality was recorded after 24, 48, and 72 hours, and LC₅₀ values were determined using linear interpolation and probit regression. Data were analyzed using analysis of variance (ANOVA) at a 5% level of significance. Phytochemical screening revealed the presence of carbohydrates, alkaloids, flavonoids, saponins, quinones, terpenoids, steroids, and cardiac glycosides, with methanol extracts containing the highest concentrations of flavonoids (22.54 mg QE/g), tannins (15.33 mg TAE/g), and alkaloids (17.42 mg AE/g), while the aqueous extract contained the highest saponin content (16.53 mg DE/g). Larvicidal activity increased significantly with concentration and exposure time. The n-hexane extract exhibited the highest larval mortality (93.3%) at 15 mg/mL after 72 hours, followed by methanol (80.0%) and aqueous (73.3%) extracts, whereas the positive control (emamectin) achieved 100% mortality. The n-hexane extract also recorded the lowest LC₅₀ value (4.6 mg/mL), while methanol and aqueous extracts had LC₅₀ values of 7.2 mg/mL and 8.4 mg/mL, respectively. Antifeedant activity also increased with concentration, with the n-hexane extract producing the highest feeding deterrence (71.7%) at 15 mg/mL. The study concludes that garlic, particularly the n-hexane extract, possesses strong larvicidal and antifeedant properties against S. frugiperda and has considerable potential as an eco-friendly botanical insecticide for incorporation into integrated pest management programs.