Efficacy of Seed Oils From Azadirachta indica and Schinus molle and Their Combination Against Anopheles gambiae s.l.

Due to the increasing resistance to synthetic insecticides and the proliferation of resistant strains of malaria vectors, plant-derived essential oils (EOs) are gaining prominence as an alternative for controlling Anopheles gambiae s.l. larvae. This study evaluated the larvicidal efficacy of EOs from Azadirachta indica and Schinus molle, both individually and in combination, against early 4th-instar Anopheles gambiae s.l. larvae under laboratory and semifield conditions. The EOs were extracted using ethanol in a Soxhlet apparatus. Twenty-five treatments were arranged in a completely randomized design for experimentation. Temephos (Abate) and distilled water served as positive and negative controls, respectively. Each treatment contained 20 larvae, which were acclimatized for 2 h prior to exposure to EOs. Treatment cups were covered with muslin cloth to prevent debris contamination. Larval mortality was assessed at 24, 48, and 72 h postexposure at concentrations of 25, 50, and 75 ppm. In the laboratory, A. indica oil exhibited the highest larvicidal activity among plant treatments, with 71.66% mortality at 75 ppm after 72 h, while S. molle and the combined treatment produced moderate effects. LC50 and LC90 values confirmed A. indica's superior potency, with significantly lower lethal concentrations across all exposure times (p < 0.05). In simulated field trials, A. indica oil also demonstrated time- and dose-dependent larvicidal activity, achieving 68.33% mortality at 75 ppm after 72 h. Synthetic larvicide Temephos (Abate) consistently caused 100% mortality within 24 h at all concentrations in both settings. These findings suggest that A. indica EO, particularly at higher concentrations and longer exposures, may serve as an effective botanical alternative for larval control in integrated vector management programs.