Efficacy of Seed Oils From <i>Azadirachta indica</i> and <i>Schinus molle</i> and Their Combination Against <i>Anopheles gambiae</i> 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 <i>Anopheles gambiae s</i>.<i>l</i>. larvae. This study evaluated the larvicidal efficacy of EOs from <i>Azadirachta indica</i> and <i>Schinus molle</i>, both individually and in combination, against early 4^th-instar <i>Anopheles gambiae s</i>.<i>l</i>. 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, <i>A. indica</i> oil exhibited the highest larvicidal activity among plant treatments, with 71.66% mortality at 75 ppm after 72 h, while <i>S. molle</i> and the combined treatment produced moderate effects. LC₅₀ and LC₉₀ values confirmed <i>A. indica</i>'s superior potency, with significantly lower lethal concentrations across all exposure times (<i>p</i> < 0.05). In simulated field trials, <i>A. indica</i> 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 <i>A. indica</i> EO, particularly at higher concentrations and longer exposures, may serve as an effective botanical alternative for larval control in integrated vector management programs.