Single and combined effects of α-Pinene and 3-Carene against the larvae and adults of Anopheles gambiae Giles (Diptera: Culicidae)

Abstract

ABSTRACT Biopesticides from botanicals are actively being investigated in mosquito control programs. In the current study, two hydrogenated monoterpenes (α-Pinene and 3-Carene were evaluated individually and in combination on fourth-instar larvae and adults of Anopheles gambiae. The terpenes were tested individually and in combination at doses of 6.25, 12.5, 25, 50, and 100 ppm on mosquito larvae, while at 1, 2, 3, and 4 mg/cm2 on the female adults, according to the World Health Organization standard protocol. The commercial insecticide DDVP (WarriorTM), tested at the recommended dose of 1000 ppm, was used as a positive control. The mortality of the larvae and adults was recorded after a 24-h exposure period to the terpenes. Individual and combined application of both terpenes at 100 ppm for larvae, then 4 mg/cm2 for adults, and a positive control (1000 ppm) resulted in 100% mortality of An. gambiae larvae and adults. Tested individually, α-Pinene was also the most toxic to An. gambiae larvae (LC50=8.16 ppm) and adults (LC50=0.98 mg/cm2) compared to 3-Carene (LC50=22.51 ppm on larvae and LC50= 4.31 mg/cm2 on adults). Among the combinations, the mixture 3-Carene 25%+α-Pinene 75% was the most effective on An. gambiae larvae (LC50 = 6.80 ppm) and adults (LC50 = 0.85 mg/cm2), resulting in synergistic actions against mosquito stages compared to the other combinations. Therefore, applications of both hydrogenated monoterpenes are recommended for use in control programs against An. gambiae larvae and adults. Keywords: Larvicidal, adulticidal, botanical, terpene, Anopheles gambiae.