Insecticidal effect of Essential Oils of Citrus limon, Cymbopogon citratus and Syzygium aromaticum and their Synergistic Combinations Against Anopheles Mosquitoes

While synthetic insecticides offer effective pest control, their many side effects necessitate exploring alternatives, this study investigates the insecticidal potential of essential oils from lemon (Citrus limon), lemongrass (Cymbopogon citratus), and clove (Syzygium aromaticum) against Anopheles mosquitoes, a prime vector of malaria, a deadly global disease. The oils were extracted via hydro-distillation, Gas Chromatography-Mass Spectrometry (GC-MS) was used to analyze the chemical profiles. The insecticidal activity was tested using a susceptibility test to evaluate the knockdown, mortality rates and time against adult mosquitoes following standard protocols. The extraction procedure yielded of 0.5, 0.48, and 0.2% were obtained for Lemon, Lemongrass, and Clove respectively. GC-MS showed limonene as the dominant compound in lemon oil (66.4%), while citral a (48.26%) and citral b (39.85%) were most abundant in lemongrass oil, and that of Clove is eugenol (68.98%). Adulticidal efficacy results put clove oil to have the best activity with a knockdown rate of 75 ± 0.75 at 14 minutes, a mortality rate of 45 ± 0.74 at 25 minutes, lemon oil exhibited the least activity with 30 ± 0.866 knockdown rate at 26 minutes, a mortality rate of 15 ± 0.47 at 42 minutes. However, the combination of Lemongrass and Clove (FM2) demonstrated an enhanced overall insecticidal efficacy beyond the capabilities of individual oils with a knockdown rate of 85 ± 0.25 at 7 minutes and a mortality rate of 60 ± 0.37 at 16 minutes. Despite mosquitoes’ resistance to the individual oil, these findings suggest that these oils can be optimized for more effective insect control when combined, consequently, this research has contributed to the quest for a better, cheaper, safer and eco-friendly for mosquito control.