The role of plants as sources of biologically active entities cannot be overemphasized. Plants belonging to different families having mosquitocidal activity have been discovered from an established ethnobotanical and laboratory-based studies. Biological control of mosquitoes using botanicals remains the safest and environmentally sound alternative to chemical control. The essential oil of two Nigerian Laggera species, L. pterodonta and L. aurita, were investigated against the fourth instar larvae of the malaria vector, Anopheles gambiae. WHO protocol was adopted for the larvicidal bioassay. Three replicates comprising of 20 larvae each were exposed to various concentrations of the essential oil. Larval mortality was observed after 24 and 48 hours. The results showed that mortality increased with increase in concentration and period of exposure. The essential oil of L. pterodonta was found most effective with LC50 values of 418 and 404 mg/L after 24 and 48 hours, respectively while the essential oil of L. aurita recorded LC50 value of 688 and 642 mg/L after 24 and 48 hours, respectively.The GC-MS results revealed the essential oil of L. pterodonta comprises 50.83% of compounds that have been reported to have larvicidal activity while the essential oil of L. aurita comprises of 43.69% compounds with larvicidal activity. The better activity of L. pterodonta essential oil could be attributed to it having higher percentage of compounds like ɤ-Terpinene and 4-Carvomenthenol with larvicidal activity. The results suggest that the essential oil of the plants have the potential to be used as eco-friendly approach for the control of mosquitoes.
thank you for this interesting paper, showing how plant terpenoids might be valuable biological compounds to control larvae propagation and fight against malaria. From a practical point, I am just curious to understand if the essential oils might be sprayed directly on the field, or inside our homes, or what would be the ideal place? Another curiosity: If the terpenoids can kill the larvae, are they also able to efficiently repel the adult insect, so another potential application?
Kind regards,
Dr. Andrea Ghirardo
Thank you for your comment.
For practical applications it could be spread on larval habitats, this includes pools of water where larvae grows, rice fields, marshes and ditches etc. I also tried using the terpenes on adult mosquitoes and it was low mortality but very good repellent. I am planning on publish that repellent activity of essential oils.
Best regards,
Fatima Dantanko