Larvicidal potential of selected indigenous lichens against three mosquito species–Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi / 中草药·英文版

ABSTRACT

Objective: Mosquitoes are the major transmitting vectors of serious human diseases, causing millions of deaths every year with undesirable effects, including toxicity to non-target organisms. Some plants with insecticidal properties have been used in recent years for the control of a variety of pest insects and vectors. In the quest for alternative natural biological control agents against mosquito larvae lichens were selected. Method: Larvicidal activity was assessed with methanolic extracts of Parmotrema reticulatum, Parmotrema kamatti, Parmotrema tinctorum, Parmelia erumpens, Leptogium papilosum, and Roccella montagnei against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. The standard WHO protocols with minor modifications were adopted and the bioassay was evaluated at the concentrations of 100–500 µg/mL for each lichen. Since all the lichen extracts showed complete mortality against C. quinquefasciatus in 100 µg/mL, the concentrations were decreased to 100, 50, 25, 12.5, and 6.25 µg/mL for C. quinquefasciatus. Larval mortality was observed for 24 h after treatment. Results: All the lichen extracts exhibited activity against third instar larvae of A. aegypti and A. stephensi at 100 µg/mL, and 100% mortality was observed against the vector C. quinquefasciatus at 100 µg/mL. The highest larvicidal activity was found with L. papilosum against A. aegypti (LC50 = 81.127 µg/mL) and A. stephensi (LC50 = 89.10 µg/mL). Similarly, P. tinctorum and R. montagnei when tested against C. quinquefasciatus with minimum concentration <100 µg/mL exhibited significant activity with LC50 values of 5.32 and 6.97 µg/mL. Conclusion: The bioassay results revealed larvicidal potential of lichens especially against C. quinquefasciatus with high mortality even at lower concentration. Hence, lichens can be used as an ideal sustainable approach for the control of lymphatic filariasis caused by vector C. quinquefasciatus.