Mosquito repellent and larvicidal perspectives of weeds Lantana camara L. and Ocimum gratissimum L. found in central India

Development of natural mosquito repellants is essential considering their safety profile unlike synthetic insecticides. Herein, novel liquid vaporizable preparations of the essential oils obtained from the leaves of weeds Lantana camara Linn (L. Camara) family Verbenaceae, and Ocimum gratissimum Linn (O. gratissimum) family Lamiaceae were developed for the evaluation of mosquitocidal and larvicidal activities against malaria vectors, Anopheles subpictus, Aedes aegypti and Culex quinquefasciatus. While mosquitocidal effect was evaluated as knockdown of mosquitoes in modified glass chamber for an exposure period of 1 h, larvicidal activity was assessed as inhibition of larval motility in petri dish at intervals of 6-, 12- and 24-hr. Combination of essential oils of L. Camara and O. gratissimum leaves prepared in ethyl alcohol at 1:5 ratio exhibited maximum synergistic mosquitocidal effect against all three test species (94-97%). This effect was comparable with that of standard 1:1 combination ratio of essential oils of Cymbopogon nardus (L.) Rendle and Eucalyptus globulus Labill. Furthermore, statistical analysis using probit regression model for determination of LC50 and LC90 revealed excellent larvicidal effect of essential oil of O. gratissimum leaves at 24-hr time-point (LC50 = 40.08 +/- 1.60 ppm and LC90 = 78.035 +/- 1.90 ppm). Our data suggest the lethal effects of essential oils of L. camara and O. gratissimum leaves on Anopheles subpictus, Aedes aegypti and Culex quinquefasciatus. Therefore, essential oil preparations of these weeds can be used as natural, harmless and inexpensive mosquito repellents.