Mosquitoes are the most deadly vectors of parasites that cause diseases such as malaria, yellow fever, and filariasis. In view of the recent increased interest in developing plant origin insecticides as an alternative to chemical insecticides, the objective of this study was to determine the repellent activity of creams formulated with methanol crude extract (MCE), hexane fraction (HF), and ethyl acetate fractions (EAFs) of Ocimum gratissimum and Lantana camara leaves in single and combined actions against female Aedes aegypti. Evaluation was carried out in the net cages (30 by 30 by 30 cm) containing 60 blood-starved female mosquitoes each and were assayed in the laboratory condition following World Health Organization 2009 protocol. All formulations (single and mixture) were applied at 2, 4, 6, and 8 mg/cm2 in the exposed area of human hands. Only acetone + white soft paraffin served as negative control and odomos (12% DEET) as positive control. All the formulations presented good protection against mosquito bites without any allergic reaction by the human volunteers. The repellent activity was dependent on the strength of the extracts and fractions. Among the tested formulations, the maximum protection time was observed in MCE (120 min) and EAF (150 min) of O. gratissimum; MCE:MCE (150 min) and HF:HF (120 min) mixtures of both plants. In addition, MCE:MCE and HF:HF mixtures from both plants showed possible synergistic effect. From the results, the combination of O. gratissimum and L. camara to formulate natural mosquito repellent using small amount of extracts can be encouraging to be an alternative to conventional DEET.

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Due to ever-growing insecticide resistance in mosquito vectors and environmental contamination by synthetic insecticides, plants may be a source of alternative agents for mosquito control. Therefore, the aim of this study was to investigate the mosquito oviposition-deterrent and ovicidal activities of different solvent fractions and essential oils from Plectranthus glandulosus and Callistemon rigidus against three mosquito species, Aedes aegypti, Anopheles gambiae and Culex quinquefasciatus. For oviposition deterrence, 150 gravid females of each mosquito species were introduced in each cage. For ovicidal bioassay, 100 eggs and 1 raft of at least 100 eggs were exposed to 500 and 1000 ppm for fractions, 150 and 300 ppm for essential oils, 1000 ppm for WARRIOR ® , and were assayed in the laboratory conditions. The same concentrations were used for oviposition deterrence. The oviposition deterrence was observed 72 h and the ovicidal activity 4 h posttreatment. P. glandulosus essential oil and hexane fraction utterly prevented gravid mosquitoes from laying eggs/rafts on oviposition traps as in WARRIOR ®. There was relatively no mosquito eggs/rafts deposited in chloroform fraction of C. rigidus as observed in WARRIOR ®. The hatching rates of P. glandulosus hexane fraction were reduced to 9.67, 15.33 and 28.33% against An. gambiae, Ae. aegypti and Cx. quinquefasciatus, respectively at 1000 ppm; 5 and 11.33%, respectively for the essential oil at 300 ppm with no egg hatched in An. gambiae treatments. Hexane fraction of C. rigidus recorded 14.33, 25.33 and 39.00% of hatching eggs against An. gambiae, Ae. aegypti and Cx. quinquefasciatus, respectively at 1000 ppm. These results revealed that P. glandulosus and C. rigidus served as potent oviposition deterrents and ovicides against An. gambiae, Ae. aegypti and Cx. quinquefasciatus.