Investigation of the Larvicidal Potential of the Essential Oils From Jamaican Hyptis Verticillata and Pimenta Dioica Against Aedes Mosquitoes

Mitigating the arboviral threat in Jamaica is predominantly dependent on vector control efforts which target the Aedes aegypti mosquito. This, however, is being hampered because of increased insecticide resistance to synthetic chemicals. Currently, environmentally friendly botanical agents are gaining interest globally as they possess promising mosquitocidal properties. In this study, the larvicidal activity of essential oils extracted from the leaves of Jamaican Hyptis verticillata and Pimenta dioica were evaluated at 24 h against Ae. aegypti, utilizing a modified World Health Organization bioassay. Subsequent gas chromatography-mass spectrometry analysis of the extracts revealed that the most abundant compounds of H. verticillata and P. dioica were cadina-4,10(15)-dien-3-one and eugenol, respectively. A dose-dependent response was noted, and LC50 values of 16.06 ppm and 56.23 ppm were obtained for H. verticillata and P. dioica respectively, against the Rockefeller laboratory strain of Ae. aegypti. Evaluation of H. verticillata against field strains showed that increased pigmentation was among the main phenotypical changes observed post treatment. The calculated resistance ratios varied across sites, with RR50 values ranging from 0.727 in Duhaney Park to 1.578 in Savanna La Mar, indicating overall low resistance across all strains. The current findings support the potential use of essential oils as alternative larvicidal agents in Jamaica.