Larvicidal, adulticidal and repellent activities against Aedes aegypti L. of two commonly used spices, Origanum vulgare L. and Thymus vulgaris L.

Abstract

The high incidence of dengue, chikungunya, and Zika indicates the importance of controlling the vector of these arboviruses in the tropical and subtropical regions of the world. However, vector control is hindered by pesticide resistance and the limited success of biocontrol programs against Aedes mosquitoes. Despite these difficulties, the study of common plant species, including those with commercial value, can offer effective and ecological tools in the fight against mosquitoes. In the present study, the essential oils obtained from the aerial parts of Origanum vulgare L. and Thymus vulgaris L. were analyzed by GC–MS and evaluated for their larvicidal, adulticidal and repellent activities against Aedes aegypti L. The main constituents of the O. vulgare essential oil were terpinen-4-ol (17.4%), carvacrol (16.0%) and thymol (10.4%), and the main constituents of the T. vulgaris essential oil were thymol (40.0%), p-cymene (19.3%) and γ-terpinene (17.3%). Both essential oils were toxic to Ae. aegypti larvae with LC50 values of 37.5 μg/mL for O. vulgare and 38.9 μg/mL for T. vulgaris. For adult mosquitoes, the LC50 values were 14.3 and 11.7 μg/mL, respectively. The essential oils of O. vulgare and T. vulgaris showed a significant repellency effect, with values ranging from 8.9% to 37.8% and 4.4% to 68.9%, respectively. In addition, morphological differences between larvae treated with the EOs and the control group were evidenced by optical microscopy. Thus, the results suggest that the essential oils of O. vulgare and T. vulgaris have potential use as an ecofriendly source to develop new insecticides for the control of Ae. aegypti.