Volatile oils of Thymus serpyllum and Artemisia absinthium: GS-MS analysis and insecticidal activity against Culiseta longiareolata

Abstract

Culiseta longiareolata (Macquart, 1838) (Diptera, Culicidae) is one of the important mosquito species distributed in Algeria. It acts as a vector of avian malaria, tularemia, Malta fever (brucellosis), and several arboviruses, such as West Nile fever and western encephalitis virus. To eliminate undesirable insect vectors of pathogens, botanical-based insecticides are increasingly recommended. This research was focused on the analysis of the chemical composition of essential oils from Artemisia absinthium (Asteraceae) and Thymus serpyllum (Lamiaceae) obtained by hydrodistillation using gas chromatography – mass spectroscopy (GC-MS). Furthermore, these oils were tested for the first time for their larvicidal activity against fourth-instar larvae of C. longiareolata. In the Th. serpyllum essential oil, linalool (25.40%) was the major constituent, followed by camphor (19.75%) and α-pinene (11.25%). In the A. absinthium essential oil, the major compound was camphor (39.01%), followed by chamazulene (14.51%). Our study found significant larvicidal effects against the fourth-instar larvae, with a direct correlation among the larval mortality rate, applied concentrations, and duration of exposure to the treatment, where the mortality increased over time. Also, the results indicated a significant difference in the mortality rate between the two samples of essential oils. The essential oil extracted from A. absinthium was highly effective against mosquito larvae, achieving the LC50 values of 10.42, 6.19 and 3.82 ppm at 24, 48, and 72 h, respectively, while the essential oil from Th. serpyllum achieved the LC50 values of 12.16, 7.79, and 6.88 ppm. Based on the current results, both the plants could be used as new alternatives for mosquito control