In vitro insecticidal activity of lavender, thyme, peppermint and clove essential oils against Ctenocephalides felis collected from cats and dogs in Istanbul

Objectives: The present study aimed to evaluate the in vitro insecticidal activity of essential oils obtained against adult Ctenocephalides felis collected from cats and dogs in Istanbul, Türkiye, and to investigate the potential of these four plant species (Lavandula angustifolia (lavender), Thymus vulgaris (thyme), Mentha piperita (peppermint), and Syzygium aromaticum (clove)) as plant-based candidates for flea control.Materials and Methods: Adult fleas were collected from cats and dogs housed in two animal shelters in Istanbul and morphologically identified as C. felis. Essential oils were obtained by steam distillation and chemically characterized using an Agilent 8890 GC-FID system coupled with a 5977B MS and 16ALS Extractor Source. The insecticidal activity of the oils was evaluated using a filter paper impregnation assay at ten two-fold serial concentrations ranging from 800-1.56 μg cm-2. Acetone and fipronil (8 μg cm-2) were used as negative and positive controls, respectively. Mortality was recorded at 15, 30, and 45 min and at 1, 2, and 12 h after exposure. Statistical analyses were performed using one-way ANOVA followed by Tukey’s post hoc test and two-way ANOVA to evaluate the effects of concentration and exposure time.Results: All tested essential oils demonstrated insecticidal activity against adult C. felis. Clove oil, characterized mainly by eugenol (82.26%), exhibited the strongest and most rapid activity, causing 100% mortality within 30 min at 800 μg cm-2. Thyme oil, rich in thymol (43.84%) and γ-terpinene (32.59%), achieved 100% mortality within 1 h at both 800 and 50 μg cm-2. Lavender oil, containing linalool (38.62%) and linalyl acetate (33.41%) as major constituents, showed moderate efficacy, whereas peppermint oil, characterized by menthol (38.85%) and menthone (29.89%), exhibited comparatively slower insecticidal activity. Mortality increased significantly with both concentration and exposure time (p < 0.05); at 12 h, thyme and clove were most potent (LC50 = 5.6 and 6.8 µg cm⁻²), followed by lavender (9.0) and peppermint (18.7 µg cm-2).Conclusions: Clove and thyme essential oils demonstrated potent and rapid insecticidal effects against adult C. felis, highlighting their potential as promising natural alternatives to conventional synthetic insecticides. The findings support further in vivo investigations and formulation studies for the development of plant-based flea control products. More broadly, these findings support essential oils as a rational and sustainable basis for developing resistance-mitigating alternatives in flea control.