Evaluation of Insecticidal Activity of Thyme, Oregano, and Cassia Volatile Oils on Cat Flea

The aim of the present study was to evaluate the insecticidal effect of the cassia, thyme and oregano volatile oils against the immature and adult flea's stages. For this purpose, the tested samples were chemically characterized by GC-FID and GC-MS. The mortality of larvae and adult fleas, eggs, and pupae of Ctenocephalides felis felis was performed through in vitro tests at different concentration levels. Inhibition of development and residual efficacy were also determined. The chemical characterization of the cassia, thyme, and oregano volatile oils presented cinnamaldehyde (91%), thymol (44.7%), and carvacrol (76.2%), respectively, as major constituents. In general, the samples showed insecticidal activity for both immature and adult flea's stages. The best LC50 values for adults were obtained by oregano volatile oils (33.5 and 21.8 mu g.cm(-2), respectively, 24 and 48 h). Cassia volatile oils showed the best results against larvae (17.2 and 10.3 mu g.cm(-2), respectively, 24 and 48 h), eggs (3 mu g.cm(-2)), and pupae (34.6 mu g.cm(-2)), as well as the lowest value for inhibition of development (2.3 mu g.cm(-2)). The oregano and thyme volatile oils showed residual efficacy greater than 80% for 6 days while cassia showed this result for 4 days. The results demonstrated the potential of volatile oils for flea control in all stages of the life cycle, with emphasis on cassia. The residual effects of the volatile oils are promising for the development of new and environmentally friendly phyto-pesticides for veterinary uses.