The diverse enzymatic targets of the essential oils of Ilex purpurea and Cymbopogon martini and the major components potentially mitigated the resistance development in tick Haemaphysalis longicornis.

The long-term use of chemical acaricides not only pollutes the environment, but also easily causes tick resistance. Plant essential oils, a kind of secondary metabolites in plants, are an important way to develop new modern pesticides. The study analyzed the acaricidal activity and molecular mechanisms of Ilex purpurea EO and Cymbopogon martini EO on Haemaphysalis longicornis (Acari: Ixodidae) unfed ticks. The chemical analysis (GC-MS) identified 7 components in I. purpurea EO and 4 in C. martini EO. The effects of the oils on unfed larvae of H. longicornis were assessed by larval packet test. The results revealed that I. purpurea EO and C. martini EO had significant toxicity against the unfed larvae. The present work evaluated the toxicity of EOs and methyl salicylate against unfed nymphs and adults of H. longicornis by immersion test. The results showed that I. purpurea EO, C. martini EO and methyl salicylate had significant toxicity against the unfed nymphs and adults. Enzyme assays showed that the oils and methyl salicylate significantly inhibited AChE and CarE activity, I. purpurea EO significantly inhibited CAT activity. These results revealed that the diverse enzymatic targets of I. purpurea EO, C. martini EO and the major components of I. purpurea potentially mitigated the resistance development in tick H. longicornis. This study revealed the mechanisms of action of I. purpurea EO and C. martini EO in nature and biotechnology. These results will open new directions for understanding how EOs interfere with tick biological systems and has broad implications for the field of acaricide design.