Assessment of the acaricidal activity of carvacrol, (E)-cinnamaldehyde, trans-anethole, and linalool on larvae of Rhipicephalus microplus and Dermacentor nitens (Acari: Ixodidae)

Abstract

The acaricidal activity of carvacrol, (E)-cinnamaldehyde, trans-anethole, and linalool was studied on Rhipicephalus microplus and Dermacentor nitens larvae. All the substances were tested at concentrations of 2.5, 5.0, 10.0, 15.0, and 20.0 μl/ml, with 10 repetitions per treatment. The modified larval packet technique was employed in the tests and the mortality was evaluated after 24 h. In the groups treated with carvacrol, the lowest concentration (2.5 μl/ml) was sufficient to cause 100% death of the R. microplus and D. nitens larvae. The same concentration of (E)-cinnamaldehyde resulted in death of approximately 99% of the larvae of both tick species and reached 100% at the other concentrations. For trans-anethole, mortality rates above 90% of the R. microplus and D. nitens larvae were only observed starting at the concentration of 15.0 μl/ml and reached 100% at the highest concentration (20.0 μl/ml). Finally, the mortality rates of the groups treated with linalool were low, only reaching 8.4 and 14.5% at the highest concentration (20.0 μl/ml) for larvae of D. nitens and R. microplus, respectively. These results show that carvacrol, (E)-cinnamaldehyde, and trans-anethole have acaricidal activity, particularly carvacrol and (E)-cinnamaldehyde, both of which resulted in high mortality rates for the larvae of these two tick species even at the lowest concentration.

Acaricidal activity of Foeniculum vulgare against Rhipicephalus annulatus is mainly dependent on its constituent from trans-anethone

“…Trans-anethole showed the best larvicidal effect as evidenced by the lowest concentration (0.56%) required to attain the LC50 meanwhile, fenchone showed weakest larvicidal effect as its LC50 reached at a concentration of 9.11%. Our results come in accordance with de Oliveira Souza Senra et al [ 41 ] as they found that the treatment with the highest concentrations of fennel oil (20.0 μl/ml) caused 100% mortality in the larvae of R . microplus and D .…”

Chemistry and Multibeneficial Bioactivities of Carvacrol (4-Isopropyl-2-methylphenol), a Component of Essential Oils Produced by Aromatic Plants and Spices

“…Treatment with carvacrol (2.5 μL/mL) induced 100% death of larvae of the cattle parasite Rhipicephalus microplus and the tropical horse tick parasite Dermacentor nitens , suggesting the potential of the monoterpene to control these two tick species in the field . A related study on the acaricidal efficacy of carvacrol and related compounds on larvae of nymphs of Amblyomma cajennense (Cayenne tick) and Rhipicephalus sanguineous parasites that afflict horses and other animals found that similar low concentrations of carvacrol and thymol (2.5 μL/mL) also cause 100% lethality in these parasites, indicating the value of further studies to evaluate these acaricides under natural conditions …”

Acaricidal activity of Cinnamomum cassia (Chinese cinnamon) against the tick Haemaphysalis longicornis is linked to its content of (E)-cinnamaldehyde

“…Likewise, ( E )-cinnamaldehyde was effective with 100% mortality at a concentration of 5 μL/mL against R . microplus and Dermacentor nitens larvae [ 38 ]. Acaricidal activity of ( E )-cinnamaldehyde was also observed against the larvae of Amblyomma sculptum (LC 50 1.40 mg/mL) and D .…”