Efeitos do trans-anetol e trans-cinamaldeído, isolados e combinados, na mortalidade e desempenho reprodutivo de carrapatos Rhipicephalus microplus (Acari: Ixodidae)

Abstract

Cattle ticks (Rhipicephalus microplus) represent one of the main threats to cattle farming, compromising productivity, animal health and welfare, as well as generating significant economic losses. Synthetic acaricides constitute the main control strategy, but their high toxicity and the risk of selecting resistant strains have led to the search for safer and more sustainable alternatives, such as plant extracts and essential oils. Among their constituents, trans-anethole (TA) and trans-cinnamaldehyde (TC) exhibit various actions, such as insecticide and acaricide. Thus, the objective of this work was to evaluate the effects of the compounds trans-anethole and trans-cinnamaldehyde, alone and in combination, on the mortality and reproductive performance of engorged female R. microplus, as well as to characterize their ovicidal and larvicidal activity. To this end, the ticks, eggs, and larvae used in the experiment were treated with different concentrations of TA and TC, isolated and combined, and also exposed to water and solvent (5% DMSO) as control groups, and a commercial acaricide (positive control). The results showed that the combinations of TA and TC presented greater acaricidal activity and also more significantly affected reproductive parameters and efficacy. One of the treatment groups that combined both compounds in the proportion of 50% of the median lethal concentration (LC50) of TA + 100% LC50 of TC showed an average mortality of 93.33% and an efficacy of 100%. In larvicidal activity, the groups treated with isolated trans-cinnamaldehyde showed the highest average larval mortality among the treatments, reaching 99.29% mortality. Therefore, trans-anethole and trans-cinnamaldehyde represent promising bioactive compounds for the control of R. microplus ticks.