Atividade acaricida do monoterpeno carvacrol sobre fêmeas adultas de Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

Abstract

Resistant strains of Rhipicephalus (Boophilus) microplus to synthetic acaricides is increasing. Herd’s infestation by this tick is a problem in Brazil and in temperate countries. These arthropods cause huge economic losses to livestock due to their feeding habits that weaken the health and transmit diseases to their hosts. The phytotherapics, and especially carvacrol, have been shown to be an alternative in the control of this tick, since they have acaricidal and repellent effects, besides setting up a partially safe method, due to the rapid degradation and low contamination of the environment, the consumer of animal products and the host. Therefore, the objective of the present study was to determine the efficacy of carvacrol on adult R. microplus females by evaluating mortality and reproductive parameters. Bioassays were performed to determine the LC50 and to evaluate the reproductive parameters of the females, both from the Adult Immersion Test (AIT). For the determination of the LC50, eleven groups (n = 360) were separated in concentrations ranging from 0.099 to 1.304% and two groups served as negative control, one distilled water (100%) and the other 50% (v/v). To evaluate the reproductive parameters, the females were submitted to AIT in treatments containing 20% (n = 10), 40% (n = 10), 60% (n = 13), 80% (N n = 20) and 100% of LC50 (n = 20), and in control treatments of distilled water (100%) (n = 10) and ethyl alcohol 50% (v/v) (n = 10). The groups were maintained at 27 ± 1 ° C and humidity> 80 ± 10%. Egg weight, egg production index, pre-oviposition period and fecundity rate of the 80% and 100% LC50 groups presented a statistical difference (p<0.05) in the control groups. The LC50 found was 20.11 mg / mL and the control efficacy of this concentration was 64.67% compared to the ethyl alcohol control 50% (v/v). Thus, the results demonstrate that carvacrol has a significant acaricidal potential, and can contribute as another alternative in the control of R. microplus.