Efeitos de extratos de fungos e folhas da aroeira sobre larvas e teleóginas de Rhipicephalus microplus (Canestrini, 1887) (Acari : Ixodidae)

Abstract

Alternative controlling methods for bovine ticks have been essential due to the high occurrence of strains resistant to conventional acaricides. Mycelial fungi and plants have been used to control this ectoparasite, but little is known about the effectiveness of bovine digestive tract fungi and the plant Myracrodruon urundeuva in controlling the bovine tick. In this study, the aim was to evaluate the effectiveness of fungal extracts of four fungi especies from digestive tract of bovines and M. urundeuva leaves against larvae and engorged felmales of Rhipicephalus microplus. Initially, the susceptibility of two strains of R. microplus from the north of Minas Gerais to the main chemical acaricides used in the properties was evaluated: amitraz, cypermethrin, deltamethrin, supone and association of cypermethrin, chlorpyrifos and citronellal. In a first study, the effects of chemical acaricides and extracts of the mycelial fungi Trichoderma longibrachiatum (isolated VN20) and Aspergillus terreus (isolated VN15) on the Xangrilá strain of R. microplus and extracts of the yeasts Rhodotorula mucilaginosa (isolated V10S and V16S) and Pichia kudriavzevii (isolated V61 and V62) on the ICAMG strain of R. microplus were evaluated. The extracts were obtained from fungi isolated from the digestive tract of Nellore cattle. Adult immersion test (AIT) and larvae pack test (TPL) were performed. For the Xangrilá strain, the acaricides based on cypermethrin, deltamethrin and cypermethrin association, chlorpyrifos and citronellal showed low efficacy, suggesting strain’s resistance to these acaricides. Both fungal isolates tested for this strain showed low efficacy in controlling the reproductive activity of engorged females and on larval mortality. For the ICAMG strain, amitraz, supone and cypermethrin association, chlorpyrifos and citronellal were tested, and all showed low efficacy, indicating the beginning of strain's resistance to these acaricides. All yeast extracts tested for this strain performed low efficacy on engorged females and larval mortality. However, the isolated V16S from R. mucilaginosa showed 35% efficiency in reducing the reproductive activity of engorged females. In another study, the efficacy of M. urundeuva leaf extracts on an ICAMG strain of R. microplus was evaluated. Aqueous extract (EA) and ethanolic extract (EE) of the leaves of the plant were evaluated by AIT and TPL. The EE at 75 and 100 mg mL-1 reduced posture capacity, which did not occur for EA. There was no reduction in hatchability for both evaluated extracts. The EE showed acaricidal efficacy in engorged females from 14.93 to 40.79%. The EA and EE performed 82.89 and 91.21% larvicidal effect, respectively, and the LC90 was estimated at 226.1 mg mL-1 for EA and 159.3 mg mL-1 for EE. M. urundeuva leaf extracts high efficiency mainly for the larval stage, standing out as potential acaricide for R. microplus. Future studies should be carried out to evaluate other concentrations, presentations, vehicles and diluents R. mucilaginosa extracts (isolated V16S) and M. urundeuva leaves and their possible effects, as well as the in vivo efficacy of these extracts in the alternative control of R. microplus.