Efeitos de óleos fixos dos frutos e extratos de folhas de buriti e xiriri em teleóginas e larvas de Rhipicephalus microplus (Canestrini, 1887) (Acari: Ixodidae)

Abstract

The Rhipicephalus (Boophilus) microplus tick stands out as one of the parasites that have a great negative impact on bovine production, showing a wide geographical distribution in tropical and subtropical regions. The losses are due to blood spillage, drop in productivity, expenses with acaricides, and the possibility of transmission of pathogens to catlle. The indiscriminate use of theses acaricides has favored the selection of multiresistant strains in different regions. The plants, in turn, are sources of bioactive compounds from their secondary metabolism, being efficient in the control of bovine tick through the use of oils and extracts of plant species. For this, the alternative control becomes promising, since it minimizes the accumulation of chemical residues in milk, meat and the environment. Thus, the objective in this work was to evaluate the effects of fixed oils and ethanolic extracts of Mauritia flexuosa L.f and Mauritiella armata Mart. in engorged females and R. microplus larvae. Engorged females were manually collected from naturally infested and non - contact animals with acaricides for at least 60 days, at a farm of Coração de Jesus city. After the collection, theses ectoparasites were washed and separated according to the size and degree of engorgement in order to obtain homogenous groups. The reproductive parameters and acaricidal efficacies were evaluated in accordance with the biocharrapaticidogram test. The engorged females were immersed during five minutes in concentrations of 25 to 100 mg / ml and of 1,25 to 10% for ethanolic extracts (EE) and for the oils of the fruits, respectively. The larvae were submitted to the same concentrations in packages with impregnated paper, evaluating the mortality after 24 hours of incubation at 28 ºC. When evaluating the EE composition of these palms by gas chromatography with electron impact ionization detector, it was verified the presence of more than 61 compounds for each extract, and the carbohydrates were the most frequent, begin many of them not yet identifiable. Gaseous chromatograms of the fixed oil of M. armata showed the presence of methyl 9-oxononanoate, dimethyl octanedioate, dimethyl nonanedioate and methyl (9Z, 11E) octadeca-9,12-dienoate, which compounds were not identified for the oil of M. flexuosa. The experiments were conducted in a completely randomized design and the data submitted to analysis of variance and the means were compared by the Scott-Knott test at 5% significance. The lethal concentration to inhibit 90% of larvae production (CL90) was estimated by the probit regression analysis. The M. flexuosa EE at 75 and 100 mg / ml and M. 100 mg / ml M. armata, as well as the oils of these 10% palm trees, were efficient for reducing the hatchability of R. .microplus, exhibiting acaricidal efficacies above 90%. In relation to the effects on the larvae of this tick, it was verified that the oils were more effective than the ethanolic extracts. Thus, these results point these bioproducts as promising for alternative control of this ectoparasite and could be indicated in the integrated control.