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Background: Among the major ectoparasites of farm animals, Rhipicephalus microplus is the largest negative impact on the economy of dairy farms. The spread of this mite is higher in tropical countries such as Brazil, and in cattle with predominance of taurine. The use of acaricides is most effectively used in their control, however, inadequate management has contributed to the selection of resistant populations to products available in the market. Little is known about the control and resistance to these products for cattle in semi-arid conditions. Thus, we aimed to evaluate the management practices used to control in dairy herds in semiarid region of northern Minas Gerais, checking the sensitivity of R. microplus to different acaricides.

Materials, Methods & Results: A total of 62 properties located in nine municipalities in northern Minas Gerais were visited. Bocaiuva, Francisco Drumont, Francisco Sa, Icarai de Minas, Juramento, Montes Claros, Pedras de Maria da Cruz, Sao Francisco and Varzelandia. The sensitivity of the ticks from cattle herds with high infestations was evaluated using the technique of biocarrapaticidograma. Semi-structured questionnaires were applied to characterize breeding systems, racial composition of the flock, season of greatest infestation, active ingredients used in tick control, forms of application of acaricides and the general management of the farm. The predominant type of exploitation was the dairy cattle representing 67.7% of the farms. The extensive system was predominant (58.06%) and crossbred animals were predominant, representing 77.1%. Most of the properties (93.54%), the practices of control of the cattle tick were not adequate and only one of them realized the strategic control. The months from November to March, representing the rainy season in the region, accounted for the greatest era of the cattle tick infestations for 56.5% of the properties.

Discussion: As the products used in the control, cypermethrin was the most frequently used (35.5%) followed by the association of active principle with chlorpyrifos and citronellal (25%). As for the sensitivity analysis of the ticks were evaluated four acaricide amitraz and suppose and showed greater efficacy with 99.8 and 86.1%, respectively. In all the studied properties was verified reduced acaricide efficacy for at least one of the active ingredients tested. Thus there was resistance in populations of R. microplus to amitraz principles, deltamethrin or association of cypermethrin and chlorpyrifoscitroneal, ranging from herds in northern Minas Gerais. Strategic control and alternative measures should be implemented to minimize the use of tick pesticides, reducing the selection pressure.