Organic plant extracts and emulsified oil of Azadirachta indica A. Juss (Meliaceae) (neem) were studied to evaluate its effects in control of engorged females of Rhipicephalus (Boophilus) microplus (Canestrini, 1887) in the laboratory. Hexane and alcoholic organic extracts, 2% (weight/volume) were used in tests of immersion for 5 minutes, prepared with seeds, solubilized in dimethylsulfoxide (DMSO) to 1%. The experiment was entirely randomized, consisting of 6 treatments and 5 replicates, each represented by 5 ticks. Control groups consisted of untreated females. Based on the results of this work, we can indicate that the seed extract (hexanic fraction) and óleo emulsionável I¹ concentration to 2% have significant adjuvant potential to control the cattle tick, because, cause the mortality in the first days after the treatment and interfere in the reproduction, showing to be an alternative to acaricides normally used.