The bovine tick, Rhipicephalus (Boophilus) microplus, has developed resistance to the main classes of chemical acaricides used for its control. In view of the above, research on natural products has been developed aiming at the search for alternatives to conventional chemical control. Due to the high hydrophobicity of some natural products, vegetable oils have been used as solubilizers for the active principles of these products to be evenly dispersed, increasing their surface area1. Therefore, it was aimed to evaluate the action of phenethylpropionate (2-PP) associated or not with eucalyptol (Euc) and castor oil (CO) against R. microplus. In the in vitro test2, the groups of females (n=15) were immersed (5 min.) in: 1- lauryl sulfate ether (LSE) (2%(m/v)); 2- ELS (2%(m/v)), CO (0,3%(m/v)) e Euc (10%(m/v)); 3- ELS (2%(m/v)), CO (0,3%(m/v)), Euc (10%(m/v)) e 2-PP (3,5%(m/v)); 4- autoclaved distilled water. The females were incubated in BOD (27 ºC, 80% umidade), to evaluate the egg laying and hatching. Statistical analysis was performed using the Kruskal Wallis e Student-Newman-Keuls tests (p>0,05) (BioEstat 5.0). The treatments 1 (6,85%) and 4 showed no statistical difference (p=0,9002) indicating that the use of LSE at (2%(m/v)) has no acaricidal effect. The acaricidal effect presented by the treatments 2 (73,74%; p=<0,0001) and 3 (49,08%; p=0,0010) presented higher and statistically different acaricidal efficiency values when compared to treatment 4. Euc and CO activity have already been confirmed for tick control since they reduce oviposition in females3,4. This fact justifies the observed efficacy for treatment 2. On the other hand, despite the 2-PP present action against fleas5, the presence of this in the treatment 3 seems to have contributed to reduce the acaricidal efficacy when associated with Euc e CO. The results suggest that LSE can be used as solubilizer in the concentration of 2%, without altering the reproductive physiology of the tick. On the other hand, the combination of 2-PP with Euc e CO promoted an antagonistic effect, reducing the acaricidal efficacy. It is expected that this results can guide the implementation of future projects which enable the development of new formulations containing natural products less polluting to the environment. It is believed to be corroborating with the national policy of encouraging Sustainable Production Systems, including Integrated Agricultural Production, since the information produced can help in the development of alternative methods of pest control. In thanks to FAPES, CAPES, CNPq and to Natural Products and Organic Synthesis Research Group (GEAPS-UFES).