Evaluation of the acaricide effect of thymol, menthol, salicylic acid, and methyl salicylate on Boophilus microplus (Canestrini 1887) (Acari: Ixodidae) larvae.

The tick Boophilus microplus is the principal species of ectoparasite that impairs dairy cattle productivity in Brazil. Its control is mainly by using synthetic chemical products during its parasitic phase. The purpose of this study is to evaluate the acaricide activity of four products of natural origin. Depending on solubility, tests were conducted with solutions in distilled water or emulsified in aqueous DMSO at 1% of the following products: thymol, menthol, methyl salicylate, and salicylic acid. Each of these was tested at three concentrations (0.25, 0.5, and 1.0%) with five repetitions. The "larval packet test" was performed on approximately 100 larvae of B. microplus at around 15 days of age. After applying the test substances, the envelopes were kept at 27 degrees C and UR >80% and opened after 24 h to count the living and dead larvae. Of the four products tested, only thymol caused significant (up to 100%) mortality of B. microplus larvae. The mortality caused by the other products varied from 0.52 to 9.76%. Hence, thymol can be considered a potential agent to control bovine ticks.