The use of chemical acaricide still remains as the main tool against the cattle tick Boophilus microplus. In Southern Brazil, amitraz applied by immersion and/or spray is the main active ingredient to control organophosphate and synthetic pyrethroid resistant strains. In consequence it is important to conduct investigations in order to prolong useful life of this ingredient. In this article, toxicological behaviour of a strain of Boophilus microplus named "Santa Luiza" collected in the locality of Alegrete, state of Rio Grande do Sul, Brazil, was analyzed against acaricides organophosphorous, pyrethroids, mixtures SP and OP and amitraz. Results showed factors of resistance from 2.3 to 3.95 to OP, 23.3 to 147.56 to SP and 3.76 to 21.57 to amitraz indicating that this strain showed multiple resistance to tested acaricides. Characterization and purification of a B. microplus strain resistant to amitraz will allow its use as a reference strain for future utilization in biological evaluation of alternative acaricides as well as to standard and to validate diagnostic methods to detect resistant to this acaricide.
Amitraz; tick; Boophilus microplus; resistance
