17 ref.

During the 1997 and 1999 years, samples of 207 random collections of engorged female cattle ticks, from populations of Boophilus microplus thoughout Minas Gerias State, Brazil, were submitted to laboratory inmersion tests for the most frequently used contact chemical groups of acaricides in this regiom. Products, respectice number of tests, susceptibility levels (different letters refer to a significant difference in efficiency, P<0.05) and their mean comparison ranks were as follow: Carbeson (Chorphenvinphos + Dichlorvos), 69 tests, 96,30 percent; Ektoban (Thiazolin + Cypermethrin High Cis), Triatox (Amitraz), 205 tests, 54,61), Supocade (Cypermethrin + Chlorfenvinphos), 205 tests, 55,53 percent; Cypermil Plus (Cypermethrin + Dichlorvos), 54 tests, 55,29 percent; Assuntol (Coumaphos), 201 tests, 50,42 percent, Amitracid (Amitraz), 130 tests, 49,88 percent; Ectoplus (Cypermtethrin High Cis + Dichlorvos), 59 tests, 48,73 percent. Flytick (Cypermethrin), 8 tests, 47,39 percent; Ectop (Amitraz), 38 tests, 38,18 percent; Butox (Delmethrin), 207 tests, 24,02 percent; Ultimate (Alfamethrin), 204 tests, 24, 3 percent. Relating to acaricide chemical groups, the following averaged susceptibility levels were obtained: organophosphates (73,36 percent), acaricides mixtures (49,66 percent), pyrethroids (31,91 percent) and amidines (47,55 percent). The results show the wide dissemination of the resistance problem to such acaricides in this region. The work is a part of a national network for diagnosis of the susceptibility of B. microplus to such acaricides throughout Brazil