Este trabalho objetivou avaliar o potencial acaricida do extrato-bruto etanólico (e.b.e.) da casca do caule de Magonia pubescens sobre larvas do carrapato bovino Rhipicephalus (Boophilus) microplus. As larvas foram acondicionadas em B.O.D. climatizada, em envelopes de papel filtro impregnados com diferentes concentrações do e.b.e., solubilizado com dimetilsulfóxido (DMSO) e água destilada, para determinação das Concentrações Letais (CL). Foram realizados os seguintes tratamentos: 1. envelopes de papel filtro seco; 2. envelopes de papel filtro umedecidos com água destilada; 3. envelopes de papel filtro umedecidos com solução de DMSO e água destilada; e 4. envelopes umedecidos com 2 mL de cada concentração do e.b.e. testada. Os bioensaios foram feitos em quadruplicata, em uma câmara climatizada a 27°±1° C, URe"80% e fotofase natural de 12 horas. A mortalidade foi observada após 48h. Obtiveram-se as CL50 de 365 e CL99 de 4.000 ppm. Não houve mortalidade significativa para os três primeiros tratamentos (p<0,05).

The acaricidal potential of the crude ethanolic extract (c.e.e.) of the stem peel of Magonia pubescens was evaluated against larvae of Rhipicephalus (Boophilus) microplus. The larvae were placed in filter paper envelopes impregnated with different concentrations of c.e.e., dissolved in dimethylsulfoxide (DMSO) and distilled water for determination of lethal concentrations (LC). The following treatments were used: 1. Envelopes of dry filter paper; 2. Envelopes of filter paper moistened with distilled water; 3. Envelopes of filter paper moistened with a solution of DMSO in distilled water; and 4. Envelopes moistened with 2 mL of each concentration of the c.e.e. to be tested. The bioassays were carried out in quadruplicate at 27°±1° C and RH e"80% and 12h light. Mortality was observed after 48 h, LC50 and LC99 values of 365 and 4,000 ppm being obtained. There was no significant mortality in larvae exposed to the first three treatments (p < 0.05).