RESUMO
Tests were conducted to assess the efficiency of the roots of Dahlstedtia pentaphylla (Taub.) Burk. (Leguminosae, Papilionoideae, Millettiae) plant against infestations of Boophilus microplus (Canestrini, 1887). These tests were performed on 30 bovine animals in the Paraíba Valley, State of São Paulo, Brazil, divided into three groups (control, extract diluted at 1:10 mL and extract diluted at 1:20 mL), after artificial infestation with some 4000 larvae/animal on days -21, -14, -7, -1, 0, 7 and 14. The extract of D. pentaphylla was obtained by dehydration, spraying and extraction in absolute ethanol, at a proportion of one part of root powder to three parts of ethanol, this being taken as standard (100%). This standard extract was then diluted in water at one part of extract to 10 and 20, for spraying on the bovines. The best result obtained (an efficiency rate of 76.10%) was seen 3 days after the application of the extract at a concentration of 1:10 mL. The extract showed no effect in inhibition of the laying or hatching of larvae on engorged females, these being collected from the bovines after treatment, and kept in the laboratory.