Acaricidal activity of extracts from different structures of Piper tuberculatum against larvae and adults of Rhipicephalus microplus

ABSTRACT The strategies to control the cattle tick, Rhipicephalus microplus are based mainly on the use of synthetic pesticides. However, the emergence, establishment, and development of resistance of ticks is rendering the main chemical groups ineffective. Finding new molecules to effectively control infestations by R. microplus is necessary to maintain the productivity of cattle herds, particularly of taurine breeds established in equatorial and tropical regions of the world. Ethanol extracts from the leaves, stems, and fruits of Piper tuberculatum were evaluated in bioassays at concentrations of 50, 25, 12.50, 6.25, 3.12 and 1.56 mg mL-1. The concentrations lethal to 50% of the individuals (LC50) of tick larvae after 24 hours of exposure were 3.62, 3.99 and 5.30 mg mL-1 for fruit, stem and leaf extracts, respectively. Against the engorged females, the highest efficacy rates were obtained at the concentration of 50 mg mL-1, corresponding to 71.57%, 68.38% and 37.03% of the fruit, leaf and stem extracts, respectively. The main effect of the ethanol extracts was on the egg hatching rate of ticks, with a reduction of 55.63% for the fruit and leaf extracts, and 20.82% for the stem extract. The results show that P. tuberculatum is a promising source of molecules for use as active ingredients in pesticide formulations for R. microplus control.