Veterinary Parasitology 175 (2011) 113–118 Contents lists available at ScienceDirect Veterinary Parasitology journal homepage: www.elsevier.com/locate/vetpar In vitro acaricidal effect of tannin-rich plants against the cattle tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) A. Fernández-Salas a,b , M.A. Alonso-Díaz a,∗ , R. Acosta-Rodríguez a , J.F.J. Torres-Acosta b , C.A. Sandoval-Castro b , R.I. Rodríguez-Vivas b a Centro de Ense˜ nanza, Investigación y Extensión en Ganadería Tropical, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Km 5.5 Carretera Federal Tlapacoyan-Martínez de la Torre, C.P. 93600, Martínez de la Torre, Veracruz, Mexico b Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Km 15.5 Carretera Mérida-Xmatkuil, Mérida, Yucatán, Mexico article info Article history: Received 1 June 2010 Received in revised form 3 September 2010 Accepted 15 September 2010 Keywords: Rhipicephalus microplus Tannins Tropical plants Plant extracts In vitro abstract The objectives of this study were to evaluate the in vitro acaricidal effects of lyophilized extracts of four tannin rich plants (Acacia pennatula, Piscidia piscipula, Leucaena leucocephala and Lysiloma latisiliquum) against diverse stages of Rhipicephalus (Boophilus) microplus, and to asses whether tannins were involved in the acaricidal effect using polyethylene glycol (PEG) to block tannins. Larval immersion (LIT) and adult immersion (AIT) tests were used to evaluate the acaricidal effect of each of the lyophilized extracts against larval and adult stages of R. microplus respectively. Larvae and adult ticks were exposed to increasing con- centrations of each plant extract (0, 1200, 2400, 4800, 9600 and 19,200 g ml -1 ) for 10 min. Larval mortality was recorded at 48 h post-incubation. Adult mortality was recorded daily over 14 days, at which point their reproductive efficiency was evaluated. PEG was added to the extracts to verify whether tannins were involved in the acaricidal effect. The effect on egg laying inhibition and larval mortality was analyzed using the GLM procedure in SAS. A Kruskal–Wallis test was used to assess the effect of PEG on LIT results. Calculation of the lethal concentration 50 (LC50) was performed using a probit analysis. All extracts reduced the viability of R. microplus larval stages (P < 0.001), and viability was restored with the addition of PEG suggesting an important role of tannins in the acaricidal effect (P < 0.001). The LC50 values of L. latisiliquum and P. piscipula plant extracts were 6.402 and 2.466 g ml -1 . None of the tannin-rich plant extracts affected adult mortality (P > 0.05). Lysiloma latisiliquum extract inhibited egg hatching of R. microplus (P < 0.01). Tannin-rich plant extracts from A. pennatula, P. piscipula, L. leucocephala and L. latisiliquum showed potential acaricidal activity. Further in vivo studies are needed to confirm this finding. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Rhipicephalus (Boophilus) microplus is the major threat to the cattle industry in tropical and subtropical areas ∗ Corresponding author. Tel.: +52 232 3243941; fax: +52 232 3243943. E-mail addresses: alonsodm@unam.mx, alonsodma@hotmail.com (M.A. Alonso-Díaz). (Dominguez-García et al., 2010). Control of R. microplus has primarily involved the frequent use of commercial chemi- cal acaricides. However, as a consequence of their extensive use on R. microplus, the species has developed resistance to all major classes of acaricides in several countries includ- ing Mexico (Rodríguez-Vivas et al., 2006a,b; Perez-Cogollo et al., 2010). The increasing number of farms with ticks resistant to chemical acaricides in Mexico highlights the necessity of exploring alternative tick control methods. 0304-4017/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2010.09.016