In Vitro Acaricidal Activity of Croton macrostachyus Leaf and Ricinus communis Seed Extracts Against Cattle-Infesting Ticks (Rhipicephalus spp. and Amblyomma spp.).

Abstract

Ticks are major ectoparasites of cattle and vectors of zoonotic and livestock diseases. Reliance on synthetic acaricides like diazinon has led to environmental concerns and rising resistance, prompting the search for ecofriendly alternatives. This in vitro study evaluated the acaricidal activity of Croton macrostachyus, Ricinus communis, and their combined extracts against Rhipicephalus and Amblyomma ticks. Adult ticks were exposed to serially diluted concentrations (125, 250, 500, and 1000 μg/mL) of plant extracts. Dimethyl sulfoxide and 0.1% diazinon served as negative and positive controls, respectively. Triplicate independent replication sets were performed. Both plant extracts exhibited significant (p < 0.05), dose- and time-dependent mortality. Croton macrostachyus showed higher activity against Amblyomma (66.7 ± 1.53%) than Rhipicephalus (63.3 ± 1.16%) at 1000 μg/mL, while Ricinus communis conferred higher activity, achieving 80.0 ± 1.00% (Amblyomma) and 73.3 ± 0.58% (Rhipicephalus) mortality-outperforming diazinon (70.0 ± 1.0%). Notably, the combined extract demonstrated synergistic effects with the highest mortality (83.3 ± 0.58%), indicating enhanced activity over the commercial acaricide. The moderate performance of diazinon supports concerns over acaricide resistance in the study area. Further in vivo trials and toxicity evaluations are essential before declaring the extracts as antitick.