Effect of Stemona spp. against Rhipicephalus microplus.

Stemona plants have been traditionally used against various insects in Thailand and Southeast Asian countries. The acaricidal efficacy of 9 species of Stemona grown in Thailand was evaluated against dairy cattle tick, Rhipicephalus microplus using adult immersion test and in vivo evaluation on infested calves. From the ten Stemona root extracts used in this study, S. collinsiae of a concentration 250 mg/ml possessed the highest activity. In vivo study revealed that S. collinsiae extract could significantly reduce the attached ticks on calf skin compared to the control and promoted not significantly different efficacy from flumethrin, a common pyrethroid used in dairy farms. No side effect was found on calves during the experiment. The results confirmed traditional use of S. collinsiae as a better source of insecticide than other species and could be used as guidance for further development of S. collinsiae as a herbal acaricide.