In vitro evaluation of the acaricidal effect of vegetal oils extracted from the kernel of Thevetia peruviana and Annona muricata on the Rhipicephalus (Boophilus) microplus larvae

The objective of this work was to study the acaricide activity of oils extracted from kernels of T. peruviana and A. muricata with the hexane at different concentrations on Rhipicephalus (Boophilus) microplus larvae aged from 14 to 21 days. For this purpose, the Larva Immersion Test was performed. Twice dilutions of both oils were tested from a starting dilution of 40% to 2.5%. There were three repetitions for each concentration and for each oil. The control solution in which these larvae were treated consisted of Tween-20, diluted at 2% in distilled water. The experimental groups were stored in an incubator at 27 ± 1 °C and at 85-90% of relative humidity for 24 hours. The larvae mortality was greater than 55% in all tested groups and reached 100% at the 40% concentration for A. muricata , while the control group had a 0% mortality. The LC 50 and CL 90 obtained were respectively 4.0331% and 10.7594% for A. muricata and 7.0942% and 41.4247% respectively for T. peruviana . These results clearly indicate that these oils all have acaricidal effects on Rhipicephalus (Boophilus) microplus larvae. However, A. muricata oil is the most toxic. It can therefore be used as an effective alternative to control the Rhipicephalus (Boophilus) microplus tick and there is a high probability that it can be used for other ticks affecting cattle and even other ectoparasites in Benin and worldwide, thereby reducing the use of synthetic acaricides which are toxic to the environment and ineffective against this tick.