Invitro acaricidal activity of ethnoveterinary plants and green synthesis of zinc oxide nanoparticles against Rhipicephalus (Boophilus) microplus

• Invitro acaricidal effects of ethnoveterinary plants was studied.
• Synthesis of ZnO NPs with leaf extract of Lobelia leschenaultiana was carried out.
• Acaricidal activity of Ll–ZnO NPs was observed against R. (B.) microplus.

The present study was designed to investigate the invitro acaricidal effects of seven ethnoveterinary plants, zinc acetate and green synthesized zinc oxide nanoparticles against the Southern cattle tick, Rhipicephalus (Boophilus) microplus. The selected ethnoveterinary plants were extracted using ethanol and aqueous (water) solvents at 0.02 mg/ml and 0.04 mg/ml concentrations. Of these seven plants, Lobelia leschenaultiana showed the highest percentage of tick mortality. The ethanol extracts of L. leschenaultiana showed 93.33% mortality at 0.04 mg/ml and its LC50 was 0.05 mg/ml. However, zinc acetate exhibited 70% mortality at 0.04 mg/ml (LC50: 0.0192 mg/ml). Further, we synthesized ZnO nanoparticle using the leaf extracts of L. leschenaultiana and zinc acetate as the precursor material to control R. (B.) microplus. The structural characterization of the synthesized ZnO nanoparticles (Ll–ZnO NPs) was performed by UV–vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microsopy (TEM). UV–vis spectra showed the absorption band at 383 nm. XRD analysis clearly showed the crystalline nature of Ll–ZnO NPs with various Bragg’s reflection peaks at 1 0 0, 0 0 2, 1 0 1, 1 0 2, 1 1 0, 1 0 3, 2 0 0, 2 0 1 and 2 0 2 planes. FTIR analysis showed the possible functional groups of Ll–ZnO NPs with strong band at 3420.63 and 2922.48 cm−1. SEM and TEM analysis revealed that the Ll–ZnO NPs were spherical and hexagonal in shape with particle size ranging between 20 and 65 nm. The mortality of R. (B.) microplus after treatment with Ll–ZnO NPs was 35, 57.5 and 82.5% at 0.001, 0.002 and 0.004 mg/ml. On the otherhand, 100% mortality of R. (B.) microplus was observed at 0.008 mg/ml (LC50: 0.0017 mg/ml). The results indicated that the Ll–ZnO NPs have good acaricidal properties compared to L. leschenaultiana leaf extract and zinc acetate.

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