Acaricidal activity of green nanoparticles (TiO₂) against Haemaphysalis bispinosa and Rhipicephalus (Boophilus)...

In the present work, the in vitro efficacy of titanium isopropoxide, Cassia auriculata flower extract and C. auriculata-mediated titanium nanoparticles (Ca-TiO₂ NPs) as an acaricidal drug against Rhipicephalus (Boophilus) microplus (larvae, nymph and adult) and Haemaphysalis bispinosa (adult) was evaluated. The synthesized nanomaterial was then characterized through UV, XRD, FTIR, Zeta potential and HR-TEM techniques. UV-Vis spectroscopy showed an absorption peak at 289 nm. Bragg's peaks corresponding to 1 0 1, 0 0 4, 2 0 0, 1 0 5, 2 1 1, 20 4, 1 1 0, 2 2 0, and 2 1 5 planes in XRD analysis confirm the crystalline structure of Ca-TiO₂ nanoparticles. FTIR analysis identified the functional groups of Ca-TiO₂ NPs in the band range of 3316-573 cm^-1. Zeta potential represents the surface charge and stability of Ca-TiO₂ nanoparticles. HR-TEM analysis showed the hexagonal shape of Ca-TiO₂ nanoparticles with size distribution in the range of 70-140 nm. All life stages were affected in R. (B.) microplus: mortality was induced in larvae, nymphs and adults after treatment with Ca-TiO₂ NPs, but only adults from H. bispinosa died. At the concentration of 100 µg/mL, the adult mortality rates of R. (B.) microplus and H. bispinosa were noted to be 74 % and 68 %, respectively, after treatment with Ca-TiO₂ NPs. R. (B.) microplus nymph and larva mortality was 90 % at 100 µg/mL and 100 % at 16 µg/mL. On the other hand, the C. auriculata flower extract gave 28 % adult mortality against R. (B.) microplus and 27 % for H. bispinosa at the highest concentration of 100 µg/mL. Larval and nymph mortality rates of R. (B.) microplus were 68.8 % (16 µg/mL) and 44 % (100 µg/mL). The light microscopy of embryos from R. (B.) microplus distinctly shows that embryonic development is arrested. Ca-TiO₂ nanoparticles showed potential acaricidal activity and egg hatchability inhibition activity compared to C. auriculata flower extract and titanium isopropoxide.