Effect of Vetiveria zizanioides L. Root extracts on the malarial vector, Anopheles stephensi Liston

Objective: To evaluate the ovicidal and oviposition deterrent potential of the ethanolic extract\udfrom Vetiveria zizanioides (V. zizanioides) roots against the malarial vector, Anopheles stephensi\ud(A. stephensi ). Methods: The dried clean V. zizanioides roots were powerdered and extracted\udwith ethanol for 8 h in a soxhlet apparatus. After evaporation, the residue was dissolved in\udacetone. One hundred freshly laid eggs of A. stephensi were exposed to the extract at differnt\udconcentrations for 48 h, and the hatch rate was calculated to evaluate the ovicidal activity. Those\udexposed to actone aqueous solution were used as control. The egg laying behavior of gravid\udfemale A. stephensi was also observed using oviposition deterrent test. Effective repellency (ER)\udwas used to evaluate the oviposition deterrent activity. Results: Exposure to the crude ethanol\udextract of V. zizanioides reduced the hatchability rate of A. stephensi eggs, and zero hatchability\udwas exerted at 375 ppm. In the oviposition deterrent test, the extract alleviated the egg laying with\udan ER of 78.9% at the highest concentration of 375 ppm and even 53.7% at the lowest concentration\udof 125 ppm. Moreover, the negative values of oviposition active index also suggests the extract was\uda good deterrent agent. Conclusions: The ethanolic extract of V. zizanioides roots may be used\udan alternative pesticide to control A. stephensi at the early stage of life history, possibly due to the\udpresence of various active chemical compounds