10.22376/ijpbs.2019.10.1.p1-12 Volume 9 Issue 3 2018 (July-September) Mosquito-borne diseases such as dengue, yellow fever, chikungunya and zika fever are among the leading causes of deaths world-wide. lessThan i greaterThan Aedes aegypti lessThan /i greaterThan is a primary vector of dengue fever and There is no effective vaccine and treatment against dengue, chikungunya and zika fever; therefore the only way to reduce these diseases is mosquito control. The development of resistance in mosquitoes to most synthetic insecticides and repellents calls for the search for alternatives from plant origin. The present study explored the effects of lessThan i greaterThan Senna alata lessThan /i greaterThan methanolic leaf extract on larvicidal, pupicidal, ovicidal and ovipositional deterrence against dengue and zika virus vector lessThan i greaterThan Ae. aegypti. lessThan /i greaterThan Phytochemical and GC-MS analysis of the plant extract were carried out. Bioassay test was conducted for testing the efficacy of methanolic leaf extract of lessThan i greaterThan S. alata lessThan /i greaterThan on lessThan i greaterThan Ae. aegypti lessThan /i greaterThan at different stages of development. The effect of methanolic extract lessThan i greaterThan S. alata lessThan /i greaterThan on the hatchability of lessThan i greaterThan Ae.aegypti lessThan /i greaterThan eggs was determined. Hatching rate was calculated on the basis of non-hatchability of eggs. The effect of methanolic extract lessThan i greaterThan S. alata lessThan /i greaterThan on oviposition of lessThan i greaterThan Ae. aegypti lessThan /i greaterThan was determined under choice and no-choice oviposition test. Considerably low LC lessThan sub greaterThan 50 lessThan /sub greaterThan /24 hours values of methanolic leaf extract lessThan i greaterThan S.alata lessThan /i greaterThan against different instar (I, II, III, IV and pupae) stages of lessThan i greaterThan Ae. aegypti lessThan /i greaterThan obtained during the present study proved the larvicidal, pupicidal property of the plant. Young larvae were found to be relatively more susceptible than the older ones.The hatchability of lessThan i greaterThan Ae. aegypti lessThan /i greaterThan eggs was decreased when placed in media of methanolic leaf extract. The reduction in percent hatch was inversely proportional to the concentration of methanolic leaf extract. Oviposition Active Index and Oviposition Deterrent Index indicated a low preference of lessThan i greaterThan Ae. aegypti lessThan /i greaterThan to methanolic leaf extract treated medium for egg laying. In conclusion, this study recommends that the methanolic leaf extract of lessThan i greaterThan S.alata lessThan /i greaterThan could be used as an alternative method in the Dengue and Zika virus vector management programs. KARTHIYAYNI.N , PRAVIN. Y, PALANIKUMAR. M, MOHANRAJ. R. S*.AND SUJATHA. P. S. Ae.aegypti. S.alata, qualitative phytochemical analysis, GC-MS analysis, larvicidal, ovicidal and ovipositional deterrence 244-255