BIO EFFICACY OF SPATHODEA CAMPANULATA P.BEAUV.(BIGNONIACEAE) HEXANE LEAF EXTRACT AGAINST DENGUE AND ZIKA VIRUS VECTOR AEDES AEGYPTI (DIPTERA:CULICIDAE)

Mosquitoes are popularly referred to as ?flying syringes?, ?tiny buzzing vampires?, ?wing devil? and ?tiny assassins?. They are responsible for the transmission of many medically important pathogens and parasites such as viruses, bacteria, protozoa and nematodes, which cause serious disease such malaria, dengue, yellow fever, filariasis and zika. Aedes aegypti exhibits ecological plasticity. Till date, specific medications and vaccinations are not available commercially for treating dengue fever; therefore, the only way of reducing the incidence of this disease is mosquito control. Many control strategies for mosquitoes have been suggested since the ancient times. Chemical insecticides are commonly considered to be the most effective control strategy against mosquito. The blind use of insecticides has resulted in the increased selection pressure on the mosquitoes leading to the development of insecticide resistance in them. During the last decade, various studies on natural plant products against mosquito vector them as possible alternative to synthetic chemical insecticides. The present study was therefore carried out to evaluate qualitative phytochemical and GC-MS analysis, larvicidal , ovicidal properties of Spathodea campanulata hexane leaf extract against Aedes aegypti. Qualitative phytochemical analysis of the plant extract were carried out according to the methodology of Harbone (1984) and Trease and Evans (1989). Bioassay test are carried out for testing the efficacy of hexane leaf extract of S.campanulata on Ae.aegypti at different stages of development viz I, II, III and IV instars and pupae. Instructions of WHO (1960) as detailed by Pampana (1963) for conducting bioassay experiment with mosquito larvae were carefully followed. Effect of hexane leaf extract of S.campanulata on the hatchability of Ae.aegypti eggs were determined and hatching rate was calculated on the basis of non-hatchability of eggs (Sahgal and Pillai, 1993). The qualitative phytochemical analysis revealed the presence of different phytochemicals such as carbohydrates, tannins, flavonoids, alkaloids, terpenoids, phenols, coumarins, and phytosteroids Considerably low LC50 ,LC90/24,48 hours values of hexane leaf extract S.campanulata against different instar (I, II, III, IV and pupae) stages of Ae. aegypti obtained during the present study proved the larvicidal, ovicidal property of the plant. Young larvae were found to be relatively more susceptible then the older ones. The hatchability of Ae. aegypti eggs was decreased when placed in media of hexane leaf extract. The reduction in percent hatch was inversely proportional to the concentration of hexane leaf extract used. As the plant of the present study is widely distributed, the commercial exploitation could provide an important step in the development of new plant based insecticide as one of the alternative to expensive and environmentally harmful chemical insecticides.