Biological activity of certain botanical extracts as larvicides against the yellow fever mosquito, Aedes aegypti.L Joish Madhasudhana Murthy and Pathipati Usha Rani* ABSTRACT As a part of a programme on possible utilization of indigenous plant extracts in pest management practices, acetone extracts of eight plant species collected in the state of Andhra Pradesh, India, were tested for their larvicidal activity against the yellow fever mosquito, Aedes aegypti L. The buds of Tail Pepper, Piper cubeba L, Capers Capparis spinosa L and Indian Black Berry, Syzygium cumini L. the florals of Indian Oleander, Nerium indicum (Mill.), Indian Cork tree, Millingtonia hortensis L. and Royal Poinciana, Delonix regia L., leaves of Wood Apple, Limonia acidissima L. and Physic Nut, Jatropha curcas L were collected locally, shade dried and extracted in the soxhelet apparatus. Six of the 8 plants studied exhibited toxicity against the 3 rd instar larvae. The extracts of D. regia and L. acidissima were most active and showed toxicity up to 100 %. The dry bud extractions of S. cumini and J. curcas also showed significant larval mortality. Acetone extract of P. cubeba and C. spinosa were less active, and needed higher concentrations to obtain 50% toxicity. Hence, these active plant extracts may be used in control of the A. aegypti causing dengue fever and many other diseases. Key words: Larvicidal, Aedes aegypti, botanicals, plant extracts. 72 INTRODUCTION Vector control is facing a threat due to the emergence of resistance in vector mosquitoes to conventional synthetic insecticides, warranting either countermeasures or development of newer insecticides (Chandre et al., 1998). At the same time these pesticides may affect other beneficial organisms and prove detrimental to animal life including man. Botanical insecticides may serve as suitable alternatives to synthetic insecticides in future as they are relatively safe, degradable, and are readily available in many areas of the world. Though several plants from different families have been reported for their mosquitocidal activity, only a few botanicals have moved from the laboratory to field use, like neem based insecticides, which might be due to the light and heat instability of phytochemicals compared to synthetic insecticides (Green et al., 1991) Aedes aegypti L., a vector of dengue, is widely distributed in the tropical and subtropical zones. About two-thirds of the world’s population lives in areas infested with dengue vectors, mainly A. aegypti . Dengue viruses, causative agents of dengue fever and more severe dengue hemorrhagic fever (DHF) /dengue shock syndrome infect over 100 million people every year (Hahn et al., 2001). The first outbreak of DHF was recorded in 1963 in Kolkata. Since then dengue has spread to all parts of India. The serious outbreak to hit the capital city Delhi was in 1996 when 10,252 cases with 423 deaths were recorded (Kaul et al., 1998). In Maharastra, dengue fever has spread to 209 villages in the state infecting 31,000 patients. There have been reports of large scale outbreak of this virus in Southern India. At least 80,000 people in Gulbarga, Tumkur, Bidar, Raichur, Bellary, Chitradurga, Davanagere, Kolar and Bijapur districts in Karnataka state and Andhra pradesh are known to have been affected since December 2005 (Ravi, 2006). However, recent reports of large scale outbreaks of fever caused by chikungunya virus infection in several parts of Southern India have confirmed the re- emergence of this virus (WHO, 2006; Enserink, 2006). Considerable amount of work has been reported on effect of plant extracts against mosquito larvae. The crude hexane extracts obtained from flower heads of Spilanthes acmella, Spilanthes calva and Spilanthes paniculata (Pandey et al., 2007), seed extract of Sterculia guttata (Katade et al., 2006); the ethyl acetate extract of fruit mesocarp of Balanites aegyptiaca (Wiesmanr et al., 2006); partially purified extracts of leaves of Vitex negundo, Nerium oleander and seeds of Syzygium jambolanum (Pushpalatha and Muthukrishnan, 1995), the petroleum ether root extract of Solanum xanthocarpum (Mohan et al., 2007), leaves of Artemisia annua and Azadirachta indica (Tonk et al., 2006), A. annua (Sharma et al., 2006), Larvicidal potency of some indigenous plants against Aedes aegypti. Journal of Biopesticides, 2(1): 72-76 (2009) © JBiopest. 58