Larvicidal effect of Mundulea sericea (Leguminosaea) plant extract against Aedes aegypti (L.) (Diptera: Culicidae)

IntroductionThe medical importance of mosquitoes as vectors forthe transmission of serious diseases that causemorbidity, mortality, economic loss, and socialdisruption such as malaria, lymphatic filariasis, andviral diseases is well recorded (Becker et al, 2003).Aedes aegypti, the main carrier for viruses that causedengue and dengue hemorrhagic and yellow fevers, isfound majorly in the tropics and subtropics. There is noeffective vaccine against dengue, and thus the only wayof significantly lowering the incidence of this disease isthrough mosquito control (Malavige et al, 2004).Chemical measures were first tried, but they failed sincetheir overuse led to disruption of natural biologicalcontrol systems and outbreak of new insect species. Inaddition, use of insecticides led to the development ofmosquito resistance, environmental pollution, andundesirable effect on non-target organisms (Brown,1986). In a bid to resolve these problems, interest ininsecticides of natural origin, specifically plant-derivedproducts has recently received close attention.Several studies have emphasized the importance ofresearch and development of herbal substances forcontrolling mosquitoes (Shaala et al, 2005). Theirresults may vary, but natural plant products may be apossible alternative to synthetic substances, as they areeffective and compatible with human and animal lifeand the environment (Chaithong et al, 2006).The genus Mundulea consists of about 15 species,widespread throughout Africa, Madagascar, Mauritius,India, Sri Lanka and Papua New Guinea. Only a singlespecies, Mundulea sericea, is found in Southern Africa.This species occurs in South Africa, Botswana, Namibiaand Angola, north to tropical Africa, and east toMadagascar, India, Sri Lanka and Papua New Guinea(Watt and Breyer-Brandwick, 1962).Mundulea sericea is one of the commonest fish poisonswhere both bark and seeds are used (Neuwinger, 2004).In addition, the Chinese used M. sericea to controltobacco budworm Heliothis virescens (Lepidopteriae:Noctuidae) (Yoshida and Toscano, 1994).The toxic principal of the plant is rotenone, anisoflavonoid (Vedcourt and Trump, 1969). Therotenoids deguelin and tephrosin are the potent activeprinciples which have been isolated from extracts of M.sericea (Luyengi et al, 1994). Deguelin is a natural plantderivedrotenoid, most commonly used as an insecticidein Africa and South America (Udeani et al, 1997).Rotenoids from the bark of M. sericea have beencommercially used as insecticide. These chemicalcompounds in the bark, leaves and seed are the activecompounds responsible for the fish poison. It isreported that the strength varies geographically (Wattand Breyer-Brandwick, 1962).The current study involved extraction and evaluation ofroot bark and seedpod of M. sericea for larvicidalactivities on Aedes aegypt