Repellent properties of Delonix elata (L.) Gamble (Family: Fabaceae) against malaria vector Anopheles stephensi (Liston) (Diptera: Culicidae)

Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The purpose of the present study was to assess the effects of leaf and seed hexane, ethyl acetate, benzene, chloroform and methanol extract of Delonix elata on repellent activity against the malaria vector mosquito Anopheles stephensi (Diptera: Culicidae). Evaluation was carried out in a net cage (45 · 30 · 45 cm) containing 100 blood starved female mosquitoes of An. stephensi. Repellent activity was carried out in laboratory conditions. Plant crude extracts of D. elata were applied at 1.0, 2.5, and 5.0 mg/cm^2 separately in the exposed forearm of volunteers. Ethanol was used as the sole control. Applied leaf and seed crude extracts were observed to protect against mosquito bites. There were no allergic reactions experienced by the volunteer subjects. The repellent activity of the extract was dependent on the strength of the extract. Among the tested solvents, both the leaf and seed methanol extracts showed maximum efficacy. The highest concentration of 5.0 mg/ cm2 provided over 210 and 180 min protection for the leaf and seed extracts, respectively. Crude extracts of D. elata (leaf and seed) exhibit the potential for controlling An. stephensi.