Repellent and toxic activities of fumes of some plant materials against Culex mosquito

Mosquito coils (bars), formulated from three plant leaves, namely; Acalypha torta, Carica papaya and Calotropis gigantica, and seeds of Peganum harmala, were tested as repellents or toxicants against laboratory reared Culex sp. adult mosquitoes when burnt as an incense. None of the plants showed toxic activity, as knockdown was less than 5% in all cases. Slight repellency was observed with Acalypha sp. (0.21) and P. harmala (0.19), as these showed significant difference (P < 0.05) from values recorded for the control, i.e. bars without plant material. The fumes from these plants had no visible deterrent effects on the mosquitoes. The possible scientific challenges posed by this 
approach to the search for possible mosquito control agent were highlighted.