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As part of efforts to explore environmental friendly alternatives to synthetic chemicals, aqueous extracts of Azadirachta indica, Caralluma tuberculata, Allium sativum, Curcuma longa, Citrulus colocynthis and Calotropis procera were used to investigate the entomotoxicity of selected plant materials against maize weevil, Sitophilus zeamais in stored maize. In order to investigate the effect of selected plant materials on the mortality of maize weevil, maize seeds (20g) were treated with 0.5, 1, 1.5, 2, 2.5 and 3% v/w of aqueous extracts in the laboratory of Entomology Department, Faculty of Agriculture, Gomal University, Dera Ismail Khan, Pakistan under controlled environmental conditions of 27 ± 10C and 65 ± 2% R.H and 12: 12 hour dark: light regimes. Experiment was laid out in Completely Randomized Design with five replications. The adult mortality of S. zeamais was recorded after 1 day, 2 days, 3 days, 7 days, 14 days and 21days, post exposure time period. The A. indica and C. longa plant aqueous extracts were found more toxic to adult maize weevil compared to other plant extracts recording (95%) and (91%) mortality at 3% concentration whereas; minimum adult mortality was recorded in C. procera (26%) at 3% concentration after 21 days’ time span compared with control (2%). The toxicity of the selected plant materials increased with increase in the concentration and exposure period. It is concluded from the present findings that the aqueous extracts of A. indica and C. longa can be used as safe alternative to chemical insecticides for the management of maize weevil under storage conditions.
Keywords: Maize weevil; Entomotoxicity; Exposure period; Plant materials; Stored maize