Studies on the Insecticidal Activities of Pseudocedrela kotschyi on Culex quinquefasciatus Larvae and the Maize Weevil (Sitophilus zeamais) Motschulsky

Abstract

Article InfoCulex quinquefasciatus is the vector that transmits the causative agent of filariasis which poses a great threat to the world at large. Storage pest are nuisance to farmers because they destroy farm products either in the store or in the farm. In this study, the insecticidal activity of Pseudocedrela kotschyi stem bark extract was tested against the fourth instar larvae of Culex quinquefasciatus and adult Sitophilus zeamais. A total of three hundred and sixty 4 th instar larvae of Culex quinquefasciatus were divided into six groups each consisting of three replicates containing twenty larvae each. Groups one to four were each administered one of the following dose: 1000mg, 250mg, 125mg and 62.5mg of the ethanolic stem bark extract of P. kotschyi. Group five was treated with a standard drug (permethrin 0.6%) and the last group was neither treated with the extract nor the standard drug. The highest concentration 1000mg of the plant extract had 98.33% mortality followed by 250mg which exhibited 61.67%, 125mg with 48.33% mortality and 62.5 with 25%. There was 100% mortality in the group treated with standard drug and no mortality in the control. Analysis of variance showed significant difference (p<0.05) in the mortality of larvae between the different extract levels.The mortality of the Sitophilus zeamais was observed for 7 daysafter exposure. The highest percentage mortality of 53.33% was recorded inthe weevils treated with 750mgof the plant extract followed by 1750mg which had 50% and the lowest concentration of 500mg plant extract had the lowest mortality of33.33%. However, there is no significant difference (p>0.05) between the mortality of the groups administered extract at different concentrations. From the result, it can be tentatively concluded here; based on this research that P. kotschyi can act as a bio-pesticide of plant origin which will be less toxic to man and other organisms.