ABSTRACT

Stored product grains are continually infested with stored product pests. In recent times, an alien population of Sitophilus oryzae was found in Benin city. In seeking bio friendly means to control them, storage pests respond to different botanicals differently. This study is focused on the use of the leaf powder of Chromolaena odorata, as well as the leaf and seed powder of Lantana camara against S. oryzae. Thirty grams of cowpea grains were placed in plastic containers, and powders from specific plant parts were introduced into each set up at various concentrations (0.5, 1.5, 4.5, 13.5g), this set up was infested with 10 newly emerged adult weevils for each treatment set, which were laid out in completely randomized design, and replicated five times. The weevils were exposed for 24, 48, 72, 96 and 120 hours, under ambient conditions (25- 29 and 61- 77% RH). Although some degree of mortality and repellency was observed, the lethal effect of the different plant materials on S. oryzae did not differ significantly, neither did repellency. Therefore, based on this study, the performance of S.  oryzae on cowpea remained unaffected in the presence of botanicals, as the various assessments conducted (percentage weight loss, percentage of damaged grains and emergence of Sitophilus after trial) did not show any remarkable difference from the control treatments. These findings suggest that S. oryzae would be a difficult pest to control using the botanicals. However, other plant materials (botanicals) may be more effective than C. odorata and L.  camara, if further studies are carried out to establish that. The implication of these findings on the cowpea supply chain is that grain sellers and farmers may continue to preserve their grains with harmful synthetic chemicals which should be discouraged.