ABSTRACT

The effectiveness of powdered leaves of Imperata cylindrica (spear grass), Sida acuta (wire weed), Chromolaena odorata (siam weed) and Gmelina arborea (Gmelina) at different dosages (0, 2.5, 5.0 and 7.5g) against Sitophilus zeamais infesting stored maize grains was assessed. Treatments were mixed with 100 g of maize grains (landrace, Esa’ ma yewangha), infested with 30 adults S. zeamais and stored in 200 ml glass jars with perforated lids. The setup was maintained under ambient conditions (25 - 30⁰C and 70 - 90% RH) between April and June, 2017. Mortality assessment was at 2, 4 and 6 days after treatment (DAT), after which all adults were sieved out and the setup kept undisturbed for 5 weeks. The trial was laid out in a completely randomized design (CRD) and replicated four times. Analysis of variance showed that Cypermethrin caused significantly higher mortality than the tested plant powders. Cumulative mortality of adult S. zeamais significantly (P ≤ 0.05) increased with increased treatment dosages and durations of storage. There were significantly (P ≤ 0.05) higher mortality in maize grains treated with 7.5 g/100 g of S. acuta (55.00 and 64.17%) and I. cylindrica (53.33 and 60.00%) compared with C. odorata (44.17 and 50.83%) and G. arborea (35.83 and 40.00%), respectively at 4 and 6 DAT. Results also showed that the efficacy of these plant powders on weevil emergence was dose dependent with higher doses providing greater protection of the maize grains. Cypermethrin treated grains had significantly (P ≤ 0.05) lower values than those treated with plant powders in all parameters tested. Significantly (P ≤ 0.05) lower mean progeny emergence (3.0 and 3.5), and grain weight loss (1.1g and 1.30g) was recorded in I. cylindrica and S. acuta, respectively in 7.5g/100g grains compared with (9.3 and 15.0) and (2.9g and 4.3g) in C. odorata and G. arborea, respectively. However, these treatments did not significantly affect seed germination. The insecticidal properties exhibited by these plant powders make them attractive in upgrading traditional post-harvest protection practices. The result of this study can encourage and serve as a possible means of ensuring a steady supply of good quality maize grains.