Effectiveness of Imperata cylindrica, Sida acuta, Chromolaena odorata and Gmelina arborea against Sitophilus zeamais (Motschulsky, 1855) (Coleoptera: Curculionidae)

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 7.5 g) against Sitophilus zeamais infesting stored maize grains was assessed. Treatments were mixed with 100 g of maize grains (landrace, Esa’ mayewangha), 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). 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.