Efficacy of Rubber Seed Oil, Palm Oil and Palm Kernel Oil as Grain Protectants against Sitophilus zeamais (Mots.) (Coleoptera: Curculionidae) in three Maize Varieties

摘要

The efficacy of rubber seed oil, palm oil and palm kernel oil as maize grain protectants against S itophilus zeamais was tested on three maize varieties [a?~Uselua?? local, SUWAN-1 and Oba Super 1 (8321-18) using a 3x5x3 factorial arrangement in a Randomized Complete Block Design. There were four replications of each of the vegetable oils using application levels of 0, 2.5, 5.0, 7.5 and 10.0 mL kg 1 maize grain. All studies were undertaken under laboratory temperature of 28?±3% rh. Fifteen sexed adult insects were used for each replicate. In all the treatments, a range of significant percentage mortality of adult weevils (55-93%) at 21 days after treatment was obtained (0.05). Mean percentage adult weevil mortality in treated grain (70.5%) was significantly higher than in the control (0.0%). The treated grains gave adequate protection by having lower oviposition (19.8%) than the untreated control (94.5%). This was also observed to have lower adult weevil emergence (8.9%) than the untreated control (85.3%). The vegetable oils gave appreciable reduction in percentage weight loss (2.2%) when compared with the untreated control (47.3%) and had no adverse effects on grain quality. From the study, the plants could be ranked in order of effectiveness thus: rubber seed oil > palm oil> palm kernel oil. The "Uselu" local was found to be more resistant to maize weevil infestation than the improved varieties (SUWAN-1) and Oba super 1 (8321-18).