Efficacy of botanical powders and cooking oils against Angoumois grain moth, <i>Sitotroga cereallela</i> O. (Lepidoptera: Gelechiidae) in stored maize

Abstract

During storage, maize grains are severely destroyed by insects and other pests. One of the most important causes of grain loss in stored maize is the damage caused by Angoumois grain moth, Sitotroga cereallela O. A study was conducted to evaluate selected locally available botanical powders and two cooking oils for their effectiveness as grain protectants against S. cereallela at Jimma University College of Agriculture and Veterinary Medicine in 2011. The plant powders and cooking oils were compared with untreated control and Malathion super dust as standard control. The experiment was laid-out in completely randomized design with three replications for each treatment. Different dependent variables such as adult mortality, F₁ progeny emergency and grain damage were assessed. The results revealed that there was an increase in adult mortality, decrease in F₁ progeny emergency and grain damage as a result of botanical powders and cooking oils application to maize grains. Among the botanicals, very low mortality of 27.80% was recorded from Maesa lanceolata (with LT₅₀ of 219.8 days) and Echinops kebericho (with LT₅₀ of 338.10 days) similar to the untreated control. Cumulative mortality of 39.00% was registered from Azadirachta indica bark powder (with LT₅₀ of 30.40 days) and Cympopogon citratus leaf (with LT₅₀ of 171 days) against Sitotroga cerealella 20 days after insect exposure to the botanicals. Maximum moths mortality, 94.4%, was recorded from standard control (Malathion) followed by the two cooking oils (77.8%). No F₁ progeny emerged from the grains treated with the two cooking oils similar to the standard chemical over the exposure period of 40 days leading to no seed with hole, minimum weight loss and maximum seed germination percentage (97.30%). Thus, the two cooking oils were found to be most potent bio-insecticides against maize grain moth on par with standard check, Malathion.

Keywords: Angomois grain moth, Sitotroga cereallela, cooking oils, exposure time, grain damage, maize grains, mortality and plant powders

African Journal of Biotechnology Vol. 12(16), pp. 1978-1986