Stored maize is a major source of food and livelihood for most rural population in the tropics. However, most of this vital food and feed source is lost during storage to several storage insect pests including the nagging cosmopolitan maize weevil Sitophilus zeamais. In an effort to seek for a low-cost grain protectant against S. zeamais to mitigate these losses, orange rind powder doses of 0.5, 1, 1.5 and 2 g as well as 1, 2, 3 and 4 g of rice husk ash and their binary combinations were tested for S. zeamais mortality, adult emergence, grain weight loss, persistency, and seed viability. A 0.025 g of Protect DP® insecticide (positive control) and an untreated control were also used. With 4 g rice husk ash, weevil mortality was dose-dependent with a peak of 66.3% mortality after 10 days. The highest mortality of S. zeamais caused by treating maize with varied dosages of orange rind powder after 10 days was 11.3% using 2 g. When fresh orange rinds were crushed in rice husk ash to imbibe the ash with essential oils from the rind, the resultant oil-impregnated ash caused significant increases in the weevil mortality within shorter periods when applied even at lower dosages. A 4 g 50:50% binary combination of rice husk ash and fresh orange rind caused the highest weevil mortality of 100% after 4 days of application, followed by 75:25%, then 25:75%. These different combinations also caused significant reductions in adult emergence and grain weight loss. The potency of the combinations decreased after five weeks of application. Application of the binary combinations did not decrease the viability of the treated seeds. Therefore these rice husk ash and fresh orange rind combinations can be exploited as low-cost, eco-friendly and sustainable grain protectants against S. zeamais in stored maize given their ease of preparation and application.
Buy this Article