ASSESSMENT OF STORAGE INSECT PESTS AND INSECTICIDE, BOTANICAL MANAGEMENT OF RICE WEEVIL, Sitophilus oryzae L. (COLEOPTERA: CURCULIONIDAE) ON SORGHUM (Sorghum bicolor L.) UNDER STORAGE CONDITION AT METEMA DISTRICT, NORTHWESTERN ETHIOPIA

Abstract

The production and storage of sorghum are threatened by a wide range of pests, with the rice weevil being one of the most devastating storage insect pests in the Metema district, northwestern Ethiopia. This pest causes significant losses to many subsistence farmers. Therefore, this study was conducted to assess the status of sorghum storage insect pests and to evaluate the efficacy of botanical and chemical insecticides against the rice weevil. The assessment was conducted in Metema district based on interviews and visiting the individual household and collecting a representative sample of grains were collected from their storage facilities to determine the infestation and damage levels of storage insect pests. The laboratory experiment was conduct University of Gondar plant pathology laboratory, the treatment consisted three botanicals (neem seed, neem leaf, and orange peel powder), two chemical insecticides (Actellic 2% dust and Malathion 5% dust), a standard check (Tanphos 56% Tab), and an untreated control treatments arranged in a completely randomized design with three replications. Data on weevil mortality, progeny emergence, percent protection, grain damage, weight loss, and germination percentage were collected and analyzed using SAS software. The survey results indicated that the most prevalent insect pests of stored sorghum were the rice weevil, maize weevil, and flour beetle. Additionally, the Angoumois grain moth, lesser grain borer, and saw-toothed grain beetle were also observed. The average grain weight loss was 7.02%, physical grain damage was 9.16%, and germination percentage was 67.3%. From laboratory results, sorghum grain treated with Malathion 5% dust at par with Tanphos and Actellic 2% completely protected the grains from F1 progeny, followed by applied neem seed powder, while the untreated control didn’t show any grain protection from the insect. After one week of treatment application, Malathion 5% dust similar with Tanphos showed maximum adult mortality followed by Actellic 2%, after twenty-eight days of treatment, the application of neem seed powder showed the highest adult mortality followed by others. Neem seed powder is showed the highest (98.41%) marginal rate of return recommended as a cost-effective treatment to manage rice weevil, and alongside the judicious use of synthetic insecticides like Malathion 5% dust, it can prolong the shelf life of sorghum grain in storage without adversely affecting human and environmental health.