Integrated Pest Management of the Pulse Beetle (Callosobruchus maculatus (F.)) Using Improved Soybean (Glycine max L.) Varieties and Botanical Powders in Northern Ghana

Abstract

Soybean (Glycine max L.) is an important grain legume that contributes significantly to food security, soil fertility improvement, and household income in Ghana. However, its storage is severely constrained by infestation by the pulse beetle, Callosobruchus maculatus (F.), which causes substantial postharvest losses. This study evaluated the resistance of improved soybean varieties and the efficacy of selected botanical powders as alternatives to synthetic insecticides within an integrated pest management (IPM) approach for protecting stored grain against C. maculatus. Two soybean varieties (Afayak and Suong-Pungun) were evaluated under five protectant treatments: an untreated control, neem seed powder, basilicum powder, hyptis powder, and Phoxtoxin. The experiment was conducted in jars using a split-plot arrangement in a randomised complete block design (RCBD) with three replications in the Crop Protection and Postharvest Laboratory of the Council for Scientific and Industrial Research-Savanna Agricultural Research Institute (CSIR-SARI), Nyankpala, Ghana. Data were collected on oviposition, developmental period, adult insect mortality, progeny emergence, grain damage, and grain weight loss using random samples of 100 grains from each treatment jar. Variety and protectant significantly influenced oviposition, adult emergence, mortality, grain damage, and grain weight loss caused by C. maculatus. Afayak recorded approximately 35% lower adult emergence, 63% lower grain damage, and 32% lower grain weight loss than Suong-Pungun, indicating greater resistance to the pest. Among the protectants, Phoxtoxin provided complete protection, with 100% insect mortality and the lowest progeny emergence. Neem seed and basilicum powders also reduced oviposition by approximately 94% and 98%, adult emergence by 81% and 77%, grain damage by 90% and 85%, and grain weight loss by 64% and 57%, respectively, compared with the untreated control. Hyptis powder showed comparatively lower protective efficacy. The findings indicate that combining a relatively resistant variety with botanical protectants can substantially reduce C. maculatus infestation in stored soybean. Neem seed and basilicum powders therefore represent promising environmentally friendly alternatives to synthetic insecticides for sustainable postharvest grain protection.