Assessment of Botanical Powder Treatments for Enhancing Post-Harvest Resistance of Cowpea (Vigna unguiculata (L.) Walp.) Varieties to Pulse Beetle (Callosobruchus maculatus F.) Infestation in Northern Ghana

Abstract

Callosobruchus maculatus (F.) is a cosmopolitan and highly destructive pest of stored pulse grains, causing post-harvest and economic losses to farmers and traders, as infestation of stored grains is difficult to prevent. This study determined the effectiveness of selected botanical powders as eco-friendly insecticides for replacing synthetic insecticides in the management of C. maculatus in stored cowpea. Cowpea seeds (Vigna unguiculata (L.) Walp.), obtained from the Savanna Agricultural Research Institute (SARI), Ghana, were subjected to five treatments, including three botanical powders: Azadirachta indica, Hyptis suaveolens and Ocimum basilicum, as well as phostoxin as a positive control. The study was arranged in a Completely Randomised Design (CRD), and data were collected on egg load, progeny emergence, adult mortality, seed weight loss and developmental period. The findings showed that Azadirachta indica and Ocimum basilicum powders were effective in controlling C. maculatus and performed similarly to phostoxin. These treatments recorded the lowest egg load, reduced progeny emergence, increased adult mortality, low seed weight loss and prolonged developmental stages of the pest. In contrast, Hyptis suaveolens powder was the least effective treatment after the untreated control. The findings indicate that Azadirachta indica and Ocimum basilicum powders are promising substitutes for synthetic insecticides because they are comparatively greener and more sustainable.