Evaluation of maize tassel ash and Xylopia aethiopica powder as protectants against cowpea seed infestation by Callosobruchus maculatus Fab. (Coleoptera: Bruchidae)

Abstract

Callosobruchus maculatus insect is a highly destructive insect pest of cowpea that causes significant damage and threatens global food security. This study aimed to evaluate the protectability potential of maize tassel ash and Xylopia aethiopica powder against Callosobruchus maculatus. Maize tassel ash (MTA) and Xylopia aethiopica powder (XAP) were mixed with 20g of sterilized cowpea seeds at sole concentrations: 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0g and a mixture of 1:1, 2:1, 1:2, 3:1, 1:3. Adult mortality, number of eggs laid, adult emergence and weight loss were recorded to evaluate the insecticidal activity. Adult mortality at 24 h in MTA sole application did not differ significantly (p<0.05) despite an increase in the dosage, compared to XAP, which exerted significant corresponding adult mortality. Seeds treated with 0.4g MTA and above resulted in 100% adult mortality at 48 h, and seeds treated with 0.2g – 0.8g XAP did not significantly differ from control. In MTA and XAP mixture ratios of 1:1, 2:1, and 3:1, 100% adult mortality was observed at 48 h. Sole MTA did not significantly suppress oviposition and adult emergence, compared to 0.2 0.6 and 0.8 XAP. While the treatment mixture significantly subdued oviposition, adult emergence and weight loss contrasted with the sole application. The treatment mixture proved effective against C. maculatus infestation and seed damage, hence recommended as a suitable alternative to synthetic chemical control. Further study is envisaged to evaluate increased application rates to develop an appropriate dosage that offers good protection.