Botanical Control of Cowpea Weevil (Callosobruchus maculatus) in Stored Cowpea Using Ocimum gratissimum and Allium sativum Powders in Lafia, Nasarawa State

An infestation of storage cowpeas caused by Callosobruchus maculatus poses a significant risk, which can lead to food shortages and economic losses especially where cowpeas are a main crop. This study investigated the insecticidal potential of Allium sativum and Ocimum gratissimum leaf powders in managing Callosobruchus maculatus infestation in stored cowpea seeds. Different amounts (5g, 10g, 15g, 20g, and 25g) of these botanical powders were mixed into batches of 100 seeds. Each batch was introduced to 20 cowpea weevils, all set up inside containers covered with muslin cloth. The experiment consisted of four treatments: the first treatment, labelled A contained O. gratissimum powder; the second B contained A. sativum ; the third C comprised the mixture of O. gratissimum and A. sativum powders in the ratios of 1:1, 2:3, 3:2, 4:1 and 1:4; and the last treatment D, served as the control, contained no powder. Data collected were subject to analysis of variance (ANOVA), and the treatment means were compared using the Duncan Multiple Range Test (DMRT) at a 5% probability level (P<0.05). Weevil mortality was found to be significantly influenced by both concentration level and exposure duration. At a 25g dosage, the highest death rate was 9.17, followed by 4.86 at a 20g dosage and 1.89 at a 5g dosage. Of all the powders, A. sativum had the highest death rate (5.20), followed by the powder combination (4.73) and O. gratissimum (3.38). The death rates for each therapy showed significant differences (P ≤ 0.05). The results suggest that these botanical powders can act as sustainable botanical pesticides to control post-harvest cowpea infestation and enhance food security by substituting chemical pesticides with more ecologically friendly alternatives.