ABSTRACT

Maize is a major food security crop in Africa and it is usually stored to provide food reserves and also serve as seed material for planting. Despite high maize yields, losses in storage are high due to the maize weevil, Sitophilus zeamais especially among smallholder farmers. The aim of the study is to evaluate two plant powders, scent leaf (Ocimum gratissimum) and hot leaf (Piper guineense), and a synthetic insecticide (permethrin dust) in the control of maize weevils in stored maize grain. The plant leaf powders were admixed with the maize grain at a combination of 3:7, 7:3 and 5:5 per 20g of maize while the permethrin dust were admixed with the maize grains at 10g per 20g of maize. In the control, no treatment was used. The plant leaves were dried under room temperature and ground into fine powders. The powders were put into separate air tight containers to ensure active ingredients were not lost before use. The experimental design adopted for the experiment was Complete Randomized Design (CRD) and each treatment was replicated four times for each experiment. Twenty (20) adult Sitophilus zeamais unsexed (taken from stock culture kept in the laboratory) were introduced into each vial including the control and were subsequently covered with muslin cloth held tightly in place with a rubber band to avoid escaping. The experiments were monitored for 28 days. The results showed that all the plant powders and permethrin dust were good grain protectants. The highest insect mortality recorded was in permethrin dust (80%) followed by the combination of Piper guineense and Ocimum gratissimum dust at the ratio of 5:5 (36%) while the combination of Piper guineense and Ocimum gratissimum dust at the ratio of 3:7 and 7:3 recorded 31% each. No mortality was recorded in the control experiments rather mating was observed. Difference between the performance of permethrin dust (4.000>0.001) and the combinations of Piper guineense and Ocimum gratissimum in the ratio of 5:5 (1.800>0.001), the ratio of 3:7 (1.550>0.001) and the ratio of 7:3 (1.550>0.001) are significant. The study suggests that botanicals should be incorporated into grain protection as alternatives to chemical insecticides in the control of Sitophilus zeamais in maize grains during storage.