Evaluation of the powder of Piper guineense and pirimiphos- Methly F for the control of cowpea beetle Callosobruchus maculatus (F.)

Cowpea is major source of dietary protein in tropical region of the world and damage caused by Callosobruchus maculatus impact negatively on its economic and nutritional values. In Nigeria today, the use of synthetic insecticides has been the major means of protecting stored grains from insect pest infestation. The drawback associated with the use of insecticides has necessitated the search for humanly safe, ecologically sound and cheap control measures. The effect of the combination of Piper guineense and Pirimiphos methyl as treatment in comparison with sole treatments of these powders was carried out in this study. Contact toxicity was tested for Piper guineense at 0.02g, 0.04g, 0.06g, 0.08g and 0.1g per 20g of cowpea seeds in separate petri-dish, while it was tested at 0.01g per 20g of cowpea seeds for Pirimiphos methyl in separate petri-dish. The combination (0.02g + 0.01g; 0.04g + 0.01g; 0.06g + 0.01g; 0.08g + 0.01g and 0.1g + 0.01 Piper guineense and Pirimiphos methyl respectively/20g cowpea seeds) of each of the concentrations was also tested in separate dish. Control with no treatment was also set up. Piper guineense at 0.10g sole concentration and 0.1g Piper guineense + 0.01g Pirimiphos methyl combined concentration significantly reduced the oviposition potential, egg hatching rate and emergence of adults Callosobruchus maculatus. The powders caused chronic toxicity and inhibit development. The inhibitory effects may due to the active ingredients that enter the digestive tract and be absorbed through it. The efficacy in respect of toxicity exhibited significant effect at 0.02g sole treatment of Piper guineense and 0.02g Piper guineense + 0.01g Pirimiphos methyl combined treatments at 12, 24 and 48 hours after infestation (HAI). All the responses were found the concentration dependent during the course of the study.