Effect of powdered extract of peppermint (Mentha piperita) on adult cowpea bruchid (Callosobruchus maculatus) mortality during storage in Jos - Plateau

Abstract

The over dependence and continues use of synthetic insecticides to control storage pests have been associated with several demerits. This study was conducted to evaluate the insecticidal effect of peppermint (Mentha piperita) leaf powder on Callosobruchus maculatus. The peppermint plant was sourced locally and the C. maculatus were cultured to obtain the adult Bruchids. The peppermint was washed, dried under ambient temperature and pulverized. Complete Randomized Design was adopted for this trial with three replications of six treatment dosages of 2.5, 5.0, 7.5, 10.0, 12.5 and 0.0 g respectively of the plant material. The trial lasted for four weeks. High Bruchids mortality was observed after treatment with Mentha piperita leaf powder extract. Phytochemical screening of the test plant revealed presence of flavonoids, tannins, saponins, carbohydrates and cardiac glycosides. Descriptive statistic and analysis of variance (ANOVA) were used to analyze the data. Means (p≤0.05) were separated using Duncan Multiple Range Test (DMRT). Dosage rate and mean mortality values at the various doses were statistically significant after 48, 72 and 96 hours. The mortality could be attributed to high presence flavonoid in the Mentha piperita leaf powder. The results suggest that the leaf of peppermint has insecticidal property against adult C. maculatus. However, further trials are required to investigate effective dosage rates for other stored grains and to isolate and characterize the active flavonoids contained in the plant.