The Effect of Storage on the Efficacy of Eugenia Aromatica (Baill.) in the control of Callosobruchus Maculatus (Fabricius) (Coleoptera: Bruchidae) Pest

The effect of storage on the efficacy of powders from Eugenia aromatica (Baill.) of different ages in the control of Callosobruchus maculatus (Fabricius), a major pest of stored cowpea seeds, were investigated in the laboratory. Powders stored for periods of < 1 month, 24, 36 and 48 months with particle size of 300 µm were tested. Contact toxicity was tested for the differently aged powders at 0.4 g of material per 20 g of seed in separate plastic Petri plates. In fumigant toxicity tests 20 g of infested cowpea seeds was suspended in a piece of muslin cloth, over 0.4 g of powder in a container. In the contact toxicity tests, all the differently aged powders killed C. maculatus adult within 48 hours. The differently aged powders significantly (P < 0.05) reduced oviposition by the introduced C. maculatus adults and adults did not emerge from eggs laid. In the fumigant toxicity test, first use of the differently aged powders prevented emergence of adult C. maculatus from fumigated eggs. In a consecutive reuse of powders, adults emerged from fumigated eggs but the numbers were significantly (P < 0.05) fewer than in the control. In conclusion, the shelf-life of E. aromatica powder as a bruchicide is at least four years.