PHYTOCHEMICAL SCREENING AND INSECTICIDAL ACTIVITY OF ZINGIBBER OFFICINALE, ALLIUM SATIVUM AND CURCUMA LONGA POWDERS AGAINST CALLOSOBRUCHUS MACULATUS .FAB. OF STORED COWPEA SEEDS

This study focused on the phytochemcial screening and insecticidal properties/activities of the powdered extracts from three different indigenous spice plants on cowpea weevil Callosobruchusmaculatus. The studied plant were Zingibberofficinale, Allumsativumand Curcumalonga.The plant powders contained the entire nutrient proximate tested such as dry matter, crude protein, crude fibre, ash, ether extract and nitrogen free extracts. The phytochemcial analysis of these extracts indicated the presence of some chemcial like alkaloids, saponins, cardiac glycosides, flavonoids, tannins and terpenoids all of which possess insecticidal properties. Tannin was absent in turmeric while terpenoid was absent in ginger and garlic. In the study,50 weevils were counted in a transparent rectangular cage and introduced to each 200guninfected cowpea in four replicated containers for each plant extract treatment.100g each of the three plant extracts were applied each to four different replicates. Data were subjected for analysis of variance (ANOVA) at 5% probability level and the percentage mortality, number of holes/punctures on the cowpea, and longevity of death of weevils for each treatments. The highest mortality of the weevil were observed in the ginger treatment while turmeric had the least mortality activity. The ginger powder reduces the mean population introduced (50) to 16.5 (mean number alive) of C. maculatus,when compared to garlic powder (24.8)and turmeric powder (32.4) respectively. The longevity in days of C. maculatusfor ginger and garlic effects were 7 days and turmeric was 14days after application. There wasno mortality recorded in the control experiment for the 42 days. Ginger powder gave the lowest mean number of holes on been seeds (16 ? 1.33)followed by garlic powder (41 ? 2.13) and turmeric powder (83 ? 3.04). The average weight loss was recorded high in control treatment (31.5 ? 1.87) and was significantly high than the bean seeds treated with turmeric powder (25.7 ? 1.67), garlic powder (15.0 ? 1.29) and ginger powder (6.0 ? 0.82) respectively. Therefore the powered extracts from these three research plants represent an alternative to chemical insecticides in preservation of stored cowpea.