Insecticidal Effects of Natural Preservatives on Insect Pests of Smoked AfricanMud Catfish, Clarias gariepinus (Burchell, 1822)

摘要

The insecticidal affects some of natural preservatives: ginger, garlic, pepper, garlic-ginger and homogenate of garlic-gingerpepper on insect pests of smoked cat fish (Dermestes maculatus and Necrobial rufipes) were investigated. Twenty each of Necrobial rufipes, Dermestes maculatus and larvae of these insects were introduced into each smoked fish product with the various natural insecticides, screened with mosquito net after which the mortality were observed and counted at every 3 days interval for a period of 7 weeks (49 days). The mortality of different species of insect pests and larvae were counted, sensory attributes of the products were evaluated using hedonic scale and ranking method. The entomological data as well as sensory data obtained by ranking the products were converted to percentage while the data obtained using the hedonic scale was subjected to kruscal wallis (H) analysis. The study revealed ginger had the highest insecticidal effect against Necrobia rufipes. However, garlic, pepper and garlic-ginger-pepper are very effective against Dermestes maculatus. The Kruskal wallis analysis of the hedonic scale indicated that there was no significant difference (p>0.05) in the taste panelist perception of the odour, flavour and texture of the various smoked catfish products during the period of study. The study established these natural preservatives are specie selective which should be considered when they are intended to be used as insecticide as garlic-ginger-pepper homogenate had more potency against Dermestes maculatus (1.7%) while ginger had more potency against Necrobia rufipes (0.2% mortality). However, the odour, flavour and of unpreserved smoked catfish was ranked as the best by the taste panelist during the period of this study.