Efficacy of Some Plant Extracts as Storage Protectants against Callosobruchus maculatus

A significant quantity of crops is lost as a result of application of non-selective crop protection agents. The agrochemical industry is faced with increasing demand for the development of new crop protection agents that are safe for the environment and consumers. This research aimed at contributing to the collation and organization of baseline data on natural insect repelling and insecticidal agents. It also aimed at discovering crop protection agents that would preferentially get rid of pests. The need to develop pest control measures as alternative to chemicals is a priority for Scientists worldwide. Therefore, it is critical to find a cost effective and non-toxic method to prevent pest attack on field or stored crops. In this study, Cymbopogon citratus (lemon grass), Citrus sinensis (orange peel) and Azadirachta indica (neem) were used to investigate and evaluate the potency of the fixed and essential oils of these plants as pest control agent for the main storage insect pest of cowpea- Callosobruchus maculatus. All extracts were toxic to adult C. maculatus and prevented egg hatching. However, Citrus sinensis showed the highest weevil mortality on the first day of exposure, followed by Azadirachta indica and the least toxic was Cymbopogon citratus in the fixed oil category of extracts while in the essential oil category, Cymbopogon citratus showed 100% adult weevil mortality within one hour of exposure and Citrus sinensis was able to achieve 100% weevil mortality at the third hour of exposure. The Gas Chromatography/Mass Spectrometry (GC/MS) analysis of the essential oils of Cymbopogon citratus and Citrus sinensis was used to identify possible components of the oils comparing with existing data. This led to the development of technique adoptable for small holder farmers and cowpea traders.