Optimization of Storage Methods of Cowpea (Vigna Unguiculata L. Walp) Bagged Pics Containing Biopesticide (Lippia Multiflora) By Central Composite Experimental Design in COTE D'IVOIRE

Cowpea (Vigna unguiculata L. Walp), the first legume of world is an important source of protein and less expensive for African peoples. Cowpea kernels contain essential amino acids. (Smart, 1964; Hignard, 1998; Archana et Jawali, 2007). It is rich in minerals, and vitamins that are essential for optimum health. Thus, cowpea is a high nutritional value of food that could help the Ivorian fight against food shortages. With a global annual production of 3.3 million tons (Kouakou et al, 2007), the cowpea are consumed in various forms in West Africa (fried, boiled, mashed, paste and sauce). The others parts of plant are used for animals food (Chapon, 2002). It also contributes to the fertility of soil by fixing nitrogen. Beyond the agronomic and nutritional interest, cowpea has also a socio economic importance (Doumma et al., 2011). It is used in funeral rites and various religious ceremonies. (Mukendi et al., 2013). Finally, cowpea is a savings in case of necessity (returned school, diseases), hence the importance of postharvest treatments, especially the storage conditions for cowpea quality. Unfortunately, storage is difficult for the farmers because of the pests as weevils. (Agyen-Sampong, 1978; Doumma et al., 2011). Environmental conditions and bad practices postharvest cause both damage. Damages start from the field where the larvae of weevil infest cowpea kernel (Huignard, 1995). After harvest, the infested kernels are stored. Studies showed that a rate of 10% of larvae sufficient to degrade 100 % of the harvest in a few months causing weight losses of up to 60 to 70% (Ngamo et al., 2007 ; Okunola et al., 2007). Furthermore, during their developing larvae remove nitrogen in the form of toxic uric acid that builds up inside the grain making cowpea parasitized undrinkable (Gauthier, 1996). Another aspect inherent in the development of insects is colonization by fungi stocks (Elmer et al., 2001; Wen et al., 2005). These storage fungi promote quality deterioration by producing mycotoxins such as aflatoxins, ochratoxin A, which are harmful to the health of consumers (Kankolongo et al., 2009; Atanda et al, 2015.). To face these destructive of stock, producers often use syntheses of pesticides (sometimes prohibited) which misuse the precautionary failure in handling and non-compliance with waiting periods can lead to insect resistance and harmful to environmental and health problems (Kétoh, 1998). 

Thus, given the magnitude of the damage caused by the use of these chemicals, the use of biopesticides as an alternative solution has been encouraged in recent decades (Bambara et al 2008. Gueye et al, 2011; Kayombo et al. , 2014). The use of plants for protection is an ancient practice that makes available almost rural food or agricultural production is seasonal as  consumer needs are spread over the entire year. These aromatic plants and their derivatives are an effective fight against pests. They are cheaper and guarantee biodiversity (Regnault-Roger, 2002; Ketoh et al., 2005; Isman, 2006; Gueye et al., 2011). In these insecticides and/or insectifuge plants, figures Lippia multiflora L. Lippia is a local plant and accessible in all regions of the Ivory Coast, which was the subject of several works on the biofunctional properties (Tia, 2012; Ekissi et al. 2014). Therefore, this work aims to determine the minimum concentration of leaves of L. multiflora to sustainably preserve the quality of cowpea beans. This approach is based on a central composite experimental design to optimize post-harvest storage of cowpea beans in PICS bags.