Comparative Assessment of Some Storage Technologies Used for Cowpea Storage in the Nadowli District of the Upper West Region of Ghana

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Pest infestation is the major storage problem in cowpea (Vigna unguiculata) storage around the world. The principal postharvest pest of cowpea in Ghana is the cowpea weevil (Callosobruchus maculatus). The main objective of the study was to evaluate the common storage methods used in the Nadowli District and their effectiveness in maintaining the quality of cowpea beans during storage. A survey was conducted to identify the major storage technologies and problems in the district. Four storage structures: barns, polypropylene sacks, earthen pots and triple bags and 3 protectants (wood ash, phostoxin, monthly solarisation) with a control were used to store ‘ormondoh’ cowpea variety. There were monthly data collections on cowpea samples taken from each treatment set up and assessed for quality for three months. Parameters that were determined were percentage weight loss, percentage damage, germination percentage, taste and colour change. Monthly solarisations of beans on all the storage structures proved to be more efficacious by killing all stages of the weevil. Also, triple bags using Purdue Improved Cowpea Storage sacks which use hermetic principle was also more effective when combined with the control or either of ash and phostoxin. The interactions between ash and storage in pots, barns and polypropylene sacks offered lower protection and recorded a high level of damage and loss of other quality parameters. Phostoxin fumigation on polypropylene sack and pot recorded a reduction in grain quality as the storage period increased because the structures were not entirely airtight. The untreated control of the barn, polypropylene sack and pot were highly ineffective in keeping cowpea grain quality. There were losses in taste and colour for all the controls for the various storages technologies with the exception of those kept in the triple bags. Monthly solarisation of cowpea in storage structures did not record any taste or colour change. The study has shown that the use of triple bag treatment with the protectants were more effective in controlling the cowpea weevil (Callosobruchus maculatus) which feeding activities cause loss in grain quality. Monthly solarisation in all the interventions should be the method of choice in the absence of triple bags in the district.
A Thesis Submitted to the School Of Research and Graduate Studies, Kwame Nkrumah University of Science and Technology, in Partial Fulfilment of the requirements for the Degree of Master of Science in Postharvest Technology.