Moisture content, insect pests and mycotoxin levels of maize on farms in Tamale environs in the northern region of Ghana

Maize production in Ghana has been increasing steadily but increases in yield are being undermined by post-harvest losses. This study is part of a larger project to characterize post-harvest losses in Ghana at different points in distribution channels. Here we determined factors contributing to losses during on-farm storage in the Northern Region of Ghana. This study was conducted in six communities: Adubiyili, Diari, Pong-Tamale, Savelugu, Toroyili and Zamnayili. Losses were determined for maize on cobs stored in thatched granary structures, shelled maize in polypropylene (PP) bags stored on the floor in farmers’ homes or small storehouses, and shelled maize in PP bags stored in warehouses. Maize moisture content, temperature, percent weight loss, percent insect damaged kernels on numerical basis (IDKnb), insect pest abundance, and mycotoxin (aflatoxin and fumonisin) levels were determined. Moisture content values of maize at pre-harvest and heaping stages in all six communities were below 15% wb. There were no insect pests on maize at the pre-harvest stage and only a few larvae were found in the heaping stage, but Sitophilus spp., Tribolium castaneum and Cryptolestes ferrugineus infested maize during storage, with significantly more found in granary structures than maize in PP bags in homes or storehouses. Warehouses had significantly fewer insects than granaries and homes or storehouses. Percent IDKnb values in all six communities were <2% per 250 g in the field. Aflatoxin levels were significantly lower at the pre-harvest stage, with average concentration below action limits established in Ghana, compared to the heaping stage, where average level exceeded the threshold. Fumonisin levels were low and similar for both stages. Data from the present study show that heaping maize on-farm prior to primary processing can increase aflatoxin beyond the acceptable level and should not be practiced.