Moisture content, insect pests and mycotoxin levels of maize at harvest and post-harvest in the Middle Belt of Ghana

Grain moisture content (MC), insect pest infestation and mycotoxin contamination of maize are challenges to food safety and security, especially in the tropics where maize is a staple grain. However, very little documentation is available on the impact of these factors on maize in Ghana. This study focused on post-harvest losses of maize and assessed grain MC, insect pests and mycotoxin (aflatoxin and fumonisin) levels on-farm at three stages, during the major and minor seasons (primary and secondary harvest seasons, respectively). Grain MC decreased significantly from the field stage (17.2–19.0%) to the post-drying stage (12.4–14.2%). The mean grain MC was significantly greater in the major season (20.4%) than in the minor season (12.5%). Maize weevil, Sitophilus zeamais Motschulsky, Angoumois grain moth, Sitotroga cerealella Olivier, square-neck grain beetle, Cathartus quadricollis Guerin-Meneville, and corn sap beetle, Carpophilus dimidiatus Fabricius were the dominant insect species that attacked maize on-farm. Mean numbers of each species were generally significantly greater in the minor season than in the major season, but in both seasons, greater numbers were detected at the heaping stage compared to field and post-drying stages. Percentage insect damaged kernels and weight loss were significantly lower at the field stage than at both the heaped and post-drying stages; statistically similar levels were observed in the latter two stages. Mean aflatoxin (ppb) and fumonisin (ppm) levels were significantly higher in the major season (29.1 ppb, 1.6 ppm) than in the minor season (3.5 ppb, 1.0 ppm). Results showed variation between locations sampled, but in general more insect damage and quality deterioration occurred during the major season compared to the minor season. Farmers should dry immediately after harvest to reduce risk of damage from insect pests and mycotoxins.