Impact of storage structures on moisture content, insect pests and mycotoxin levels of maize in Ghana

Authors: DANSO, J - KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY; OSEKRE, E - KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY; OPIT, G - OKLAHOMA STATE UNIVERSITY; ARTHUR, FRANKLIN; Campbell, James - Jim; MBATA, G - FORT VALLEY STATE UNIVERSITY; MANU, N - KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY; Armstrong, Paul; MCNEILL, S - UNIVERSITY OF KENTUCKY

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2018
Publication Date: 2/25/2019
Citation: Danso, J.K., Osekre, E.A., Opit, G.P., Arthur, F.H., Campbell, J.F., Mbata, G., Manu, N., Armstrong, P.R., McNeill, S.G. 2019. Impact of storage structures on moisture content, insect pests and mycotoxin levels of maize in Ghana. Journal of Stored Products Research. 81:114-120. https://doi.org/10.1016/j.jspr.2018.11.012.
DOI: https://doi.org/10.1016/j.jspr.2018.11.012

Interpretive Summary: Corn (maize) stored in the country of Ghana is vulnerable to infestation from stored product insects, and can also be contaminated with fungal pathogens such as aflatoxin and fumonisin. Corn can be stored as de-husked cobs or shelled corn, in various types of structures such as open cribs, bins, or as bagged corn in flat warehouses. There is little information as to how the storage structure will affect vulnerability of the corn to insect pests and mycotoxins. We conducted a study by sampling corn stored in different structures, during both the major season from September to December and the minor season from January to April. Insect pests were much more prevalent during the major season compared to the minor season. However, the specific insect pests found in the corn varied with the structure; maize weevil populations were low in crib storage while Angoumoius grain moth populations were greatest in crib storage compared to the bin and warehouse. The maize weevil caused the most product damage in terms of damaged kernels and weight loss. Aflatoxin content was also greatest in the major season compared to the minor season, and exceeded the safe storage levels of 15 ppb. Fumonisin content was always below safe storage levels. Results show that corn stored in Ghana is most vulnerable to insect and mycotoxin infestations during the major season, and emphasis should be placed on expanded sampling and monitoring during the major season to ensure quality maintenance. The high aflatoxin content is also a cause for concern because of potential effects on human health.

Technical Abstract: Maize stored as de-husked cobs or shelled maize in a ventilated crib and a metal bin, and in bags in warehouses, was monitored monthly in Ghana from October of 2015 to December of 2015 (the major season) and from January to April of 2016 (the minor season). Temperature, moisture content, insect pests, and associated damage were assessed monthly, and samples were taken in October, December, January, and April for mycotoxin analysis. Moisture content, which ranged from 9 to 15% during the year was occasionally greater in the bin and warehouse compared to the crib, and greater in months associated with the major season compared to other months. Temperatures varied with season but were generally warmer in the bin compared to the warehouse and crib. The predominant insect collected was Sitophilus zeamais (Motschulsky), with the lowest populations in the crib, but in each structure populations were about 10x greater in the major season compared to the minor season. Sitotroga cerealella (Olivier) was the second most-prevalent species, but populations of this species were greater in the crib compared to the bin or warehouse. Scattered populations of other stored product insects were collected from the maize samples and in pheromone traps. Percentage insect damaged kernels (IDK) and weight loss were also greater in samples from months where S. zeamais was present. Aflatoxin was above 10 ppb only in the warehouse in December, while fumonisin levels in all the storage structures were < 0.5 ppm for all months. Results show that maize stored during the major season in Ghana is at risk from insect damage, and metal bins could be utilized more frequently to store de-husked or shelled maize provided the moisture content is at an acceptable level for safe storage.