Effects of hermetic bag storage on insect pest damage, mould infection and a flatoxin contamination on maize grain in Makueni County, Kenya

Abstract

For centuries, maize producers in sub-Saharan Africa have been plagued by post-harvest losses from insect infestation and mould infections, with small-scale producers representing the most vulnerable populations. Participatory on-farm trials were conducted to assess the effectiveness of triple layer hermetic (PICS™) bags for storage of maize in small-scale farmers’ stores in rural villages in Makueni County,Kenya. PICS bags are three-layer hermetic bag-system that forms a barrier against the influx of oxygen and the escape of carbon dioxide.Shelled maize grain was purchased from the participating farmers, filled into jute,woven polypropyleneor PICS bags, and kept in the farmers’ own stores for 35 weeks. Temperature and relative humidity in the trial site and in all the bags, as well as oxygenand carbon dioxide levels in the PICS bags were also monitored.Grain moisture, live insect population, grain damage and weight loss, total mould count and mould incidence levels were examined at onset and after every 7 weeks while total aflatoxin contamination was examined at onset and after 14, 28 and 35 weeks.Initial moisture content of maize varied from farmer to farmer and ranged between 12.4 – 15.0%. Oxygenand carbon dioxide compositions demonstrated that PICS bags are capable of sustaining good air-barrier properties. Generally, moisture contentof maize stored in PICS bags was significantly higher (P < 0.05) than moisture content of maize stored in woven polypropylene and jute bags in the last 14 weeks of storage. Maize stored in hermetic bags remained free from insect infestation and the weight loss due to insect damage was below 1%. In contrast maize stored in woven polypropylene and jute bags permitted profuse build-up of insect populations and grain damage reached 77.6% and 82.3% corresponding to 41.2% and 48.5% weight loss respectively.Total mould count and aflatoxin contamination of maize stored at an initial moisture content< 13% and 13% ≤ m.c. ≤ 14%increased significantly in woven polypropylene and jute bags but not in PICS bags. After 35 weeks, total aflatoxin of maize stored in the woven polypropylene and jute bagsat initial moisture content < 13% and 13% ≤ m.c. ≤14% increased 5 - 8 folds. Total mould and aflatoxin contamination of maize stored at initial moisture content > 14% increased in the three types of bags. These findings demonstrate that PICS bags are effective in controlling losses caused by storage pests and can prevent mould infection and aflatoxincontaminationon maize in rural farmers’ stores if grain moisture is < 14%.