We conducted an experiment in Niger to evaluate the performance of hermetic triple layer (Purdue Improved Crop Storage- PICS) bags for the preservation of shelled and unshelled groundnut Arachis hypogaea L. Naturally-infested groundnut was stored in PICS bags and woven bags for 6.7 months. After storage, the average oxygen level in the PICS bags fell from 21% to 18% (v/v) and 21%–15% (v/v) for unshelled and shelled groundnut, respectively. Identified pests present in the stored groundnuts were Tribolium castaneum (Herbst), Corcyra cephalonica (Stainton) and Cryptolestes ferrugineus (Stephens). After 6.7 months of storage, in the woven bag, there was a large increase in the pest population accompanied by a weight loss of 8.2% for unshelled groundnuts and 28.7% for shelled groundnut. In PICS bags for both shelled and unshelled groundnuts, by contrast, the density of insect pests did not increase, there was no weight loss, and the germination rate was the same compared to that recorded at the beginning of the experiment. Storing shelled groundnuts in PICS bags is the most cost-effective way as it increases the quantity of grain stored.

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Experiments in Niger assessed whether extreme environmental conditions including sunlight exposure affect the performance of triple-layer PICS bags in protecting cowpea grain against bruchids. Sets of PICS bags and woven polypropylene bags as controls containing 50 kg of naturally infested cowpea grain were held in the laboratory or outside with sun exposure for four and one-half months. PICS bags held either inside or outside exhibited no significant increase in insect damage and no loss in weight after 4.5 months of storage compared to the initial values. By contrast, woven bags stored inside or outside side by side with PICS bags showed several-fold increases in insects present in or on the grain and significant losses in grain weight. Grain stored inside in PICS bags showed no reduction in germination versus the initial value but there was a small but significant drop in germination of grain in PICS bags held outside (7.6%). Germination rates dropped substantially more in grain stored in woven bags inside (16.1%) and still more in woven bags stored outside (60%). PICS bags held inside and outside retained their ability to maintain internal reduced levels of oxygen and elevated levels of carbon dioxide. Exposure to extreme environmental conditions degraded the external polypropylene outer layer of the PICS triple-layer bag. Even so, the internal layers of polyethylene were more slowly degraded. The effects of exposure to sunlight, temperature and humidity variation within the sealed bags are described.

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Several postharvest technologies are currently being commercialized to help smallholder farmers in sub-Saharan Africa reduce grain storage losses. We carried out a study in Northern Benin to compare the effectiveness of five technologies being sold to protect stored grain. Maize that had been naturally infested by insects was stored in four hermetic storage technologies (SuperGrainbag™, AgroZ® bag, EVAL™, and Purdue Improved Crop Storage-PICS™ bags), an insecticide impregnated bag (ZeroFly®), and a regular polypropylene (PP) woven bag as control. Oxygen levels in hermetic bags fluctuated between 0.5 ± 0.0 (v/v) and 1.0 ± 0.3 (v/v) percent during the seven months of storage. No weight loss or insect damage was observed in grain stored in any of the hermetic storage bags after seven months. However, grain stored in ZeroFly® and PP woven bags had weight losses of 6.3% and 10.3%, respectively. These results will help farmers and development agencies when making decisions to use and/or promote storage technologies to reduce postharvest grain losses.