Maize is the most important staple in sub-Saharan Africa (SSA), with highly seasonal production. High storage losses affect food security, but good estimations are lacking. A new method using focus group discussions (FGDs) was tested with 121 communities (1439 farmers, 52% women) in Kenya's six maize-growing zones, to estimate the maize losses to storage pests and analyze farmer practices. As control strategies, half of the farmers used chemical pesticides (49%), while hermetic bags (16%) and botanicals (15%) were also popular. Relative loss from weevils in the long rains was estimated at 23%, in the short rains 18%, and annually 21%. Fewer farmers were affected by the larger grain borer (LGB) than by maize weevils: 42% in the long rainy season and 32% in the short rainy season; losses from LGB were also smaller: 19% in the long season, 17% in the short season, and 18% over the year. Total storage loss, from both species combined, was estimated at 36%, or 671,000 tonnes per year. The greatest losses occur in the humid areas, especially the moist mid-altitudes (56%), and with smaller loss in the drylands (20-23%). Extrapolating the point data and overlaying with the maize production map shows the geographic distribution of the losses, with the most important area found around Lake Victoria. FGDs provide convenient and cheap tools to estimate storage losses in representative communities, but a total loss estimate of 36% is higher than is found in other studies, so its accuracy and framing effects need to be assessed. We conclude that storage pests remain a major problem, especially in western Kenya, and that the use of environmentally friendly technologies such as hermetic storage and botanicals needs more attention, both by the public extension service and private agrodealers.

Smallholder farmers in Bangladesh often use low-density polyethylene (LDPE) bags contained within woven polypropylene bags to store wheat seed during the summer monsoon that precedes winter season planting. High humidity and temperature during this period can encourage increased seed moisture and pests, thereby lowering seed quality. Following a farm household survey conducted to inform trial design, eighty farmers were engaged in an action research process in which they participated in designing and conducting trials comparing traditional and alternative seed storage methods over 30 weeks. Factorial treatments included comparison of hermetic SuperGrainbags® (Premium RZ) against LDPE bags, both with and without the addition of dried neem tree leaves (). SuperGrainbags® were more effective in maintaining seed moisture at acceptable levels close to pre-storage conditions than LDPE bags. Both seed germination and seedling coleoptile length were significantly greater in hermetic than LDPE bags. Neem had no effect on seed moisture, germination, or coleoptile length. SuperGrainbags® were also more effective in abating seed damage during storage, although inclusion of neem within LDPE bags also had significant damage. Quantification of seed predating insects and diseases suggested that SuperGrainbags® also suppressed Coleopteran pests and blackspot, the latter indicative of . Conversely, where farmers used LDPE bags, neem also had an additional though limited pest suppressive effect. Post-storage treatment scoring by farmers revealed a strong preference for SuperGrainbags® and no preference differences for or against neem. This study demonstrates a process by which farmers can be involved in the participatory co-design and testing of alternative wheat storage options, and stresses the need to develop SuperGrainbag® supply chains so hermetic storage can be made widely available.

Soybean seed quality is affected by high relative humidity (r.h.) during storage in the humid tropics resulting in loss of germination. This study assessed the effectiveness of hermetic bags in preserving soybean seed quality when stored at high r.h. over three months. Treatments consisted of Purdue Improved Crop Storage (PICS) and control polypropylene (PP) woven bags kept at 30 and 80% r.h. Moisture content and germination were measured each month. Moisture content did not change, except in seed stored in PP bag at 80% r.h. where it more than doubled after one month. There was no significant difference in germination rates between soybean seed stored in PICS bags at 30 and 80% r.h. over three months. Soybean seed stored in PP bag at 30% r.h. had germination rates similar to those observed in PICS bags at 30 and 80% r.h., except after the third month where it significantly decreased compared to PICS bags at 30%. Germination rates of soybean seed stored in PICS at 30% and 80%, and PP bags at 30% decreased by about 3, 6, and 7%, respectively. However, the germination rates of soybean seed stored in PP bags at 80% r.h. dropped by 98% after three months. There was a significant negative correlation of -80.6% (Pearson correlation) between moisture content and seed germination. Farmers and seed producers/traders in the humid tropics can safely preserve soybean seed using commercially available hermetic bags.

Hermetic storage technologies (HSTs) have been disseminated in Sub-Saharan Africa (including Kenya) to reduce grain storage losses among farmers. We carried out a study in three counties in eastern Kenya to assess the use and profitability of HSTs among farmers. Data were collected from 613 farmers using a semi-structured questionnaire and Kobo Toolbox via android tablets. Results showed an increase in use of HSTs among farmers from 53.7% in 2015 to 91.2% in 2017. PICS was the most used hermetic bags by farmers (84%) in 2017. Majority of farmers (73.5%) received training in the use of HSTs from extension agents and agro-dealers. About 40% of respondents purchased additional (one to five) bags after their first experience using them. The quantity of grain produced made up about half of the farmer's decision to store. The primary reason (87%) farmers used hermetic bags was the need to manage insect pests. Maize and beans were the most produced and most stored crops; but maize was the most stored in HST. Grain price seasonality showed a near doubling effect between the lean and harvest seasons. Estimates of the return on investments (ROI) ranged between 13 and 80% for all crops and maize stored in hermetic bags had the highest ROI. Awareness and trainings are key in increasing adoption and proper use of HSTs.

The PICS bags, originally developed for cowpea storage, were evaluated for sorghum (Sorghum bicolor) preservation. Batches of 25 kg of sorghum grain were stored in 50 kg PICS or polypropylene (PP) bags under ambient conditions for 12 months and assessed for the presence of insect pests and their damage, seed viability and, oxygen and carbon dioxide variations. The grain was incubated for 35 days to assess whether any insects would emerge. After six months of storage, oxygen levels decreased in the PICS bags compared to polypropylene bags. After 12 months of storage, only two pests, and were found in the PICS bags. However, in PP bags there were additional pests including and and . Grain weight loss and damage caused by these insects in the PP bags were significantly higher compared to those stored in PICS bags. Germination rates of sorghum grains stored in PP bags decreased significantly while no changes were observed in grains stored in PICS bags when compared to the initial germination. After the incubation post storage period, there was a resurgence of R. dominica in sorghum grains from PICS bags but the population levels were significantly lower compared to polypropylene bags. PICS bags preserved the quality and viability of stored sorghum grains and protected it from key insect pests. The PICS technology is effective for long-term sorghum storage but the potential resurgence of insects in low-oxygen environment calls for further research.

We assess the impact of a package of post-harvest technologies on aflatoxin contamination of maize through a randomized trial in rural Kenya. Some elements of this package (training and provision of plastic sheets for sun-drying) were provided free of charge to all participants in treatment villages and were widely adopted. Others (a mobile drying service and hermetic storage bags) were provided free to a subset of randomly selected farmers in treatment villages while others had to pay. Overall, the intervention reduced aflatoxin contamination by over 50%. Most of this reduction appears to be due training and the use of drying sheets, the lowest-cost of all the technologies offered.

Insect pests such as Fabricius and Hübner cause substantial losses to grain during postharvest storage. In the last few years, hermetic storage technologies have been successfully used by smallholder farmers in Africa and Asia to protect their harvested grain against insect pests. Hermetic technologies owe much of their effectiveness to restricting oxygen availability to insects confined in the containers. There is a need to better understand the biology of specific storage insect pests and their responses to hypoxia. We employed a novel and non-invasive analytical technology, the OxySense 5250i, to measure oxygen levels in closed containers, and evaluated its effectiveness in measuring the total oxygen consumption of two insect pests during their development: and . The total amount of oxygen consumed by during its larval development period determined with the OxySense apparatus was not different from that previously recorded using another instrument, the Mocon Pac Check 325 gas analyzer. Using the OxySense 5250i, we found that consumes nearly three times as much oxygen per insect over its larval-to-adult developmental period compared to . Information on the lifetime oxygen consumption of insects provides relevant information to the effectiveness and ability of hermetic technologies to protect stored products against insect pests.

Purdue Improved Crop Storage (PICS) bags were designed to reduce grain storage losses on smallholder farms. The bag consists of three layers: two high-density polyethylene liners fitted inside a woven polypropylene bag. Recently, farmer groups, development relief programs, and government food security agencies have shown interest in PICS bags for large-scale use. PICS bags are conventionally closed by a twist-tie (TT) method, which involves twisting, folding, and tying the lip of each layer individually with a cord. This is not only time and labor intensive, but also may affect the integrity of the liners. We evaluated three new bag closure methods: i) inner liner rolled onto itself and middle liner fold-tied (IR), ii) both liners folded together and tied (FT), and iii) both liners folded and tied separately (FS), along with the conventional twist tie (TT) method. The time to close partially or fully filled 50 kg-capacity PICS bags filled with maize grain was assessed. Results showed that FT was the most time-saving method, reducing bag sealing time by >34% versus the usual TT method. The average internal oxygen levels reached <2% within a week in bags containing grain highly infested with , while it remained >5% levels for less-infested bags. In both cases, insect population growth was suppressed. Oxygen depletion rates among tying methods remained the same regardless of the closure method used. When large numbers of bags need to be closed, the time-saving FT method is a good alternative PICS sealing method over the conventional twist-tie approach.

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.

Small hermetic bags (50 and 100 kg capacities) used by smallholder farmers in several African countries have proven to be a low-cost solution for preventing storage losses due to insects. The complexity of postharvest practices and the need for ideal drying conditions, especially in the Sub-Sahara, has led to questions about the efficacy of the hermetic bags for controlling spoilage by fungi and the potential for mycotoxin accumulation. This study compared the effects of environmental temperature and relative humidity at two locations (Indiana and Arkansas) on dry maize (14% moisture content) in woven polypropylene bags and Purdue Improved Crop Storage (PICS) hermetic bags. Temperature and relative humidity data loggers placed in the middle of each bag provided profiles of environmental influences on stored grain at the two locations. The results indicated that the PICS bags prevented moisture penetration over the three-month storage period. In contrast, maize in the woven bags increased in moisture content. For both bag types, no evidence was obtained indicating the spread of from colonized maize to adjacent non-colonized maize. However, other storage fungi did increase during storage. The number of infected kernels did not increase in the PICS bags, but the numbers in the woven bags increased significantly. The warmer environment in Arkansas resulted in significantly higher insect populations in the woven bags than in Indiana. Insects in the PICS bags remained low at both locations. This study demonstrates that the PICS hermetic bags are effective at blocking the effects of external humidity fluctuations as well as the spread of fungi to non-infected kernels.

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 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 (Herbst), (Stainton) and (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.

A follow-up study on the quality of maize for sale in West African public markets was carried out in Benin and Niger from August 15-28, 2013. Complementing the earlier study, this present assessment included not only retailers but also wholesalers and maize producers. Samples were evaluated for parameters related to the physical quality of the maize and for aflatoxin contamination. Most maize value chain actors process their offered grain using traditional methods for threshing, winnowing and drying. Maize for sale in the markets surveyed had an average moisture content ranging between 12 and 14%. Non-grain impurities amounted to 0-2.3% while mouldy grains ranged between 0.2 and 0.8%. The impurity level in grain was three times higher among wholesalers compared to retailers and producers. An insect pest, the Larger Grain Borer ( (Horn) was found only in Benin but Motschulsky, Stephens, and Herbst, were present in maize for sale in the markets in of both countries. Insect pest frequency was 16 times higher in wholesalers' grain compared to that of retailers and producers. Aflatoxin levels exceeding the accepted standard of 20 ppb were noted in markets in both countries. The highest proportion of aflatoxin-contaminated maize was in wholesalers' grain in Malanville market.

We assessed the performance of hermetic triple layer Purdue Improved Crop Storage (PICS) bags for protecting grain against storage insects. The major storage pest in the grain was a bruchid, sp.. When we stored infested H. grain for six months in the woven polypropylene bags typically used by farmers, the population increased 33-fold over that initially present. The mean number of emergence holes per 100 seeds increased from 3.3 holes to 35.4 holes during this time period, while grain held for the same length of time in PICS bags experienced no increase in the numbers of holes. Grain weight loss in the woven control bags was 8.6% while no weight loss was observed in the PICS bags. Seed germination rates of grain held in woven bags for six months dropped significantly while germination of grain held in PICS bags did not change from the initial value. PICS bags can be used to safely store grain after harvest to protect against a major insect pest.

Postharvest insect pests threaten the nutritional and financial security of smallholder farmers in the developing world. Hermetic storage, a technology that protects grain against insects by blocking their supply of oxygen, alleviates the problem of insect-caused losses. PICS (Purdue Improved Crop Storage) bags represent one hermetic technology that improves food availability and incomes of farmers. The polyethylene liners of PICS bags are sometime damaged during use, acquiring small holes or tears. Observations in the laboratory and field suggest that insect development remains localized around the point where the bag is damaged. We hypothesized that the grain within a hermetic container that has minimal localized damage (such as an insect hole), helps retard leakage of oxygen into the bag and contributes to limiting insect damage and to the overall protective effect. To test this hypothesis, we filled 4 cm dia. by 10 cm long PVC pipes with (F.) infested cowpeas and sealed them with caps having a single, insect-sized hole in its center. A vertical tube positioned above the cowpea-filled PVC pipe was filled with one of three different grains (sesame, sorghum, and maize) to different depths (0, 5, 15, 30, 50 cm). Seed size and grain barrier depth significantly reduced the level of bruchid damage to the stored cowpea in the PVC container. Smaller sized grains used for the barriers retarded insect development more effectively than larger sized grains, while deeper grain depth was more effective than shallower barriers. The grain held in a hermetic container contributes in a small, but significant, way to the effectiveness of the containers.

Purdue Improved Crop Storage (PICS) bags are used by farmers in Sub-Saharan Africa for pest management of stored grains and products, including maize. These bags hermetically seal the products, preventing exchange with external moisture and gases. Biological respiration within the bags create an environment that is unsuitable for insect development and fungal growth. This study was conducted to determine the impact of routine opening of the storage bags for maize consumption on fungal growth and aflatoxin contamination. Maize with moisture contents (MC) high enough to support fungal growth (15%, 16%, 18% and 20%) was stored in PICS bags, which were opened weekly and exposed to humid conditions (85% RH) for 30 min over a period of 8 weeks and 24 weeks. Monitors indicated that oxygen defused into the open bags but did not reach equilibrium with the bottom layers of grain during the 30-min exposure period. Fungal colony forming units obtained from the grain surface increased 3-fold (at 15% MC) to 10,000-fold (at 20% MC) after 8 weeks. At both 8 weeks and 24 weeks, aflatoxin was detected in at least one bag at each grain moisture, suggesting that aflatoxin contamination spread from a planted source of . -colonized grain to non-inoculated grain. The results indicate that repeatedly breaking the hermetic seal of the PICS bags will increase fungal growth and the risk of aflatoxin contamination, especially in maize stored at high moisture content. This work also further demonstrates that maize should be properly dried prior to storage in PICS bags.

Essential oils from sweet basil, Ocimum basilicum, and African basil, O. gratissimum, (Labiatae) grown in Guinea were obtained by steam distillation. Following exposure of newly emerged adult beetles (Callosobruchus maculatus) to 12h of fumigation using pure essential oils at a dose of 25&mgr;l/vial, 80% mortality was recorded for O. basilicum, 70% for O. gratissimum and 0% in the control. A significant difference was observed between the responses of males and females with males exhibiting greater sensitivity. When 1g of aromatized powder was applied to adults, a 50% lethal concentration at 48h was found to be 65&mgr;l/g for O. basilicum and 116&mgr;l/g of O. gratissimum oils. The essential oils from the two plant species exhibited a significant effect both on the egg hatch rate and on the emergence of adults. The egg hatch rate was reduced to 3% with O. basilicum and 15% with O. gratissimum using an essential oil concentration of 30&mgr;l, whereas the egg hatch rate for the control was 95%. When compared with the control (97%), adult emergence dropped to 0% with O. basilicum and to 4% with O. gratissimum. Storage bioassays were run to assess the long-term effect of powders aromatized with essential oils of Ocimum. Complete protection was observed over 3 months starting at a dose of 400&mgr;l in the case of both oils. From a germination test, it was concluded that aromatized powders have no significant effect on the seed germination rate. After 5d, a rate of 88% germination was seen in seeds treated with aromatized powder and protected from insects, compared with 97% for untreated seeds that were not exposed to insects.

Phosphine fumigation trials were carried out on bag-stacks of paddy rice to study the differences in gas loss rates and concentration-time (Ct) products achieved during the treatment of indoor and outdoor stacks. Stacks (89-132t) were fumigated singly under 250&mgr;m thick polyethylene sheeting, which was sealed with a double layer of sand-snakes to the concrete floor. Phosphine was applied as an aluminium phosphide formulation and the fumigations continued for 7 days. In the first experiment, stacks of paddy rice with moisture contents ranging from 12.2 to 13.7% were held in either indoor or in outdoor storage and subjected to fumigation at the rate of 2, 3 or 4g of phosphine/tonne. The outdoor stacks held relatively low levels of phosphine with Ct products for the indoor stacks of 135, 171 and 294gh/m(3), respectively, whilst the corresponding values for the outdoor stacks were 70, 85 and 166gh/m(3) only. The average gas loss rate was 14.5% per day for the indoor stacks and 29.5% for the outdoor stacks. In the second experiment, old stacks of paddy rice inside a godown, one each with grains at 8.8 and 9.8% moisture content, were fumigated at 3g phosphine/tonne. Release of phosphine was delayed and fumigant sorption was less and therefore higher Ct products of 204 and 216gh/m(3) were achieved. In the stacks built outdoors, the resident infestations of Rhyzopertha dominica, Cryptolestes sp. and Oryzaephilus surinamensis were completely controlled despite lower Ct products. On the other hand, in the stacks of old paddy, R. dominica survived the treatment. Subsequent testing showed that the population had a degree of resistance to phosphine.

Peas (Pisum sativum) are toxic to some stored-product insects. The repellent effect of fractions of pea seed to stored-product insects was evaluated in multiple-choice tests in which wheat kernels were dusted with fractions rich in either protein, fibre or starch at 0.001 to 10% (wt:wt). There was a negative correlation between pea protein concentration and the number of adults found in grain for Cryptolestes ferrugineus and Sitophilus oryzae, but not for Tribolium castaneum. Pea fibre repelled C. ferrugineus adults but not S. oryzae and T. castaneum. Pea starch did not repel any of the insects. One-week old and 6-week old C. ferrugineus were equally repelled by pea protein. Repellency was detectable 1h after exposure. Cryptolestes ferrugineus and S. oryzae did not become habituated to the repellent action of pea protein even after 4 weeks of exposure. Habituation was observed, however, when C. ferrugineus was exposed to pea fibre for 4 weeks. In a two-choice bioassay (0 vs. 0.1% and 0 vs. 1% pea protein), the pea-protein-treated grain had significantly fewer insects (C. ferrugineus, S. oryzae, Sitophilus zeamais, T. castaneum, and Tribolium confusum) than untreated grain. The properties of the pea protein fractions seem well suited for developing a natural stored grain protectant.

This study evaluated the efficacy of ozone as a fumigant to disinfest stored maize. Treatment of 8.9tonnes (350bu) of maize with 50ppm ozone for 3d resulted in 92-100% mortality of adult red flour beetle, Tribolium castaneum (Herbst), adult maize weevil, Sitophilus zeamais (Motsch.), and larval Indian meal moth, Plodia interpunctella (Hübner) and reduced by 63% the contamination level of the fungus Aspergillus parasiticus Speare on the kernel surface. Ozone fumigation of maize had two distinct phases. Phase 1 was characterized by rapid degradation of the ozone and slow movement through the grain. In Phase 2, the ozone flowed freely through the grain with little degradation and occurred once the molecular sites responsible for ozone degradation became saturated. The rate of saturation depended on the velocity of the ozone/air stream. The optimum apparent velocity for deep penetration of ozone into the grain mass was 0.03m/s, a velocity that is achievable in typical storage structures with current fans and motors. At this velocity 85% of the ozone penetrated 2.7m into the column of grain in 0.8d during Phase 1 and within 5d a stable degradation rate of 1ppm/0.3m was achieved. Optimum velocity for Phase 2 was 0.02m/s. At this velocity, 90% of the ozone dose penetrated 2.7m in less than 0.5d. These data demonstrate the potential usefulness of using ozone in managing stored maize and possibly other grains.

The new fumigant carbonyl sulfide offers an alternative to both methyl bromide and phosphine as a grain fumigant. Separate mathematical models for levels of kill, based on quantitative toxicological studies were developed for adults and eggs of the rice weevil Sitophilus oryzae (L.). These models suggest that fumigation exposure times for carbonyl sulfide will be a compromise between those of methyl bromide (typically 24h) and phosphine (7-10d) to achieve a very high kill of all developmental stages. S. oryzae eggs were more difficult to kill with carbonyl sulfide fumigation than the adults. At 30 degrees C, a 25gm(-3) fumigation killed 99.9% of adults in less than 1d, but took 4d to kill the same percentage of eggs. Models were generated to describe the mortality of adults at 10, 15, 20, 25 and 30 degrees C. From these models it is predicted that fumigation with carbonyl sulfide for 1-2d at 30gm(-3) will kill 99.9% of adults. Furthermore the models illustrate that fumigations with concentrations below 10gm(-3) are unlikely to kill all adult S. oryzae. Significant variation was observed in the response of eggs to the fumigant over the temperature range of 10 to 30 degrees C. Models were generated to describe the mortality of eggs at 10, 15, 20, 25 and 30 degrees C. As the temperature was reduced below 25 degrees C, the time taken to achieve an effective fumigation increased. Extrapolating from the models, a 25gm(-3) fumigation to control 99.9% of S. oryzae eggs will take 95h (4d) at 30 degrees C, 77h (3.2d) at 25 degrees C, 120h (5d) at 20 degrees C, 174h (7.5d) at 15 degrees C and about 290h (11d) at 10 degrees C. The role of temperature in the time taken to kill eggs with carbonyl sulfide cannot be ignored. In order to achieve the desired level of kill of all developmental stages, the fumigation rates need to be set according to the most difficult life stage to kill, in this instance, the egg stage.