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In Ethiopia, post-harvest losses caused by insects are a major challenge in crop production systems. Dried maize is particularly susceptible to insects during storage. Storage loss affects the livelihoods of small-scale farmers leading to food insecurity and loss of income. Therefore, the objective of this study was to assess the cost-benefit analysis of Purdue Improved Crop Storage (PICS) bags on maize storage in Northwest Ethiopia. Cross-sectional data was collected from 392 randomly selected households from both users and non-users of PICS bags, using stratified sampling technique. A structured questionnaire, key informant interviews, focus group discussions, individual in-depth interviews, and field observations were used to gather the data. A cost-benefit analysis was computed to evaluate the viability of PICS bags for maize storage. The binary logistic regression model was used to identify factors that affect the use of PICS bags. Descriptive statistics (percentage, mean, and standard deviation) and inferential statistics (t-test and chisquare test) were employed to analyze the data. The benefit-to-cost ratios (BCRs) of insecticide with both ordinary and PICS bags were greater than one, but PICS bags resulted in more than two-fold higher values as compared to insecticide with ordinary bags. The net present value (NPV) at 15% discount rate in 2018 was 20.73 USD and 25.35 USD per 100 kilograms of stored maize when insecticide was applied to ordinary and PICS bags, respectively. Sensitivity analysis with a 10% cost increment and up to 50% price discount showed that both technologies would still be viable for maize storage. However, PICS bags had higher NPV and BCR; making the technology more viable than insecticide with ordinary bags. The results of binary logit model indicated that educational level, gender, awareness, training, accessibility of the technology, perception of the technology, involvement in leadership activities in the community, and total income of the household positively influenced farmers' decisions to use PICS bags, whereas price negatively affected the use of the PICS bags. PICS bags had clear economic advantage over insecticide with ordinary bags for maize storage in Northwest Ethiopia. Efforts should be made to disseminate and improve access to PICS bags for strengthening food security and increasing incomes of maize farmers in Northwest Ethiopia. Key words: Hermetic bag, smallholder farmers, profitability, post-harvest management, food security, INTRODUCTION In Ethiopia, post-harvest losses caused by insects are a major challenge in crop production systems. Stored maize is highly susceptible to pests, particularly insects [1]. Reducing food losses increases [...]

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Accelerating oxygen depletion during hermetic storage can minimize pest damage and preserve product quality. This study evaluated the effectiveness of hand warmers in accelerating hypoxia to control insect pests inside hermetic containers. We used one, two, or four hand warmers to deplete oxygen in a 4-gallon hermetic jar with 4 kg of cowpea and cowpea bruchids, alongside a non-hermetic control with cowpea bruchids and no hand warmers. Oxygen levels, insect mortality, egg counts, seed moisture content, and germination rates were monitored over 2, 5, or 8 days of storage. Only the four hand warmers treatment reduced oxygen levels below 1% within 12 h and maintained them for up to 168 h. The other treatments did not achieve this level. Insect mortality was higher with more hand warmers and extended storage duration, reaching 100% after 5 and 8 days with four and two hand warmers, respectively. Similarly, increased hand warmers and extended storage durations reduced egg counts and adult emergence. The treatments did not affect the moisture content or germination rates of the stored cowpea seeds. Hand warmers proved effective in accelerating hypoxia during hermetic storage, resulting in high insect mortality and reduced reproduction, without compromising grain quality.

Maintaining maize quality while drying during a rainy season is a major challenge for smallholder farmers in developing countries. We conducted a study to evaluate the impact of temporarily storing wet maize of 18, 21, and 24% moisture content (m.c.) in hermetic Purdue Improved Crop Storage (PICS) and polypropylene (PP) woven (control) bags for 21 days. Oxygen and carbon dioxide concentrations were monitored, and m.c., germination, and visual mold were assessed. In PICS bags, oxygen dropped below 1% within 7, 11.5, and 21 days for maize at 24, 21, and 18% m.c., respectively. After 21 days, the m.c. of maize stored in PICS bags remained constant, but decreased in PP bags. Germination of maize in PICS bags decreased by 0.5, 6.2, and 95.5 percentage points for 18, 21, and 24% m.c., respectively. In PP bags, germination decreased by 17.5, 15.2, and 39.5 percentage points for the respective moisture levels. After 21 days of storage, visible mold was present on maize stored in PP bags at both 21 and 24% m.c. No mold was observed on maize stored in PICS bags, but a fermentation smell was released from maize at 21 and 24% m.c. The results indicate that maize can be effectively stored in PICS bags at 21% m.c. or below for 21 days with minimal germination loss or mold growth. These findings highlight the potential of using hermetic bags for short-term grain quality preservation just before and during drying. This new utility adds to the current use of hermetic bags for protection against pests during long-term storage. Hermetic bags' dual functionality could significantly improve postharvest management on smallholder farms, thereby enhancing food and nutritional security and safety. Field testing is required in order to integrate this approach under smallholder farmers' conditions (e.g., temperature, m.c., drying practices, etc.).

Millions of smallholder farmers use airtight (hermetic) storage to preserve stored commodities. However, relying on biological agents (i.e., insects) to deplete residual oxygen in airtight containers can occasionally extend the process, potentially resulting in grain damage or nutrient loss. Current oxygen scavengers used to remove this residual oxygen are unavailable and unsuitable on smallholder farms in developing countries. We evaluated the effectiveness of germinating seeds for oxygen depletion. Treatments comprised 10, 20, and 30 germinating cowpea seeds in 2 L jars filled with infested cowpea grains. Insect mortality and grain quality were assessed after 24, 48, 72, 96, and 120 h. Progeny development was monitored for 49 days post-treatment. The results showed that all germinating seeds depleted oxygen to 5% or below within 48 h. Complete adult mortality was achieved after 72 h for both 20 and 30 germinating seeds and 120 h for 10 germinating seeds. As germinating seeds increased, egg counts decreased. No adults emerged post-treatment after insects were exposed for 96 and 120 h to hypoxia from 30 and 20 germinating seeds, respectively. However, 120 h insect exposure to hypoxia from 10 germinating seeds had negligible progeny development. Moisture content increased slightly in grains exposed to 30 germinating seeds. Germinating seeds are as effective as controlled atmospheres in accelerating insect deaths, but further research is needed for field application and their effects on stored product quality.

Hermetic storage methods are effective at protecting grain against insect pests. Biotic and abiotic factors influence oxygen depletion during hermetic storage. We investigated the dual effects of temperature and initial pest infestation level on oxygen depletion during airtight storage. Glass jars filled with cowpea grain were infested (25 or 50 adult cowpea bruchids), then hermetically sealed and stored at 20, 30, or 40 °C for 30 days. Oxygen depletion, relative humidity, and temperature were monitored. Germination, grain moisture content, grain damage and weight loss, and adult emergence were assessed. Oxygen depletion varied by temperature and insect infestation level. However, 30 °C was the optimum temperature for oxygen depletion (reaching 5% or less in 10 days) regardless of insect infestation level. No changes were observed in germination and grain moisture content, minimal grain damage, or weight loss (<1%). Only at 20 °C were adult insects able to survive after 30 days and emerged 45 days post-treatment under normoxia. Therefore, hermetic storage containers should remain closed for more than 30 days to minimize re-infestation of grain in areas where average ambient temperatures rarely exceed 23 °C. Further research is needed to assess the effect of low temperatures on oxygen depletion and insect survival in hermetic storage beyond 30 days.

Maize is a major crop grown in many regions of the world for human consumption, starch production, and animal feed. After harvest, maize is dried to avoid spoilage caused by fungal growth. However, in the humid tropics, drying maize harvested during the rainy season poses challenges. In such instances, temporary storing maize under hermetic conditions may preserve grain quality while waiting for conditions suitable for drying. Wet maize at the moisture contents (m.c.) of 18, 21, and 24% was stored for up to 21 days in both hermetic and non-hermetic jars. The stored maize was assessed, every 7 days, for germination and related parameters, presence of visible mold, and pH. After 21 days of storage at 18, 21, and 24% m.c., maize germination decreased by 28.5, 25.2, and 95.5 percentage points, respectively, in hermetic jars; and by 28.5, 25.2, and 94.5 percentage points in non-hermetic jars (control). There was visible mold on maize stored in non-hermetic jars after 21 days regardless of m.c. Maize at 21 and 24% m.c. stored in hermetic conditions underwent lactic acid fermentation that reduced the pH. The findings suggest that maize at 18 and 21% m.c. can be stored for 14 and 7 days, respectively, under hermetic conditions without significant loss of quality. Further research is needed to thoroughly assess the application of these findings for temporarily storing and subsequently drying maize on farms and along the grain value chain.

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., Competing Interests: The authors declare the following financial interests/personal relationships, which may be considered as potential competing interests: Dieudonne Baributsa is a co-founder of PICS Global Inc., a social enterprise that commercializes postharvest technologies (including PICS bags) to small-holder farmers around the world and hence declares a conflict of interest. Ibrahim Boukary Baoua declares no conflict of interest. The funder (10.13039/100000865Bill and Melinda Gates Foundation) had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results., (© 2022 The Authors.)

On-farm preservation of wheat flour is a challenge due to insect pests and high relative humidity. This experiment was conducted to assess the effectiveness of hermetic bags in preserving wheat flour stored by women during the wintertime when relative humidity is high. Forty women (households) from two districts in Herat province, Afghanistan, stored their wheat flour for 6 months. Each woman stored 25 kg of wheat flour in a Purdue Improved Crop Storage (PICS) bag and a polypropylene (PP) woven bag. Moisture content, insect population, flour color, bread taste, and profitability of storage were assessed. Moisture content and insect population significantly increased in PP bags after six months of storage, while no changes were observed in PICS bags. There was a significant negative correlation between wheat flour color and moisture content (r = −70.7, p < 0.001) and insect population (r = −79.9, p < 0.001). Wheat flour stored in PICS bags for 6 months retained its color and produced better bread than that stored in PP bags. Storing wheat flour in PICS bags for six months showed a return on investments (ROI) of +16.9% against −33% for the PP bag. Farm households and other wheat value chain actors can safely store wheat flour in hermetic bags for up to six months under high relative humidity conditions. This would help improve food security for millions of wheat consumers in developing countries.

Sitophilus oryzae is one of the most destructive pests of stored grains. It leads to significant quantitative and qualitative losses, resulting in food and income insecurity among farmers. Chemical pesticides are the most common methods used by farmers and other grain value chain actors to manage this pest. However, pesticides are increasingly becoming unattractive for pest control due to health hazards posed to applicators, consumers, the environment, and insect resistance. Modified atmospheres have the potential to manage stored insect pests as an alternative to pesticides. There is limited understanding of when insect pests die when grain is stored in airtight containers. This experiment was conducted to assess the time required to reach mortality of adult S. oryzae when exposed to 1, 3, and 5% oxygen levels. Results revealed that the LT50 for 1, 3, and 5% of oxygen were reached after 69.7 h, 187.8 h, and 386.6 h of exposure, respectively. No adult emergence was observed on infested grains following exposure to 1 and 3% oxygen levels. This result provides vital rationale for storing grain in hermetic storage conditions for at least 39 days to achieve adult S. oryzae mortality and minimize grain reinfestation.

Farmers continue losing substantial quantities of grain during storage due to damages from pests including insects. Hermetic bags, being promoted in Ethiopia, could be viable alternatives to traditional methods and insecticides that are commonly used by farmers to store grain. However, the economics and determinants behind farmers' decisions to use different storage methods are poorly understood. This study sought to ascertain the economics of hermetic grain storage technology among 450 representative small-scale maize farmers in northwestern Ethiopia. Gross margin (GM), and the marginal rate of return (MRR) were employed to estimate the economic costs and benefits of storage methods, while a multivariate probit regression model was employed to analyze the determinants of farmers' decision to store maize with a given storage method. The results show that farmers used a combination of different storage techniques: 19.6% did not store grain, 87.8% used traditional methods with pesticide, and 66.7% used Purdue Improved Crop Storage (PICS) hermetic bags. Farmers who used hermetic bags also used other mentioned storage techniques. PICS had the highest GM (US$21.77 100 kg -1 ) and MRR (3.196), indicating that they were the most profitable. Moreover, a household could obtain an additional net cash flow of US$5.02 100 kg -1 PICS bag per season after 9.6 months of storage. Farmers' decisions to use PICS bags were influenced by several factors including access to information, the initial cost, and storage capacity of the technology. Thus, increasing awareness and improving supply chain efficiency to reduce the cost of the PICS bags would improve adoption rates., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Dieudonne Baributsa is a co-founder of PICS Global Inc., a social enterprise that commercializes post-harvest technologies (including PICS bags) to smallholder farmers across the world and hence declares a conflict of interest. The other authors declare no conflict of interest. The funder (BMGF) had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results., (© 2020 The Author(s).)

Alfalfa (Medicago sativa) is the most cultivated fodder crop in Peru with 172,000 ha cultivated (MINAM 2019), and Arequipa is the top producing region with 40% of the national production in 2015 (Santamaría et al. 2016). In January-April 2019 (av. 20°C and 70% RH), most alfalfa fields in Majes-Pedregal, Arequipa were affected by an unidentified foliar disease. One of the fields was located at the farm of the Universidad Nacional de San Agustín de Arequipa (16°19'29.6" S, 72°12'59.9" W). Symptoms appeared as elliptical light brown spots witdark brown borders (Fig. S1a and b). The field (~60 × 60 m) was divided into ~30 × 12 m sections and two plants in each section were collected (20 plants total). Plants were digitized and the leaflet diseased area was calculated with ImageJ 1.53a, from which an incidence of 100% and a severity of 38.7 ± 4.4 % were estimated. Microscopical observations at the leaflet spots revealed consistently the presence of oblong multiseptated conidia (23.6-42.8 × 16.5-25.2 µm; av. 33.3 × 20.9 µm; n = 40) of the genus Stemphylium (Simmons 1969; Woudenberg et al. 2017) (Fig. S1c). We obtained 10 pure cultures by placing conidia from the spots directly onto potato dextrose agar medium with the aid of stereoscope and sterile forceps. Two isolates (UNSA-StemV01 and UNSA-StemV02) were incubated further until ascospore production at room temperature with no special light stimulus. After 45 days of growth, globose pseudothecia and ellipsoidal ascospores (25.4-38.7 × 11.2-16.6 µm; av. 31.9 × 13.7 µm; n = 30) formation occurred (Fig. S1d and e). We extracted the DNA from these two isolates using Wizard® Purification Kit (Promega Corp., Madison, WI) and sequenced the internal transcribed spacer 1 and 2 intervening 5.8S rDNA subunit (GenBank accessions: MT371236-37), and the glyceraldehyde-3-phosphate dehydrogenase (MT375513-14) and the calmodulin (MT375515-16) genes, highly resolutive markers to identify Stemphylium species, following Woudenberg et al. (2017). We retrieved sequence data available from 43 isolates of nine Stemphylium species (Han et al. 2019; Woudenberg et al. 2017), and built a mid-point rooted phylogeny with the three-loci concatenated data set (Fig. S2). We identified our isolates as S. vesicarium (Fig. S2). Koch's postulates were fulfilled by spray-inoculation with conidia from isolate UNSA-StemV01 suspended in sterile water (1×104 / mL) to two healthy 50-day old alfalfa plants growing on pots in the university greenhouse (av. 25°C and 70% RH). Two plants sprayed with sterile water without conidia served as control. Symptoms appeared after 21 days of inoculation, and when conidia were re-isolated, they were the same as originally obtained. No symptoms developed in the control plants. This confirmed that S. vesicarium is the causal agent of the alfalfa disease in Majes-Pedregal, identified as Stemphylium leaf spot. revious studies documented S. vesicarium on asparagus and onion in Peru (Castillo Valiente 2018; Vásquez Salas 2018; Vásquez Sangay 2013), but molecular characterization has only been applied to S. lycopersici from potatoes (Woudenberg et al. 2017). Stemphylium vesicarium has been documented in various crops, including alfalfa, and countries in Europe, North America, Africa, Asia and in Australia and New Zealand (Han et al. 2019; Woudenberg et al. 2017). This occurrence is the first report of S. vesicarium on alfalfa in Peru. The disease compromises the quality of this fodder crop, so actions need to be taken in Arequipa.

Little is known about the major issues leading to postharvest losses in Peru, which are estimated to be 15-27%. We surveyed 503 farmers from the lowlands and Andean regions of Arequipa to learn more about the major grains produced and issues encountered during drying and storage. Rice, common bean, and quinoa were the most grown crops in the lowlands while starchy maize was the most cultivated crop in the highlands. Most farmers (90%) dried their crops in-field directly on the ground, which exposes them to rodents, birds, and insect pests. The majority of farmers (92%) used subjective methods to assess grain moisture content. About 77% of farmers identified insects as a major challenge during storage but only 44% said they used preventive measures such as the application of insecticides. Among farmers who stored grain, the main reason was for household consumption (61%); while among those who did not store, the main reason was the need for immediate cash at harvest (75%). Farmers who experienced insect problems, who stored seed or grain for sale, who stored longer, or farmers from the lowlands were more likely to apply insecticides on their stored products. These findings provide an opportunity for researchers, development organizations, and government agencies to improve postharvest handling and storage in Arequipa by disseminating drying technologies, moisture assessment tools and hermetic storage solutions among farmers., Competing Interests: Dieudonne Baributsa is co-founders of PICS Global, a private company that is commercializing the PICS bags around the world; hence declare a conflict of interest. This study was conducted to assess postharvest challenges among farmers in Arequipa Peru for the purpose of exploring potential dissemination of handling and storage technologies including PICS bags. This competing interest does not alter our adherence to PLOS ONE policies on sharing data and materials. The other co-authors do not have any conflicts of interest.

Cowpea stored on smallholders' farms suffers serious losses to insect pests. A study conducted in Niger compared five postharvest technologies marketed in sub-Saharan Africa to protect stored grain. Naturally-infested cowpea stored for eight months showed adult Callosobruchus maculatus (F.) mortality of 97% to 100% in the hermetic bags (PICS TM , SuperGrainbag TM , AgroZ ® , EVAL™, and ZeroFly ® bags). There was no change in grain damage and weight loss of cowpea stored in hermetic bags. There was, however, a loss of up to 10 to 16% in germination when the grain was stored in hermetic bags. Results observed for grain stored in ZeroFly ® bags impregnated with deltamethrin were substantial and similar to those in control woven bags. In both ZeroFly ® and woven bags, (1) adult C. maculatus population augmented by 35.7% and 78.6%, (2) increased weight losses of 27.3% and 25.2%, and (3) reduced germination of 37.0% and 28.8%, respectively. After opening the bags, abrasions were noted on the liners of hermetic bags, potential damage that could limit their reuse if they only have a single liner. Smallholder farmers in the Sahel can safely store their cowpea in all the hermetic bags tested. However, further research is needed to mitigate insect damage on liners of hermetic bags to improve their performance and reusability.

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.

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, Rhyzopertha dominica and Sitophilus zeamais were found in the PICS bags. However, in PP bags there were additional pests including Tribolium castaneum and Oryzeaphilus mercator and Xylocoris flavipes . 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.

Modified atmospheres such as hermetic storage are widely used for the control of stored grain insect pests. To improve their effectiveness, there is need to better understand insect responses to low-oxygen environments. Adult Callosobruchus maculatus F. (Coleoptera: Chrysomelidae: Bruchinae) on cowpea and Sitophilus oryzae L. (Coleoptera: Curculionidae) on wheat were exposed to hypoxia treatments consisting of 1, 3, and 5% oxygen levels for 14 d. Acoustic activity was monitored during the experiment, and insect mortality and grain quality were examined immediately after the hypoxia treatments. Adult emergence was assessed 45 d post-treatment. All three hypoxia treatments eliminated acoustic activity of both species within 4 d. There was neither insect survival for both species nor significant grain damage immediately after 14-d exposure to hypoxia treatments. No adult insects emerged 45 d post-exposure on grains maintained at 1% oxygen level for 14 d. However, at 3 and 5% oxygen levels, there were eggs on cowpea, holes in wheat, and emerging adults for both insect species 45 d post-exposure. Although insect activity ceased within 4 d when hypoxia was maintained below 5%, there is need to explore exposure beyond 14 d for 3 and 5% oxygen levels, to ensure to avoid potential adult emergence from eggs and other insect life stages post-treatments. Maintaining 3-5% hypoxia conditions for a longer duration would ensure insufficient oxygen is available for progeny development., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America.)

Hermetic technologies are being promoted in Africa as safer and more effective methods of grain storage on smallholder farms. However, farmers and policy makers lack knowledge of their efficacy in controlling major stored grain pests. An on-station study was conducted to evaluate the triple layer Purdue Improved Crop Storage (PICS) airtight bags against two major storage insect pests. Two sets each of PICS, jute and polypropylene bags were filled with 50 kg maize grain per bag. Each set was replicated four times. One set of PICS bags was each infested with 50 insects each of the larger grain borer P. truncatus and the maize weevil S. zeamais ; while the other set was not. One set of jute and polypropylene woven bags was treated with a cocktail of 1.6% Pirimiphos methyl and 0.3% Permethrin, serving as positive controls; while the remaining sets with untreated maize grain formed negative controls. Gas analysis in the PICS bags followed the expected trend with oxygen levels falling sharply below 10% and carbon dioxide increasing to almost 10% after 12 weeks hence resulting in insect death. After 16 weeks, increase in oxygen levels may be attributed to perforation of the bags from outside by the P. truncatus . Results showed that PICS bags were significantly ( P < 0.05) superior to treated and untreated controls of polypropylene and jute bags in suppressing insect development, maize grain damage and weight loss during storage. Weight loss in polypropylene and jute bags reached 40% and 41%, respectively, at 24 weeks after storage compared to PICS (2.4-2.9%). These results demonstrate that PICS bags can be used to store maize against P. truncatus and S. zeamais attack.

Groundnut Arachis hypogaea (L.), is an important legume crop after cowpea Vigna unguiculata (L. Walp) in Niger. However, there has been a decline in its economic importance due to several challenges. A survey of 800 farmers was conducted in 40 villages in the Maradi and Zinder regions to assess constraints and opportunities to improve groundnut production and marketing. Average land size and yield varied by region: 1.3 ha per farmer and 461.3 kg ha -1 in Maradi, and 1.7 ha per farmer and 417.2 kg ha -1 in Zinder. Insect pests (aphids) were the most important production constraint. Groundnut is typically stored for six to eight months after harvest but 91% of farmers do not take any precautions to protect the grain. Storage enables farmers to earn high profit margins of up to 33 and 113% for unshelled and shelled groundnuts, respectively. Most farmers (71.5%) sell their groundnut in unshelled form in local and urban markets. Traders are the main buyers according to 61.7% of farmers while processors were mentioned as purchasers by less than 20%. Sales are mostly done by individual farmers while very little is sold through cooperatives. Given that groundnut is a profitable crop adapted to the Sahelian zone, there is need to improve its production, storage, and value addition through processing., (© 2019 The Author(s).)

Cereals and legumes play a major role in the production systems and diets of farmers in the semi-arid eastern region of Kenya. Efficient postharvest management can tremendously contribute to food security in these regions. A study was carried out in three counties in eastern Kenya to assess pre and postharvest management practices among farmers. Data was collected using semi-structured questionnaires designed and administered using Kobo Toolbox via android tablets. Results showed that farmers cultivated three main crops: maize (98%), beans 66%), and pigeon peas (28%). The most saved seed crops were beans (80%) and pigeon peas (50%). Majority of the farmers (80%) experienced pre-drying losses due to insects (48%), rodents (40%) and birds (39%). Farmers stored grain for consumption (80%) and for sale (19%). About 48% of farmers stored the grain for more than 9 months. Challenges during grain storage were insects (57%) and rodents (43%). Primary methods of grain preservation included hermetic methods (61%) followed by insecticides (33%). While progress is being made in addressing storage challenges, there still a need to continue building awareness about improved storage technologies and find solutions for pest infestations in the field and drying after harvest., (© 2019 Copyright for this article is retained by the author(s), with first publication rights granted to the journal.)

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 Sitophilus zeamais , 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.

Insect pests such as Callosobruchus maculatus Fabricius and Plodia interpunctella 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: C. maculatus and P. interpunctella . The total amount of oxygen consumed by C. maculatus 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 P. interpunctella consumes nearly three times as much oxygen per insect over its larval-to-adult developmental period compared to C. maculatus . 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.

Acoustic monitoring was applied to consider hermetic exposure durations and oxygen levels required to stop adult Callosobruchus maculatus activity and economic damage on cowpea. A 15-d study was conducted with six treatments of 25, 50, and 100 C. maculatus adults in 500 and 1000 mL jars using acoustic probes inserted through stoppers sealing the jars. Acoustic activity as a result of locomotion, mating, and egg-laying was measured by identifying sound impulses with frequency spectra representative of known insect sounds, and counting trains (bursts) of impulses separated by intervals of <200 ms, that typically are produced only by insects. By the end of the first week of storage in all treatments, oxygen levels declined to levels below 4%, which has been demonstrated to cause mortality in previous studies. Concomitantly, insect sound burst rates dropped below an acoustic detection threshold of 0.02 bursts s &minus;1 , indicating that the insects had ceased feeding. Statistically significant relationships were obtained between two different measures of the acoustic activity and the residual oxygen level. Based on the experimental results, a simple equation can be used to estimate the time needed for oxygen to decline to levels that limit insect feeding damage and thus grain losses in hermetic storage containers of different insect population levels and various volumes.

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.

Hermetic storage is used to protect grain against insect pests, but its utility is not limited to whole grains. We evaluated hermetically-sealed, polyethylene terephthalate (PET) bottles for preserving wheat and maize flour against red flour beetle (RFB, Tribolium castaneum, Herbst) population growth. Flours infested with RFB and kept in sealed PET bottles experienced much less weight loss over a three-month storage period than infested flour kept in unsealed bottles. RFB populations in wheat flour kept in sealed bottles did not increase, while populations in unsealed bottles grew about 50-fold during the same three-month period. Flour in sealed bottles had lower levels of oxygen and moisture than flour stored in unsealed bottles. Similar trends were observed for oxygen and moisture levels in maize flour held in hermetically sealed bottles. Hermetically-sealed bottles were effective in preventing RFB population growth and preserving maize and wheat flour. Farmers, consumers and food processors can safely store grain flour in hermetic sealed containers.

Interest in using hermetic technologies as a pest management solution for stored grain has risen in recent years. One hermetic approach, Purdue Improved Crop Storage (PICS) bags, has proven successful in controlling the postharvest pests of cowpea. This success encouraged farmers to use of PICS bags for storing other crops including maize. To assess whether maize can be safely stored in PICS bags without loss of quality, we carried out laboratory studies of maize grain infested with Sitophilus zeamais (Motshulsky) and stored in PICS triple bags or in woven polypropylene bags. Over an eight month observation period, temperatures in the bags correlated with ambient temperature for all treatments. Relative humidity inside PICS bags remained constant over this period despite the large changes that occurred in the surrounding environment. Relative humidity in the woven bags followed ambient humidity closely. PICS bags containing S. zeamais-infested grain saw a significant decline in oxygen compared to the other treatments. Grain moisture content declined in woven bags, but remained high in PICS bags. Seed germination was not significantly affected over the first six months in all treatments, but declined after eight months of storage when infested grain was held in woven bags. Relative damage was low across treatments and not significantly different between treatments. Overall, maize showed no signs of deterioration in PICS bags versus the woven bags and PICS bags were superior to woven bags in terms of specific metrics of grain quality., Competing Interests: The authors have declared that no competing interests exist.

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 Callosobruchus maculatus (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 A . flavus -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.

Modified atmospheres present a residue-free alternative to fumigants for controlling postharvest pests of grain during storage. How sub-lethal applications of this method affects the reproductive fitness of target pests, however, is still not fully understood. We examined how low levels of ambient oxygen influence the reproduction of the female cowpea bruchid (Callosobruchus maculatus), a pest of cowpea. We used three low-oxygen atmospheres-2%, 5% and 10% (v/v) oxygen-and observed their effects on: (1) the number of eggs laid by bruchids compared to insects held in normoxic (~20% oxygen) conditions; (2) the total number of eggs laid; and (3) the number of progeny that reached maturity. Low oxygen did not significantly affect the number of eggs laid during 48 or 72 h of exposure, but 2% and 5% oxygen did negatively affected total egg production. Increasing the exposure time from 48 to 72 h further depressed lifetime reproductive output. Maternal and egg exposure to hypoxia reduced the number of progeny that reached adulthood. Lower adult emergence was observed from eggs laid under low oxygen and longer exposure times. These data demonstrate that hermetic conditions depress the egg-laying behavior of cowpea bruchids and the successful development of their progeny.