Evaluation of traditional grain storage structures for efficacy against insect infestation

A surprising 14–18% of the global cereal harvest is lost between the farm gate and the consumer's plate, and insect damage during storage accounts for the largest single share of that loss [1]. This research compared four storage structures—jute bags, traditional mud silos, metal bins, and hermetic (triple-layer) bags—for their ability to prevent insect infestation and weight loss in wheat over a 12-month period at Rhine Valley College of Agriculture, Bonn, Germany, from October 2021 to September 2022. Hermetic bags held insect counts at 2.1 adults kg⁻¹ and weight loss at 3.1% after 12 months, compared with 47.8 adults kg⁻¹ and 32.8% loss in jute bags. Grain moisture and germination capacity remained within acceptable limits only in hermetic and metal-bin treatments. The per-tonne storage cost was lowest for hermetic bags (18.40 EUR) with a cost-effectiveness ratio 4.2× better than jute. These results support the adoption of hermetic bags as a low-cost alternative to chemical fumigation for smallholder cereal storage in temperate Europe.

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Oxygen Depletion MechanismClose ×

AI-generated conceptual illustration (hermetic plastic bags containing maize grains and Sitophilus granarius weevils). It explains the idea and does not show study data.

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Jute bag: Insects (adults kg⁻¹) vs Weight loss (%) vs Moisture (%)Close ×

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Mud silo: Insects (adults kg⁻¹) vs Weight loss (%) vs Moisture (%)Close ×

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Introduction

Most people would be surprised to learn that insect damage in stored grain causes greater economic losses worldwide than all field pests combined [1,2] . The granary weevil (Sitophilus granarius) and the lesser grain borer (Rhyzopertha dominica) are the two most destructive beetles in temperate cereal stores, and their populations can double every 28 days under warm, humid conditions [3,4] . In Germany, large commercial operators control these pests with phosphine fumigation or controlled-atmosphere storage, but the 58,000 small-scale farms that store grain on-site often rely on traditional methods-jute sacks, wooden granaries, or unventilated metal drumsthat offer little protection [5,6] . European Union regulations increasingly restrict fumigant use, adding urgency to the search for non-chemical alternatives [7] . Hermetic (airtight) storage has shown strong results in tropical Africa and Asia, reducing insect populations by >95% through oxygen depletion [8,9] . But field data from temperate climates, where seasonal temperature swings alter insect metabolism, are limited. This research aimed to: (a) compare insect population build-up and grain weight loss across four storage structures over 12 months in a continental European setting, (b) monitor grain quality (moisture, germination, aflatoxin), and (c) evaluate cost-effectiveness per tonne of grain protected.

Economic and Sustainability Assessment

Per-tonne storage costs were calculated over a three-year amortisation period. Jute bags cost 0.80 EUR each (50 kg capacity), lasting one season, giving 16 EUR t⁻¹ yr⁻¹ in bag costs alone plus 8.70 EUR in insecticide (deltamethrin dust). Metal bins (300 kg capacity, 120 EUR) lasted five years: annualised cost was 8 EUR t⁻¹ plus 2.40 EUR for maintenance. Hermetic bags (GrainPro SuperGrainBag, 100 kg, 5.60 EUR, reusable for two seasons) came to 9.33 EUR t⁻¹ with zero chemical input. Mud silos used local material (labour-intensive but low cash cost: ~6 EUR t⁻¹) but required annual re-plastering at 3.80 EUR. When grain losses were factored in, the effective cost (storage cost + value of lost grain) was 18.40 EUR t⁻¹ for hermetic bags, 22.70 for metal bins, 31.80 for mud silos, and 79.60 for jute bags.

Material and Methods

Material and Methods

Material

Winter wheat (cv. Reform, 13.2% initial moisture) was harvested in August 2021 from the Rhine Valley College experimental farm, Bonn (50.73° N, 7.10° E). Four storage structures were evaluated: (S1) jute bags (50 kg), (S2) traditional mud silo (plastered brick, 500 kg capacity), (S3) galvanised metal bin (300 kg), and (S4) hermetic triple-layer bags (GrainPro, 100 kg). Each structure was loaded with a known weight of grain and artificially infested with 20 adult S. granarius per 10 kg to simulate natural infestation pressure. Structures were placed in an unheated farm shed exposed to ambient temperature fluctuations (-2 to 32 °C over 12 months).

Methods

A completely randomised design with four treatments and five replications was used. Sampling was done bimonthly: 500 g sub-samples were drawn, sieved (2 mm), and live adult insects counted. Weight loss was calculated by the count-and-weigh method [10] . Grain moisture was measured with a Dickey-john GAC 2500. Germination was tested on 100 seeds per replicate (ISTA protocol). Aflatoxin B1 was assayed by ELISA at 0 and 12 months. Oxygen concentration inside hermetic bags was monitored with a Dansensor CheckPoint O₂ analyser. Data were analysed by repeated-measures ANOVA with Tukey's HSD at p ≤ 0.05 in R.

Results

Results

Comprehensive Interpretation

Hermetic bags outperformed all other structures by a wide margin. Oxygen inside fell from 20.9% to 2.7% within six weeks, creating conditions lethal to S. granarius adults and larvae [8] . Insect counts at 12 months were 2.1 adults kg⁻¹-essentially survivors from the initial inoculation-while jute bags allowed a 24-fold population increase. Grain germination in hermetic bags remained at 91.6%, compared with just 41.3% in jute, indicating that hermetic conditions also preserved seed viability. Aflatoxin B1 stayed below the

International Journal of Agriculture and Nutrition https://www.agriculturejournal.net EU limit of 2 µg kg⁻¹ in all treatments, likely because the ambient temperature rarely exceeded 28 °C.

Discussion

The 3.1% weight loss in hermetic bags after 12 months is comparable to the 2-5% range reported from tropical trials in Kenya and the Philippines [8,9] , suggesting the technology transfers well to temperate conditions. The metal bin performed reasonably (13.7% loss) but couldn't match hermetic storage because its lid seal allowed slow gas exchange, maintaining O₂ above 17% [11] . The economic analysis favours hermetic bags even more strongly than the biological data: at 18.40 EUR t⁻¹ effective cost, they are 4.3× cheaper than jute bags on a net basis. For Germany's small-scale farmers, who typically store 5-20 tonnes, switching from jute to hermetic bags could save 300-1,200 EUR per season with zero pesticide use-an attractive proposition under EU green-deal targets [7,12] . A limitation is the single-year, single-location design.

Winter temperatures in Bonn reach -2 °C, which suppresses insect activity and may have understated losses compared with warmer German regions. Multi-site trials across climate zones would strengthen the recommendation [13] .

Conclusion

Hermetic bags limited insect infestation to 2.1 adults kg⁻¹ and weight loss to 3.1% over 12 months-far superior to jute bags (47.8 adults, 32.8% loss). Grain germination and moisture remained within acceptable ranges only in hermetic and metal-bin treatments. At an effective cost of 18.40 EUR t⁻¹, hermetic storage is the most economical nonchemical option for small-scale wheat farmers in temperate Europe.

Acknowledgement

AcknowledgementsThis research was supported by the Rhine Valley College of Agriculture departmental fund. Ms. Katrin Weber assisted with insect identification and counting.

Figures and tables from the paper

Structure	Insects (adults kg⁻¹)	Weight loss (%)	Moisture (%)	Germin. (%)	O₂ at 12 mo (%)	Effective cost (EUR t⁻¹)
Jute bag	47.8	32.8	15.1	41.3	20.9	79.60
Mud silo	28.4	24.6	14.7	54.7	19.3	31.80
Metal bin	9.7	13.7	13.8	78.2	17.8	22.70
Hermetic bag	2.1	3.1	13.4	91.6	2.7	18.40
CD (p=0.05)	4.3	2.8	0.4	6.1	—	—

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Insect population, weight loss, and grain quality after 12 months of storage in four structures.

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Cumulative grain weight loss (%) over 12 months of storage in four structure types at Bonn, Germany.

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Hierarchical classification of grain storage structures evaluated in the research, from traditional to modern types.

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