Common Damages During Storage of Horticultural Produce

Every year, a staggering amount of horticultural produce never makes it from the storage facility to the consumer’s plate. According to the FAO, post-harvest losses of food grains in developing countries due to mishandling, spoilage, and pest infestation can reach up to 25 percent. For perishable horticultural crops like fruits and vegetables, those numbers can climb even higher. The culprit? A range of damages that occur during storage – some obvious, some hidden – driven by insect infestations and environmental factors. Understanding these damages is the first step toward preventing them.

Why does storage damage matter? 🔗

Horticultural produce is living material. Even after harvest, fruits, vegetables, and root crops continue to respire, lose moisture, and undergo biochemical changes. When stored improperly, these natural processes accelerate, and external threats like insects, rodents, and fungi exploit the situation. The World Bank has estimated that India alone loses roughly 12 to 16 million metric tons of grains annually to post-harvest waste – enough to feed about one-third of the country’s poor population. For horticultural produce specifically, losses between harvest and retail have been estimated at around 22 percent globally, and nearly 40 percent in low- and middle-income countries, as noted by researchers in a study published in Postharvest Biology and Technology.

Storage damages are broadly classified into two categories: direct damages, caused by pests physically feeding on and contaminating the produce, and indirect damages, resulting from environmental changes triggered by pest activity or poor storage management.

Direct damages during storage 🔗

Direct damages are the most visible and economically measurable forms of deterioration. They are caused by living organisms – primarily insects, but also rodents and birds – that feed on or contaminate stored produce.

Weight loss from pest feeding 🔗

One of the most significant direct damages is weight loss. Storage insects such as weevils, moths, and beetles bore into grains, fruits, and dried produce, consuming the interior contents and leaving behind hollow or partially eaten material. According to Colorado State University Extension, direct feeding by stored-grain insects leads to measurable reductions in weight, nutritional value, germination capacity, and market value. Rodents compound this problem further, especially in bulk storage settings where large quantities are accessible.

A comprehensive review published in Frontiers in Sustainable Food Systems notes that insect species alone can cause 10 to 20 percent of total storage losses. When you factor in mites, rodents, birds, and microorganisms, the damage becomes substantially higher. For smallholder farmers in tropical and subtropical regions who store produce in traditional containers like earthen pots, gunny bags, or wooden buckets, losses can be especially severe.

Nutrient depletion 🔗

Beyond just reducing the physical quantity of stored produce, pests degrade its nutritional quality. Insects preferentially feed on the nutrient-rich parts of grains and produce. For example, weevils tend to consume the endosperm (rich in carbohydrates), while rodents often target the germ, which is high in protein and vitamins. A review published in PMC confirms that insect infestation alters the chemical composition of stored products, reducing carbohydrate content and changing protein profiles.

This nutrient loss is particularly harmful in regions where stored produce serves as a primary dietary staple. Even if the produce looks visually acceptable, its food value may have been significantly diminished by the time it reaches the consumer.

Contamination from insect excreta and body parts 🔗

Perhaps the most concerning direct damage is contamination. When insects infest stored produce, they leave behind droppings, shed skins, cocoons, and dead bodies. This biological debris introduces bacteria, fungi, and other microorganisms into the stored material. The result is produce that may be unsafe for human consumption and that fails food safety regulations.

Insect activity in stored grains and produce can also promote the growth of mycotoxin-producing fungi. Research has shown a strong link between insect infestation and contamination by aflatoxigenic fungi such as Aspergillus flavus, particularly in commodities like maize. These mycotoxins pose serious health risks, including potential carcinogenicity, making contamination one of the most dangerous outcomes of storage pest activity.

Indirect damages during storage 🔗

While direct damages come from pests physically consuming and contaminating produce, indirect damages are subtler and often more insidious. They result from the environmental changes that pest activity creates within a storage facility.

Heat generation by insect metabolism 🔗

All living organisms produce heat through their metabolic processes, and storage insects are no exception. When insect populations grow within stored produce, their collective body heat raises the temperature in localised areas, creating what are known as “hot spots.” According to the Agriculture and Horticulture Development Board (AHDB), grain weevil larvae feeding inside kernels can raise the local grain temperature, encouraging further pest activity and making early detection difficult.

These elevated temperatures accelerate chemical reactions within the produce itself. Oils become rancid more quickly, vitamins degrade faster, and proteins undergo denaturation. What begins as a small, localised insect colony can cascade into a facility-wide spoilage event if not caught early.

Moisture migration and fungal growth 🔗

Heat generated by insect activity also drives moisture migration within the storage environment. Warm air rises from hot spots, carrying moisture to cooler areas of the storage structure, where it condenses. This redistribution of moisture creates pockets of high humidity that are ideal breeding grounds for moulds and fungi.

The AHDB highlights that when grain moisture content reaches or exceeds 18 percent, storage fungi can produce harmful mycotoxins like ochratoxin A – and regulatory limits for such toxins can be exceeded in as little as two weeks under high-temperature conditions. Most mite species also thrive in high-humidity environments and do not breed below 65 percent relative humidity, meaning moisture control is critical to breaking the pest reproduction cycle.

Environmental factors that worsen storage damage 🔗

Storage damage does not happen in a vacuum. Several environmental factors interact with pest activity to accelerate deterioration.

Temperature 🔗

Temperature is the single most influential environmental factor in storage. Most storage pests are cold-blooded, meaning their reproduction and development rates are directly linked to ambient temperature. Higher temperatures lead to faster insect life cycles, more rapid population growth, and consequently greater damage. However, each pest species has an optimal range – temperatures significantly above or below this range slow down or halt development.

For horticultural produce, the FAO recommends maintaining storage temperatures as close to the optimum for each specific commodity as possible. Cooling produce immediately after harvest and maintaining the cold chain throughout storage are among the most effective strategies for reducing both physiological deterioration and pest pressure.

Relative humidity 🔗

Relative humidity affects both the produce and the pests. Most horticultural products store best at about 90 percent relative humidity to prevent wilting and moisture loss. However, high humidity also favours fungal growth and mite reproduction. Managing this balance is one of the central challenges in horticultural storage – the produce needs moisture to stay fresh, but excess moisture invites biological threats.

Maturity at harvest 🔗

The condition of produce when it enters storage significantly impacts how well it holds up. The FAO notes that produce harvested too early may shrivel in storage and become more susceptible to storage disorders, while over-mature produce tends to break down faster and has a shorter shelf life. Getting harvest timing right is an often-overlooked preventive measure against storage damage.

Preventive measures to minimise storage damage 🔗

Prevention is far more effective – and economical – than dealing with established infestations. A successful storage protection programme combines several strategies.

Sanitation and facility preparation 🔗

Before any produce enters a storage facility, thorough cleaning is essential. Old produce residues, debris, and spilled material are the primary sources of pest infestations. Colorado State University Extension recommends a six-step prevention programme that starts with keeping bins clean and repaired – never storing new produce on old, and removing all debris from walls, floors, and crevices. Holes should be sealed to block rodent access, and roofs should be inspected to prevent moisture entry.

Proper drying and moisture control 🔗

Reducing moisture content before storage is critical. For grains, the recommended moisture level is generally below 10 to 12 percent to prevent insect buildup. For fresh horticultural produce, maintaining the right humidity balance through ventilation and aeration systems helps prevent both desiccation and fungal growth. Proper aeration also eliminates temperature differentials that cause moisture migration and hot spots.

Fumigation 🔗

Fumigation remains one of the most effective tools for controlling established insect infestations. Fumigants are gases that penetrate through stored produce, reaching and killing pests at every life stage – eggs, larvae, pupae, and adults. The two most commonly used fumigants are phosphine (generated from aluminium or magnesium phosphide) and methyl bromide, though methyl bromide use is declining due to its ozone-depleting properties.

The FAO’s manual on post-harvest grain loss prevention explains that the success of fumigation depends on three key factors: correct dosage, adequate exposure time, and – most importantly – airtight sealing of the storage structure. If the storage space leaks, fumigant concentration drops, insects recover from narcosis without dying, and resistance develops over time. After fumigation, thorough ventilation is mandatory before the space can be safely accessed again.

Regular inspection and monitoring 🔗

Even with preventive measures in place, regular monitoring is non-negotiable. Inspections should be conducted weekly when temperatures are above 12-15°C and biweekly in cooler conditions. Using grain probes, sticky traps, and sensors helps detect early-stage infestations before they escalate. Early detection allows for targeted, cost-effective interventions rather than expensive broad-scale treatments.

Integrated pest management (IPM) 🔗

No single method can fully protect stored produce on its own. An integrated pest management approach combines sanitation, environmental control (temperature and humidity), biological methods, physical barriers, and chemical treatments as needed. This reduces dependence on any single strategy and minimises the development of pesticide resistance among storage pests.

The economic case for proper storage management 🔗

Investing in proper storage infrastructure and management practices may seem costly upfront, but the returns are substantial. For small-scale farmers, reducing storage losses by even a few percentage points can mean the difference between food security and food shortage, or between profit and loss. At a national level, cutting post-harvest waste is one of the most efficient ways to increase food availability without expanding agricultural land or water use.

Research increasingly shows that postharvest loss reduction also has significant environmental benefits. Every kilogram of produce lost in storage represents wasted land, water, energy, and labour – plus unnecessary greenhouse gas emissions from the decomposition of that waste.

What do you think? Given that storage losses disproportionately affect small-scale farmers in tropical regions, what role should government policy and international organisations play in making modern storage technologies more accessible? And how might climate change, with its rising temperatures and shifting humidity patterns, alter the landscape of storage pest management in the years ahead?

References

1. https://www.fao.org/4/t0073e/t0073e01.htm
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC5296677/
3. https://www.sciencedirect.com/science/article/pii/S0925521423002521
4. https://extension.colostate.edu/topic-areas/insects/insect-damage-to-farm-stored-grain-5-545/
5. https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2022.993341/full
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC10217422/
7. https://ahdb.org.uk/knowledge-library/how-the-grain-store-environment-affects-pest-fungi-insects-and-mites-levels
8. https://www.fao.org/4/s8620e/S8620E07.htm
9. https://www.fao.org/4/x5065e/x5065E0g.htm