Store Environment and Treatment in Agricultural Storage Management

In most cases, agricultural products are stored without further handling for a shorter or longer period. Unfortunately, losses of 25 percent for stored grain crops and 40–50 percent for vegetables are not unusual in the tropics.

For the farmers, these products fulfil various purposes and must be handled properly. For example, if seeds or tubers are not stored well, some will not germinate when planted, which means the farmer will have to plant many more to get enough plants.

The seed grains may also grow at different speeds, which will cause problems for cultivating and harvesting the crop. Some insects eat out the best parts of the grain, which contain the vitamins and minerals that make the food nutritious. Farmers may not see this loss, and therefore need to know how to prevent it.

Key Requirements for a Functional Agricultural Store

1. Keep the temperature and humidity as low as possible through controlled ventilation.
2. Avoid large variations in temperature, as this can cause condensation of water in the store.
3. Prevent the entry of pests by sealing the store (windows, doors, ventilation facilities) with insect-proof gauze.
4. In conditions with low humidity, airtight storage gives good protection against storage pests.
5. To avoid fungal growth, care should be taken to ensure that the produce stays dry (i.e. no condensation forms inside the container).

This is particularly important for long-term storage in warm, dry areas. It is advisable, however, not to store seed for planting for more than a few months.

A small amount of seeds can be stored in a strong airtight container with a close-fitting lid (glass, ceramic or strong plastic). Ceramic pots that do not have lids must be covered very carefully or topped up with dry soot, ashes or fine dry soil.

In conditions where the relative humidity is high, airtight storage is not recommended due to the risk of fungal growth.

The site chosen for a good seed store must be airy, shady, cool and dry. Temperature variations should be as small as possible, because these encourage condensation of water, which in turn promotes fungus development. The whole building should be well aired and if possible fumigated.

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Storage Hygiene Measures for Agricultural Products

Always keep the store and its surroundings clean.
Before newly harvested crops are stored, the store should be carefully prepared well ahead of time.

Old stored products should be removed and the room completely cleaned. The walls, roof and floor should be both watertight and rat-proof, and small holes and cracks, which are potential breeding places for storage insects, should be sealed.

Inspection of the Storage Facility

Periodic inspection (weekly to fortnightly) and removal of any infested produce is essential.
Check for droppings and footprints of birds and rodents.

Look for flying moths at dusk. Brush stacks of bags with a stick or broom to disturb and discover resting moths. Lift bags in order to detect moth cocoons along the line where bags touch each other.

When looking for beetles, pay particular attention to cracks, bag seams and ears where they often hide. Empty individual bags in a thin layer onto a sheet and examine the contents for beetles and larvae.

This should be done in the shade so that the insects do not flee immediately. Insects can also be sieved out using a box sieve with a mesh of 1–2 mm. Identify the insects found in order to choose the correct treatment.

Inspecting in these ways should help prevent the breeding of carry-over insects from former crops. The surroundings should also be cleared to discourage easy re-infestation by insects and rodents.

Infection with fungi can be detected by the mouldy smell, which is noticeable even before any visual changes to the product can be seen.
Pay attention to water marks on bags. They indicate that the crop may have become wet. Even if the bags have dried, the crop can become mouldy.

Store Disinfection Practices in Agricultural Storage

After the store has been cleaned completely and all old deposits of dust (that could contain insect eggs) have been removed, it is good practice to dust the whole store with diatomaceous earth, lime or ashes as a further preventive measure.

If the wood in the construction has been attacked by larger grain borers, it should be treated with any of the approved wood preservatives or thoroughly sprayed with kerosene or an oil mixture to get rid of any surviving grain borers.

Methods of Store Disinfection Using Local and Mineral Resources

1. Mineral Substances: Fine sand, clay dust, lime and wood ash can be mixed with seeds, causing invisible injuries to food pests and leading to their dehydration.

These substances also fill the spaces between the grains, making it difficult for the pests to move and respire. The amount of these substances required ranges from 50–100 g per kg of stored product, except for sand, which has to be added in larger amounts.

2. Wood Ash: Mixing seeds with wood ash, either alone or together with powdered chilli pepper, is an efficient method of pest control. However, it does not control the larger grain borer, and ash may affect the taste of the crop.

The success of this method depends on the amount of ash added. 2–4 percent ash by weight of grain is said to give 4–6 months protection if the moisture content of the grain is below 11 percent.

3. Lime: Mixing seeds with 0.3 percent lime (calcium oxide) has given good results in weevil control.

4. Sand: In areas where fine sand is easily available, it can be used to protect stored products. It is best used with bigger seeds, intending that all the spaces between the larger seeds should be filled by sand, which can easily be removed by sieving. The more sand used the better, but at least equal amounts of sand and seed should be used.

5. Diatomite: Diatomaceous earth (DE) is mined in several African countries and can be obtained at a very reasonable price. DE consists of tiny fossil diatoms whose skeletons are made mostly of silica and form the diatomite deposits.

DE is a very effective and non-poisonous insect killer. As a dust, it can absorb a lot of water and kills insects by drying them out. It has been used in South Africa for many years by organic farmers in various kinds of insect control. Farmers using as little as 75 g DE per bag of 25 kg of grain do not experience any problems with weevils and other insects.

6. Bacillus thuringiensis: Bacillus thuringiensis is a bacterium that is active against insects. In powder form mixed with fine sand, it is effective against potato tuber moth. It may be used against grain moths as well.

7. Vegetable Oils: Oils of coconut, castor bean, cottonseed, groundnut, maize, mustard, safflower, neem and soybean affect the egg laying, and egg and larval development of stored pests. Care should be taken with castor bean oil, because it is very poisonous.

Some oils can go rancid during storage and cause crop spoilage. The addition of vegetable oil is particularly useful in protecting legumes against pulse beetles (Bruchids). Losses in pulses can be prevented with the addition of 5 ml oil per kg of grain/seed.

To be effective, the seed must be fully coated with oil. Sunflower oil is not very effective. The effect of oil treatment decreases with time, so seeds stored this way should be treated again at any new sign of infestation.

Small seeds may lose some of their germination capacity after oil treatment. If neem seed oil or any other non-food oil is used, the bitter taste can be removed by immersing the seed in hot water for a few minutes before food preparation.

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Admixture of Plant Parts for Traditional Agricultural Storage

Traditionally, many different types of plant parts are used against storage pests.

Examples of Plant Materials for Protection of Stored Agricultural Products

Plant NamePlant PartsTreatmentAloe (Aloe vera)Whole plantPlants dried and ground; dust mixed with the seedsChilli peppers (Capsicum sp.)Ripe, dried pods with ashes, dung or fine clayWhole pods mixed with grain or dusted as powder on beansPyrethrum (Chrysanthemum cinerariifolium and C. coccineum)Flower headsPick on hot days. Dry in the shade. Crush to powder and mix with seedsSun hemp (Crotolaria juncea)SeedsMix seed between gaps in stored larger size seedsDatura (Datura stramonium)Leaves and stemsDry and mix with produce (seeds are very poisonous)Derris (Derris sp.)All partsStored produce dusted or sprayedEucalyptus (Eucalyptus sp.)LeavesLayered or mixed with stored produceLantana (Lantana sp.)LeavesCrushed and placed among seedsSyringa (Melia Azedarach)Leaves, ripe seedsDried, powdered, mixed with stored grain (2% if seed powder, 4% if leaf powder)Mexican Marigold (Tagetes lucida)Whole plantsAdd dried plants in layers, mix in powdered plant or place 3–5 cm layer of crushed plants in base of grain binsSpearmint (Mentha spicata)Whole plant4% leaf powder gives good protection for more than 4 monthsNeem (Azadirachta indica)Leaves, crushed seeds, extracts, and oils*

The dosages of plant substances required are generally around 50 g per kg of stored product. The addition of ash, fine sand, lime, diatomaceous earth, and mineral or vegetable oils is particularly useful for protecting a small storage area or for storing small amounts for replanting.

However, this is not always practical for large quantities of seed in terms of labour required. For larger amounts of grains and seeds, it is often more practical to simply mix the seed with any strong-smelling plant material available to repel insects. Some plants such as pyrethrum and derris can actually kill storage insects.

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