Using airtight bags to prevent post-harvest crop loss

The summer season is upon us and brings along heat, humidity and insects – not a good combination for stored grain. The Purdue Improved Storage (PICS) bag, is an airtight storage bag that provides a solution for smallholder farmers to extend the storage time for their seeds and crops.

The PICS bag is a hermetic, or airtight, storage solution for smallholder farmers who suffer severe losses due to insects. The bags provide an effective method of controlling insects on maize for smallholder farmers and preserves the quality of the grain being stored.

According to the PICS website: “The use of PICS bags provides farmers the flexibility to sell their grains when they choose while supplying healthy, clean and insecticide-free food to their families throughout the year.”

PICS’ bags enable farmers to store their grains for longer periods and they are not forced to sell their grains directly after the harvest, when the market is already flooded and prices are low.

A demonstration of the PICS bag is presented to a women’s group in Kenya in March 2014. (Purdue International Programs in Agriculture photo/Dieudonné Baributsa)


PICS’ bags were first developed by prof. Larry Murdock, an entomologist at the Purdue University in the United States, to prevent losses during cowpea storage in Cameroon, but farmers started using the bags to store other crops like cereals, pulses, coffee beans and cocoa beans with great success.

The use of the bags spread to more African countries through several international aid projects with the aim to enhance the livelihoods of smallholder farmers.

The bag consists of three layers of plastic to ensure that it is airtight to prevent insects from surviving inside the bag, as well as to ensure a robust bag. This ensures that farmers can re-use the bag even if it suffers minor damage.

  1. Outer layer – made from woven polypropylene, which is usually used to store agricultural products.
  2. Inner layers – made from two high density (80 microns) polyethylene layers that seals the bag and prevents the insects from entering the bag.
The Purdue Improved Crop Storage is a three-bag, non-chemical hermetic storage system that limits the reproductive capacity of cowpea weevils that consumes grain after harvest. The system was developed by Purdue entomologist Larry Murdock and has been licensed to Kano, Nigeria-based Lela Agro Industries Nigeria Ltd. (Purdue University Agricultural Communications photo)

The advantages of using this bag include:

  • No need to add insecticides – the bag is more environmentally friendly.
  • Can be re-used.
  • Can be used for several different grains.
  • The quality of the grains is preserved.
  • Farmers can sell their crops during the off-season for higher prices.
  • No training or extra maintenance needed.
  • Available in different sizes.

If the bags are damaged, farmers can use them to store crops that are less sensitive to pests. The separate layers can be recycled if it is not usable.

Only dried grain (dried to below 13% moisture content) should be stored in the bags.

The bags are available in 50 kg or 100 kg sizes.

Hermetic storage

Hermetic storage provides an airtight or sealed storage option for cereals and pulses.

The PICS bag is designed to enable farmers to create an airtight seal (hermetic seal) to prevent oxygen from entering the bag. Insects need oxygen to produce their own water and when the oxygen in the bag is depleted, the insects die of thirst. This method is specifically useful in tropical and semi-tropical areas with high temperatures and humidity.

Up to 98% of the insects found in the bags are killed after one month, leading to reduced damage and weight loss when grains are stored over long periods.

It can be used in hot, humid climates, is chemical-free, controls moisture content, and there is no need for refrigeration. This method kills insects and aids to the control of mould. It can reduce storage losses to less than 1%.

Hermetic storage is less effective in cold climates since insects take longer to die in these colder climates due to slower metabolic rates.

Research also found that the lack of oxygen is detrimental to the growth of mould that produce mycotoxins like aflatoxins and ochratoxins.

Although there are several other hermetic storage solutions available to farmers, PICS bags are the cheapest option for smallholder farmers.



Mr Ganesh Teli
Polythylene Products (Z) LTD
Lusaka, Zambia
Tel +0260 211 287860/1
Cell: + 26 976 440083


Mr Pradeep
Polypack Ltd
Blantyre, Malawi
Tel +265 999 406 156


Mr Sudaj Devani
Manufacturers of TanSack
Dar Es Salaam, Tanzania
Cell: +255784249100


Ms Lunah Njeri
Bell Industries
Nairobi, Kenya
Tel: Tel: (+254)-20-6535828/9, 20-2368703
Cell: (+254) 725521525 0733764562


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