To manage and reduce post-harvest losses, we take you through some facts about aflatoxin contamination and how to reduce its effect on your maize cobs or grains — as part of crop farming management.
Heavy rains at the time of maize harvesting have serious effects on the quality of maize. Some varieties of maize tend to open their ears too early — if it starts raining, the water goes into the maize cob causing rotting.
Pests also easily enter the maturing maize cob and destroy it before it is harvested.
High levels of moisture in maize make it easy for mould to develop leading to aflatoxin contamination.
Aflatoxin is a highly toxic substance, produced by the fungus Aspergillus flavus. Aflatoxin, which causes cancer, suppresses the body’s immune system, retards growth, causes liver damage and even death if consumed by humans, chickens, and other farm animals.
This is one reason maize farmers need to harvest their mature maize early even if rains persist.
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Here are some things you can do to prevent aflatoxin contaminations:
1. Dry and store your maize well
After harvesting, maize should be properly dried before storage. Most farmers are, however, likely to face the problem of drying their crops during the rainy season.
Heavy cloud cover makes it difficult for farmers to dry their maize, and this may force farmers to store it even before it has attained a moisture content of about 13.5 percent, which is the recommended moisture level before maize, beans, sorghum, and other cereal grains can be safely stored.
You can press the grain with your thumb to see how hard it is — dry grain is difficult to press.
2. How aflatoxins develop
The UN World Health Organization (WHO) estimates that billions of people in Africa and the other developing world are at risk of chronic exposure to aflatoxins through contaminated foods.
Aflatoxins cannot be seen by the naked eye; infected maize may look normal which makes it difficult for farmers to tell if their maize is infected.
Aflatoxins can develop in maize when it is still growing in the shamba before it is arranged in stakes and harvested. This usually happens when maize takes too long before it is harvested.
Damage through broken grains and holes drilled by pests like weevils and stem borers allows the fungus to invade seeds in the field and stores.
3. Aflatoxin biocontrol product
Scientists in the USA use several methods to control biologically aflatoxin in growing maize.
One recommended method is the use of Aflasafe® which is, a biocontrol solution. Aflasafe® is broadcast in maize while it is still growing.
The harmless strains of the Aflasafe® fungus compete with the poisonous strains blocking them from multiplying – this process reduces aflatoxin production in grains during both crop development and post-harvest storage.
This technology is particularly effective as it addresses the source of aflatoxin (the fungus in the soil) before it can contaminate the crop before harvesting.
4. Tips on maize drying and storage
• Harvest early, when the maize has matured.
• Separate rotten maize from healthy maize to reduce contamination.
• Dry the maize until it is completely dry (if you have a moisture metre ensure maize to be stored has at least a 13.5% percent moisture content).
• Do not throw harvested maize on the bare ground where it comes into contact with soil.
• Clean the maize store thoroughly by removing any previous grains as they may harbor pests.
• Ensure maize to be stored is shelled before storage – this reduces pest damage, maize on the cob is more prone to pest damage compared to shelled maize.
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5. Use diatomite for maize storage
Farmers facing pest problems in their stored maize can use diatomite. Diatomite is a fine powder made up of fossilized microscopic plants called diatoms. Diatomite contains millions of small particles which have very sharp edges.
When diatomite’s sharp edges come into contact with an insect or a parasite, their protective coating is pierced, causing the insect to dehydrate and die.
This makes diatomite an excellent and natural pesticide that does not have negative side effects. Farmers across the world have used diatomite for decades to control pests.
Diatomite can be mixed with maize, wheat, barley, wheat, oats, beans rice, sorghum at a rate of a half kg (500g) for every 90 kg of any of these grains.
Diatomite is safe for both humans and animals. Cereals preserved with diatomite can be stored for up to 4 years or longer without damage so long as they are kept in a cool dry place that has no signs of rat damage.
Grain that has been treated with diatomite has to be washed and dried before cooking or milling. The only limitation for farmers is that diatomite is not available in most agro-vet shops.
Farmers groups can come together and purchase the powder and share it among themselves.
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