How to secure your crop against aflatoxin

Healthy maize on a farm. A farmer should plant early to avoid drought and insect damage. Photo: Courtesy

There is a need for farmers to be informed on the best agronomic practices and post-harvest practices to control and prevent aflatoxin contamination of crops.

During planting

Farm practices in growing grains like maize to avoid aflatoxin according to uaex.edu include planting early to avoid drought and insect damage.

A farmer should irrigate often to avoid drought stress, planting BT maize and harvesting on time.

Irrigated crops are less likely to be infected with the fungus as they have better growing conditions away from the drought and excessive heat.

The World Health Organization Food Safety Digest says that aflatoxin can be controlled before harvesting by plant breeding or through genetic engineering of crops to resist fungal infection or by preventing the production of aflatoxins by invading the fungus.

However, these processes are labourious and time-consuming thus effective, sustainable and universal methods are needed, WHO adds.

One method that has worked as reported by WHO the biological control is using non-toxigenic A. flavus isolates which occupy the same niches as the naturally occurring toxigenic strains, and are capable of competing and displacing the toxigenic strains and has sometimes worked on maize in Africa.

An online publication by the University of Georgia advises that:

Aflatoxin causing fungus thrives in high temperatures and moisture content above 13.5 percent should not be exceeded.

During harvesting

All harvesting, handling, drying and storage equipment should be properly cleaned to make it aflatoxin free.

All broken grains, dust and remains should be removed to ensure no moisture that may cause contamination.

Damaged grains on the seed coat should be removed as they allow the easy entrance of moulds and fungi which promotes fast rotting in high moisture and high-temperature conditions.

Aflatoxin can develop within 24 hours in mould and fungi infected maize stored in those conditions, even though the grains were previously free of aflatoxin, notes the University of Georgia Extension.

Harvesting should be done in a way that prevents damage to the grains and the seed coat.

Harvesting should ideally be done immediately the crops mature when the moisture levels are about 28 to 30 percent, then dried.

High moisture grains should be handled properly by not being held in wagons or trucks for more than six hours as it is supposed to be as cool as possible or dried before transporting.

The ideal drying is moderate heat over a short period of time then cooled for storage to outside air temperature.

Grains should be dried through the common sun-drying which is the oldest or most common way which takes two to three days, air drying, solar drying or mechanical drying.

For proper storage facilities the moisture content should be maintained below 12 to 13 percent which is not favourable for aflatoxin development.

Maize should be treated to control insect infestations before storage.

Post-harvest

According to agrilinks.org the use of hermetic bags and hygrometers is recommended to prevent post-harvest crop losses and harmful food toxin contamination.

The bags when sealed properly prevent oxygen from getting in or out thus the anaerobic environment suffocates insects and prevents any fungal growth adds agrilinks.org.

A farmer uses a hygrometer to measure moisture content after drying to know if the maize is safe for storage or not.

Regular testing of the maize before processing or consumption is important as aflatoxin is not visibly evident.

Frequent inspection of maize or grains should also be done to check out for any presence of mould, insects or spoilage.

However, chemicals can be added to contaminated maize to reduce the toxic levels of aflatoxin for consumption by swine, poultry and cattle adds uaex.edu instead of throwing it way.