Storage Moulds and Mycotoxins

It is useful to distinguish fungi that infect the crop in the field from those that develop in storage. Field fungi, including many Fusarium species, colonise grain on the growing plant, especially under wet conditions around flowering and maturity, and can produce toxins such as deoxynivalenol before harvest. Storage fungi, chiefly Aspergillus and Penicillium species, grow on grain after harvest when it is held too moist or too warm; some Aspergillus species produce aflatoxins, particularly in warm climates and on crops such as maize and groundnuts.

This distinction matters for prevention. Field infection depends largely on weather and crop management, whereas storage mould growth is strongly within the control of the person storing the grain, through drying and temperature control.

Mycotoxins are toxic compounds produced by some fungi as they grow. They are of concern because they can harm human and animal health, they are not removed by ordinary cooking, and they can be present even when visible mould is limited. Because of these risks, many countries set legal limits for major mycotoxins in food and feed, and contaminated lots can be rejected, downgraded, or condemned.

• Dry grain promptly to a safe moisture content and avoid delays that let mould start.
• Store grain cool, dry, and clean, and prevent moisture migration and condensation.
• Manage crops in the field to reduce Fusarium and Aspergillus infection where possible.
• Sort out visibly mouldy and damaged grain, and monitor stored grain for heating and mustiness.
• Test high-risk crops and lots for relevant mycotoxins against food and feed limits.