The most important and effective control measure in post-harvest handling and storage is the control of moisture content and hence, the water activity of the crop. Ensuring that susceptible crops are harvested at a safe moisture level, or are dried to a safe level immediately after harvest is vital to prevent mould growth and aflatoxin production during storage. The safe moisture level varies between crops – for maize it is approximately 14% at 20oC, but for groundnuts it is much lower, about 7%. These moisture levels must be maintained during storage and transport.
It is also important to ensure that the moisture content does not vary too much in a bulk-stored crop. Small localised ‘wet spots’ can develop mould growth and these can extend to neighbouring areas as the fungus produces metabolic water during respiration. Insect and animal pest damage can also act as focal points for fungal growth.