The Aspergillus fungi that produce aflatoxin are naturally present in soil, which makes groundnuts particularly susceptible since the nut grows underground. The fungi can be found to infect many crops in most any climate, but are a particular challenge in hot, humid climates.
The factors behind aflatoxin accumulation are complicated. Some cropping seasons that seem prone for A. flavus development and aflatoxin accumulation, do not result in high levels of contamination.
Some factors that have been found to be associated with high aflatoxin include:
- End of season drought
- Insect and mechanical damage to nuts
- Insufficient drying of the crop
- Poor storage