In the southeastern United States this environmental condition occurs more frequently and is the main reason why Aspergillus infections and aflatoxin contamination are more consistently, but not exclusively, a problem in the Southeast. Furthermore, drought stress, nitrogen stress and other stresses that affect plant growth during pollination can increase the level of aflatoxins produced by the Aspergillus fungi. In the past, insect injury to the maturing ear of corn was considered necessary for infection to occur. This is now known to be false. However, insect damage to ears provides wounds that allows Aspergillus to more readily infect the kernels.
Insects also transport Aspergillus spores to the silks and the kernels.
Therefore, insect damage, especially during pollination in drought-stressed corn, can increase the occurrence of Aspergillus and the levels of aflatoxins. Several other factors play a role in the development of Aspergillus mold and aflatoxin production. Because drought stress plays such an important role, practices that reduce drought stress in plants should reduce the levels of infection and toxin production. Irrigation has been shown to be very effective in reducing Aspergillus infection and aflatoxin development even if done only during pollination. Tillage practices have not been as effective and have only been demonstrated to reduce aflatoxins by subsoiling in areas with hardpans.