The 2026 corn growing season in North America yet again provided extreme weather events including record high temperatures and excessive rainfall in some places while others are experiencing severe drought conditions. Many factors influence the risk for mycotoxin contamination in crops, but climatic conditions play a critical role. While maximizing yield is often the goal, considerations for crop condition are also important heading into harvest. This article will provide an overview of major mycotoxigenic molds and key factors which influence the production of mycotoxins in corn. This will set the basis for next month’s article which will dig deeper into what contamination profiles might look like with the 2026 corn crop.

Factors related to the weather including temperature and humidity are critical in the development of fungal diseases and subsequent mycotoxin production in crops. Often, we see regional differences in mycotoxin contamination profiles because different climates support different types of molds as molds have variable temperature and moisture requirements to grow. Additionally, anything that stresses the plant, ranging from drought to excess rainfall, insect or hail damage, weed pressure, or a variety of other stressors, increases plant susceptibility to mold colonization and mycotoxin production.

Most mycotoxin-producing molds live in the soil and can survive on crop residues. Corn plants are especially at risk to the fungal pathogens which cause ear rots around silking. Mold spores can be transferred to silks via wind, splashing water, or by insects. Soilborne spores can also infect plants via uptake by the roots. Damage or lesions from insects, wildlife, hail, wind, or other mechanical injury also provides a pathway for molds to colonize the plant. 

Foliar diseases also play a role in crop health and some key leaf diseases in North America caused by fungi include Gray Leaf Spot, Northern Corn Leaf Blight, Common Rust, Anthracnose, and Tar Spot. Although these diseases are not caused by mycotoxin-producing molds, such foliar diseases stress the plant, can be detrimental to grain yields, and leave the plant at risk for secondary disease by molds that can produce mycotoxins.

At this point it is difficult to accurately predict what mycotoxin contamination patterns will look like for most acres of corn planted in the North America, but Table 3 highlights some potential situations that may have occurred during the growing season and circumstances to keep in mind while heading into harvest that can increase the risk for fungal disease and subsequent mycotoxin production. It’s important to remember that the risk for mycotoxins to accumulate continues for the duration of the plant lifecycle and into grain storage through the time of feeding out.