This past September, our team visited some corn fields in Minnesota, and we were surprised by the abundance of corn smut found in damaged ears. Corn smut is a fungus, known formally as Ustilago maydis in the plant world.
Corn smut grows as galls that can develop in the aerial part of the corn plant, particularly in the ears. It is an easily recognizable bundle often made of garlic-clove shaped growth with a characteristic light blue color when physiologically mature.
In Mexico, it is called “huitlacoche,” and it is considered a delicacy of earthy flavor, sold fresh, canned, or dried. Most of the fungus in late September was already past its prime and had a dark, almost charred look.
This fungus proliferates when the corn plants are wounded or debilitated by stress. Common stressors can be hail or wind. In this case, the fields had been subjected to extreme wind that resulted in either some lodging or even green snap, depending on the hybrid. The concern for livestock nutritionists is not corn smut but that the fungus is a telltale sign of plant stressors that allow other pathogenic molds to proliferate. Even some old dried-up galls showed mold growth in their periphery.
The Biological Control of Pests Research Unit from USDA’s Agricultural Research Service (ARS) division recently conducted an experiment over a two-year period on corn smut and its cross contamination with other mycotoxin-producing fungi. The results showed the presence of mycotoxins in corn smut galls during ear development at various physiological stages.
Fumonisin was the most frequent mycotoxin detected in corn smut gall samples. It was found in 63% of sample levels less than or equal to 150.7 micrograms per gram (μg g-1). Next, aflatoxin was found in 30.6% of samples at a rate of less than or equal to 10.8 nanograms per gram (ng g−1).
Continue reading this article published in Hoard’s Dairyman.
