Fumonisin: A Serious Threat to Corn Markets

	Donald White Professor Department of Crop Sciences (217) 333-1093; d-white@illinois.edu
		Michael Clements Graduate Research Assistant Department of Crop Sciences (217) 333-3098; mclement@illinois.edu

Fusarium ear rot is the most commonly occurring ear rot disease of corn. Symptoms of the disease vary depending upon genotype, environment, and disease severity. Normally, individual kernels or groups of infected kernels are randomly scattered on the ear. Whitish-pink to lavender fungal growth may occur on the surface of kernels (Figure 1). Infected kernels also may exhibit white streaks radiating from the point of silk attachment to the cap of the kernel (Figure 2).

Fusarium ear rot was not considered to be economically important in much of the world until 1988, when a group of mycotoxins named fumonisin was found to be produced by the fungi that cause Fusarium ear rot. Fumonisin is now known to cause a variety of diseases of both animals and humans. It has been linked to laucoencephalomalacia in horses, pulmonary edema in swine, cancer in laboratory mice and rats, human esophageal cancer, and human birth defects.

Figure 1. Whitish-pink to lavender
fungal growth on kernels.

The American Association of Veterinary Laboratory Diagnosticians recommends that feed for horses contain less than 5 Fg/g fumonisin and feed for swine contain less than 10 Fg/g fumonisin. Standards are now being considered for corn grain and human food products, and most estimates suggest that an acceptable level will be below 1 or 2 Fg/g in corn grain used for processed corn-based human food products. It is not clear if this will be a Food and Drug Administration action level (i.e., required by law) or an advisory level (no action required by law, only suggested). Presently, Canada will not import white corn with fumonisin levels greater than 2 Fg/g.

White streaks radiating from the point of kernel attachment.

Figure 2. White streaks radiating from the point of kernel attachment.

A number of studies have shown that fumonisin levels of 2 Fg/g or higher can be found in much of the corn crop grown in the southwestern United States in most years. In 1990, a range of 5 to 20 Fg/g fumonisin was found in a group of 15 widely used dent corn hybrids grown in six locations in Illinois. In a 1991 survey of corn produced in Illinois, 13.8 percent of nearly 50 samples had greater than 6 Fg/g fumonisin. Surveys done in Iowa in 1993 and 1994 found 8.7 and 12.4 percent of the corn samples with greater than 2 Fg/g. Surveys done in 1995 and 1996 in Missouri found 10.2 and 8.3 percent of the corn samples had greater than 5.0 Fg/g.

Fumonisin in processed food is rare; however, fumonisin levels above 2 Fg/g have been reported in corn meal, muffin mix, corn bread, and blue tortilla chips purchased at various locations in the United States. Products made from stone ground whole corn produced in the southeastern U.S. are most likely to be higher in fumonisin.

Corn is a component of a large and diverse number of human food products. Therefore, even a minimal possibility of human health problems associated with consumption of these products could produce serious public health concerns. Since fumonisins normally occurring in corn produced in much of the U.S. are at levels bordering concern, procedures should be implemented for their control.

Currently, research at the University of Illinois is attempting to identify resistance. In future years, depending upon the availability of funding, we will incorporate this resistance into useable, commercially inbred lines.

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Department of Crop Sciences
College of Agriculture, Consumer and Environmental Sciences
University of Illinois Extension