Mycotoxins in the 1995 corn crop

In 1995, the Iowa ear rot and mycotoxin survey conducted by the National Agricultural Statistics Service and the USDA National Veterinary Services Laboratory was expanded to include samples from Illinois and Missouri. A total of 639 samples were collected from fields near harvest and analyzed for aflatoxin, fumonisins, vomitoxin, and zearalenone. Iowa samples also were examined for symptoms of ear rot.

Because of dry summer weather, Gibberella ear rot was much less prevalent than in the past two years, appearing in only 4.2 percent of the Iowa samples. This fungus can produce vomitoxin and zearalenone. Fusarium ear rot was very prevalent, as it was in 1993 and 1994, appearing in 88.7 percent of the samples. Average severity of Fusarium ear rot was slightly greater in 1995 than in previous years. This fungus can produce fumonisins. Aspergillus, which can produce aflatoxins, was found in only a few samples.

Mycotoxin levels were low, especially in the Iowa samples. Results are shown in Table 1, below:

Fumonosin B1 Vomitoxin
<0.5 ppm 0.0-5.0 ppm >5.0 ppm <0.5 ppm 0.0-5.0 ppm >5.0 ppm
Iowa 61.1 36.4 2.5 94.0 3.5 2.5
Illinois 55.4 34.1 10.5 94.6 4.7 0.8
Missouri 44.9 44.9 10.2 78.6 9.2 12.2

For fumonisins, levels below 5 ppm are generally considered safe. For vomitoxin, levels below 1 ppm are generally considered safe. Only one sample contained aflatoxin above the regulated limit of 20 ppb. This sample was not from Iowa. Only one sample had a zearalenone concentration higher than the recommended 1 ppm.

These results indicate that serious mycotoxin problems were not common in Iowa in 1995. Nevertheless, there were isolated cases of corn deliveries that were rejected because aflatoxin concentrations were greater than 20 ppb. Additionally, a few cases of fumonisin poisoning of horses were reported in 1995 in Iowa. I do not know if these were associated with 1995 crop or stored corn

This article originally appeared on pages 4-5 of the IC-476 (1) -- January 26, 1996 issue.

Updated 01/25/1996 - 1:00pm