As growers wrap up corn harvest this season, they should give special attention to fields inundated by floodwaters earlier this year in parts of northwest and north central Ohio.
Pierce Paul, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, said that corn ears submerged in water for a long period of time may have turned moldy, and moldy grain may cause health problems in livestock.
“If the grain seems moldy, it’s important that growers conduct a toxin analysis before feeding it to livestock,” said Paul, who also holds an Ohio State University Extension appointment. “There are some concerns that corn coming off those fields in flood-damaged conditions and subjected to wet, humid conditions may be moldy and toxin-contaminated.”
In Ohio, the three main ear mold-causing fungi are Diplodia, Gibberella and Fusarium. However, when the integrity of the grain is compromised, as was the case in some flooded areas, other organisms may colonize and cause problems.
Diplodia ear rot is characterized by a thick, white mold that covers the entire ear, a shrunken and lightweight ear, and kernels that appear glued to the husks. A sign of Gibberella ear rot is a pinkish to reddish mold that starts at the tip of the ear and progresses to the base. Fusarium ear rot covers individual kernels with a white, cottony mold.
All three diseases reduce grain quality, but Gibberella ear rot and Fusarium ear rot also produce toxins that may be harmful to livestock.
Gibberella fungi produce vomitoxin, the same mycotoxin that is also produced in head scab in wheat. Hogs are particularly sensitive to vomitoxin, which can cause feed refusal at concentrations in grain at around 1 part per million. The FDA advisory level for vomitoxin in corn to be fed to hogs is 5 parts per million and this is not to exceed 20 percent of the diet.
Fusarium fungi produce a mycotoxin called fumonisin. Horses are particularly sensitive to fumonisin, and cattle and sheep are relatively insensitive.
Fungi can also produce aflatoxin, another mycotoxin that is potentially harmful if fed to livestock. For information on aflatoxin visit OARDC’s Department of Plant Pathology “Ohio Field Crop Diseases” Web site.
Paul recommends that growers send samples to toxicology laboratories if they feel grain is infected or if they believe infection levels may be high.