With corn still in the bins and spring bringing warmer temperatures, growers may not be out of the woods just yet when it comes to moldy grain and mycotoxin problems.
Wet conditions in the fall followed by a late corn harvest resulted in the development of ear rots and the presence of vomitoxin – a mycotoxin that makes grain undesirable for livestock feed. The problem has been so severe and widespread in some areas across the Midwest that plant pathologists and agronomists fear the problem might persist into the 2010 growing season.
"If conditions in the bins were kept cool and dry, vomitoxin levels would likely not increase from the levels seen in the fall. But if conditions were not kept cool and dry, it's likely that growers will see an increase in moldy grain and vomitoxin levels this spring relative to what they saw in the fall," says Pierce Paul, an Ohio State University Extension plant pathologist. "Even if they kept the grain cool and dry, with normal environmental conditions this time of year being warm naturally, it may be impossible for growers to keep that grain cool enough, and the problem might just very well flare up again in infected bins."
Anticipating any potential problems this spring, Paul is re-emphasizing the importance of testing grain to see if vomitoxin is present and at what levels before feeding it to livestock.
"If you choose to feed the moldy grain to livestock, keep it away from pigs because they are highly sensitive to the vomitoxin," says Paul, who also holds an appointment with the Ohio Agricultural Research and Development Center. "Other livestock, such as sheep and goats, are more tolerant, but again it depends on how high levels are as to whether you should feed the grain to those livestock or not."
Paul says that growers should be taking steps both in the grain bins and in the fields to keep inoculum levels low and prevent any ear mold flare-ups that may occur in this year's corn crop.
"To get rid of moldy grain, some growers may be tempted to spread it out in the field. You are not going to have a problem from a vomitoxin standpoint by doing that, but if there is active fungi on the kernels spread in the fields, you can run the risk of spreading the inoculum to this year's crop," says Paul. "The fungus can cause stalk rot and ear rot in corn and head scab in wheat. Spreading moldy grain will just increase your chances of spreading spores and causing these additional disease problems."
In addition to keeping the fields clean, grain bins need to be cleaned as well.
"You want to get rid of as much of the mold as possible, so once the grain bins are empty, washing and scrapping them clean will help get rid of any fungal residue," says Paul. "Also get rid of the fine particles and impurities. They can be more contaminated than the grain itself."
Paul also emphasizes that mycotoxin and mold go hand-in-hand.
"Mycotoxin itself will not stay in the walls of the bins if there is no mold. Mycotoxin by itself isn't a problem in the bins. It has to move with the fungus," says Paul. "Get rid of the fungus and mold and you'll be rid of the mycotoxin in the bin."
When it comes to planting crops this year in fields identified with ear mold problems, growers are encouraged to exercise caution.
"This is the same disease that causes head scab. This is the same disease that we've now shown, when inoculum is really high, can affect soybean seedlings," says Anne Dorrance, an OSU Extension plant pathologist. "We have high inoculum density right now and we have to get it knocked down or this problem is going to continue to expand."
Dorrance recommends that growers either apply a seed treatment or perform some management practices to reduce the inoculum levels, such as chopping up corn residue or covering it over with soil.
"Getting those levels down is really important for the long-term health of soybean seedlings and this year's corn crop and wheat crop. We don't need a head scab epidemic," says Dorrance, who also holds an appointment with the Ohio Agricultural Research and Development Center.
Growers aren't encouraged to plant corn after corn in no-till situations because of the increased disease problems associated with the practice, says Paul.
"If they choose to do, they should be prepared to plant resistant varieties for the most important foliar diseases like gray leaf spot and northern corn leaf blight and use a fungicide application management program," says Paul. "There isn't much you can do with fungicides for ear mold, however. If a grower can identify a resistant variety, then plant it."
A new fact sheet, "Gibberella Ear Rot and Mycotoxins in Corn: Sampling, Testing and Storage" is now available for download. The publication provides up-to-date information on the development of Gibberella ear rot; sampling and testing for mycotoxins, with an emphasis on vomitoxin; and storage and handling of moldy grain.