farmgate: Do You Know What Is Lurking In The Depths Of Your Cornfield?
This “Goldilocks” of a growing season, where it was too wet, too dry, too cold, too hot, and not “just right” really anywhere, many farmers will find further evidence in the form of ear and stalk rots in their corn. If you had an unusual growing season there is an increased chance of some type of fungus that really liked the environment in your field.
The presence of ear rots means the potential for mycotoxins that may produce fumonisin or aflatoxin which will have limited use in the market place and can cause problems that could create liability issues. Not wanting that, your need is to scout cornfields to see if there are fungal issues that can be isolated. Extension specialists have reported a significant number of incidents of ear and stalk rots, and Cornbelt farmers should take a serious look at their fields.
Plant pathologist Alison Robertson at Iowa State University suggests stripping back the husks on at least 100 plants scattered through each corn field. She says, “If more than 10% of the ears have significant mold that is greater than 25% of the ear, the corn should be harvested in a timely manner and dried to below 15% moisture as quickly as possible to prevent further mold growth and, in some cases, mycotoxin accumulation.” Her fact sheet on ear rots says it is important to recognize ear rots, but also keep in mind that the presence of a fungus on an ear of corn may or may not mean that mycotoxins are present, but if they are, they can be managed.
Plant pathologist Laura Sweets at the University of Missouri says little can be done to protect corn from being infected with fungi. In her fact sheet, she also stresses management of the grain, “Adjust harvest equipment for minimum kernel damage and maximum cleaning. Before storing grain, clean bins thoroughly to remove dirt, dust and any grain left in or around bins. Thoroughly clean grain going into storage to remove chaff, other foreign material and cracked or broken kernels. Dry grain to 15% moisture as quickly as possible and monitor grain on a regular basis throughout storage life to insure moisture and temperature are maintained at correct levels. Protect grain from insects.”
Robertson at Iowa State says do not store moldy grain, but sell it, or feed it after testing for mycotoxins. A qualified laboratory can test the grain to determine if a mycotoxin is present, how much is present, and that will help you and a veterinarian determine whether and how much can be fed to livestock. Keep in mind also that different species and different ages of animals have different degrees of sensitivity to mycotoxins. What cannot be fed to dairy cattle, may be a candidate for a feedlot. Sweets says mycotoxins can remain in the grain long after the mold has died.
Fusarium: white to pink cottony mold, can produce fumonisin
Diplodia: dense white mold, does not produce mycotoxins. Diplodia ear rot is favored
by wet weather just after silking and is more severe when corn is planted following corn.
Gibberella: white to pink mold, can produce vomitoxin
Cladosporium: gray to black or dark green mold
Aspergillus: gray, green powdery mold, can produce aflatoxin
Penicillium: clumps of blue-green mold that have invaded the kernel. Also called blue-eye mold since it has discolored the embryo.
Robertson says stalk rots should also be assessed this year by checking at least 100 plants throughout a field. If more than 15% are rotted, schedule that field for the earliest possible harvest to reduce problems from lodging.
In her stalk rot fact sheet, Sweets says many types of stress may have initiated the problem and allowed the fungus to enter. Management of the problem begins with selection of hybrids have that have good stalk strength and are not prone to lodging. Other factors that can cause stalk rot issues are population density, improper fertility, and stress during pollination and grain fill.
Summary:
If you have a fungal problem in your corn fields that has deteriorated stalk integrity and caused ear rots, you are not alone. Multiple fungi are being reported throughout the Cornbelt, some capable of causing mycotoxins that can reduce the value of the corn because of toxicity to livestock. Nothing can be done for the grain at this time, other than to harvest it as quickly as possible to retard fungal growth. If problems are detected, have the grain checked by a laboratory to determine what can be done with it, if it cannot be stored or fed to livestock.
Posted by Stu Ellis on October 2, 2008 12:09 AM to farmgate