Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information


Downloadable and Printable Version

August 15, 2005

September 23, 2005




Aflatoxin and Other Ear Molds


I am receiving many reports of corn grain being rejected at elevators, ethanol plants, and river terminals because of aflatoxin.


In brief, aflatoxin is created by a gray-green to yellow-green mold called Aspergillus flavus, which might be observable in a field or which may become observable any time before harvest.  However, the presence of the mold does not necessarily mean that aflatoxin is present.  In addition, Aspergillus flavus may be working on the inside of the kernels with no outward signs.


Each hybrid in each field should be checked now and once every two weeks until harvested for any visible signs of Aspergillus flavus.  Check 10 - 30 ears per field, being sure to check all areas of the field.  Iowa State University publication Pm-1800 “Aflatoxins in Corn” has good pictures of Aspergillus flavus.


If you see anything suspicious, or if you have a load rejected, the first thing to do is call the crop insurance adjuster.  Corn damaged by aflatoxin in the field is an insurable loss, but corn that has aflatoxin in a bin will be considered a storage loss and not covered by insurance unless the crop insurance adjuster has verified the condition of the grain before it goes into a bin.


If you have harvested corn with aflatoxin above the 20 parts per billion (ppb) tolerance for general trade, what can you do?

·        It can be fed to breeding meat animals if the corn has less than 100 ppb aflatoxin.

·        It can be fed to finishing swine if the corn has less than 200 ppb aflatoxin.

·        It can be fed to finishing cattle if the corn has less than 300 ppb aflatoxin.

·        It can be run through a good grain cleaner.  Kernels infected with Aspergillus flavus tend to be lighter and may be smaller or misshapen, so a good cleaning may lower the level of aflatoxin to acceptable levels for feeding.

·        It can be professionally treated with anhydrous ammonia or aqua-ammonia (UAN).  The ammonia will react with the aflatoxin and render it harmless.  The grain will not be acceptable in general trade, but it will be safe to feed.  There may be a feed rejection problem by swine.

·        It can be blended with less contaminated grain to make the entire lot acceptable for feeding.  Grain that is known to be contaminated with aflatoxin cannot legally be blended with better quality grain to make it acceptable for interstate commerce.


If you have unharvested corn, what can you do?

·        Harvest as soon as possible (ASAP); the longer the corn stands in the field, the worse any Aspergillus flavus infection will be.  For storage, dry the grain to 15% moisture or less ASAP.  Then, as the fall progresses, cool the grain to 35 – 40 degrees.  Even with expensive energy, this is still the thing to do if there are any signs of Aspergillus flavus in the field.

·        Spend extra time adjusting your combine.

o       As stated above, kernels infected with Aspergillus flavus tend to be lighter, so carefully adjusting the fan to blow out the light kernels may help.

o       As stated above, kernels infected with Aspergillus flavus may be smaller or misshapen, so careful adjustment of the separation units may help.

o       Be especially conscious of the concave adjustments, trying to minimize grain damage, especially if the grain is going into on-farm storage.  Damaged grain will be more likely to be infected with Aspergillus flavus.


Store infected corn separate from non-infected corn to minimize exposure of the non-infected corn to Aspergillus flavus.


Check stored grain at least once very two weeks.


Iowa State University publication Pm-1800 “Aflatoxins in Corn” will answer many of your additional questions.  Also, the following may be helpful:

·        Iowa State University Grain Quality Initiative Aflatoxin Site

·        University of Kentucky publication ID 59 “Aflatoxins in Corn,”

·        University of Illinois publication RPD 1105 “Mycotoxins and Mycotoxicoses,”

·        North Carolina State University publication DRO-30 “Drought Advisory for Corn Production,”

·        “Aflatoxin in the Corn Crop?” from pages 188 – 190 of the University of Illinois Pest Management and Crop Development Bulletin” (includes links to other references), and

·        “Grain Quality and Grain Handling Issues in Drought Areas” and “Risk of Aflatoxin Contamination Increases with Hot and Dry Growing Conditions” on pages 184 – 185 of the September 12, 2005 ISU Integrated Crop Management Newsletter.


In addition, be sure to watch for other ear molds as described on pages 158 – 160 of the October 6, 2003 (Fall 2003 Special Edition Drought Issue) of the ISU Integrated Crop Management Newsletter and by the Plant Pathology Department at North Carolina State University.


If you are interested in testing grain using one of the commercial test kits described on page 2 of Pm-1800, sources include:




1238 Anthony Road
Burlington, NC 27215

(Tel. 336-226-6311)
(Fax. 336-229-4471)


Intl. Diagnostic System Corp.
Suite 100
2620 South Cleveland Avenue
St. Joseph, MI 49085

(Tel. 616-428-8400)
(Fax. 616-428-0093)

Several kits

Neogen Corporation
620 Lesher Place
Lansing, MI 48912

(Tel. 517-372-9200)
(Tel. 800-234-5333)
(Fax. 517-372-2006)

Several kits

313 Pleasant Street
Watertown, MA 02172
(Tel. 617-926-7045)
(Tel. 800-338-4381)
(Fax. 617-923-8055)


Romer Laboratories

1301 Stylemaster drive

Union, MO 63084-1156

Tel. 800-769-1380

Fax. 636-583-6553



500 Riverside Industrial Parkway

Portland, ME 04103

Tel. 866-408-4597

Fax. 207-797-7533


QuickTox Kit

Strategic Diagnostics

111 Pencader Drive

Newark DE 19702-3322

Tel. (800) 544-8881

Fax. (302) 456-6782




7950 Old US 27 South

Marshall, Michigan 49068

Tel. (877) 789-3033

Fax. (269) 789-3070





If you have any questions, please feel free to contact the Iowa State University Extension Office.
maroon ball East Central and Southeast Iowa Crops Home Page maroon ball ISU Extension and Outreach maroon ball ISU maroon ball ISU Extension Agronomy maroon ball ISU Agronomy
maroon ball Calendar maroon ball Search maroon ball Jobs maroon ball Feedback maroon ball Internet Resources maroon ball State Extension Sites in Other States maroon ball Local Extension Offices in Other States

Last Update: September 27, 2005
Contact: Virgil Schmitt

Nondiscrimination Statement and Information Disclosures