Corn Grain and Silage Sampling and Mycotoxin Testing

***Updated in 2025, this version replaces the previous 2016 Grain and Silage Sampling and Mycotoxin Testing publication.***

If corn ear rots are a significant problem (e.g. damaged ears observed on greater than 10% of the plants examined) in the field, it is essential to test harvested grain and whole-plant silage for mycotoxins. Obtaining a representative sample for mycotoxin testing is critical for accurate results. It’s also important to know the available testing methods and how they may vary in accuracy.

Sampling Requirements

The accuracy of a mycotoxin test largely depends on the collection process and quality of the grain or silage sample. The United States Department of Agriculture (USDA) Grain Inspection Handbook and the Canadian Grain Commission recommend specific sampling methods to ensure that samples accurately represent the composition of the grain load and silage mass. Sample collection methods vary depending on whether the sample is collected from the field (via combine), a grain truck, a shipping container, feed bunk, storage bin, an elevator, or at the point of sale.

What does a representative sample consist of?

Although sampling methods vary, the size of the representative sample remains consistent. According to the USDA Grain Inspection Handbook, a representative sample should weigh at least 4.4 pounds (2 kg), with a preferred weight of 5 pounds (2-2.5 kg). In practice, several subsamples are collected and combined into a single composite sample for submission and the testing sample is then taken from this composite sample (Fig. 1).

For grain sampling, collect subsamples several times from a moving stream during grain loading or unloading. For stationary loads of grain, sample probes are commonly used, and multiple probe samples should be obtained from various locations of the load. Silage subsamples should be collected from vertical and horizontal facing areas of the silage mass to ensure a representative sample.

Don’t Rely on Appearance Alone

There are several technologies for testing mycotoxin concentrations in corn grain and silage. Never rely solely on visual methods such as the black light test, which may be used to test for presence of the fungus Aspergillus (Fig. 2). Visual test results can be inconsistent and do not quantify mycotoxin levels, so always test samples using recommended methods or send them to professional laboratories.

Testing Kits

Several companies sell kits designed to detect and measure specific mycotoxins. While purchasing the necessary testing equipment may require an initial investment of several thousand dollars, the cost of testing a single grain sample (a subsample of a larger sample) for one particular mycotoxin is relatively low, though it can vary depending on the company and technology used (Fig. 3).

Some companies that sell mycotoxin detection equipment and test kits include:

Charm Sciences, Inc.

EnviroLogix

Neogen Corporation

R-Biopharm AG

Romer Labs

VICAM

Professional Laboratories

Local laboratories, state plant disease diagnostic clinics, and grain inspection services may test corn samples for mycotoxins. Below is an incomplete list of select grain testing providers. Check with your local Extension office for a more complete list of grain testing facilities in your area. For a list of labs in Ontario, visit here. Costs and sample submission procedures vary by provider.

Breathitt Veterinary Center (Hopkinsville, Kentucky)

Cumberland Valley Analytical Services (Hagerstown, Maryland; Batavia, New York; Zumbrota, Minnesota)

Dairy One (Ithaca, New York)

Dairyland Laboratories (Arcadia, Wisconsin)

EMSL Analytical, Inc. (Baton Rouge, Louisiana, plus locations in Florida, Georgia, North Carolina, and Texas)

Eurofins Central Analytical Laboratory (Forsyth, Georgia; New Orleans, Louisiana)

Fort Worth Grain Exchange (Fort Worth, Texas) 817-626-8213

Holmes Laboratory, Inc. (Millersburg, Ohio)

Indiana Animal Disease Diagnostic Laboratory (ADDL) at Purdue University (West Lafayette, Indiana)

Indiana Crop Improvement Association (Lafayette, Indiana)

Kansas Grain Inspection Service (Topeka, Kansas)

Midwest Laboratories (Omaha, Nebraska)

Midsouth Grain Inspection Services (Memphis, Tennessee; Stoneville, Mississippi; Little Rock, Arkansas)

Minnesota Valley Testing Laboratories, Inc. (New Ulm, Minnesota)

NCDA&CS Feed Program (Raleigh, North Carolina)

Quanta Lab (Selma, Texas)

Rock River Laboratory (Watertown, WI Headquarters; Various Locations Nationally and Internationally)

Romer Labs (Union, Missouri)

Trilogy Analytical Laboratory, Inc. (Washington, Missouri)

Waters Agricultural Laboratories, Inc. (Owensboro, Kentucky)

Waypoint Analytical (Leola, Pennsylvania)

Acknowledgments

Authors

Damon Smith, University of Wisconsin-Madison; Tom Allen, Mississippi State University; Martin Chilvers, Michigan State University; Travis Faske, University of Arkansas; Tom Isakeit, Texas A&M University; Daren Mueller, Iowa State University; Trey Price, Louisiana State University AgCenter;  Albert Tenuta, OMAFA; and Kiersten Wise, University of Kentucky.

Reviewers

Daisy Ahumada, North Carolina State University; Alyssa Betts, University of Delaware; Mandy Bish, University of Missouri; Alyssa Collins, Penn State University; Maira Duffeck, Oklahoma State University; Paul Esker, Pennsylvania State University; Dean Malvick, University of Minnesota; Boyd Padgett, LSU AgCenter; Alison Robertson, Iowa State University;  Madalyn Shires, South Dakota State University; and Darcy Telenko, Purdue University.

Sponsors

Funding for this project was provided by the United States Department of Agriculture - National Institute of Food and Agriculture (USDA-NIFA) project Integrated Management Strategies for Aspergillus and Fusarium Ear Rots of Corn. NIFA Award Number: 2013-68004-20359. We also thank the Grain Farmers of Ontario for their support.