Aflatoxin on Corn:
Aflatoxin is on the “radar” of corn producers in Kentucky and elsewhere. Reports indicate that the incidence of contamination appears to be low thus far, although occasional rejections from buyers always get the attention of producers. In addition to aflatoxin, fumonisin may show up in occasional corn lots, though I have heard of no reports yet.
Scouting non-harvested corn fields for Aspergillus ear rot and Fusarium ear rot is advisable. Scouting information, including numerous photos, is available at: http://www.ca.uky.edu/agcollege/plantpathology/extension/KPN%20Site%20Fi.... Scouting helps flag fields with potential problems. Knowing that the field has Aspergillus ear rot may help a producer decide whether or not to test the grain for aflatoxin, and/or whether to market/use the crop as feed for sensitive animals (see ID-59, at http://www.ca.uky.edu/agc/pubs/id/id59/id59.pdf, for information on animal sensitivities).
Some producers have asked whether they should be testing their corn for mycotoxins. Available testing kits (such as http://www.gipsa.usda.gov/fgis/tech-servsup/metheqp/testkits.pdf) are good tools. However, I don’t think widespread testing by producers is necessary or advisable. One reason is simply the expense of testing. However, a much more important reason is variation in sampling. In a corn field with aflatoxin contamination, the results of testing are really driven primarily by the high level of sampling variability that is natural when testing at the parts-per-billion level. What this means is that, even if a grower samples the corn with the recommended sampling procedure (which is very difficult in standing corn), they will get 10 different results from 10 well-collected samples. This sampling variability is inherent in sampling grain at the parts-per-billion level. This extreme variability isn’t anything growers can avoid.
Testing would probably make the most sense for sensitive end-uses, like dairy cows and chickens. Scouting for ear rots is free, and it can help flag potentially problematic fields. Scouting isn’t foolproof, since grain can become contaminated with aflatoxin without showing rot, but generally it is helpful to scout. Another issue regarding aflatoxin is this: Consider all harvested corn stored as grain to be “inoculated” with Aspergillus flavus, the fungus that produces aflatoxin. I don’t mean that the corn is contaminated with the toxin itself. What I am saying is that the microscopic spores of A. flavus could be there on the kernels, waiting for the chance to grow on the harvested grain. It is always important to store grain properly, but maybe just a little more so this year. It is very possible for clean-looking corn to go into the bin with no aflatoxin, and to emerge from the bin with aflatoxin. It is very important to pay attention to sound storage practices, in order to keep that from happening. See the article by Sam McNeill in http://www.ca.uky.edu/agcollege/plantpathology/extension/KPN%20Site%20Fi....