Take a load of corn to the elevator and the normal procedure is to have the corn probed, often by an automatic probe, and a sample checked for moisture and graded for possible damage. If it's new corn coming out of the field, the person receiving the grain may check for mechanical damage or foreign matter. This year, he may also do an additional test. He may take a sample of the grain from the load and put it under a black light.
It's not a magic trick, assures Charles Woloshuk and Kiersten Wise, two Purdue University plant disease Extension Specialists. Instead, it's one of the first ways to test to see if Aspergillus fungus is present in the sample. It's an ear rot that typically appears in years and in fields hard hit by stress, especially drought stress. Because it can produce aflatoxin, and there are federal limits on how much aflatoxin is allowed in corn, elevators will be particularly careful because they don't want to accept and intermingle corn that might contain the fungus with other corn at the facility.
What do they see when they put the corn under the light and it indeed has the fungus present on some of the kernels or kernel fragments? Often the kernels are broken before being placed under the black light for testing. If the mold is present, a particular glowing color will appear. If it's not, the sample won't glow.
Suppose it does flunk the black light test. Does that mean that the corn has aflatoxin? "No, it doesn't," Woloshuk says. "The test just indicates that the fungus that produces it is present in the corn. However, since there's a good chance that if the fungus is there is also aflatoxin, the elevator may want to do further testing before accepting the corn to determine if in fact it contains aflatoxin. "
The elevator may refuse to accept the corn if it contains the fungus. If aflatoxin levels are high enough, they can cause detrimental reactions in different types of livestock if used for feed. It can even cause cancer in chickens.
The good news is that so far, no reports of aspergillus either in the field or uncovered in a black light test at an elevator have been reported to either of the disease specialists. However, that doesn't mean that the fungus isn't out there, or might not yet develop. So don't be surprised if your elevator insists on placing a sample under the black light.