The combine was black when a farmer pulled out of the field last week. He had just finished running corn. Located in the Lafayette area that received some rains when others didn't, the field made 120 bushels per acre. However, both the tenant and landowner usually expect 200 bushels per acre or more on that ground. Heat hurt the pollination.
The black color and black dust rolling around the combine while harvesting was from mold spores, knocked into the air as the combine disturbed molds growing on stalks and perhaps ears. Molds in field are beginning to be reported at an increasing rate.
The eminent worry is that Aspergillus fungus will invade ears of stress-damaged corn and produce aflatoxin. This toxin is very damaging to livestock and especially dairy. Very low tolerances are allowed for corn containing any aflatoxin, and especially for corn headed to dairy farms or into the human food chain.
The good news is that every mold that grows in the field is not Aspergillus. Some other molds can produce mycotoxins, but those aren't typically as problematic as aflatoxin. However, they may still cause pigs to go off feed, for example, if used to make hog feed.
Betsy Bower, an agronomist with Ceres Solutions, Terre Haute, and a member of the Indiana Certified Crop Advisers, says that if you still have corn in the field, you ought to check for signs of mold, especially moldy ears, by pulling back the husks. Aspergillus is distinctive because it has an olive green color, often starting at the base of the ear, notes Chuck Woloshuk, a Purdue University plant pathologist.
However, don't rely on what you think the mold is, Bower says. First send samples to the Purdue plant diagnostic lab in West Lafayette. They will be able to tell you which molds you have. She notes that some of the ears she has sent in from west-central Indiana have actually contained two molds on the same ear.