Maybe you still have grain stored in bins because you were waiting for the price to go up. You've kept grain this long in the past without issues. This year wasn't like most years. The winter was the fifth warmest in history, or at least since 1930, in Indiana. And it also did not feature a week or so of days in a row where it was cold enough to move a cooling front through the bin with aeration to drop the temperature of the grain to levels that you can usually get to in a more normal winter.
If you have grain in the bin and don't have temperature cables or an in-bin controller on the aeration system, don't just assume everything is alright. Richard Stroshine, Purdue University corn quality specialist, says it's important to be checking on that grain, if you haven't already. He's hearing from any people running into problems who normally store grain successfully into this time of the year or even longer.
One way to tell if you have a problem is to turn the fan on and check odors from the exhaust air. "Be careful, however," Stroshine says. "Breathing air with mold spores can make you sick. Often you develop symptoms similar to having the flu."
Another option is to push a rod into the grain surface inside the bin at various locations. Make sure you lock out electricity to the unloading auger and take other precautions, such as having someone with you outside the bin, before you make these checks.
"Let the rod stay in the grain for at least 15 minutes until it reaches the temperature of the grain," he says. "If you pull the rod out and it's warm, that's an indication of heating below the surface of the grain."
Klein Illeleji, another Purdue University ag and biological engineering Extension specialist, adds that if you begin to smell moldy grain, it's already very late in the molding process. You can assume that at this point, there has already been significant mold development.
If you don't smell a moldy odor and the moisture content of the grain that you check is between 14 and 15%, and the temperature of the grain inside the bin, on average, is within plus or minus 5 degrees of the ambient, or outside air, temperature, it's probably safe. There are no guarantees however. Frequent checking is necessary.
If the temperature is 15.5% and above, and temperatures are at about ambient temperature inside the bin, deterioration is going to occur, Illeleji says confidently. Use a simple probe thermometer and take periodic samples, he suggests.