If you stopped to watch someone combining this fall in a field stressed by drought, you may have seen plenty of dust following the combine. And if you went for a ride in the combine, odds are your hand was covered with blackish grime by the time you got to the top of the ladder. Paper towels and window cleaner for the combine windshield and wet wipes for hands to remove the sooty dust were standard equipment for some operators this fall.
The situation was worse on naturally droughty soils, like those underlain by gravel and not irrigated. But it wasn’t limited to those fields. Dave Nanda says some of the blackish material was likely anthracnose stalk rot. It produces black material that begins as dots on the outside of the stalk, and can cover the lower part of the stalk if left in the field long enough. The more stressed the corn, the greater likelihood that anthracnose will cover lower stalks.
Nanda, an independent crops consultant, also found stalk rot in corn growing on silty clay loam soils that are naturally poorly drained. Dry weather in August likely gave the disease a foothold.
“Hybrids vary in susceptibility to various diseases,” Nanda says. “In the field where I found anthracnose on those poorly drained soils, it was much worse in one hybrid than another.”
He went down the rows, pushing stalks. “If stalks don’t snap back, they fail the push test,” he says. “It’s usually because stalk rot has invaded. When I examined many of those stalks, I found the blackish specks, which are the trademark of anthracnose, on the outside. I also found signs that the pith was beginning to deteriorate on the inside when I split stalks open.”
Whether or not stalk rot hurts yield depends upon when it comes into the field and how severe it is, Nanda says. The more normal threat is lodging should a storm occur.
He suggests working with your seeds sales representative to make sure you know the resistance each hybrid has to various diseases. Susceptibility to stalk rot may not prevent you from planting a high-yielding hybrid, but it may help you decide where to place it, and it also alerts you to watch that hybrid and consider those plants for early harvest the next fall.
Check out the slideshow to see some examples of stalk rot.