In mid-May, someone asked Bob Nielsen what to expect in fields where heavy rains and cool weather had set in after mid-to-late-April planting. The Purdue University Extension corn specialist noted that if corn germinated and emerged, it still faced a threat from seedling diseases.

Why? Because seed treatments applied to corn to protect against fungi that cause seedling diseases only last so long, Nielsen says. If it remained cool and wet long enough to slow emergence and growth, the fungi might have an opening to infect plants.

The Corn Watch ’17 field experienced that weather scenario. Dave Nanda walked the field when corn was about knee-high. It didn’t take him long to find plants that were wilting and off-color. He suspected a disease issue.

Nanda is an independent crops consultant based in Indianapolis. He dug up a couple of the infected seedlings and split open the stalks. Sure enough, the inside of the stalk showed signs of seedling infection.

“You could see the tissue beginning to turn brown in the lower part of the stalk,” he says. “The growing point was either dead or dying. That plant won’t be there when you take harvest stand counts.”

INSIDE THE STALK: Here is the inside view of a diseased corn plant. Note the dark area in the lower stalk, which indicates the plant is dying.

Nanda suspects that pythium is the disease causing issues in this case. What he knows for sure is that the culprit is a seedling disease. So Nielsen was right in his prediction, Nanda says. The only question mark is how many plants were affected, and if enough were affected to make a difference by the end of the season.

Possible impact
Based on walking the Corn Watch field and doing stand counts in several locations, what looked like “a plant here and there” turned out to be 3% or more of the stand, Nanda observes. Is 3% plant loss something to worry about?

If the field yields 200-bushel corn, a 3% yield loss would be 6 bushels per acre. Even at $3.50 per bushel, a loss of 6 bushels per acre means $21 less gross revenue per acre.

“The point is that it all adds up,” Nanda says. “If you lose 3% here and 3% there, you wind up with more loss than you might imagine just by walking the field.”

Once seedling blight infects a plant, there is nothing that can be done for that plant this season, Nanda adds. You should file it away in your memory bank so it plays into your decision-making process the next year.

Will the threat of losing even 3% of plants to disease if you plant early and it turns wet keep you from planting early? Perhaps not, and maybe it shouldn’t. Nanda is a firm believer in early planting.

What it might do, however, is help you reconsider planting the wettest field you have when it’s early and the forecast is for a high percentage of rain, perhaps heavy rain. Nanda believes that’s a practical way to use this type of information in decision-making situations.

Seed Genetics-Direct, Washington Court House, Ohio, sponsors Corn Watch ’17.