What's Knocking Down Your Yields?

October 11, 2016 03:00 PM
Down Corn

Corn that once stood more than 8’ tall now lies flat on the ground, appearing almost as if a tornado tore through the field. A hot, wet summer meant this corn developed devastating stalk rots, which, paired with strong winds, knocked down this farmer’s corn and his livelihood for the year.

“When you think about stalk rots, they are opportunistic, so anything that causes stress amplifies the opportunity for stalk rot,” says Andrew Friskop, North Dakota State University Extension cereal crop plant pathologist. “We’ll see stalk rots every year. Some years are just more severe. I think the weather has been a big culprit.”

Stalk rots are widespread this year, so it is important that as you scout your fields, you take good notes and identify areas with the highest risk next year.

“I typically prioritize fields over 20%, but it becomes a problem when we’re looking at 60% to 80% of plants that fail the push test,” Friskop explains. “One of my big principles is scouting, because just because one field has it doesn’t mean that all fields have it.”

When you’re scouting, look for a few general symptoms first. With stalk rot, you will typically see wilting, premature dry down, lodging and plants that fail the push or pinch test. Check about 100 plants, and stay away from the end rows to gather a fair estimate of field conditions.

Once you know the situation in a field, you can move forward.

"If you have more than 10% to 20% (of stalks that fail the push or pinch test), you’ll want to get in and harvest as soon as possible,” Friskop says. “Next year, consider these pathogens in your hybrid selection. Some (hybrids) have stalk rot or stalk strength ratings, so look for these traits.”

You'll also want to take extra care with that future crop. "Try to reduce stress .... with proper population, fertilizer, insect control and decreased foliar diseases," he says. 

Scouting for Stalk Rot: Things to Notice

If you notice stalk rot in your fields, you'll want to pay close attention. Depending on conditions, the stalk rot may be caused by one or multiple pathogens in that field. Here are some common stalk rots so you can identify them and if needed, appropriately adjust your plans for harvest this year and next year's planting season. 


“Fusarium species always have some type of color. Look for white to pink on nodes,” Friskop says. If you see white to pink fluffy growth on outer nodes and deterioration of the inner stalk that turns a tan to brownish color, you could have Fusarium stalk rot. Insect injury and other plant stress increase your risk for this pathogen. It infects the plant after pollination during warm, dry weather. Be sure to note this pathogen because it overwinters in corn residue. That means your fields could be susceptible to this disease in following years. 



Anthracnose overwinters in corn residue and can infect the stalk, leaves and ears. If you see shiny black blotches, it’s a good indication you have Anthracnose stalk rot. The pith can be black in color, but sometimes it will appear to be healthy. In some cases, the internodes will be rotten and easy to crush in the pinch test. Anthracnose enters the plant after pollination, and symptoms appear just before the plant reaches maturity.



Diplodia infects the stalk through the roots, crown and lower stem. Plant injury from birds and insects can encourage this pathogen, according to the University of Nebraska. Look for dark brown or black spots on the stalk that look very similar to pepper grains. They will feel rough to the touch. Like Fusarium, Diplodia overwinters in crop residue, so if you've seen it in your fields, consider that in your seed selection in the future.


Charcoal Rot

Charcoal rot infects corn, sorghum, alfalfa and especially soybeans. The rot turns the pith a dark gray or black color and can cause plant death. It infects the plant after pollination and favors hot and dry weather where crops have seen insect damage. Look for charcoal rot to stay in fields year after year in crop residue.



Gibberella stalk rot deteriorates the inner stalk after pollination. Warm, wet weather helps push this pathogen to a more devastating level. Look for  a deterioration of the inner stalk that leaves only reddish vascular bundles and small black specks on the stalk surface. Plant stress and insect injury make the crop more susceptible to Gibberella.


Ultimately, stalk rot can put a farmer between a rock and a hard place. If you wait for corn to dry in the field, you may lose yield from ear rots or down corn, but if you harvest early, you may be hit with discounts at the elevator for moisture. Weigh your options and choose what is best for your farm and unique situation.

Have you seen any stalk rots in your fields this year? Which ones? Let us know in the comments. 

Better yet, take AgWeb’s own quiz – Down Corn Dilemma: What Kind of Rot Have You Got?It will help diagnose which of five common stalk rots could be afflicting your farm. When you take the quiz, you’ll be automatically entered to win one of four prize packs that include Farm Journal Corn College gear and a Season 1 DVD of Corn College TV.

Click here to get started.

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Spell Check

Mark C. Daggy
Humboldt, IA
9/22/2015 07:58 AM

  Much like human health, what the corn has available to fight disease is very important. We began to test our soils for not only NPK nine years ago, but considered what micro-nutrients were being hauled off with each bushel. Testing the soils for availability for micro-nutrients was also done with the guidance of Michael McNeill, who is experienced in this area. Adding 1 or 2 micro-nutrients per year, 1st dosing the depleted areas and now spreading a uniform amount on all acres for maintenance, our lodging disappeared. Too many tenant farmers have been mining the soils and are now suffering the consequence of spending their profits on machinery and toys when they should have invested in the soils. We rented the farms for 12 years and the tenant mined our farms. The organic matter should have been 5% to 6% in our area and was down to 2.3% and thye tenant did not lime for 12 years and my pH were as low as 5.1 to 5.3. My P was 3 ppm in places. Over the past 9 years we have fixed the farms and will never allow a tenant on the land again. We have a ways to go and with Michael McNeill's help are getting great soils.

Adam Switzer
Bettendorf, IA
9/22/2015 08:05 AM

  All the more reason for a VT application of Headline AMP! The stalk integrity variation between treated and untreated is AMAZING this year in addition to the yield protection!


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