2. CRAZY TOP AND BACTERIAL ROTS

Crazy Top is an easy disease to spot, as its name implies. Corn tassels and upper leaves grow wildly and roll and twist into giant Medusa-like structures. Corn ears can also get caught up in the mess.

The downy mildew fungus that causes Crazy Top thrives in flooded fields, Jackson-Ziems said.

"The disease has swimming spores, so it has to have those saturated soils to infect," she explained. "It will infect early on, but you don't see the symptoms until later when the plant puts on tassels and an ear."

Bacterial infections can also rot a plant later in the season, most commonly within the stalk. Silt or soil sitting on top of previously flooded plants can help introduce these pathogens that enter through the whorl or plant wounds.

"It causes the whole plant to die and it stinks really badly," Jackson-Ziems said. "Often you'll smell it before you see it."

3. RESTRICTED ROOTS AND SMALLER PLANTS

Corn roots that were flooded early can become restricted for a variety of reasons, from heavily compacted soils to root rots and stunted growth in saturated, oxygen-starved soils.

Nielsen says compaction will be a major cause of this problem in Indiana this year.

"Once the rain started in late April, I don't think there were many days when the soil was fit for any tillage or fieldwork," he said.

Plants with restricted root systems will be at a greater risk for lodging later in the season. They're also likely to be poor performers throughout the season.

"If it turns dry, they'll be the first to suffer, and if we keep getting too much rain, they'll be the first to suffer," Nielsen said. "They're just not able to avoid effects of severe weather easily."

Without a good root system, the plants will be smaller and will struggle to produce ears and fill them, he added. Kernel abortion can occur and reduce yield quickly.

Even if ears do fill well, the smaller plant may have to cannibalize itself during grainfill, leading to hollowed stalks prone to lodging.

4. NUTRIENT DEFICIENCIES

"With rains throughout May, there are a lot of opportunities for loss of soil nitrate by leaching in coarser, sandier soils or denitrification (nitrogen lost via gases) in heavier soils," Nielsen said.

The same holds true for sulfur, which is also prone to leaching from soils in sulfate form, he added.

Sometimes nitrogen and sulfur just move lower in the soil profile and are available to deeper roots later in the season. In other cases, they completely leave the soil profile and a true deficiency results.

Sulfur-deficient plants will look yellow, with striping of the leaves.

Nitrogen-deficient plants will appear yellow and stunted. Yellowed or dying (firing) leaves lower in the canopy are a good sign of nitrogen loss, Nielsen said. This occurs when plants remobilize nitrogen from the lower stalk and leaves up to newer leaves.

"It's a crude indicator but an indicator nonetheless," Nielsen said. If you spy this phenomenon close to tasseling time, it may be worthwhile to consider a rescue nitrogen application with a high clearance rig, he added.

For more help on testing for nitrogen loss, see this Iowa State guide: http://bit.ly/….

For more details on all the late-season effects of ponding or saturated corn fields, see an article from Nielsen here: http://bit.ly/….

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

(PS/AG)

© Copyright 2017 DTN/The Progressive Farmer. All rights reserved.