Dodge Down Corn

ST. LOUIS (DTN) -- It's time to rough your cornfields up a little. Conditions are right in many fields for stalk rot this year. A firm push to the plant can alert you in time to minimize harvest losses, said University of Nebraska plant pathologist Tamra Jackson-Ziems.

Plants with the symptoms of stalk rot -- hollow or rotting, weakened stalks -- won't withstand the bullying, she pointed out. "You're basically simulating what wind does, and if you have stalk rot, the plants will not snap back up," she explained. "They'll fall over or stay bent, and you have a potential problem."

The same fungi that encourage stalk rot can also produce ear rots like Diplodia, Gibberella, and Fusarium, Jackson-Ziems noted.

A GOOD YEAR FOR BAD STALKS

Plant pathologists from Indiana, Iowa, Missouri, Minnesota and Nebraska are urging growers to scout now for stalk rots because many Midwestern fields saw the right combination of conditions to produce them this year.

A wet start to the growing season, such as much of the Midwest had, can encourage the early growth and infection of stalk rot pathogens, Jackson-Ziems said. Damaging events later in the season such as hail can exacerbate the problem.

"The pathogens that cause it are pretty much everywhere, and they're very opportunistic; they're sitting around waiting to infect the plant," Jackson-Ziems said. "Leaf wounds are just an open door for the pathogen to infect the plant."

Leaf diseases like Northern Corn Leaf Blight and Gray Leaf Spot were reported in many Midwestern corn fields this summer, and they also play a role in stalk rot.

"The plant is genetically programmed to fill grain at all costs, so it's going to continue to put carbohydrates into those kernels," Jackson-Ziems said. To feed the growing kernels, the plant turns to its "factories" -- the corn's leaves. So when a disease or hail event destroys the leaves, the plant is forced to do a quick and grisly re-routing. "It cannibalizes its own stalk tissue," Jackson-Ziems explained.

Healthy plants with especially high-yielding potential can also be vulnerable to this stalk-sucking phenomenon, noted Iowa State plant pathologist Alison Robertson.

The favorable growing conditions this summer delivered cornfields brimming with kernels, Robertson explained to growers in a university Crop News publication. "The corn plant will do everything to finish off the grain at the expense of using carbohydrates stored in the stalk, consequently leading to increased risk of stalk rots," she concluded.

To evaluate your field for this problem, plant pathologists recommend pushing at least 100 corn plants in a field to test their strength. Alternatively, you can pinch the lower stalk, between nodes, to feel for soft or hollow stems. If more than 10% of the tested stalks prove weak, move that field to the top of your harvesting list.

"Some people say you should even harvest them a little earlier, even if it means you have pay to dry the grain down," Jackson-Ziems added. "Because the alternative is if we have a lot of wind this fall, these plants are going to fall over, which makes harvest a nightmare, and farmers will leave yield on the ground."

In western Ohio, corn and hog farmer Jeff Wuebker is already eyeing one of his varieties with just this concern in mind. The field was hit hard by leaf diseases all summer and an early September windstorm knocked the tops of the corn plants off. "I'll prioritize getting those out of the field because they're not going to be in shape for the long haul," the Versailles, Ohio, farmer told DTN. "It's one that I was hoping to harvest about two to three weeks from now, but I guess if I have to, I can harvest it sooner."

Farmers can look for standability ratings on corn hybrids as they choose hybrids for 2015. However, stalk rot is so dependent on yearly agronomic conditions, prioritizing that trait might not always pay off, Jackson-Ziems added.

For more information on the different kinds of stalk rot, see this UNL publication: http://goo.gl/….

KEEP AN EYE ON YOUR EARS

Ear molds favored by wet growing conditions are also likely to plague some growers this fall, plant pathologists in several Midwestern states have noted.

Look for green corn plants with prematurely dry or yellowing corn husks, Jackson-Ziems said. Pulling back the husks might reveal the distinctive white-gray mold of Diplodia ear rot near the base or the pink-tinged mold near the tip of the ear that indicates Gibberella ear rot.

Corn molds produce mycotoxins, which can be harmful to both humans and livestock at certain concentrations. Some mycotoxins are more harmful than others, and university plant diagnostic clinics can identify any mold you find and alert you to the mycotoxins it is most likely to produce, Jackson-Ziems said.

For more information on the identification of various ear molds and the mycotoxins they can produce, see this UNL publication: http://goo.gl/….

Growers who find ear mold in their fields should try to harvest it as soon as possible, dry it down to less than 15% moisture and cool it to stop fungal growth, Jackson-Ziems said.

Moldy grain should also be segregated, if possible, Wuebker noted. Since the Ohio farmer feeds up to 80% of his corn to his hogs, scouting and segregating moldy corn is an essential part of his operation.

"Normally I'll walk all my hybrids every year, because if I see some ear rot, I will sort that corn out, because I don't want anything with mold at the hog operation," he said.

Picking corn hybrids with good disease resistance to ear molds is a must for his operation, Wuebker added.

After a particularly bad infestation, growers should also consider crop rotation, Robertson added.

"Since stalk and ear rot pathogens survive in infested residue, rotation to a nonhost crop such as soybean may help reduce inoculum," she explained.

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

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

(PS/AG)

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