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Get a Grasp on Greensnap
By Pamela Smith
Friday, August 5, 2022 10:18AM CDT

DECATUR, Ill. (DTN) -- Oh snap! Another storm tore through Kevin Harsch's Nebraska cornfields in late July -- breaking off an estimated 10% of the stalks. Adding insult to injury, the field had already been replanted due to an earlier wind and hail event.

Several factors influence the occurrence and severity of greensnap -- the condition where strong winds break stalks at the nodes, typically below the primary ear. The severity of the storm, management practices and hybrid differences can all play a role. Even the new short-statured corn hybrids being tested can take a hit if the winds howl hard enough.

But there are some things farmers can do to battle back. While Harsch can't stitch his battered stalks back together, he can and does take note of which hybrids weathered the storms to guide seed selection.

"Greensnap is more of a second-tier selection factor for us," he said. "If it is a racehorse high-yield number with everything else good, we may roll with it. But if it has any other potential problem, then that will put us over the edge to say no."

In the case of the most recent event, he didn't have much of an option. It was a late replant, and the seed was what was available at the time.

Hybrids vary in their genetic vulnerability to greensnap, agreed Lance Tarochione, Bayer technical agronomist. "It's like any physical characteristic -- just as some people have blonde hair and some have black hair -- some hybrids differ in their ability to handle wind. No hybrid is completely immune, but some hold up better than others just by virtue of their cellular structure," Tarochione said.

HYBRID RATINGS HELP

To give farmers a heads up and help guide seed selection, most seed companies rate hybrids for greensnap. Since storms can't be assured or called up on command, researchers often use artificial wind generation to try to replicate windy conditions. At Bayer, helicopters are used to put hybrids to the wind test, Tarochione said.

At Bayer, hybrids are rated for greensnap at tassel. Ratings run on a scale of 1 to 9, with products rated from 1 to 3 considered the best choice in areas prone to greensnap. Tarochione said hybrids rated over 6 don't make the seed catalog.

"Some hybrids are brittle enough that we simply don't sell them. Others are such that we may not recommend they be planted if the area (such as the Western Corn Belt) has a history of wind that corresponds to greensnap events," Tarochione noted. "Other growers may try a more susceptible hybrid on some acres but reduce the risk by carrying good wind insurance.

"Greensnap happens somewhere every year. The reality is that if you are choosing a hybrid that is susceptible to greensnap, it had better be lovable in some other way," he added.

COMPLICATING CONDITIONS

When winds blew through southern and south-central Illinois in June 2022, it snapped young corn that was still in vegetative stages. Technically, greensnap is defined as the stalk breaking off below the ear, Tarochione observed. Breakage at early growth stages is sometimes referred to as brittle snap.

"It's the same issue. What I see is that every individual hybrid has a growth stage at which it is the most brittle and that stage is different for every hybrid," he said.

Environmental conditions are a big part of the greensnap picture. Late-planted corn that is growing fast like some has in 2022 may be more susceptible. Often, the faster corn is growing, the more brittle the stalks become.

Temperature and time of day can make a difference too. Corn plants are more rigid during cool temperatures. During heat, they may become limp and more able to bend when hard winds hit.

"The worst time to get a windstorm is early in the morning," Tarochione said. "Overnight, the plant refreshes itself and fills back up with water. Plant cells regain their turgor pressure.

"In the afternoon, those plants may be more wilted, and drought stressed and almost rubbery. I'll take an afternoon wind event over a morning event every time," he said.

Row orientation can also make a difference in how stalks catch wind gusts. Higher populations tend to be more brittle because stalks are often smaller and less sturdy. Wet soil conditions may mean more of the crop lays over, rather than snaps, he added.

High-level management can make cornstalks more susceptible to greensnap. Stalk girth tends to decrease as plant populations increase.

"The better job you do growing corn, the more brittle you make it," Tarochione said. "That's not a reason to short-change the crop. It's just something to understand."

Keep in mind that growth regulator herbicides, such as 2,4-D and dicamba, are auxins that can promote rapid growth and stalk brittleness. Labels for those herbicides can vary regarding maximum corn height, depending on the product. Additional label restrictions exist when soybean is nearby, noted University of Illinois Extension Weed Science Specialist Aaron Hager.

SHORT CORN CONSIDERATIONS

The short-statured corn varieties currently working their way through Bayer's pipeline show promise for being better able to handle wind events, Tarochione acknowledged. Compared to traditional hybrids, short-statured plants stand about 25% shorter with a lower ear set at least 24 inches above the soil surface.

"I would say that bad things start to happen to normal corn at about 40- to 45-mile-per-hour winds. That's where snappy hybrids start to snap," Tarochione said.

"By comparison, short corn is more likely to endure 75- to 80-mile-per-hour range," he said. "You can't make corn immune to greensnap. If winds blow hard enough, it is going to break. But I think we move that threshold higher with shorter hybrids." Short-statured corn hybrids will also receive greensnap ratings as they reach commercialization, Tarochione said.

How much corn snaps during a wind event is hard to predict and depends on so many factors, Tarochione added. The worst storm damage he's witnessed has been a 90% snap.

"As farmers head into seed selection, we recommend watching greensnap ratings and spreading risk by choosing multiple hybrids. If a hybrid is selected with a higher greensnap rating and the region prone to erratic weather, crop insurance is advised," Tarochione added.

For a look at what happened to corn after the 2020 derecho: https://www.dtnpf.com/….

For more information on greensnap: https://crops.extension.iastate.edu/….

Pamela Smith can be reached at pamela.smith@dtn.com

Follow her on Twitter @PamSmithDTN


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