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Get a Grasp on Greensnap      08/05 10:18

   Why Some Corn Hybrids Are More Brittle Than Others

   As you head into seed selection season, it's a good time to review greensnap 
ratings.

Pamela Smith
Crops Technology Editor

   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/agriculture/web/ag/crops/article/2020/08/20/evaluating-win
d-damaged-corn-check.

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

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

   Follow her on Twitter @PamSmithDTN




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