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Battling brittlesnap

Rural residents repeat the phrase “he's a goooood farmer” with the same reverence reserved for the papacy and royalty.

You know the type. He or she picks the best corn hybrids and maximizes yield potential with timely planting, spraying and fertilizing. During mid-July, the corn exhibits a deep green hue as neighbors oooh and ahhh at its growth.

Then it happens. A wicked windstorm snaps these stratospheric stalks in two. Neighboring corn that hasn't been as diligently cared for continues to grow, while its sliced counterparts wither and die.

So much for being a “goooood farmer.” This phenomenon — called brittlesnap — scourges the strong and spares the weak.

“It's so insulting,” says Dan Berning, Pioneer Hi-Bred International agronomy manager for Nebraska. “A grower who does everything right tends to have the fields that are the most susceptible. Fields that are under stress tend not to experience the same severity of brittlesnap that the better fields have. That's what makes it so emotional. It's so tough to go out and look at it.”

History of loss. Plant breeders and agronomists still aren't exactly sure why brittlesnap occurs. They do know it is related to plant physiology and environmental conditions.

Brittlesnap normally occurs at the knee-high to tassel stage. “In older literature, people call it the ‘grand phase of growth,’” says LeRoy Svec, corn product characterization and commercialization manager at Pioneer Hi-Bred International's York, NE, research facility. During this time, plants grow so rapidly that they have not had the chance to add lignin — a stiffening substance — into their internodes.

Brittlesnap isn't new. “I've looked at old Nebraska literature written from the early '30s into the '50s, and it said hybrids have the potential to break if the wind is severe when rapid elongation occurs,” Svec says.

However, the problem appears to have worsened as industry developed higher-yielding hybrids. “There are lines across the broad family of corn plants that grow rapidly and have a high yield potential,” Svec adds.

Changing weather patterns during the 1990s also worsened brittlesnap outbreaks. High-speed windstorms — particularly in the Great Plains — frequently occurred.

In 1993, many Nebraska farmers endured a “one-in-500-year storm” in which some fields suffered up to 100% stalk breakage.

That year's adverse early spring weather compounded the damage. Because many farmers could not timely plant their corn, they shifted to a handful of earlier-maturing hybrids that were susceptible to brittlesnap. Because of the large number of acres planted to these hybrids, losses were staggering.

“We had $200 million in damage in Nebraska that year,” says Roger Elmore, a University of Nebraska agronomist. A smaller but significant Nebraska windstorm again triggered brittlesnap losses in 1994.

Such losses are less frequent in the eastern Corn Belt. However, winds periodically key brittlesnap breakage in a specific area, says Emerson Nafziger, University of Illinois extension agronomist. “There was a case in west-central Illinois in 1998 in which high winds broke rapidly growing corn,” he says.

It's the hybrid. Agronomists have learned that the type of hybrids you buy can key brittlesnap outbreaks.

“All corn hybrids can snap, but some hybrids are more sensitive to brittlesnap due to the growth rate pattern that they exhibit,” says Jim Bueltel, area agronomist with Garst Seeds, Carrol, IA. “Hybrids with a little slower growth rate and with cells that have not expanded tend not to snap as much as those hybrids that have cells that are growing rapidly and stretched past their limit. Ideal corn-growing weather also makes brittlesnap more prevalent.”

What makes brittlesnap difficult to battle is that it occurs at random. “There isn't any place in the state that we can point to and say it's most likely to happen,” says Dale Hicks, University of Minnesota extension agronomist.

Equally maddening is that breakage randomly occurs within a field. Windstorms have “microbursts” of wind that snap three to five plants within a row. Then it spares several yards of plants. “Even if a field is planted to the same hybrid, you may have 20% damage in some areas and not any in other areas,” Svec says.

Farmers can protect themselves somewhat by buying hybrids with brittlesnap tolerance. Many companies assign brittlesnap ratings. For example, Pioneer ranks its hybrids on a 1 to 9 brittlesnap basis, with 1 being highly susceptible and 9 ranking highly tolerant.

Fortunately, ratings have no correlation with yield. “Just because you are high in brittlesnap resistance doesn't mean that you'll be low in yield potential,” Svec says.

Even though brittlesnap can devastate fields, Hicks doesn't believe farmers should select hybrids mainly based upon brittlesnap tolerance.

“The most important thing that producers still need to do is choose good-yielding hybrids,” Hicks says. “If they know that the hybrid has the propensity to snap and have had past problems with brittlesnap, only then should they consider it. If they haven't had the problem, I wouldn't look at it.”

“The most important thing that producers still need to do is choose good-yielding hybrids.”
Dale Hicks, extension agronomist University of Minnesota

Seed company brittlesnap ratings are not foolproof. “They will tell you that based on history and crop genetics that it should be resistant against brittlesnap, but it's not for sure,” Elmore says.

Companies are improving brittlesnap screening. Pioneer uses a mechanical snapper to induce brittlesnap pressure across numerous locations, years and hybrid growth stages. The snapper simulates the stress of a wind-related event by placing pressure on the ear node and the three nodes below it. These areas are the most sensitive to breakage at the pre-tassel stage.

Pioneer researchers are also examining where in the growth cycle hybrids are most susceptible to breakage. In 2000, studies verified that the most sensitive time for all corn hybrids is a few days before silking. With this knowledge, researchers can test experimental hybrids during that time to accurately evaluate a hybrid's susceptibility to brittlesnap.

“I don't know if we'll ever eliminate brittlesnap, but we are trying to reduce the severity when it does happen,” Berning says. “We also are trying to reduce the time frame in which hybrids are susceptible to it.”

Other strategies. Here are some other ways to reduce the incidence of brittlesnap.

Apply growth-regulator herbicides early. Because they tend to increase growth rates, growth-regulator herbicides like 2,4-D and dicamba have been linked to brittlesnap. “They've always been associated with increased brittleness because they do affect the rate of cell enlargement,” Nafziger explains.

When growth regulators do trigger brittlesnap, applications made to taller corn often are the culprit, says Wayne Fithian, agronomy systems manager for The J.C. Robinson Seed Co./Golden Harvest. “If you apply them early in the season to smaller corn, you're less likely to have a problem with brittlesnap later on,” Fithian says.

A cousin of brittlesnap, greensnap, occurs during the six- to eight-leaf phase, says Steve Sodeman, a Trimont, MN, crop consultant. He advises clients to back off label rates during this time. He tells them that instead of spraying corn with a full pint of dicamba, they should cut the rate in half to avoid early-season damage.

Plant a mix of hybrids. “That way, you won't have a high percentage of acreage tied up in one hybrid, which happened to Nebraska growers in 1993,” Svec says.

Farmers who plant just one or a handful of hybrids are setting themselves up for disaster, Sodeman says. “That's lousy risk management,” he states. “You should not plant the same variety on more than 10% of your acres.”

One of Sodeman's clients, Doug Scholl of Trimont, MN, benefits by planting more hybrids.

“We got hit hard in 1999, when one field had 50% damage,” Scholl says. “Before that, I had severe losses in 1995. One hybrid that I planted across 30% of my acres really got hurt. I took about a 30 to 40% loss across 30% of our acres. Back then, we only planted two or three hybrids. We plant nine hybrids now. It's a pain in the tail when we're planting, but greensnap's no fun. It got our attention in a hurry.”

Spread out planting of hybrids in susceptible areas. “We see a difference in the window of susceptibility with different hybrids,” Svec says. “You can plant the same hybrid five days apart, have a wind during a crucial time, and one hybrid will go down and the other one will stand.”

He adds that staggering planting dates may not be realistic, because farmers need to weigh brittlesnap potential against yield losses caused by planting delays. But in brittlesnap-prone areas, spreading out planting dates can help ensure that all fields are not in the same stage of growth in late June and July.

Plant both east-west and north-south rows. “In most cases, when a wind comes through, it seriously impacts east-west rows, but not north-south rows, and vice versa,” Elmore says. Planting in both directions ensures that some of your crop will survive a brittlesnap outbreak.

Apply fertilizer over a broader application window. Applying a high percentage of nitrogen at sidedressing creates rapid growth, which can help trigger greensnap. “You'll see less rapid growth if you spoonfeed nitrogen throughout the season,” Berning says.

However, Berning says this must be weighed against the expense of changing nitrogen application equipment.

Replant if damage occurs early. After a late June 1998 storm damaged a few Illinois fields, a few farmers replanted. “As the year turned out, it was a good decision. We normally wouldn't give corn planted that late much of a chance to produce respectable yields,” Nafziger says.

Plant different maturities. “By planting different maturities, you won't have all of your crop in the same stage of growth when it's susceptible to brittlesnap,” says Don Bockelman, a Monsanto corn breeder.

Take out brittlesnap insurance. That's what Doug Scholl did in 2000. Although brittlesnap didn't occur last year, the protection gave him peace of mind.

The insurance is available as an option to crop/hail insurance. In Scholl's county, the premium averages between $0.50 and $0.70 for every $100 worth of coverage.

Plant crops other than corn. The 1993 and 1994 Nebraska storms did not damage soybeans or grain sorghum, Elmore says.

Plant windbreaks. University of Nebraska researchers found that wind speeds within corn canopies sheltered by windbreaks in 1993 were generally less than 20 mph with no stalk breakage. Meanwhile, wind speeds exceeded 40 mph and stalk breakage was considerable in exposed areas.

Brittlesnap control strategies

Avoid brittlesnap-sensitive hybrids.

Apply growth-regulator herbicides early.

Plant a mix of hybrids.

Spread out planting of hybrids in susceptible areas.

Plant both east-west and north-south rows.

Apply fertilizer over a broader application window.

Replant if damage occurs early.

Plant different maturities.

Take out brittlesnap insurance.

Plant crops other than corn.

Plant windbreaks.

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