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Even with engineered corn, pests can rob yields

Dec. 13, 2012 | 0 comments

As cost of growing an acre of corn rises, farmers should consider new pest controls

Farmers are increasingly getting used to planting corn varieties that are engineered to resist insects, but nothing in nature stands still and many fields in the Midwest are starting to see increasing insect pressure that can cause yield depression before the plant has a chance to defend itself.

During a session sponsored by Landmark Services Co-op last week at Poynette, agronomy and seed specialists talked about "what worked in 2012" and what farmers need to be on the lookout for next year.

Larry Fiene, with Winfield Solutions, a Land O Lakes company, said corn is a crop that can tolerate some insect damage when it has grown, but it is very sensitive to insect damage when it's young.

Last year was the biggest corn replanting year in history, said Fiene, who covers Wisconsin and northern Illinois for his company. The mild winter of 2011-2012 protected insects, which were then able to survive and live to damage early-planted corn crops.

"In many parts of Wisconsin there were no below-zero days last winter."

Another year with high over-wintering populations of insects will mean that farmers have to find new ways to protect their crops from wireworms, seed corn beetles, seed corn maggots and other insects. "These problems tend to be worse in no-till fields."

Another place that finds high insect pressure is land that is coming out of the Conservation Reserve Program (CRP.) According to Fiene 60,000 acres have come out of CRP in the last four years.

That ground, he said, has the worst insect pressure as does land coming out of pasture or sod.

Before corn plants were engineered to kill worms, U.S. farmers used 35 million pounds of corn rootworm insecticide, which helped the corn emerge and start growing.

Insect pressure is less likely today if soils are dry, the ground is conventionally tilled, if there is a history of low insect population, very little manure application, a good crop rotation and a previous broadleaf crop.

Those fields likely to have dangerous insect populations are those that have moist soil, no-till practices, a higher history of insect pressure, more residue because that provides and insulation blanket to protect insects through the winter and corn after corn.

The Western corn rootworm is an insect that damages the tip of the corn plant's root, the portal through which 70 percent of the water and nutrients get into the plant.

When those rootworms damage the tips of the roots early in the life of the corn crop it will impair the plant's development. The corn plant must also rebuild the roots that have been damaged.

"If they're using stored carbohydrates to rebuild their roots they won't have it later to fill ears with."

Feine's message to farmers is this: as you see these things moving toward us, let's be ready.

There are a variety of corn rootworms. The Northern corn rootworm isn't as sturdy a pest as the Western corn rootworm. "They're more aggressive. They're Western," he said. "They're gunslingers."

These gunslingers lay more eggs and can do so at greater depths in the soil - sometimes eight to 10 inches or even a foot to 18 inches, he said. If we see another warm winter it may mean that these populations have risen to dangerous levels.

The reason it's important for farmers to know if they have high populations of these insects is that it takes three hours for the genetically engineered Bt gene in the corn to kill these worms. If the pest population stands at 20 to 35 million worms per acre they can do a lot of damage before the plant can kill them.

Fiene has seen cornfields in Illinois and Indiana where Western corn rootworm pressure was so high that plants couldn't stand up. Those kinds of populations are now moving into northern Illinois and southern Wisconsin.

"You want to scout for them. Watch for them."


Seed corn treatments are one line of defense but agronomy companies are at work developing other ways to protect emerging corn crops.

Dave Wheeler of FMC Ag Products, spoke with the Poynette group about "Capture LFR" an insecticide that has been used successfully in Nebraska, Kansas, Indiana, Minnesota and Michigan.

"2013 stands to be the most expensive corn crop you've ever planted." Wheeler told farmers that they can expect it might be around $1,000 an acre to plant corn.

Using an insecticide to control the bugs Feine had talked about can cost as little as $7-$8 per acre but if it moves the yield up by 10 bushels it can improve the margin 10-fold, he said.

Some corn industry people think it might be possible to get the average U.S. corn yield up to 300 bushels by the year 2030. Part of what will make that possible is controlling pests at the root of the plant as its beginning to grow.

Herbicide practices will need to be scrutinized because if certain weeds are left in the field, it will give pests a spot to over-winter by creating a habitat for them.

The Capture insecticide he spoke of at the meeting creates a protective root zone around the plants and eliminates most insects before they have a chance to feed on the delicate roots as corn plants start to grow. The insects never get a chance to nibble on the Bt corn plants and then breed - which could create resistant worms.

The insecticide can go in with liquid fertilizer making it a little easier to use and it is used in much smaller amounts than granular materials, Wheeler said.

The LFR in its name stands for "liquid fertilizer ready."


There will be supply challenges for the seed corn industry going into next year, said Kevin Sloane, a regional corn and soybean product manager for WinField Solutions.

The drought and heat of last summer were hard on seed production. Male and female hybrids that are planted to cross-pollinate are more fragile than the corn farmers grow and seed production suffered.

"I encourage you to have discussions with your seed corn dealers," he said.

Producers may think that seed production can be ramped up in places like Chile and Argentina in South America to make up for losses here but even that is rolling the dice, says Sloane. Fields in those countries can't produce enough to fill the corn planters in the United States.

Sloane, who is headquartered in Viroqua and covers the state of Wisconsin, said the genetic potential of the seed industry keeps going up.

One of the tools that is helping that process is marker-assisted breeding or molecular breeding. "We can now go through and screen the DNA of corn for yield, a drought-resistance gene, many others. It gives us the ability to see certain desirable and undesirable traits through markers on the DNA."

Each corn plant has 50,000 genes on 1,000 base pairs. As molecular technology has improved it has revolutionized corn breeding.

In 2000 it would take 12.5 days to analyze the genetic makeup of corn. By 2010 it was possible to do 200 per day, Sloane said. And in the two years since then a lot more information on plants has become available.

"Molecular breeding changes everything we know about the seed industry."

As a results, 40 percent of the new corn hybrids have been released in the last three years, Sloane said, and they have picked up 8 ½ bushels of genetic gain.

But even with all that molecular information, there is still a need to plant varieties and record data on them. The "Answer Plots" have 200 sites in the United States, Canada and Mexico to evaluate different varieties. If all those plots and replications are counted Sloane said there are a million plots devoted to evaluating agronomic solutions.

"Not all plots are created equal." More replications of various trials mean that the results are more reliable.

The Answer Plots, Sloane said, are most likely the largest database in the world for hybrid performance.

In the West Salem, WI plot, for example, Sloane said there are different maturity trials. Trials also test certain agronomic practices. "One example might be first-year corn, with high nitrogen and a high population or that same hybrid as first-year corn with high nitrogen and a low population. Or corn on corn. It's sound science because it's got data behind it.

"We need to understand what kind of environment these hybrids do best in."

There are Answer Plots scattered all over Wisconsin that produce data that feeds into hybrid analysis.

Marker-assisted breeding is also happening in soybeans and real yield advantages are becoming obvious. "In the 25-plus years I've been in the seed business this is the most exciting time I've ever seen."

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