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Corn+Soybean Digest

Routing Out Rootworms

Farmers looking for a convenient way to protect corn roots found their answer in newly introduced hybrids that are genetically enhanced to resist corn rootworms.

Like hybrids first introduced to stop European corn borers, the new rootworm-resistant hybrids derive their insect-protection power from a bacterium, Bacillus thuringiensis (Bt), that is genetically inserted into plants to produce proteins that sicken and kill certain insects that ingest it.

According to the National Center for Food and Agricultural Policy, farmers planted 3 million acres to rootworm-resistant Bt corn hybrids this year, which increased yields by an estimated 754 million pounds and helped reduce insecticide use by an estimated 1.98 million pounds.

One farmer who planted rootworm-resistant hybrids on a limited basis in 2003 and on a wider scale in 2004 is Len Wiese, Versailles, IL.

“Last year it did well, and this year it did really well,” says Wiese. “The rootworm-resistant hybrids gave us a 20-30 bu. advantage over non-resistant hybrids.”

Wiese compared hybrids applied with or without Capture liquid insecticide to hybrids containing Monsanto's rootworm-resistant, YieldGard Rootworm technology in several continuous-corn test plots.

His highest-yielding plot was an experimental, rootworm-resistant Golden Harvest hybrid, EX 39190RW, which yielded 249.4 bu./acre, he says.

Two other rootworm-resistant hybrids also performed well, Wiese says. Golden Harvest H-8896RW, yielded 226.7 bu./acre and Asgrow 718 YGRW yielded 204.9 bu./acre. Both yielded considerably better than their non-rootworm resistant counterparts, he adds.

“The roots on the YieldGard Rootworm hybrids had a little feeding damage on them, but they were still in good shape,” he says. “The non-rootworm hybrids were pretty well chewed up.”

The worst yields came from a non-YieldGard Rootworm hybrid, which yielded only 159.4 bu./acre without an insecticide. However, with Capture, it yielded 204.4 bu./acre.

Results like these were fairly typical across the Midwest, says Dave Rhylander, director of traits for Monsanto. “Our data indicates that farmers are seeing 6-10 bu./acre higher yields with YieldGard Rootworm and YieldGard Plus technology than they are from comparable, non-transgenic hybrids applied with an insecticide or high-rate seed treatment,” he says. “With YieldGard there is less rootworm damage and larger root systems, which capture more moisture and nutrients to produce higher yields than hybrids that are severely damaged by corn rootworm.”

YieldGard Plus technology, which was first offered on a limited trial basis in 2004, offers in-plant protection for both corn borers and corn rootworms, says Rhylander. “Sales of YieldGard Plus were limited to about 2,000 farmers on up to 75 acres each this year,” he says. “In 2005, most seed companies will have YieldGard Plus hybrids available in significant quantities.”

Also in 2005, Monsanto plans to roll out the first triple-stacked trait, YieldGard Plus, with Roundup Ready Corn 2 technology, says Rhylander. “We already have clearance in the U.S. and we anticipate approval from Japan by Dec. 31,” he says. “All approvals should be done in time for planting.”

However, Rhylander reminds farmers that both YieldGard Rootworm and Roundup Ready Corn 2 technology have yet to be approved for markets in the European Union. Farmers need to ensure they have appropriate markets for these hybrids before they purchase the seed.

Kerry Miller, Waverly, IL, is one of the lucky ones who doesn't have to go far to market transgenic corn. “There's a big new elevator just two miles from my farm that will accept any kind of corn,” he says. “They ship it to Texas for feed.”

Miller says he planted limited quantities of two YieldGard Plus hybrids, Asgrow RX718 YGPL and DeKalb DKC60-14 (YGPL) on continuous corn acres this year. “The 718 handled our conditions really well,” he says.

Yields averaged between 210 and 214 bu./acre with the Asgrow hybrid, notes Miller. “The plant health and yield were excellent, with no lodging and no signs of damage,” he says. “A lot of our neighbors had rootworm problems this year, but we didn't on these hybrids.”

Yet, Miller's DeKalb YieldGard Plus hybrid didn't fare as well as expected. “It looked good early on, but then it got gray leaf spot and it went to pieces,” he says. “It still managed to yield between 185 and 190 bu./acre.”

Even with the mixed results, Miller says he plans to plant more YieldGard Plus hybrids next year.

“I can't handle the fumes from insecticide applications,” he explains. “So the main reason is because of health concerns, but also because of convenience — the ease of handling — and there's no need to calibrate anything. Another reason is that I think the technology works.”

Both on-farm and university research trials in Nebraska and other Midwest states, such as Illinois, show that YieldGard Rootworm hybrids protect roots from corn rootworm feeding as well as or better than granular insecticides, says Bob Wright, University of Nebraska Extension entomologist.

“YieldGard has worked well in our trials,” Wright says, “but there is some rootworm injury even with YieldGard.”

Farmers may face sticker shock when they view the seed price for certain transgenic corn hybrids, Wright warns. However, he encourages farmers to compare costs to traditional methods before dismissing their use entirely.

Non-financial issues are also valid factors to consider when deciding on a particular corn rootworm control strategy, he adds. “It's hard to put a cost on a grower's time,” Wright says.

For Duaine Davis, who farms near Luana, IA, convenience and yield are the main factors contributing towards his interest in growing rootworm-resistant hybrids.

“The biggest plus is that I didn't have to handle insecticide,” he says, “but the yields were tremendous — 190 bu./ acre or more.”

Davis says he planted 12 bags of rootworm-resistant corn in 2003 and 100 bags in 2004. This year, his DeKalb DKC53-29 YieldGard Rootworm hybrid was “healthier and yielded 10 bu. better” than non-rootworm resistant hybrids planted to continuous corn acres, he says.

In 2003, his rootworm-resistant corn yielded 30 bu./acre better than its non-rootworm resistant sister hybrid.

“Last year rootworm pressure was heavier than this year,” he says. Still, Davis says he's pleased. In years prior to YieldGard Rootworm, yields on his continuous corn acres averaged only 160-170 bu./acre.

“Corn on corn is where YieldGard Rootworm does best,” he says. “That's where it really shines.”

Sales Tips For Transgenic Corn

Farmers concerned about finding markets for their transgenic corn can obtain help through a program developed by various grain and seed industry organizations and businesses, called Market Choices.

Although Market Choices grain has not yet gained European Union approval, more grain elevators in the Midwest are buying it than in previous years, says Dave Rhylander, Director of Traits for Monsanto.

“Almost every farmer can find an elevator within 20 miles that will buy Market-Choices grain,” says Rhylander.

Market Choices hybrids contain one or more of the following insect-protecting technology: Herculex I, Liberty Link, Roundup Ready, YieldGard Rootworm or YieldGard Plus. When farmers buy these transgenic traits, they agree to deliver the corn to an appropriate grain handling facility that will ensure the grain or its processed products stay out of Europe.

To find out more about the Market choices program, farmers can contact their local seed or grain dealers or log on to

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