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A new era for corn rootworm control

AS EXPECTED, LIMITED SUPPLIES of corn hybrids with built-in corn rootworm protection virtually sold out in their 2003 introductory year. It will be no surprise if the second season is a near sellout as well, even with an expected major increase in supplies for 2004.

Despite the anticipated increase in transgenic corn rootworm hybrid plantings, manufacturers of soil insecticides are expecting only modest sales declines in 2004. In fact, with the expected increase in U.S. corn acres this year, growers are likely to apply nearly as much granular and liquid insecticides to control corn rootworms in 2004 as they have in the past. And sales of seed-applied insecticides are likely to climb.


Corn rootworm hybrids performed well in their first season, university tests show.

“In the presence of moderate to severe rootworm pressure, the corn rootworm hybrid kicked butt,” says Kevin Steffey, University of Illinois extension entomologist.

The story was the same at Iowa State University, where insect researchers said the hybrids offered “superb protection” from larval feeding.

Although the new hybrids offer consistent, excellent root protection, yield drag/yield lag questions are beginning to dog them, both in coffee shops and among competitors. But yield drag hasn't shown up in university research.

“This yield drag thing may be a rural myth,” Steffey says. “As soon as a new transgenic comes out, people start talking about yield drag. The data I see don't indicate a yield drag at all. I heard the same thing when Bt corn for corn borer control first came out.”

Scientists define yield drag as a negative performance effect from introducing a new gene into a specific crop. Yield lag, on the other hand, occurs when a conventional hybrid outyields a corn rootworm variety, but the hybrids are different genetically. Scientists say this can easily occur, but does not prove that an introduced gene reduces yield.

Part of the challenge for university researchers in responding to yield questions is that their corn rootworm research tends to focus on root damage, not yield. So university corn rootworm control data comparing yields are sparse. Meanwhile, farmer test plot yields that sometimes fuel yield drag/yield lag talk aren't reliable because field variability skews results, Steffey says.

ISU research conducted in 2003 appears to refute yield drag concerns. It showed that the corn rootworm hybrid used in tests yielded as much or more than insecticide treatments on the hybrid that was identical to the corn rootworm hybrid, but without built-in corn rootworm protection.

Seed treatments

In addition to larger supplies of corn rootworm hybrids, the greatest change in the corn rootworm control market is the widespread availability of the seed-applied insecticides Cruiser and Poncho in 2004, both of which were registered last year. Cruiser-treated seed was planted on about a million acres last year, with about 5% targeted for corn rootworm control. However, the registration for Poncho came too late to treat a significant amount of seed. This year, hundreds of seed companies are offering either or both products.

Sales of the seed treatments are expected to climb dramatically in 2004, in part because Monsanto requires seed companies selling YieldGard Rootworm hybrids to be treated to control secondary insect pests. Both insecticides will be available at two rates: a lower rate to control early-season pests, and a higher rate to add control of corn rootworm.

As farmers make decisions on how to control corn rootworms in 2004, marketers of granular and liquid insecticides continue to point out that their products provide superior protection against corn rootworm larvae feeding compared to seed treatments, as measured by root ratings. They advise growers to select corn genetics with the best overall performance potential, then determine how best to control corn rootworms, assuming control isn't built in.


Here are updates on corn rootworm and secondary seedling pest-control products, including changes in labels, prices, grower programs and availability.

YieldGard Rootworm options broaden

Supplies of YieldGard Rootworm hybrids will be about seven times greater in 2004 than they were last year. Industry sources estimate that seed companies will have seed for nearly 3 million acres, up from about 400,000 in 2003. In 2004 the YieldGard Rootworm mix also will include modest quantities of hybrids stacked with the Roundup Ready gene, which also were available in small amounts in 2003. YieldGard Plus, with both built-in corn borer and corn rootworm control, also is expected to be available in limited quantities in 2004. The technology received U.S. federal approval late in 2003. It will be made available once it receives Japanese import approval, which Monsanto expects to occur by planting time.

YieldGard Rootworm hybrids will be available in a range of maturities from more than 100 seed companies, including Monsanto flagship brands DeKalb and Asgrow. Both Pioneer Hi-Bred International and Mycogen will offer four YieldGard Rootworm hybrids in 2004, though quantities will be limited. At press time, Syngenta Seeds was the only major seed company without a license to YieldGard Rootworm technology, according to Monsanto.

In 2005 or 2006, seed companies also could begin offering trait-protected corn rootworm seed from Pioneer and Dow AgroSciences, which have submitted the trait to the EPA for registration.

As in 2003, Monsanto requires all YieldGard Rootworm licensees to treat seed with an insecticide for control of secondary pests. Cruiser, Gaucho and Poncho and insecticides are on the approved list.

Growers new to YieldGard Rootworm hybrids will need to implement an insect resistance management program. As with YieldGard Corn Borer hybrids, 20% of a field containing a YieldGard Rootworm hybrid must be planted with a hybrid without built-in rootworm resistance. The refuge portion of the field can be treated for corn rootworm larvae and other soil pests with soil-applied, seed-applied or foliar-applied insecticides. The corn refuge also can be treated with non-Bt insecticides for late-season pests, such as corn borer. However, in that instance, the YieldGard Rootworm hybrid must also be treated.

YieldGard Plus hybrids, once available, will have two refuge options. The first option, a common refuge, is identical to the YieldGard Rootworm option, except that the refuge hybrid cannot contain either built-in corn rootworm or corn borer protection.

The second, separate-refuge option allows separate refuges for corn rootworms and corn borers. In this case, a 20% corn rootworm refuge is required in the same or adjacent field. This would allow a hybrid with built-in corn borer protection to serve as the rootworm refuge. A separate 20% corn borer refuge would be required in a field that could be up to a half mile away.

As with Roundup Ready corn hybrids, YieldGard Rootworm and YieldGard Plus hybrids are not approved for export to the European Union. Growers who plant these hybrids are required to use the grain on the farm or market the corn through elevators and other outlets that segregate these hybrids for sale to approved markets only. The hybrids carry the Market Choices symbol and direct growers to a list of elevators maintained by the American Seed Trade Association at

Cruiser Extreme Pak offers insecticide/fungicide combo

Cruiser, a seed-applied insecticide from Syngenta, was registered in the fall of 2003, too late for many seed companies to work into their treatment plans. In 2004, it will be widely available, primarily as part of Cruiser Extreme Pak and Cruiser Extreme Pak BB/CRW, which contain the active ingredient in Cruiser, plus three fungicides: Dynasty, Maxim XL and Apron XL.

Cruiser Extreme Pak contains an insecticide rate needed to control early-season pests, including wireworm, seed corn maggot, white grub, grape colaspis, flea beetle, southern corn leaf beetle and chinch bug. As its name implies, Cruiser Extreme Pak BB/CRW has a higher insecticide rate, which adds control of billbug and corn rootworm, says Mark Jirak of Syngenta.

The Cruiser products will largely replace Force ST seed treatment from Syngenta Seeds, which will be phased out after this year. Force ST will be available on about five hybrids, down from 33 last year. Corn rootworm control from Cruiser is comparable to control with Force ST, but Cruiser controls additional above-ground pests, Jirak says.

He expects 20 to 25% of U.S. corn to be commercially treated with a seed-applied insecticide in 2004, both for secondary insects and for corn rootworm. Syngenta recommends using Cruiser on light to moderate corn rootworm infestations.

Check with seed companies for availability and order cutoff dates, which may already have passed for Cruiser Extreme Pak BB/CRW at many seed companies.

Poncho replaces Gaucho, Prescribe

After a limited introduction in 2003, Gustafson's new seed-applied insecticide, Poncho, will replace Gaucho and Prescribe for control of secondary corn pests and corn rootworm in 2004. Gaucho will continue to be sold for use on other crops.

Poncho received EPA registration last spring, too late for treating seed, but in time to allow use in seed corn company demonstration plots.

At press time, about 130 seed companies had plans to supply Poncho-treated seed for 2004, according to Paul Holliday of Gustafson. They will be offering Poncho 250-treated and/or Poncho 1250-treated seed.

Poncho 250-treated seed is coated with 0.25 mg/kernel of the active ingredient, the rate necessary to control such early-season pests as cutworm, wireworm, white grub, seed corn maggot, grape colaspis, flea beetle and chinch bugs.

Poncho 1250-treated seed is coated with the active ingredient at 1.25 mg/kernel. At that rate, it also controls corn rootworm and billbug, as well as other early-season pests on the Poncho 250 label.

At high-infestation levels, root damage with Poncho 1250-treated seed may be greater than with granular soil insecticides or corn rootworm hybrids, Holliday acknowledges. However, company tests show that Poncho 1250-treated seed has a yield advantage compared to use of soil-applied insecticides because of its control of a broad range of insects, he says.

“There is not necessarily a linear relationship between root ratings and yields,” Holliday says. “Our full pest spectrum is one of the reasons we feel so confident people will see a performance advantage with the Poncho products.”

At this point, growers may have to scurry to find additional Poncho-treated seed that they haven't already booked. Holliday says most seed companies had December or January cutoff dates for ordering Poncho-treated seed.

Grape colaspis to be added to Aztec 2.1 label

Grape colaspis is expected to be added to the list of secondary insects controlled by Aztec 2.1, says Andrew Seitz of Bayer CropScience.

Capture Acres Ahead program adds new seed firmers

FMC will offer early commitment discounts on shorter, lower-profile Keeton seed firmers for use with Capture insecticide liquid application systems in 2004. The lower profile allows a Capture T-band application to be made directly on the seed, says Jamie Leifker of FMC. Participating John Deere dealers also will carry Capture application system parts.

Helena adds plant growth regulator (PGR) to Empower formulation

After two years on the market, Empower soil insecticide has been reformulated to add a PGR. Empower2, the only corn soil insecticide with a PGR, is designed to boost early root growth, nutrient uptake and yield potential, says Frank Yopp of Helena Chemical Company.

Empower2 uses patented Asset Formulation Technology to combine the PGR and the insecticidal active ingredient, bifenthrin, on clay granules. Bifenthrin, a pyrethroid, is the same active ingredient that is in Capture liquid insecticide from FMC.

Helena says Empower2 can provide extended residual control of insects, depending on environmental conditions, because the active ingredient is released slowly by the clay granules. In addition to corn rootworm larvae, it controls wireworm, cutworm, white grub, seed corn maggot and seed corn beetle.

Fortress 2.5G “aggressively priced” for 2004

Fortress 2.5G will be “aggressively priced” in 2004, says Ted Ramirez of AMVAC Chemical Company. The 2.5G formulation, which is applied through traditional insecticide boxes, was reintroduced with a new rate structure two years ago to complement Fortress 5G and Aztec 4.67G insecticides, which use SmartBox row units.

Dow AgroSciences stresses value, secondary pest control of Lorsban 15G

Dow AgroSciences has not announced any label, pricing or grower program changes. It will continue to emphasize that Lorsban 15G controls corn rootworm and important secondary seedling pests, while improving seedling health.

BASF focuses on Regent

In 2004, BASF will emphasize the application convenience of its corn insect control products, including Regent and Counter, says Neil Bentley of BASF. This is the first year BASF has marketed Regent, which it purchased last year from Bayer CropScience. Federal regulators required the sale after Bayer CropScience merged with Aventis, which had marketed Regent. BASF will continue to offer assistance toward purchase of 1-Pass application systems through Redball LLC.

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