With the YieldGard Rootworm technology available in hybrids across the Corn Belt, Monsanto has moved to the next level — stacking corn rootworm-resistant and corn borer-resistant traits in YieldGard Plus hybrids.

“We're estimating that corn growers will plant more than two million acres of YieldGard Rootworm and YieldGard Plus hybrids in the upcoming growing season,” says Dave Rhylander, traits lead for the U.S. with Monsanto. According to Monsanto, more than 100 different seed companies are offering a limited number of hybrids containing YieldGard technology for 2004.

YieldGard Plus has received registration from the EPA as well as state-level registration from all major states in the Corn Belt, according to Rhylander. “Our pledge on YieldGard Plus is that it will not be launched until we have Japanese import approval,” he says. “We're looking for that approval before the 2004 planting season.” Orders of YieldGard Plus will be filled with either YieldGard Rootworm or YieldGard Corn Borer, if Japanese approval is not granted.

Rhylander stresses that growers still must be made aware that YieldGard Rootworm and YieldGard Plus grain must be channeled to either livestock feed or ethanol use. Grain containing this technology cannot enter the commodity grain stream for export to the European Union.

Corn growers and their agronomists must decide if the potential economic losses from rootworm feeding warrant the use of the YieldGard Rootworm and YieldGard Plus technologies, just as they would when choosing to apply a corn insecticide.

“There are a number of corn growers who would like to get rid of their insecticide boxes and the cost and maintenance that goes along with them,” says Joe Shirbroun, a grower near Farmersburg, IA. “However, the producer also needs to weigh the cost/benefit ratio for his operation against proven yields with his regular hybrids.”

Even if farmers adopt YieldGard Rootworm technology, they won't be losing their insecticide boxes any time soon. YieldGard Rootworm hybrids require at least a 20% refuge, and those acres will need soil-applied insecticide treatment or seed-applied insecticide treatment to protect yield levels.

According to Rhylander, YieldGard Rootworm technology benefits include better yields, reduced insecticide handling, improved worker safety and convenience. For early-season corn rootworm attack, the technology helps protect the corn plant's root mass, resulting in higher yields later in the growing season.

“The YieldGard Rootworm technology seems to be reducing losses to corn rootworms,” reports Don Holt, branch manager of Midway Co-op in Bellaire, KS. “However, lack of moisture during the past two growing seasons is helping decrease corn rootworm numbers as well.”

Many corn growers are experimenting with limited acreages of YieldGard Rootworm technology. “I think they are excited but they want to see it studied more,” Shirbroun says. “They want a better look at efficacy and sales programs.”

“Seed companies are adding YieldGard Rootworm and YieldGard Plus to their corn hybrids and are putting it in their best germplasm,” Rhylander says.

Ultimately, the overall demand for YieldGard Rootworm and YieldGard Plus will depend on perceived or proven insect levels and their potential for damage and resulting yield loss.

“Where corn rootworm infestations are above the economic damage threshold, hybrids containing corn rootworm technology may show a yield advantage,” says Marc Hennen, corn marketing manager at NK Brand Syngenta Seeds. “The yield boost will be dependent on the interaction of variety, geography and corn rootworm pressure.”

“We're anticipating good demand on our four hybrids with YieldGard Rootworm technology,” says Jerry Harrington, sales and marketing — public relations manager for Pioneer Hi-Bred International. “For protection against corn rootworm in 2004, our customers have the choice of an insecticide seed treatment with Poncho 1250 or the hybrids with YieldGard Rootworm protection, though supplies will be limited among the latter.”

As with corn borer technology, YieldGard Rootworm and YieldGard Plus require the use of a corn refuge. Under current guidelines, no more than 80% of corn acreage can be planted to YieldGard Rootworm technology with the remaining 20% serving as a refuge.

The matter is complicated slightly by planting YieldGard Plus, which has two refuge planting options: one that uses a common refuge for both corn rootworm and corn borer; and a second option that allows for greater corn borer management and requires one refuge for corn rootworm and a separate refuge for corn borer (see sidebar).

Monsanto's YieldGard technologies are priced to seed companies through a confidential royalty.

“YieldGard Rootworm is a great deal for farmers,” Rhylander says, “probably a little higher per acre than a comparable hybrid treated with an insecticide, but the farmer will have more money at the end of the day through higher yields.”

Shirbroun reports that YieldGard Rootworm costs run slightly higher in his operation. “For operations with corn on corn, extended diapause rootworms, or vulnerable soybean acres in Illinois, the technology is definitely a consideration,” he says.

“For our growers in Kansas, hybrids containing the YieldGard Rootworm technology are priced lower and we have good availability,” Holt reports.

“Growers should work with their seed dealers to choose hybrids with the best agronomic performance for their field situation and management practices, as well as choosing different maturities to spread risk,” Hennen stresses. “In the early years of a new technology introduction, growers need to look closely at their hybrid choices to be sure they are not walking away from yield potential to control an insect.”

Weather patterns and geography will continue to play a role in the sales of YieldGard technologies. Drought tends to reduce corn rootworm numbers, whereas the corn borer has a more established geography for potential damage.

According to Shirbroun, approximately 30% of the corn acres in northeastern Iowa and nearly 70% of the corn acres in central Iowa are planted to Bt hybrids. “Producers are weighing the cost and benefits for an average year when they make their hybrid decisions,” he says.

Although NK Brand Syngenta Seeds will offer corn hybrids stacked with corn rootworm and corn borer traits for 2004, it also is relying heavily on its insecticide and seed treatment products.

“We're offering a more competitive pricing structure in insecticide and seed treatments,” Hennen says. “Growers will get broader spectrum control with Cruiser Extreme Pak CRW, including control of billbug, flea beetle and chinch bug, than they will with YieldGard.”

A 20% refuge requirement seems pretty straightforward until you realize that corn rootworms and corn borers are both Bacillus thuringiensis (Bt) species. These basic guidelines give some sense of the complexity of the refuge issue when you start stacking traits.

• Plant at least 20% of the corn acres to a corn refuge that does not contain Bt technology for control of western, northern and Mexican corn rootworm.

• The corn refuge can be treated for control of corn rootworm larvae and other soil pests with soil-applied, seed-applied or foliar-applied insecticides.

• The corn refuge can be treated with a non-Bt insecticide to control late-season pests such as corn borer; however, the YieldGard Rootworm corn also must be treated.

• Plant the refuge within or adjacent to YieldGard Rootworm cornfields; the refuges can by separated by a ditch or road but not by another field.

• Plant a common refuge for both corn borers and corn rootworms with corn hybrids that do not contain Bt technologies. This refuge must represent at least 20% of the YieldGard Plus corn acres.

• This common refuge can be treated with a soil-applied, seed-applied or foliar-applied insecticide to control rootworm larvae and other soil pests. The refuge also can be treated with a non-Bt foliar insecticide for control of late-season corn borer.

• If rootworm adults are present at the time of foliar application, then the YieldGard Plus field must be treated in a similar manner.

• Plant a separate refuge for corn borers and a separate refuge for corn rootworms. This is an option for farms with expected high levels of corn borer infestation.

• For the corn rootworm refuge, follow the guidelines for the YieldGard Rootworm refuge.

• The corn borer refuge must represent 20% of the total corn borer-protected acres (YieldGard Plus and YieldGard Corn Borer combined).

• The refuge must be planted with a hybrid that does not contain a Bt technology for control of European and southwestern corn borers and must be planted within ½ mile of the YieldGard Plus field.

• The corn borer refuge can be treated with a soil-applied, seed-applied or foliar-applied insecticide for corn rootworm larval control.

• It also can be treated with a non-Bt foliar-applied insecticide for corn borer control if pest pressure reaches an economic threshold for damage.

These are abbreviated explanations of refuge requirements. Growers should read and follow the complete refuge requirements for YieldGard Rootworm and YieldGard Plus detailed in the Monsanto 2004 Technology Use Guide or YieldGard IRM guides.

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