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Is Roundup ready for corn?

Early results show many farmers are satisfied with Roundup Ready corn.

Kevin Koepp was one of more than 13,000 farmers who tried Roundup Ready corn for the first time this year. The Belle Plaine, MN, farmer and his brother, Curtis, planted 40 of their 1,000 acres to Dekalb's DK493RR. They planted another 20 acres to conventional DK512 for comparison.

"I wish I could have started planting it three or four years ago," says Koepp, who reports a 2- to 5-bu. yield advantage with the Roundup Ready over the conventional hybrid. "We have woolly cupgrass up here, and two passes of Roundup Ultra takes care of it."

He says each pass cost him $10/ acre versus $25 to $30/acre with conventional herbicide programs. Next year the Koepps plan to more than double their Roundup Ready corn acres.

Mark Sybesma, farmer from Hull, IA, was another first-time planter of the corn technology. He planted Dekalb's DK512RR along with two non-Roundup Ready numbers DK566Bt and Pioneer 36F30. Harvest results showed the Roundup Ready hybrid yielded equal to DK566Bt but 10 bu. lower than the Pioneer. He says the weed control was good and the cost was comparable to his conventional herbicide program. Will he plant it next year? "I don't know yet," Sybesma replies.

Side-by-side comparisons. Yield results were still coming in at press time for this genetically altered seed corn that allows you to apply Monsanto's Roundup Ultra over the top of the crop. Dekalb was the first and only company to market it in 1998 with five numbers that ranged in relative maturity (RM) from 99 to 108 days.

Dr. Tracy Klingaman, product manager of corn agronomic traits with Dekalb, is encouraged by the reports he has seen. "Throughout the summer, farmers were really positive about the tolerance and weed control of the Roundup Ready program and were saying, If it yields we will plant more in 1999,'" Klingaman says. "Now that it is yielding, growers are confirming their purchases for next year."

Product comparisons conducted across the Corn Belt by Dekalb show the following results.

DK493RR (99-day RM) yielded an average of 0.5 bu./acre lower than competitive Bt and conventional hybrids of 97- to 109-day RM in 226 comparisons. However, it was 1.9 percentage points drier, resulting in a $6.37 economic advantage assuming $2/bu. corn and $0.025/pints/bu. dockage at 15% moisture.

DK512RR (101-day RM) yielded an average of 1.4 bu./acre more than competitive Bt and conventional hybrids of 99- to 109-day RM in 62 comparisons and was 1.9 percentage points drier for a $9.79/acre advantage.

DK545RR (104-day RM) yielded an average of 4.6 bu./acre higher than competitive Bt and conventional hybrids of 99- to 114-day RM based on 59 comparisons and was 1.3 percentage points drier for a $14.31/acre advantage.

Results for the other two 1998 releases DK566RR and DK580RR were not available.

In addition to an economic advantage, other reported benefits of the technology are weed control, crop safety and a wide window of application, Klingaman says. "When I ask customers what they liked about the Roundup Ready corn system, their first response is weed control," Klingaman says. "It gives you perennial control of tough weeds like wirestem muhly that you can't get with a lot of other herbicide programs. And it is equally effective on annual weed species."Monsanto sponsored its own study in August. Of the 500 Roundup Ready corn growers surveyed, 75% said they were very satisfied and 21% were somewhat satisfied with the overall performance of Roundup Ready corn. Satisfaction levels are as high as they were for Roundup Ready soybeans when that crop was introduced in 1996, Monsanto says.

In addition, more than nine out of 10 growers surveyed said the seed technol ogy met or exceeded their expectations, citing satisfaction in such areas as overall crop safety, weed control, stand quality and application flexibility. Seven out of 10 growers surveyed said Roundup Ready corn was a much better or somewhat better value than traditional corn programs.

New for 1999. Monsanto says at least 80 other companies will be selling Roundup Ready corn seed next year. Dekalb has introduced an additional 12 new numbers for 1999, for a total of 17 that range in relative maturity from 83 to 116 days. The hybrids will carry an $18/bag technology fee, or $6/acre. Prices for the seed will remain essentially flat.

"With Monsanto's recent $10/gal. price cut on 30-gal. jugs of Roundup Ultra, this herbicide system is now an even greater value for farmers," says Jim Badger, Dekalb's corn products communications manager.

New application option. Due to a label revision, farmers will have the option of applying up to two treatments of Roundup Ultra, at rates up to 32 oz., over the top of growing corn. This is an increase from the single over-the-top treatment of up to 32 oz. allowed on the 1998 label.

Two other treatment options are a preemerge grass herbicide application like Harness or Harness Xtra followed by an in-crop application of Roundup Ultra before weeds become competitive to the crop; and an in-crop tank-mix application of Roundup Ultra with Harness or Harness Xtra herbicide to allow postemergence residual control. The latter tank mix should be applied before weeds become competitive with the crop.

What about resistance? Klingaman says farmers who plant Roundup Ready soybeans and are considering rotating to Roundup Ready corn can do so without concern that the weeds will become resistant to Roundup Ultra. The reason, he says, is that its mode of action is unique and is rated by weed scientists as having a low probability of developing resistance.

Farmers worried about volunteer Roundup Ready corn in their Roundup Ready soybeans can control it with labeled rates of Assure II and Select.Regulatory approval of grain harvested from seed of Roundup Ready corn is pending in certain export markets and may not be received before the 1999 harvest. As a result, growers should be prepared to feed the grain domestically or sell it for use in domestic markets only.

For more information, contact your local Dekalb dealer or Dekalb Genetics, Dept. FIN, 3100 Sycamore Rd., DeKalb, IL 60115-9600, 815/ 756-3333.

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