Herbicide-resistant corn finds niche in Tennessee

Jon Ed and Tripp Powers have been trying to shoot holes in their herbicide-resistant corn program for several years now. The result? This year, they increased their Clearfield corn to 500 acres.

The Powerses, brothers Jon Ed and Tripp and their father Burnie, with a little help from brother Kelley, who's still in college, farm 3,000 acres of soybeans, 1,000 acres of corn and 800 to 1,000 acres of wheat around Union City, Tenn.

This year, the Powerses will plant about half their corn acreage — most of which is no-till — in Clearfield corn, going with Mycogen 2799 and 2832 and Pioneer 34B28.

Clearfield corn is resistant to the imidazolinone herbicides, including Lightning. The product controls both grasses and broadleaves and has contact and residual activity. Other herbicide-resistant corn programs available to Mid-South corn producers include Liberty Link and Roundup Ready corn.

Clearfield corn has recently become a popular weed control technology for Midwest corn producers. And in Kentucky, more than 200,000 acres are planted to varieties with the herbicide-resistant technology. But it's been a slow go in the Mid-South and Jon Ed thinks he knows why.

“An early problem was lack of yield in the varieties,” he said. “Pioneer had one of the first varieties, 3395 IR, which did not yield well.”

However, he sees a parallel between Clearfield corn and the development of Roundup Ready soybean varieties. “When Roundup Ready first came out, they put it in the older varieties, and the conventional varieties were just beating the socks off it. People said there was a yield drag in Roundup beans, but we weren't comparing apples to apples. Now we're seeing the Roundup gene in the good varieties and it's competing. I think the same thing is happening in Clearfield corn. We're seeing some high-yielding varieties.”

Early on, corn producers may not have had an adequate knowledge of how to time their weed control applications in Clearfield corn either, noted Jon Ed. “I think a lot of folks were trying to spray corn with Lightning when the corn was too big. I think they got a little damage from that.”

Early planting

Recently, there's been a change in production practices in northwest Tennessee, which may open the door for planting more herbicide-resistant corn.

Traditionally, northwest Tennessee corn producers have depended largely on pre-emerges for weed control and a post herbicide application usually was not required. In fact, local pre-emerge dealers frequently pay for a post application if a guaranteed rate of a pre-emerge is used at planting.

Herbicide-resistant weed control programs not only require a post application but the spray can come at an inopportune time for many producers. “Growers hadn't been able to make the post application in May because they were starting to plant beans and top-dress corn,” Tripp said.

But over the last three years, many northwest Tennessee corn producers have been forced to plant earlier to minimize the impact of late-season drought and heat on corn pollination. “As soon as the soil temperature gets above 52 degrees for three days in a row at 7 a.m., you put your overcoat on and start planting corn,” Jon Ed said.

That also puts a different spin on the need for a post application. “You're putting your grass herbicide and your atrazine (pre-emerge) at the end of March at planting,” Jon Ed explained, “but the soil temperature is not going to warm up until the middle of April to germinate the weeds that you want to kill, especially with signalgrass.

“When we apply our pre-emerge herbicide, whether it's the end of March or the first of April, it's sitting there for a long time in all that residue. We start getting these rains and the pre-emerge is dropping down a little bit. We're still controlling the other weeds, but the signalgrass germinates in the top of the soil and the pre-emerge is below the root zone of the signalgrass.”

The Powerses still go with the pre-emerge on all their corn varieties, even when planting early. But these days they know that they're more than likely going to have to go with post application on a good deal of their acreage.

The question then is which post products do the best job.

On conventional corn, the Powerses will go with Accent/atrazine if a post is needed. It does a good job, but they say it doesn't provide the same level of residual activity that a Lightning/atrazine post provides on Clearfield corn.

“The Clearfield system gives us better season-long weed control,” Tripp said. “With the Lightning, it's planned. With the Accent, you do it if it needs it. And that's usually where you mess up. If it's planned, you can get it done in one day.”

The post application still comes at a bad time for the producers, but this fall they purchased a John Deere 4700 sprayer with 90-foot booms. “I can have my whole corn crop sprayed in a few days,” Tripp said.

On their Clearfield corn, as soon as the ground is dry enough to support field equipment, the producers will put out phosphorus and potassium. They burn down with Gramoxone Max and atrazine about a week before planting. They'll also include the insecticide Warrior for cutworm control. That is followed by a planned post of Lightning with a quart of atrazine before corn is 20 inches tall.

“The later you get into planting your corn, you may want to think about a cut rate of Guardsman followed by Lightning and atrazine,” Jon Ed said.

“We also target the Clearfield varieties on fields where we have a lot of ryegrass,” he said. “We had been spraying our burndown around planting with our other pre-emerge, Bicep. But with ryegrass, you're going to have to spray it twice. After we burned down, when corn was just coming up, we had these big clumps of ryegrass coming out.

“It will eventually cycle out since it's a winter annual. But if you have very much of it, you're going to have to go back in and spray over-the-top before any of the other weeds germinate. That's a plus for Lightning. You go in with atrazine and Gramoxone to burn it back. With the Lightning, you're planning on coming back with a post anyway. It's not as strong a product on ryegrass, but after it's been hit once, the Lightning can finish the job.”

All the Clearfield program needs is a more diverse variety selection, according to Jon Ed. “Mycogen's 2799 and 2832 are based on the same line of genetics. That line, maturity-wise, is about 113-day corn. The Pioneer 34B28 is a 109-day corn. I want something that is 110-day.”


e-mail: elton_robinson@intertec.com