Herbicide-resistant weeds top agenda at cotton, rice conference

News Release Distributed 02/11/11

BATON ROUGE – Farmers from across the Midsouth, along with researchers from the LSU AgCenter and several other universities, met here recently (Feb. 1-2) to share techniques and ideas at the National Conservation Cotton and Rice Conference.

Much of the 14th annual conference concentrated on herbicide-resistant weeds. LSU AgCenter researchers confirmed the presence of herbicide-resistant pigweed in two north Louisiana parishes recently. Last year, resistant pigweed and johnsongrass were confirmed in Louisiana.

LSU AgCenter weed scientist Daniel Stephenson was among the 54 researchers to present results of their work. Stephenson advised farmers to use herbicides with varying modes of action, and that means glyphosate with 2,4-D or dicamba and not relying on glyphosate alone.

“We’re going to have to go back to using residual herbicides,” Stephenson said. Residual herbicides should also be used for burndown applications, and farmers would be prudent to consider returning to tillage along with more frequent crop rotations.

Tall waterhemp in some areas of Louisiana is suspected of being herbicide resistant, he said.

University of Arkansas weed scientist Ken Smith said herbicide-resistant pigweed is presenting a major problem for commercial agricultural production. “It is much worse than I ever anticipated.”

He said one pigweed plant can produce 1.8 million seeds.

More than three dozen farmers gave presentations on their operations and the various conservation practices they use. Herbicide-resistant weeds often were included in their discussions.

Steve Stevens from southeast Arkansas said he uses Liberty Link cotton as an alternative to Roundup Ready crops. He said a yield drag was noticeable in the first few years, but it has become less of a problem.  He said Ignite herbicide seems to be weaker on some grasses, and it is less effective during a drought, even more so than Roundup.

LSU AgCenter soybean specialist Ron Levy said Liberty Link soybeans are a good option for farmers facing herbicide resistance. “Ignite herbicide controls a broad spectrum of weeds including most glyphosate resistant weeds,” he said. “The rate for Ignite is 36 ounces for a single application or two 22-ounce applications.”

Wayne Wiggins, of Arkansas, said herbicide-resistant pigweed appeared on his farm rapidly. “I was just stunned at how fast it came on.”

He said it’s important to talk with neighbors about their weed problems and be prepared for resistance issues. “You’ve got a narrow window. When you get behind, you are over and done.”

Wiggins said he uses atrazine on corn for its residual effects. “I’ll use a residual on all my bean fields this year.” He said rice is a good rotation crop to address pigweed, but the weed must be controlled on levees.

Tim White, a crop consultant in Concordia Parish and president of the Louisiana Agricultural Consultants Association, said he worked with a farmer who had a cotton field with resistant pigweed in one area that could not be controlled. It was the first field where the problem was confirmed in Louisiana. The weeds had to be removed by hand, he said.

Farmer Wes Simon, who grows soybeans and rice near Morse with his father, Glenn Simon, discussed the no-till practices they use.

He said stubble in fields for second-crop rice is flail mowed, and the field is flushed immediately. The Simons rely on an automatic steering system on their tractors for its efficiency.

Mark Fry, who farms near Morganza with three brothers, said they use polyethylene pipe for irrigating rice, corn, wheat, soybeans, sugarcane and crawfish.

Farmer Charles Cannatella, of Melville, said he is using more pre-emergent herbicides to keep herbicide resistance out of his fields. He said it seems that improved genetics may be keeping his soybeans green longer, so he uses a harvest aid two weeks earlier than usual.

Vendall Fairchild, of East Carroll Parish, said he irrigates soybeans, rice and corn. He said 18-inch poly pipe is the best size for his needs. “If you’ve got the pump capacity, 18 inches is worth the extra money over 15-inch pipe.”

Richard Fontenot, of Evangeline Parish, farms with his father and brother. He said land leveling has made a significant difference in their 3,000-acre operation. They apply poultry litter on the soil in areas that have been cut deeply.

Grid sampling every 2.5 acres helps determine nutrient needs, he said. And a yield monitor provides an indication whether a fertilizer program is working.

Two Tensas Parish brothers, Darrell Vandeven and Donnie Vandeven of St. Joseph, were recognized as Cotton Farmers of the Year.

Mississippi State University agronomist Tim Walker discussed his research on fertilizing the rice variety CL151, developed by the LSU AgCenter. Farmers have complained that CL151 is prone to lodging – or falling over before harvest.

Walker said the variety was grown on a third of Mississippi’s 300,000 acres of rice last year, and it is a high-yielding choice. “It’s one we don’t want to give up on right now.”

Research has shown that 135 pounds of nitrogen per acre is optimum, he said. More than 180 pounds increases lodging but does not significantly boost yields. Seeding rate also has a relationship to lodging, Walker said, and a rate of 65 pounds per acre appears to be the best rate.

LSU AgCenter rice agronomist Dustin Harrell said his seeding rate research may allow for reductions in recommended rice seeding rates in the future.

University of Arkansas soil fertility professor Richard Norman said the accepted practice of obtaining soil samples from a 6-inch depth is not adequate to get a true picture of nutrient needs. An 18-inch depth gives a more accurate sample.

Trent Roberts, assistant soil fertility professor at the University of Arkansas, said rice roots have the ability to penetrate hardpan soil to a depth of 18 inches and can even go as deep as 24 inches. He demonstrated a technique using a 1-inch auger bit in a cordless drill to drill 18 inches into soil and to transfer a sample into a 5-gallon bucket.

Each sample has to be tested individually and not mixed, he said. The samples are used to obtain a truer indication of nutrient needs, and the technique has produced surprising results.

“The tallest, greenest rice is not the top-producing rice,” Rogers said. It’s possible that tall, green rice might incur more diseases.

He said the deeper sampling will provide a variable nitrogen rate on a field, prescribing how much should be used in specific areas and likely reducing fertilizer costs. The University of Arkansas will conduct more research on the project, and cooperating universities include the LSU AgCenter, Texas A&M and Mississippi State University.

Also speaking at the conference was Arkansas Congressman Rick Crawford. He said the federal agriculture budget is likely to be cut but direct payments are as much of a national security issue as energy. He said it will be difficult to defend agricultural expenditures in the federal budget because a majority of the representatives on the House Agriculture Committee is from urban areas.

Crawford also said he hopes Congress can rescind a federal requirement for farm operations to have a fuel tank containment system, even though the regulations go into effect in November.

Bruce Schultz

2/11/2011 8:05:20 PM
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