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Effective weed management a must for successful soybeans

JOHNNY DODSON grows soybeans corn cotton and wheat on his Halls Tenn farm
JOHNNY DODSON grows soybeans, corn, cotton, and wheat on his Halls, Tenn., farm.

Johnny Dodson takes a field-by-field approach to preventing pigweed in soybeans and other crops. He holds losses from the wicked weeds to a minimum. But he knows resistance management plans for his farm and others in the South should be revised regularly to maintain solid weed control. The Halls, Tenn., grower relies on soybeans for the success of his overall crop rotation.

His ground is mostly in the Mississippi alluvial valley, and ranges from clay to sandy loam on Mississippi River and other regional river bottomland, to silt loam on upland acres.

Weather can vary from one of the worst droughts ever in 2012, to major river flooding in the spring of 2011.

Soybeans are planted in either 38-inch or 15-inch rows. Full-season beans are mostly no-till and are rotated with cotton. Other beans are double-cropped after winter wheat. Corn is also in the rotation mix.

“Commodity prices, the amount of rainfall a field has received and what was planted there the previous year determines what we plant,” says Dodson, a past president of the American Soybean Association. He stresses that pigweed, or Palmer amaranth, can attack in every field if it is not continually controlled.

“Pigweed resistance is the major issue for this part of the world,” he says. “It’s such a prolific weed, with 300,000 to 500,000 seeds produced by each plant. To control it, every field requires its own set of management practices.”

For full-season soybeans, he normally plants Roundup Ready or Roundup Ready 2 Yield soybeans for glyphosate over-the-top protection and increased production.

Residual herbicides are included in tank mixes or in separate applications. Those and other chemistries are sometimes used for double-crop beans.

“We use multiple sources of residual herbicides,” Dodson says. “It all depends on what crops we had before or whether or not it has rained. That can change what type herbicide we use.”

For variety selection, he relies heavily on information provided by University of Tennessee Extension soybean trials. UT weed management research also helps identify control measures.

“A lot of credit goes to Larry Steckel (UT Extension weed specialist) for getting the message out to use residual herbicides and multiple modes of action,” he says.

Disease and insect prevention is also essential for Dodson. He closely examines UT Extension recommendations on varieties that perform best under potential disease and insect pressure. Soybean information from the University of Arkansas and Mississippi State University research is also important to him. “It’s all part of seeing what works best in our Delta soils,” he says.

He takes no chances with late season leaf spot, rust or other disease threats. “We look at the disease package of each variety,” he says, “then make our selections with that in mind.”

Asian soybean rust was apparen tin some areas south of his farm in 2012, partly a result of Hurricane Issac. He was ready for it if it drifted north.

“All of our soybean and corn seed is treated with a fungicide,” he says. “And we usually make a fungicide application at the R5 stage of growth, when the plant begins to see pods about a quarter inch long.”

His leading disease problem is frogeye leaf spot. “Some areas have seen some frogeye resistance,” Dodson says. “So we now apply both a triazole and strobilurin fungicide to help control that disease. It appears to be doing the job. We are seeing good disease control with those combinations.”

Some will argue that fungicides shouldn’t be applied unless a disease threat is discovered. However, Dodson has seen proof that fungicide treatments improve yields.

“For years we’ve made a fungicide applications on soybeans,” he says.  “It paid dividends. Our normal soybean yields are in the mid-40 bushel range. Use of a fungicide probably improves our yields by 10 percent to 15 percent. I’m convinced you can improve yields every year by making a fungicide application.”

Insects can be a problem throughout the South. But the drought of 2012 prevented many heavy infestations. “We didn’t meet an economic threshold on any insect during the year,” Dodson says.

However, he has a plan for when stink bugs, earworms and other caterpillar pests and other damaging insects chomp down on soybeans. As with weed and disease control, different insecticide chemistries are used to manage bad bugs. Several sprayings of different pyrethroids are sometimes in his insect program.

As a leader and close follower of national soybean promotion and research, Dodson is encouraged by the numerous production traits that are in the seed pipeline.

“We know that Monsanto has the dicamba resistance trait in line for growers to compliment glyphosate,” he says. “Other companies also have new chemistries that will be available for weeds, insects and diseases.” 

Among those that have his eye is Monsanto’s Second-Generation Insect-Protected Genuity Roundup Ready 2 Yield soybeans. They are designed to offer multiple modes of action for improved durability, a wider spectrum of insect protection, including armyworms, and the opportunity to reduce the size of the structure refuge.

“Farmers are welcoming the new technologies that are in the pipeline,” Dodson says. “We need new technologies to help increase our yields. It’s all about keeping the plant as healthy and happy as you can.”

As a long-time state and national soybean association leader, he encourages farmers to support their regional and state soybean groups and other commodity associations.

“There is still a lot of important soybean research being conducted at our land grant universities,” he says. “Many of those programs are partially funded by state and national farmer associations. That funding needs to continue at a strong level. It’s up to us farmers to make sure that happens.”

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