Research Highlights

Research for Best Weed Management Continues to Evolve in Oklahoma

Weeds that plague soybean fields across the country, such as Palmer amaranth and waterhemp, are no strangers to Oklahoma growers either. Todd Baughman, weed science professor at Oklahoma State University, has been studying the best ways for farmers to gain control over these weeds and others.

“The bulk of our work involves all the different technologies for weed management such as LibertyLink^® and GT27, and in the last few years mainly Xtend^® and Enlist™,” Baughman said.

Baughman and his weed science team focus their time on finding pre-emergence herbicide programs that work best these soybean technologies. The goal is to find programs that effectively manage herbicide-resistant weeds such as Palmer amaranth, and also to protect the new technology.

“We can develop a program where farmers can make these technologies work,” Baughman said.  “But much like Roundup^®, if we want these technologies to last, we’ve got to look at other herbicide programs that will work with them.”

The studies — supported by the Oklahoma Soybean Board for nearly a decade — are conducted at research station sites and on private farms where growers are facing other weed issues. The research stations have areas that are left fallow each year so weed populations can get a strong, uniform establishment. Growing weeds on purpose may seem counterintuitive but Baughman said this helps them evaluate the various programs better.

He is working with several farmers who have particular weed issues, which provides an opportunity to look at weed populations he hasn’t encountered at the research stations. It also offers a chance to work one-on-one with farmers on feasibility and implementation of different weed management programs.

“Palmer amaranth is seen throughout most of the state and tall waterhemp is primarily a problem in Northeast Oklahoma,” Baughman said. “We’re working with one farm that has prickly sida and one has spreading dayflower. These are mainly isolated cases but there are areas of Oklahoma that are seeing more problems with these weeds.”

Strategies for weed management

Over the last few years, Baughman and his research team have found some general solutions to help control Palmer amaranth and waterhemp.

“We have had our best results with pre-mixes that contain a PPO herbicide as part of the mix,” he said. “We’ve also had success using metribuzin as part of the pre-mix. Using a PPO and metribuzin together in a pre-mix primarily has become our base program.”

If farmers are dealing with a heavy population of Palmer amaranth in soybean fields with LibertyLink technology, Baughman suggests a more aggressive herbicide program up front. Having this kind of pre-emergent program provides farmers more flexibility and helps the beans perform better, Baughman said.  Under Oklahoma’s dry climate, LibertyLink soybeans can perform inconsistently depending on the weather conditions.

There is a little more flexibility with the Xtend or Enlist technology, Baughman said. With these technologies, the timing isn’t as crucial as with LibertyLink and allows applications to be planned better around weather events to reduce the potential for drift.

Another system where Baughman has seen good results is adding products such as Dual, Warrant or Zidua to post-emergence mixes, providing a second layer of residual protection. Baughman has recommended this to growers who have seen good results on their farms as well.

As technology evolves for improvement in soybean herbicide tolerance, weed survival also evolves. Finding the best combination of soybean traits with an effective weed management system is not an easy task. But with Baughman’s help, Oklahoma soybean farmers will continue to have solutions for weed control in their fields.

Published: Oct 12, 2020