Weed management comes with the territory, you could say. Best practice is to stay ahead of it by taking a long-term approach. Thanks to the Arkansas Soybean Promotion Board’s invested checkoff dollars, Arkansas weed science experts are constantly researching weed resistance and learning new management practices.
“We’re not selecting resistance or putting all of our effort into one method which could fail, and put us out of luck,” said Dr. Tommy Butts, University of Arkansas Extension weed scientist. “We can use multiple little hammers which work on it at the same time, but still control that weed species.”
Recently, Dr. Butts was joined by UofA’s Dr. Jason Norsworthy, Dr. Tom Barber, and Dr. Nilda Burgos in a collaboration to discover best practices producers can incorporate into their operations during the 2020 growing season. The team’s efforts were refined using an integrated weed management approach. By testing multiple weed management tactics at once, the research team is able to minimize its risk of herbicide resistance.
So far, this checkoff-funded project has identified Palmer amaranth resistant to six different sites of action in Arkansas. Resistance to some sites of action among the six identified are fairly common like WSSA Group 3 (root growth inhibiting), EPSPS inhibiting (glyphosate) and acetolactate synthase (ALS) inhibiting herbicides, but new ones like HPPD-inhibiting, protoporphyrinogen oxidase (PPO)-inhibiting and WSSA Group 15 (shoot growth inhibiting) herbicides have been discovered across several counties as well.
This research has also brought metabolic resistance into focus. The team is working to identify and manage this newer, more challenging type of resistance in which the plants “digest” the herbicide.
At present, many integrated weed management practices, like deep tillage in the fall, crop rotation and cover crops continue to be studied and encouraged. However, residual herbicides have proven the most effective tool in managing Palmer amaranth.
“Anymore, weed control is a long-term game. Managing from a long-term perspective is really what we need to focus on,” Butts said. “It may be challenging now, but if it can help us a couple of years down the road, it will make our farms a lot more successful and profitable.”
Understanding spray water has proven to be extremely useful too. Samples are taken and tested for pH and water hardness. Herbicides thrive in acidic environments and soft water, so if growers can be aware of a high pH or hard water from the beginning, management practices can be implemented to make the herbicide more active.
Like, for example, adding ammonium-sulfate (AMS) to the spray tank. The AMS binds to cations like calcium and magnesium, thereby freeing up the herbicide active ingredient in the spray solution and making it more effective.
Of course, there are equipment-based practices as well, and 21st century technology is only improving these practices. The See and Spray, from Blue River Technology, uses cameras to identify and target weeds with precision herbicide application.
Companies are also using GPS-based, unmanned sprayer machines. Another innovation in weed management worth mentioning is the Harvest Weed Seed Destructor, which is the focus of some ongoing research at the Newport Extension office.
Overall, the team-approach here provides a key benefit to this project and its results by allowing the researchers the ability to evaluate their shared experiences. This helps deliver the most refined and accurate recommendations to Arkansas growers, which is the ultimate goal of all checkoff-funded research.
“Thank you to our soybean producers and the Arkansas Soybean Promotion Board for this funding, because without it, we wouldn’t have the research and science-based information to be able to provide these recommendations,” Dr. Butts said.