As Mid-South pigweeds continue to be stubborn and hard to control, methods to combat them are expanding. In mid-January, the University of Arkansas released a software package (http://bit.ly/2kBMIwn) to assist growers in making informed decisions managing Palmer amaranth.
“It’s a unique software tool in that you can select whether you have glyphosate resistance, ALS resistance, or PPO resistance,” says Jason Norsworthy, weed scientist. “From there, you devise potential herbicide management strategies over a 10-year period. We’re very proud of the program.”
The package is also an economic software tool that will show how much return a grower will have on his investment on an annual basis as well as over the 10-year period. “Growers can set the price of commodities – corn, soybean, and cotton – they need. All the different traits are available: Xtend, LibertyLink, conventional, Roundup Ready.
“The software is able to predict how many pigweed seed you’ll have in the soil seedbank each year. It will tell you how many pigweed will escape the control program you use in the field and when in the season they are likely to escape.”
There’s also a tool – a diversity index – “to measure how much diversity you’ll have in your program over the decade. The beauty of that is as you begin to increase your diversity you reduce the risk of developing pigweed resistance to the herbicides in your system.
“We believe this is something growers can use to maximize returns as well as minimize pigweed escapes. It allows you to compare different programs and technologies side-by-side. You can look at different rotation schemes and other things.”
Why did the university personnel settle on a decade?
“There’s nothing magical about the 10-year period. When we look at management, we need to think long-term management, beyond a one-year fix.
“The 10-year time period really allows you to measure how much diversity you’re planning. With only one or two years, it doesn’t tell you much. I might have one year of an Xtend crop or a LibertyLink crop. That gives me no assessment of whether I have diversity in my weed control program.”
There are options for tillage in the new software, options for cover crops. “The only way to know the impact you’re having on the soil seedbank is to plan for an extended period. To goal is always to drive that soil seedbank to extinction.
“The amount of resistance you have in the field really dictates how successful your weed control program is. If you go into the software and select ‘no glyphosate resistance’ ‘no ALS resistance’ and ‘no PPO resistance’, those herbicides will be quite effective over those 10 years. You’ll very quickly be able to achieve a very low soil seedbank.
“Add in resistance – and we’re seeing more and more ALS, PPO, and widespread glyphosate resistance – you begin to limit the options for establishing an effective program.”
How was the software developed?
“About three years ago, we had a USDA Integrated Pest Management project funded.
“Before that, in 2013, I gave a keynote address in Australia on the current status of herbicide resistance in the United States. While there, I had a chance to interact with some counterparts and saw a program they’d developed called RIM (Ryegrass Integrated Management). While talking to Australian growers, I realized they were using it to devise strategies to drive down the ryegrass soil seedbank.”
Norsworthy came home with the software in mind. “At the time, I had a post-doctoral student, Muthu Bagavathiannan, and I sent him to Australia for six weeks. He learned all about the RIM program and when he returned we began work on our pigweed version.”
Shortly after that, Dr. Michael Popp, university ag economist, came on board and began handling the economic side of the project. Since then, “it’s been a laborious process to get the software ready, getting bugs worked out, putting user manuals together, etc. We also tested a beta version with folks.”
Ease of use/regional
“If folks will just devote 30 minutes to learn to use it, it really will make a difference. Consultants who use it can better advise their farmer clients. I think industry will also find it useful because you can put products head-to-head. You know how will Company X’s product versus Company Y’s product shake out at the end of the day? What product or tools will have the greatest impact on the pigweed soil seedbank? Plus, growers will know the costs associated with using those products.”
Norsworthy says the software is “a simple tool with a lot of power. I believe it can be quickly learned. We have some quick tutorials prepped for that.
There are three main pages for users to go through. It’s straightforward and user manuals are available at the website (http://bit.ly/2kBMIwn).”
How broad a region is the software applicable for?
“This is for the Mid-South. All the data used for the software is from the Mid-South. Herbicide prices built into the software are also somewhat regional.
“I don’t expect anyone in Wisconsin will use this. But there are some major concepts you can learn by using the software. What’s the value of adding tillage to my weed control program? Is there an advantage in doing that? What impact does it have on a drill-seeded soybean versus those planted in wide rows? What would integrating a cover crop do for my production system?”
Mold-board plow is an option to choose. “We don’t recommend that annually, but a grower may want to use a mold-board plow every five years. Well, does that offer an advantage?”