As the competition against weeds intensifies, growers have more choices than ever before, and it’s critical they choose the system best tailored for their field conditions. Identifying problematic weeds and selecting the right seed is the first step to starting 2019 on the right foot.
Looking back at 2018, Iowa soybean growers started last year with a never-ending winter followed by significant weed pressure. “Winter annuals and marestail are the biggest problem weeds for no-till acres in Iowa,” says Mark Storr, BASF senior technical service representative at Nevada in central Iowa. “However, waterhemp and now Palmer amaranth are the key drivers across the state.”
With these problem weeds, selecting the right seed and herbicide system with rotating modes of action to help reduce the field’s “weed-seed bank” is critical. Growers are quickly losing efficacy on both Palmer amaranth and waterhemp due to increasing resistance. However, group 15 herbicide products are most effective on these two weeds for preemergence and postemergence. Liberty and Engenia herbicides are effective options.
Start with right preemergent
“To start the season, growers want to know the most efficient and effective ways to reduce the amount of weed seeds they have in their field. They want to protect yield,” says Bill Backhaus, a BASF Iowa agronomist. “There are a lot of choices out there, and starting off with a strong preemergence herbicide followed up with a choice that’s available in your herbicide program will help extend the residual control of weeds such as waterhemp. Waterhemp is continuing to display strong levels of adaptation and resistance development in Iowa fields.”
North-central Iowa grower Jim Legvold, farming 1,300 acres near Humboldt, has been a conventional tiller, no-tiller and now strip tiller. In 2018, two of his concerns for beans were waterhemp and marestail.
“Once weeds germinate, you’re behind the eight ball, specifically with beans. You need to start clean to stay clean, or you’ll be fighting weeds all year round,” Legvold says. “A residual herbicide needs to be applied to have success in keeping the weeds away. With these tough economic times, it’s important to get the biggest bang for your buck.”
Having seed and weed management system choices with rotating modes of actions allows growers to become better stewards of the land to ensure their farming operation is around for future generations. Two popular options growers can choose from are dicamba-tolerant and LibertyLink cropping systems.
Controlling weed-seed bank
“We want to control our weed-seed bank in fields and keep it down for the future generations of farming,” Backhaus says. “When deciding on a herbicide program, it comes down to the grower’s choice and what technology they are most comfortable using. There are limitations and advantages for both Engenia and Liberty herbicides. Working with your local retailer can help you decide what system is best for your farm.”
To select the best bean system to fit your operation, look at the weeds you have and decide what system will allow you to best control the weeds. One new seed option for 2019 is Credenz LibertyLink GT27. These varieties allow growers greater flexibility to manage weeds, he says. With tolerance to both Liberty herbicide and glyphosate, growers can now include glyphosate with Liberty herbicide applications.
“Selecting bean varieties to succeed this year depends on your management style, herbicide system choices, desired variety characteristics and germination rates,” Backhaus says. “Double-check germination of the seed, be prepared to adjust the population if needed, and do whatever you can to protect it with a full seed treatment, strong herbicide system, and post fungicide and insecticide applications as needed. This approach will protect yields all the way to harvest.”
Use strong residual preemergence
“Since I’m not tilling my land, I’m even more careful to manage the weeds in my farming operation,” Legvold says. “As a strip tiller, I apply a preemergence herbicide that includes a residual to carry through and help manage the grasses.”
Legvold feels strongly about using a residual herbicide preemergence along with a “kicker” herbicide to control any emerged weeds. In 2018, his preemergence herbicide plan on his dicamba-tolerant soybeans included Zidua herbicide, glyphosate and Engenia herbicide to help clean up his field after weeds started to germinate due to later planting at the end of May. Engenia herbicide is an EPA restricted-use pesticide, and additional state restrictions may apply.
“I needed a good kill with the weeds being taller than I wanted, due to the later planting in 2018,” Legvold says. “Roundup doesn’t do it all anymore, and I needed to layer in different products preemergence to get all the weeds.”
Legvold and Storr believe residual herbicides will be critical to weed management success in 2019. “BASF has great options and solutions with Zidua herbicide, or Zidua PRO as a PRE to prevent those weeds from germinating. And you can clean them up with products like Liberty or Engenia should the weeds require it,” Storr says.
Soybean grower decisions
“On a strip till or no-till farming operation, you need a good group 15 herbicide that has great staying power to control small-seeded broadleaf weeds, so Zidua will be the backbone of my plan for 2019,” Legvold says.
Of course, it’s critical for growers to always read and follow label instructions that correspond with the products in their integrated weed management plan.
As a soybean grower you have a lot of choices to make, he notes. Are you going to use tillage? What seed will you plant? How will you manage your weeds?
Starting this year with a clean field either through tillage or an effective burndown herbicide, followed by an effective group 15 preemergence and a timely postemergence application will help you best manage weeds, say Storr and Backhus. Consulting local, trusted crop advisers is also critical for Iowa soybean growers to overcome and learn from last year’s challenges as they meet 2019 head on, they say.
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