Across the country, Extension weed scientists are rewriting the rules of acceptable weed pressure in corn and soybeans. For many, tolerance for a few late-season escapes of tough weeds—like Palmer amaranth and waterhemp—is a thing of the past. Increasingly, the Extension community is encouraging farmers to draw some harder lines. One of those is for zero tolerance for weed seed production.
“We have really kind of shifted to this idea largely because of herbicide resistance. That is a huge threat for our crop production systems,” explains Sarah Lancaster, Kansas State University weed management Extension specialist and assistant professor.
Lancaster emphasizes that effective weed control is no longer about picking one or two individual tools to address weeds and prevent seed dispersal. Instead, it is about stacking as many tools as feasible into a single season.
“If you think about this as a multiple-choice answer, it’s not about using A, B, or C. The right answer is D—use all of the above,” she says.
Herbicides, cultural practices, strategic tillage, cover crops, rotations, and sanitation all play a role in stopping weeds.
During a recent episode of The Crop Science Podcast Show, available here, Lancaster addressed specific tools and practices to help farmers work toward the “zero tolerance” goal this season. Here are five for consideration:
1. Herbicides Will Still Be A Core Tool For Weed Control.
Despite the push for diversification, Lancaster believes herbicides remain the central tool for row-crop farmers.
“In our conventional broad-acre ag systems, herbicides are still going to be the most efficient, most economical way to [control weeds]—I’m going to say for the rest of my career,” she says.
However, decisions about product selection, rates, application timing, and application quality are increasingly critical—even more so under stress conditions like heat and drought. In western Kansas, Lancaster sees farmers adjusting their practices to meet these challenges.
“When it gets hot and dry, our farmers are really good at modifying their herbicide applications to make sure they’re still going to be efficacious in those very difficult conditions,” she explains. “They know that if they skimp on the water, they’re wasting their time, so they do a good job of accounting for that, modifying their adjuvants, and knowing when to adjust.”
2. Use Cultural Practices To Make The Crop Competitive.
Lancaster stresses that managing the crop can be just as important as managing the weeds.
“Other things that we talk about would be cultural control practices, looking at planting dates and row spacings,” she says. “How do we manipulate that crop to make it as competitive as possible and maybe support our herbicides a little bit better, so that we have fewer weeds to control?”
For growers, this means considering narrower rows, if suitable for the cropping system, and using optimal planting dates to favor the crop over the weeds.
These tactics don’t replace herbicides, Lancaster adds, but they make every herbicide dollar go further.
3. Consider Using Strategic Tillage In No-Till Systems.
In Kansas, no-till is widely adopted to conserve soil and water, but Lancaster points out that it can reshape the weed spectrum and the tools required to manage it.
“Here in Kansas, no-till is a very important soil conservation practice, but it brings its own set of weed management challenges,” she notes. “The number one reason that tillage is a good thing is to kill weeds. When you remove that, you’re 100% reliant on herbicides.”
She believes there are scenarios in no-till where strategic or occasional tillage has a place. One example is the return of perennial warm-season grasses in long-term no-till fields, such as tumble windmill grass.
“That’s an example of a situation where strategic or occasional tillage is becoming a more accepted, more common idea for managing some of these key weeds,” Lancaster says.
Her bottom-line message is to use tillage strategically whenever tough weeds require it.
4. Technology Can Help Improve Control, Reduce Rates, Cut Costs.
Lancaster sees real promise in camera- or sensor-based systems that spray only where weeds are present, such as “See & Spray” or “Weed-It” systems. She finds the technology is especially beneficial on fallow ground or in stubble.
She notes that in some cases, these tools are what make no-till financially viable. Referencing one farmer she works with, Lancaster sayss they used this technology to stay aggressive on weed control while actually reducing input costs.
“They’ve looked at the economic numbers, and now they know that they can kill the weeds with herbicide applications and drop that herbicide cost below the cost of running a sweep plow,” she says. “It’s allowed them to gain those benefits of conserving moisture.”
5. Prioritize Prevention and Sanitation.
Lancaster urges farmers to lean into prevention and sanitation—two tools she believes are often undervalued. In Kansas, where many farmers also raise cattle, she sees clear risks in how feed and manure are handled.
“Livestock manure is very valuable, but if it’s not been composted well, or if that animal has had a diet that’s full of weed seeds, that’s going to introduce a whole other set of problems,” she warns.
People, vehicles, and animals are potential vectors for weed seeds. Lancaster advises farmers to be intentional about cleaning all equipment—including combines—to prevent spreading seeds from one field to another.
She extends this advice to anyone moving between multiple farms, especially.
“I remind students that if they’re a field scout in the summer, they need to be careful to not make their four-wheeler or their work boots a weed seed dispersal instrument,” she says. “It only takes one instance of seed introduction to have a serious problem for a long time.”
