How to Counter Unpredictable Weed Pressure

Something went wrong. Please try again later...
Christian Guenthner

Unseasonable dry fall conditions can lure you into believing that weed pressure is minimal until early spring moisture brings with it a flush of healthy weed growth. The effect may be amplified in no-till production systems where the seedbed remains relatively undisturbed.

“Our seedbed often includes kochia, pigweed and Russian thistle. In 2021, many of these weeds emerged after our normal herbicide timing and produced a ton of seed,” says Christian Guenthner, an agronomist with Valley Farmers Supply in Worden, Montana.

In 2022, many of Guenthner’s grower-customers began planting their spring cereal crops in March or even earlier for those with irrigated ground.

“With adequate rainfall and frequent, wet snow, we had ample moisture this year,” Guenthner says. “We planted early and fought rain in some areas, so we were often late with spring herbicide applications.”

“Rezuvant burns weeds down, and they don’t come back. WideMatch works more slowly, but it sticks around preventing weed regrowth.” — Christian Guenthner

That often meant increased wild oat, kochia, Russian thistle, bindweed, lambsquarters, mustards, rye and downy brome (cheatgrass) pressure. Herbicide resistance also was sometimes a challenge.

Guenthner varies his herbicide recommendations depending on the weed species in a field and potential resistance issues. That’s where the broad selection of cereal herbicides by Corteva Agriscience comes into play.

Among his frequently recommended products are Rezuvant®, OpenSky®, WideMatch®, Pixxaro® EC, Stinger® and Starane® Flex herbicides.

“Pixxaro is perfect on dryland winter wheat, triticale and spring wheat,” Guenthner says. “It has a wide weed spectrum and works well on kochia, Russian thistle, prickly lettuce, pigweed and burndown for bindweed. It’s nice because it’s a low use rate.”

Rezuvant is frequently used in malt barley, targeting wild oat plus broadleaves and grasses. “It’s a nice all-in-one jug,” he says.

Guenthner often recommends Rezuvant, OpenSky and Stinger herbicides to control curly dock and volunteer alfalfa, especially after an alfalfa rotation. He also recommends using WideMatch for curly dock and tougher-to-kill weeds, and OpenSky for use on dryland, non-Clearfield® wheat, primarily targeting cheatgrass and wild oat. For Canada thistle control, he recommends Stinger or a Stinger tank-mix, and says Starane goes out on almost everything in a tank mix targeting kochia and Russian thistle.

“The residual activity of WideMatch looked good this year, and so did the Rezuvant,” Guenthner says. “Rezuvant burns weeds down and they don’t come back. WideMatch works more slowly, but it sticks around preventing weed regrowth.”

Pixxaro® EC, Rezuvant®, OpenSky®, Starane® Flex, Stinger® and WideMatch® are not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.