Weed Warnings for 2019

Vines in mature corn ( Darrell Smith )

From the seat of the combine you see the sins of the season. Perhaps one of the most frustrating? Weed escapes.

“How well did your weed control program work—what can you do next year?” asks Brent Tharp, Wyffels agronomy and product training manager.

Reflect on the season. Did you follow best management practices? Did Mother Nature get the best of you or were there other issues that allowed weeds to escape? Use this information to plan weed control strategies for 2019.

“Managing weeds in season is more difficult, especially in soybeans,” says Harmon Wilt, Dekalb technical agronomist in Minnesota. “Corn is easier because it canopies so much quicker. Growers learned if we didn’t put a pre-[emergent herbicide] down it was difficult to control weeds.”

Pre-emergent herbicides are your crop’s first line of defense. Your goal should be to plant into a weed-free field. Think back to planting—was it weedless? Or did a few weeds outcompete your seedling crops? That simple misstep steals sunlight, water and nutrients from crops.

“Waterhemp, for example, emerges all season long,” Wilt adds. “We need residuals for about two months.”

In some areas, farmers were resistant to use pre-emergent herbicides, according to Erich Eller, owner of ForeFront Ag Solutions. “We see guys use fewer residual products on soybeans, on corn we tend to use more. Granted, with the amount of rain we had this year the residual got used up faster.”

Weather, while uncontrollable, is important to consider when reviewing weed management efficacy. Rain and moisture could mean you miss the ideal window to spray, allowing weeds to grow tall and beyond controllable size, or the residual impact is negatively affected.

“One thing I’m doing in 2019 is documenting and tracking the weather,” Eller adds. “When did that weed break through? Was it raining? What was the impact on the residual?”

Take note of what happened and do what you can to mitigate that risk next year.

“This year I saw a lot of volunteer corn in soybeans,” Tharp says. “I think with the Xtend program guys didn’t come in with a grass killer. The concern with that is if you have corn rootworm the volunteer corn can act as a bridge and make the pest a bigger problem in corn the following season.”

Note what weeds you saw throughout the season. Whether it’s volunteer corn, waterhemp, lambsquarter or whatever, you need to know what you’re up against before you purchase herbicides and herbicide tolerant trait packages. Double check that your herbicide plan will kill the weeds, preferably with at least two modes of action.

The 2018 season can act as a lesson for the 2019 season. Learn from mistakes and missteps to make next year better, keep weed banks from building and help yields soar.