Editor’s note: This is the fourth in a series of articles about nine of the most troublesome weeds and tips for eradicating them from your no-till operation.

While it may not be the biggest weed concern for no-tillers in the Corn Belt, giant ragweed is still very much a threat.

“It’s one of the most competitive weeds in corn and soybean fields,” says Emilie Regnier, an Ohio State University weed scientist. “If you have a population of one plant per square meter, it would cause a yield loss of over 50% in corn, and more than 75% in soybeans.”

With a long emergence window and a growing resistance to ALS-inhibiting and glyphosate herbicides, this summer annual is becoming more of a challenge. But with due diligence and a commitment to no-till, growers can keep this weed in check.

Weed Behavior

One of the most challenging aspects of giant ragweed is its ability to emerge as early as March through early August, Regnier says. It’s also a tall weed, capable of reaching 15 feet or higher, which is why it’s a bigger threat in soybeans because it can easily outgrow the crop.

Regnier adds that giant ragweed also branches heavily, with large, opposite leaves that are typically three-lobed.

Genetically it’s very diverse, she says, so there can be a lot of variation in regards to herbicide resistance. But giant ragweed requires cross-pollination to produce seeds, so if the plants flower at different times or one giant ragweed plant is isolated by…