Too late for herbicide: Farmers need to control toxic cressleaf groundsel

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cressleaf groundsel
Cressleaf groundsel is getting an aggressive start in many Ohio pastures, hayfields and wheat fields. It can be a problem for livestock producers because it is poisonous to cattle, horses, goats and sheep. The weed is also poisonous to humans. (Purdue University photos)

COLUMBUS — Cressleaf groundsel is on the rise in fields across Ohio due to a mild winter that’s allowed many weeds to get an aggressive start this growing season.

And while cressleaf groundsel isn’t a new problem, it is being reported in fairly high numbers in hay and wheat fields, according to Mark Loux, a weed scientist in the College of Food, Agricultural, and Environmental Sciences at The Ohio State University.

And that could be a problem for livestock producers, because it is poisonous to cattle, horses, goats and sheep, Loux said. The weed is also poisonous to humans.

The weed is typically found in no-till corn and soybean fields that have not yet been treated with burndown herbicides, so some livestock producers may not be familiar with it.

Cressleaf groundsel is a winter annual that emerges in late summer or fall and infests late-summer seedings of forages and hay. It has a hollow and grooved stem, is purplish in color and has yellow sunflower-like flowers.

Focus on management

“This year so far has definitely been a big year for cressleaf groundsel, as the mild winter allowed more of the weed to survive,” Loux said. “It’s caught many hay producers by surprise.

Applying herbicides to hay fields now likely won’t reduce the risk of toxicity in animals, Loux said. And it’s too late for wheat growers to apply any herbicide to their wheat crops. The winter annual is best controlled with herbicides in the fall or early spring when the plants are smaller and more susceptible.

“But at this point, the plant is flowering and there are many more of them,” he said.

He said growers should prevent them from going to seed and avoid letting the weed get into the supply chain for straw when baling.

Timely mowing

That means taking steps to mow infestations in time to prevent seed production, and to know what the risk of toxicity in hay or straw based on the level of cressleaf groundsel infestation, Loux said.

“Drying or ensiling the plants during the hay or straw making process doesn’t reduce the toxicity of cressleaf groundsel,” he said.

Producers should also avoid harvesting areas of the field that have high concentrations of cressleaf groundsel. And instead of leaving the plant residue in the field, they could instead bale and discard hay or straw from those areas, Loux said.

More information on cressleaf groundsel, including how to identify it and manage it, can be found on Ohio State’s weed science website at u.osu.edu/osuweeds. A factsheet can be found on the “Weeds” pull-down menu on the site under “Other weeds.”

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