“Under the Canopy!”: the Asian Copperleaf

Oct 18, 2022

There’s a new weed in town, and Iowa farmers aren’t feeling cool about it in the least bit.

Hello, Asian copperleaf. A nasty plant from the spurge family (but without the milky sap), it can grow as high as 2-3 feet, but normally stays under 18 inches (in Iowa at least).

Its leaves have serrated edges and grow 2-3 inches long. With circular/heart-shaped bracts beneath its flowers, an Asian copperleaf is more identifiable after flowering.

The kicker: The weeds remain under the crop canopy, emerging late in season, and stay under the crop canopy throughout the growing season.

Oh and this: It poses a giant threat to row crops within its native range. Some say the weed has shown resistance to Group 9 (glyphosate) and Group 14 (PPO inhibiting) herbicides.

Soundbite: “Is this plant emerging late underneath the canopy? Does it survive well in shade and doesn’t mind the competition? Or is it surviving through herbicide application? That’s a big question that we’re not sure about,” said Meaghan Anderson, field agronomist at Iowa State University.

Disappearing act: Asian copperleaf was first discovered in Iowa in 2016 near Cedar Falls. Before this, it had only been found in NYC, in the only other documented North American infestation.

That all changed a few weeks ago when they found the plant in a soybean field almost 30 miles from the original infestation in Grundy County, Iowa. The weeds were in patches, indicating they’ve been there a while prior to being caught.

Asian copperleaf is native to Australia, China, and Japan.

Plant discoveries have been made during harvest, so the Iowa Department of Agriculture and Land Stewardship requests that farmers watch for this unwelcome field guest.

If seen: Call the Iowa Department of Agriculture and Land Stewardship at 515-725-1470, or email entomology@iowaagriculture.gov.