By Scout Nelson
A new weed species called Asian copperleaf (Acalypha australis) is raising concerns among farmers and weed experts after its discovery in a corn field in Rice County, Minnesota, in fall 2025.
The plant is native to eastern Asia and has spread to parts of the United States. Its arrival in Minnesota raises concerns about its possible spread in corn and soybean fields. Early identification and control are important to prevent the weed from becoming more widespread.
Sithin Mathew, Weed Science Graduate Student, Matt Pfarr, Former Crops Extension Educator, and Debalin Sarangi, Extension Weed Scientist shared information about this emerging weed threat.
Where Does Asian Copperleaf Come From?
Asian copperleaf is native to countries in eastern Asia, including China, Japan, Korea, the Philippines, and parts of Russia. It grows in grasslands, on slopes, in cultivated fields, and in disturbed soil.
The first known detection in the United States occurred in New York in 1990. The weed was later found in an Iowa corn field near Cedar Falls in 2016. Since then, it has been reported in at least eight Iowa counties and in Illinois.
The discovery in Minnesota suggests that the weed may continue spreading across the Midwest. Farmers should watch their fields closely, especially during harvest, when plants hidden beneath crop canopies become easier to see.
Why Is Fall the Best Time to Scout?
Asian copperleaf is an annual broadleaf weed that grows from seed each year. Seeds usually begin germinating in late April or early May, and new plants may continue emerging throughout summer.
Young plants can look like other weeds, making early identification difficult. By fall, the plants are more developed and may show clear features that help distinguish them from similar species.
Under full sunlight, Asian copperleaf can grow 2 to 3 feet tall. Plants growing beneath corn or soybean canopies often remain shorter, reaching up to about 18 inches, with fewer branches.
As crops are harvested, combines expose areas where the weed may have grown unnoticed. The upper leaves can also turn reddish or copper-colored in late summer and fall, making the plant easier to spot.
How to Identify Asian Copperleaf?
Farmers should look for several features when checking fields for Asian copperleaf.
Leaves: The leaves are about 2 to 4 inches long and range from lance-shaped to egg-shaped. Their edges have small, blunt teeth, and the surfaces appear wrinkled because of their raised veins.
Plant shape: Plants grow upright and may reach 2 to 3 feet in sunny areas. They are often shorter in shaded fields.
Leaf color: Upper leaves may develop a reddish or coppery color late in the season.
Flowers: Unlike waterhemp, which produces long flower spikes, Asian copperleaf has flowers along the stem.
Bracts: A toothed, heart-shaped to nearly round structure sits beneath each flower. Native copperleaf species have more deeply divided bracts, which helps distinguish them from Asian copperleaf.
Farmers should examine these features together rather than relying on leaf color alone.
Seed Production and Spread
Asian copperleaf reproduces through seeds. Each plant can produce hundreds of seeds, and these seeds may remain in the soil for several years. The exact length of time they survive in Midwestern soils is not yet known.
The weed may spread through contaminated farm equipment, crop residue, and soil moved between fields. Plants growing along field edges or beneath crop canopies can escape notice and produce seeds before farmers recognize the problem.
Cleaning equipment and checking fields regularly can help reduce the risk of spreading seeds to new areas.
Why Is Asian Copperleaf a Concern?
The USDA classifies Asian copperleaf as a “high-risk invasive weed.” Its ability to grow in crop fields and produce many seeds raises concerns about its future spread.
Herbicide resistance is another concern. Resistant populations in Asia have been reported for glyphosate (Group 9), ALS inhibitors (Group 2), and PPO inhibitors (Group 14). These herbicide groups are widely used in Midwestern crop production, so resistance could make management more difficult.
Research from Asia also shows that heavy infestations can reduce yields by as much as 50% in crops such as cotton, pulses, and vegetables. The level of yield loss in Minnesota corn and soybean fields is not yet established, but early monitoring can help limit the weed's spread.
What Should Farmers Do?
Farmers should scout corn and soybean fields during harvest, paying special attention to field edges, shaded areas, and patches of unusual weeds. They should avoid moving potentially contaminated soil or plant material between fields and clean equipment when needed.
If Asian copperleaf is suspected, farmers should contact Dr. Debalin Sarangi at dsarangi@umn.edu or their local Extension office. Experts can help confirm the plant's identity and provide management advice.
Photo Credit: University of Minnesota
Categories: Minnesota, Crops, Corn, Soybeans