Illinois farmers urged to scout fields for new invasive weed threat
Corn and soybean farmers are being advised to watch for a new weed during the upcoming growing season. Asian copperleaf, also known as Acalypha australis, has been identified for the first time in an Illinois farm field located in Stephenson County. This marks the first confirmed record of this weed species in the state.
“It is more advantageous to remain in front of a new weed challenge rather than allow it to get in front of researchers and producers,” said Aaron Hager, weed science professor and University of Illinois Extension faculty specialist in the Department of Crop Sciences, part of the College of Agricultural, Consumer and Environmental Sciences.
Asian copperleaf is a non-native plant to the United States. It was first recorded in New York in 1990 and later identified in Iowa in 2016. Since then, the weed has spread to several counties in Iowa. Illinois is now the third state where this species has been confirmed.
Crop specialists are concerned because Asian copperleaf spreads quickly and produces large amounts of seed. Reports from other countries show that the weed can develop resistance to herbicides. If left unmanaged, it could become difficult to control in crop fields.
The weed grows as a summer annual plant and reproduces only by seed. Its exact emergence timing is still not well understood. Reports suggest that it is often noticed at corn harvest, but seedlings have also been seen around soybean planting time.
“Asian copperleaf’s relatives are native to Illinois, growing in grassy areas, woods, and sometimes as yard weeds,” said David Zaya, associate research scientist and botanist with the Illinois Natural History Survey at U. of I. “The best way to tell Asian copperleaf apart is the leafy tissue under the flowers.”
Identifying Asian copperleaf can be challenging, especially before flowers appear. The plant has alternately arranged leaves with serrated edges and pointed tips. One key feature is the leafy tissue called bracts, which grow below the female flowers. These bracts help separate Asian copperleaf from similar native plants found in Illinois.
Experts explain that native copperleaf species usually have bracts shaped like small hands or stars. In contrast, Asian copperleaf bracts are shaped more like hearts or eggs with pointed tips. Large, dense populations in farm fields are also a strong indicator of this invasive weed.
Farmers are encouraged to scout fields before planting and throughout the growing season. Preventing seed movement is important to reduce future spread. Fields with Asian copperleaf should be harvested last, and equipment should be cleaned before moving to other fields.
Photo Credit: Iowa State University Extension and Outreach