The University of Illinois reported on May 6 that Asian copperleaf, a non-native weed species, has been identified in Stephenson County in northern Illinois following last fall’s corn harvest. This marks the first confirmed presence of Asian copperleaf (Acalypha australis) in the state.
The emergence of this weed is significant because it could pose new challenges for corn and soybean farmers. Reports from other states suggest that Asian copperleaf can spread quickly and may develop resistance to herbicides, making early identification and management important.
“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. Hager also said, “Our goal is to give Illinois farmers and weed management practitioners the information necessary for them to scout and identify populations of Asian copperleaf. We hope this will allow any additional populations to be identified so that management can be implemented to reduce the movement of seed to additional fields.”
Asian copperleaf was first documented in New York in 1990 before being found again in Iowa seed corn fields starting from 2016. It has since been confirmed across ten counties in Iowa, with Illinois now becoming only the third state where its presence is established. Identifying this plant before reproductive structures appear can be difficult; its leaves are alternately arranged with serrated margins, pointed tips, and rounded bases. The bracts beneath female flowers help distinguish it from native species such as Virginia copperleaf or rhomboid mercury.
“Asian copperleaf’s relatives are native to Illinois, growing in grassy areas, woods, and sometimes as yard weeds,” said David Zaya, associate research scientist at the Illinois Natural History Survey at University of Illinois Urbana-Champaign. Zaya explained how distinguishing features include leafy tissue under flowers: “The best way to tell Asian copperleaf apart is the leafy tissue under the flowers.” He added that if there are hundreds of thousands present in an agricultural field or if bracts look like a heart or egg with a pointed tip rather than a small hand or lopsided star shape typical for native species—it likely indicates Asian copperleaf.
Farmers are encouraged by experts at University of Illinois Extension to scout for this species throughout planting season as well as after harvest since preventing seed spread is crucial for managing future infestations. They advise harvesting affected fields last and cleaning equipment between fields.
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