Asian Copperleaf Makes a Return

May 24, 2024
ICM News

As of this spring, we’ve identified Asian copperleaf (Acalypha australis) in crop fields in six counties, and it's likely in more. As we find more populations, it is easier to monitor their development through the growing season. Field agronomists have been monitoring two of the infestations this spring and have observed many emerged seedlings in Boone and Franklin counties. As farmers scout fields and prepare for postemergence herbicide applications, it is important to keep an eye out for this new Iowa weed.


Asian copperleaf is in the spurge family but lacks the milky sap produced by many spurges. Seedlings have round cotyledons, often with several prominent veins (Figure 1). The first set of true leaves will have opposite leaf arrangement, while subsequent leaves will be alternate. Leaves may be about 2-4 inches long, lanceolate to egg-shaped, with fine, blunt teeth and deep veins; young leaves may have a copper color (Figure 2). Plants can reach heights of 2-3 ft., though may be smaller if under a crop canopy.

Figure 1. Seedling Acalypha species will have round cotyledons and lanceolate leaves with blunt teeth. Photo courtesy of Meaghan Anderson and Bob Hartzler.

Virginia copperleaf and three-seeded mercury are two other Acalypha species present in Iowa with a similar growth habit. These two species are more common in home landscapes, woodlands, and disturbed natural areas; it is unusual to find them in crop fields. The distinguishing characteristic of Asian copperleaf from the other Acalypha species are the bracts located beneath the flowers. The bracts are circular to heart-shaped with a toothed margin (Figure 3). Both Virginia copperleaf and three-seeded Mercury have deeply-lobed bracts (Figure 4). It is difficult to confidently differentiate these species prior to flowering and development of the bracts.

Figure 2. Asian copperleaf has lanceolate to egg-shaped leaves with blunt teeth and deep veins. Meaghan Anderson, Iowa State University.

Figure 3. Asian copperleaf has circular to heart-shaped bracts beneath flowers. Meaghan Anderson, Iowa State University.

Figure 4. Deeply-lobed bract typical of Virginia copperleaf and three-seeded mercury (left) compared to a heart-shaped bract from Asian copperleaf (right). Photos courtesy of Bob Hartzler.

Keep an eye out for this species ...

Figure 5. A dense infestation of Asian copperleaf present at crop harvest. Photo courtesy of Meaghan Anderson.

In past years, farmers have alerted us to Asian copperleaf presence at harvest, where it formed thick mats under the canopy in both corn and soybean (Figure 5). We will be monitoring populations this summer to gain a better understanding of their emergence patterns and the effectiveness of postemergence herbicides on this species.

While scouting this growing season, please keep an eye out for this species. If you find a plant you suspect might be Asian copperleaf, please contact your local Iowa State University Extension and Outreach field agronomist for assistance with identification. While the magnitude of the threat posed by this weed in Iowa remains unknown, it is a significant agronomic weed in other areas of the world, has evolved resistance to several herbicide groups, and has been found at high densities in several Iowa fields in recent years.

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on May 24, 2024. The information contained within may not be the most current and accurate depending on when it is accessed.


Meaghan Anderson Field Agronomist in Central Iowa

Meaghan Anderson is a field agronomist in central Iowa and an extension field specialist at Iowa State University Extension and Outreach. Educational programming is available for farmers, agribusinesses, pesticide applicators, certified crop advisors, and other individuals interested in...