Last fall, we identified yet another field with an infestation of Asian copperleaf (Acalypha australis). For more background, check out this ICM News article from last fall.
While most reports of this species have been at harvest when it is noticeable under the crop canopy, we’ve also received reports of A. copperleaf in June, around the time when postemergence herbicide applications are happening. While it’s not known exactly when this species germinates in Iowa, it’s important to monitor fields for this new species as other summer annual weeds emerge.
Asian copperleaf is in the spurge family but lacks milky sap common in many spurges. Seedlings have round cotyledons. 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. Plants can reach heights of 2-3 ft., though may be smaller if under a crop canopy.
Virginia copperleaf and three-seeded mercury are two other Acalypha species present in Iowa with a similar growth habit. The distinguishing characteristic of Asian copperleaf 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 unlikely that anyone could confidently differentiate between these species prior to flowering and development of the bracts.
Keep an eye out for this species
As scouting begins this growing season, please keep an eye out for this species in crop fields. 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 is 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 23, 2023. The information contained within may not be the most current and accurate depending on when it is accessed.