Asian Copperleaf Makes a Return

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.

Identification

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.

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.

Keep an eye out for this species ...

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.