While we don’t typically think of harvest time as prime time for scouting fields, this fall is a great time to watch for Asian copperleaf (Acalypha australis) lurking under the crop canopy. This new weed to Iowa farms has been confirmed in eight counties so far:
- Calhoun
- Humboldt
- Boone
- Wright
- Franklin
- Hardin
- Grundy
- Black Hawk
Although the threat this species poses remains uncertain, it’s a significant agronomic weed in other areas of the world. It has developed a resistance to several herbicide groups used in Iowa row crops and has been found at high densities in numerous Iowa fields in recent years.
Farmers already have reported significant difficulty managing this species with herbicides. Populations appear to emerge from late April or early May through most of the summer, similar to waterhemp. Early identification of this species is key to adopting effective management tactics to reduce its spread to other fields.
Appearance
Asian copperleaf has alternate leaves that are 2-4 inches long, lanceolate to egg-shaped, with fine, blunt teeth and deep veins. Plants can reach heights of 2-3 feet, although they may be shorter under a crop canopy. Plants that receive more sunlight are highly branched, while those under the canopy have few branches.
As fall approaches, the upper leaves on plants also may develop a reddish or coppery color. Unlike waterhemp, Asian copperleaf does not have long flowerheads or inflorescences at the tops of stems. It instead produces flowers and seed primarily along stems.
HEART-SHAPED BRACTS: Asian copperleaf has circular to heart-shaped bracts beneath flowers.
Look for bracts
The key to identifying Asian copperleaf from other similar species is the bracts beneath the flowers that occur along the stem. Asian copperleaf bracts are circular to heart-shaped with a toothed margin. The combination of its low height, reddish color to upper leaves and the heart-shaped bracts should make identification at harvest time simple.
Due to the ease of identification this time of year, keep an eye out for this species during harvest. If you find a plant you suspect might be Asian copperleaf, contact your local Iowa State University Extension and Outreach field agronomist for assistance with identification. You can report sightings yourself at go.iastate.edu/FGA4NK.