New Weed Species Confirmed in Iowa Fields a Second Time
During his career as an Extension weed scientist for Iowa State University, Bob Hartzler has seen a lot of weeds.
"After a few years in the business, you seldom encounter a weed you haven’t dealt with before," he used to tell students.
This summer, a weed he first saw and identified in an Iowa cornfield in 2016 – Asian Copperleaf (Acalypha australis) – has been found in the state again. This time, the weed was found in soybeans.
“The plant is not included on the list of weeds considered a threat to the U.S., according to the Federal Noxious Weed Act. However, a USDA APHIS Report states the plant has potential to be harmful to row crops, and that the plant is adapted to survival in about 75% of the United States,” Hartzler says, in the Integrated Crop Management article he wrote about the weed six years ago (see bit.ly/3FxtsJl).
It took several attempts for Hartzler to find someone who could identify the weed. He eventually shared images of the weed with a taxonomist who then sent the images to a spurge expert who was able to identify the plant.
The weed is native to China, Australia, Japan and other countries in the region.
Until its appearance in Iowa, sightings of Asian copperleaf in the U.S. had been confirmed in only one other, unlikely place: New York City.
Unknown Threat to U.S. Crops
Both times, in 2016 and this year, a thick patch of Asian copperleaf was present in fields. The severity of the infestations raises concerns, according to Meaghan Anderson, Iowa State University Extension field agronomist in central Iowa.
“Two sources note this species has populations resistant to HG 9 (glyphosate) and HG 14 (PPO inhibiting) herbicides in its native range,” she says. “A USDA Risk Analysis completed in 2012 stated that the species did not show ‘any strong invasive or weediness characters,’ but because of a high level of uncertainty, the plant was classified as ‘high risk’ in 57% of the simulations.”
Hartzler adds, that based on resources and experts he consulted, “the plant is adapted to survival in about 75% of the United States.”
It is unknown how the plant was introduced to Iowa, but it is likely the two reported infestations are related, Anderson says in an IPM article (see bit.ly/3zh5DkN).
What To Look For
Anderson says Asian copperleaf is in the spurge family but lacks milky sap common in many spurges (see provided photo below).
"It is an erect plant that can reach heights of 2 feet to 3 feet, but most plants found in Iowa were less than 18 inches in height. Leaves are 2 to 3 inches with serrated edges. The distinguishing characteristic of Asian copperleaf are the bracts located beneath the flowers. The bracts are circular to heart-shaped with a dentate margin," she says.
Asian copperleaf seems to emerge late in the season and remains under the crop canopy throughout the growing season.
Just last week, the Iowa Department of Agriculture and Iowa State University asked Iowans to report any sightings to determine the potential scale of the infestation.
If you detect the plant, contact the Iowa Department of Agriculture at 515-725-1470.
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