It can be tough to tell the difference between Palmer amaranth and waterhemp.
Still, University of Illinois weed specialist Aaron Hager says identifying the weed is key to controlling these weeds. Proper identification leads to proper treatment, which helps protect yield potential.
Hager notes the two weeds look extremely similar in their early vegetative stages.
"During the 1990s, waterhemp provided an excellent example of how difficult it can be to differentiate among the various Amaranthus species, especially when plants are small," he adds.
To help, U of I is asking farmers to send in suspected Palmer amaranth plants. In the lab, they'll use molecular biology to determine whether the plant is Palmer amaranth or another Amaranthus species. Information on how to collect and submit tissue samples from suspected Palmer amaranth plants is described on the Palmer amaranth identification form, found at http://tinyurl.com/k34z3yf. Download the form, provide as much information as possible, and submit it along with the tissue samples to the address listed at the top of the form.
"Proper management of Palmer amaranth populations can help reduce the potential for seed production that will augment the soil seedbank and perpetuate the population in future growing seasons," Hager says.
Moving to Illinois
Palmer amaranth (Amaranthus palmeri) is a summer annual broadleaf weed species taxonomically related to other pigweed species (waterhemp, smooth, redroot) common in Illinois agronomic cropping systems. Palmer amaranth is not indigenous to Illinois, but rather it evolved as a desert-dwelling species in the southwestern U.S., including areas of the Sonoran Desert, Hager says.
"Genotypic and phenotypic adaptability have allowed Palmer amaranth to expand its distribution and colonize the vastly different agricultural landscapes across much of the eastern half of the United States, including Illinois," he explains.