Palmer Amaranth Biology, Identification and Management was created by Purdue Extension weed scientists Bill Johnson and Travis Legleiter in an effort to curb the weed’s expansion to the northern U.S. The 11-page publication can be downloaded at https://www.the-education-store.com, where it can be found by searching for “WS-51.” Print copies can be ordered for $2.10 each, plus shipping and handling.
“We’re very concerned about the competiveness, the seed production and the impact Palmer amaranth can have on Midwest crops,” Johnson said. “We feel this is a weed we really need to get on top of before it becomes very widespread.”
Palmer amaranth is a green, hairless, flowering weed with multiple seed heads.
“It’s arguably the worst weed problem to hit agronomic crops in the southern United States,” Johnson said. “We’ve watched cotton fields being mowed down before harvest because of Palmer amaranth.”
In recent years, Palmer amaranth has spread north to Indiana, Ohio, Illinois and Michigan, and both Legleiter and Johnson want farmers to know the potential threat it poses to crops. They are most concerned with how this weed could affect area soybeans.
“We have a number of herbicides that we can use in corn to control it, but in soybeans we’re really limited on the number of herbicides we have to control it because most populations are going to be resistant to both glyphosate and ALS – acetolactate synthase,” Johnson said.
The publication offers management recommendations based on research from the South and Michigan State University since this is a relatively new problem in Indiana.
Farmers should rotate crops so they can use additional herbicides that may work for corn but not beans, practice deep tillage to bury Palmer amaranth seeds, and monitor field ditches and borders for weed emergence.
Johnson and Legleiter recommend farmers use a multipronged management approach to control this weed because it is highly adaptable and has a high chance of survival.
“Bad control in one year can lead to a lifetime of problems because of the amount of seed it can produce, Johnson said.
(Source: Purdue Ag Communications/Purdue Agriculture photo/Travis Legleiter)