Palmer amaranth identification
Palmer amaranth is popping up in new locations around Indiana this summer and for farmers scouting the weed, Purdue Extension weed scientists are offering a new video to identify it. Bill Johnson and Travis Legleiter are in a Cass County field with a heavy infestation of the weed and are able to show it at various growth stages.
Johnson says this weed’s prevalence is expanding and that’s a concern.
“It has become somewhat widespread, particularly across the northern one-third of the state, and we feel like we need to do all that we can to continue to raise awareness of this weed because it does present arguably the most serious agronomic weed challenge that we’ve had in Indiana in quite some time.”
Palmer amaranth resembles other related weeds in the pigweed family so Legleiter says the first thing to look for when scouting is whether there are hairs on the plant.
“Your red root, smooth pigweed that are common in the state are going to have hairs on them,” explains Legleiter in the video. “Palmer amaranth and common waterhemp will not have hairs on them so in these plants, if we look in at the growing points, we cannot find any hairs on the stems or on any of the leaf surface, indicating to us we either have Palmer amaranth or waterhemp.”
Palmer amaranth grows rapidly and seeds quickly, threatening crop yields and bucking many herbicide control methods. It’s a growing problem and a growing concern for the entire industry because of that resistance.
“This isn’t a problem that we’re going to face as individuals,” Johnson says. “As an industry it’s going to take an integrated approach from a number of different people in order to try to keep this thing at bay.”
The purdue specialists would like to monitor the statewide progress of the weed so they encourage growers to send pictures of suspected Palmer amaranth. They are asking for multiple in-focus photos of the plant’s characteristics, as outlined in the video, to be emailed along with location information. The addresses are to wgj@purdue.edu for Johnson tlegleit@purdue.edu for Legleiter.
Palmer amaranth has been confirmed in 17 counties statewide: LaPorte, Newton, Jasper, Pulaski, Cass, Benton, Porter, St. Joseph and White in the northwestern part of the state; Adams, Kosciusko, Huntington and Noble in other northern areas; Henry in east-central; Clay in the west; and Posey and Vanderburgh in the extreme southwest.
Palmer amaranth updates are published frequently in Purdue Extension’s Pest and Crop Newsletter at https://extension.entm.purdue.edu/pestcrop/index.html.