Looking for Palmer Amaranth

I'm sure most of you have heard of Palmer amaranth (Amaranthus palmeri). If not, it's an extremely aggressive, invasive broadleaf weed, native to the desert southwest, that is usually very glyphosate- and ALS-resistant. To date it's been found in northwest and southwest Indiana.

I'm not aware that any has been found in Clinton County and I've been keeping an eye out as I've been driving around this summer. However as you'll soon be getting into your fields for harvest, I have a request; if you come across any Palmer amaranth when you get in the field, please let me know. I'll send that information on to Bill Johnson at Purdue's Botany and Plant Pathology Department. Purdue has a longstanding policy regarding pest reporting; when they identify where a pest is located to inform the public, they say what county it's located in, not where in the county.



Palmer Amaranth: Photo from Purdue Extension Publication WS-51, Palmer Amaranth Biology, Identification, and Management

At the bottom of this post I'll include a link to the Purdue publication on Palmer amaranth but for ID purposes, here's what to look for. The main distiguishing characteristic at this point in the plant's life will be an extremely long seed head, up to three feet long. Its leaf is wide and ovate and is not lobed like giant ragweed.

If you come across this weed, please let me know, either by calling the extension office or by e-mailing me at cemanuel@purdue.edu. Feel free to send me some pictures if you're not sure if this is what you're seeing, or yank out the plant and let me know and I'll come take a look at it.

Purdue Extension Publication on Palmer amaranth

Source: Purdue Extension Publication WS-51, Palmer Amaranth Biology, Identification, and Management by Travis Legleiter and Bill Johnson, April 2013.