Not since the days of johnsongrass in the pre-Roundup Ready crops era has one weed commanded so much attention. Palmer amaranth, an innocent-looking cousin of redroot pigweed – a weed that's existed in Indiana for decades – is anything but innocent. There are photos of crews in the South cutting it and pulling it out by the wagonload to prove it.
Now you can access a free publication hot off the press, or zinging off the keyboard as the case may be, from Purdue University. Purdue weed control specialists Bill Johnson and Travis Legleiter authored Palmer amaranth biology, identification and management. You can download this 11-page bulletin free form the Purdue Education Store, which handles distribution of Purdue publications. Look for WS-51. If you want a paper copy you can order them at the same Website for $2.10 each, plus shipping and handling.
Part of the problem with Palmer amaranth is its ability to produce tremendous amounts of seed, Johnson says, up to one million seeds per plant. Seed heads can be more than 20 inches long and extend well above the crop canopy.
If you're looking to identify it, it's a green, hairless, flowering weed with multiple seed heads per plant.
It's already been dubbed the worst weed ever in the South, and that's something, considering the South is also full of kudzu.
The key here is prevention, the specialists believe. Palmer amaranth was detected here in nine counties a year ago. The weeds in the counties around Evansville were resistant to glyphosate. Mark Lawson, an agronomist with Syngenta, recommended residual herbicides going into the season, whether you had seen the weed or not. He believes the best policy is to assume you have it on your farm and take steps to defeat it early.
The weed has been identified as far north as Michigan. The reason for the publication is to help people become familiar with it and what it takes to control it, Johnson concludes.