Mark Lawson waited until he had confirmation from the Purdue University Plant and Disease Diagnostic Lab before he contacted me. Lawson is a regional agronomist for Syngenta near Danville. He also operates a small farm.
He wanted to be sure of the information passed along because it was potentially a hot potato. A grower had called him in, and Purdue had confirmed the dreaded Palmer amaranth within the state of Indiana. Lawson's first find came from Fulton County. Since then, he notes that other Syngenta reps in various locations are running across what they believe to be Palmer amaranth.
This relative of redroot pigweed is dreaded in the south because it has literally taken over some cotton fields. The weed grows fast and can become large. Unless you plan ahead for it, it can become very hard to control.
Bill Johnson, Purdue University Extension weed control specialist, says the threat is real and it's time Hoosiers pay attention to it. The amaranth can be controlled, but it takes first understanding the problem, then planning for it.
Johnson confirms that it has been positively identified in Fulton, Cass, Jasper and Vanderburgh Counties. They will be growing seeds out to determine if it's glyphosate resistant. However, the plants in the Evansville area withstood 7 gallons of generic glyphosate without being fazed.
Johnson intends to work closely with Bryan Overstreet in Jasper County to develop programs for it, and will be discussing it at his winter meetings this year.
"The problem is that it grows so fast, you've got to do something besides just wait and hit it with Roundup," Johnson says. There are options in corn and soybeans, involving both pre's in corn and primarily post products in soybeans.
There are other species of pigweed in Indiana, including redroot, smooth, waterhemp, now Palmer, and spiny pigweed, which has been here for a long time, primarily in pastures.
The discovery of palmer amaranth shouldn't be taken lightly, he concludes.