ESSEX, Ill. — University weed specialists have spread the
word the past few years about Palmer amaranth and how its move northward will be
a game-changer in weed management strategies.
Existence of the “frankenweed” has been confirmed in nearly
30 counties throughout central, northeast and southern Illinois, and more than
one-third of those counties had glyphosate-resistant Palmer amaranth.
The potentially devastating weed was the focus of a Bayer
CropScience “Respect the Rotation” tour at a Kankakee County field research
Palmer amaranth is a summer annual broadleaf weed species
related to other pigweed species — waterhemp, smooth and redroot — common in
Research has demonstrated that Palmer amaranth has a higher
growth rate and is more competitive than other pigweed species.
Growth rates approaching three inches per day and yield
losses of 78 percent in soybeans and 91 percent in corn attributed to Palmer
amaranth have been reported in the scientific literature.
The female plants can produce hundreds of thousands of seeds
per plant, and once the plant has grown to four or more inches, the
effectiveness of herbicide treatments dramatically drops.
As is the case with its waterhemp cousin, Palmer amaranth is
capable of developing resistance against a variety of herbicides, and the
greatest likelihood for successful control is an integrated management approach.
The need to “Respect the Rotation” is evident in controlling
the fast-growing and difficult-to-control Palmer amaranth, and the field tour
featured the weed’s prodigious growth and/or control with the use of various
Daren Bohannan, Bayer CropScience tech services
representative, said the “Respect the Rotation” is an initiative the company
began about six years ago to elevate the importance and grower adoption of
“It’s an initiative to collaborate with universities,
establish research on existing biotypes of resistance weeds and to basically
give us a platform which to work with these universities, rent ground and do
research on the three Rs, which are rotate modes of action, rotate crops, and
rotate herbicide-tolerant traits,” he said.
“We bring the universities into these sites to do work, we
encourage them to approach the other chemistry manufacturers, make sure that
they’re represented and we can work together and come up with solutions.”
This marked the first year at the Kankakee County site.
“Up until last year no one was aware that Palmer amaranth
was growing in this area. We started looking at this and found that it wasn’t
(herbicide) resistant waterhemp it is Palmer,” Bohannan said.
Soybean and cotton growers in the southern U.S. have become
the unwilling and unfortunate case study in the expansion of herbicide-resistant
Larry Steckel, University of Tennessee row crop weed
specialist, said at the tour it is a costly weed to control.
From 2006 to 2014, herbicide costs to control these
resistant weeds in cotton have risen from $60 an acre to $100 to $120 per acre,
University of Tennessee studies show.
“For soybeans using Roundup, we’re at $80 to $100 an acre,
and we were at $30 per acre,” Steckel said. “It’s increased our cost in corn to
$60 to $70 per acre, and it used to be $30.”
Steckel said one farmer in Tennessee collected data that
showed from 2006 to 2012 his fertilizer cost increased 48 percent, seed cost
increased 50 percent and his herbicide cost went up 250 percent in that same
“The good news is we’re able to control it. We’re spraying a
lot, and we also have chopping crews going out that at $20 to $25 per acre on
top of these herbicides,” he said.
“The thing that’s concerned me is these commodity prices are
not so great any more and you start to really wonder about sustainability.”