Farm Press Editorial Staff
THAT LAYBY APPLICATION you made, or
didn’t make, matters when it comes to continued pigweed control in cotton, and it can
help preserve a valuable tool.
“A lot of our growers are challenged with
their time, and unfortunately a lot of them
have decided to not use a layby application,
or hooded application. Our research is saying
that’s a really bad idea when it comes to fighting Palmer amaranth. That layby application
allows us to do several things,” said Stanley
Culpepper, University of Georgia Extension
Culpepper was one of the presenters of the
30 stops at the annual Sunbelt Ag Expo Field
Day held in Moultrie, Ga., July 25.
With a layby application, Georgia cotton
growers get a valuable chance to deploy sub-
stitute urea chemistries, such as diuron, which
are not used in any other agronomic crop.
“And these chemistries are very effective, not
only in controlling the emerging pigweed,
but they also give excellent residual control to
let the cotton close out. … When our growers
pull these precision, timely applications out
and they go over the top, a lot of times we
don’t get good enough coverage of those
weeds high under the cotton.”
In a cotton test plot at the Sunbelt Ag Expo
farm, Culpepper applied a pre-emergence,
which is always needed, and then delivered
sequential Roundup-Dicamba applications
over the top, or what would be considered
a standard program. He then came in with
a layby application of Roundup plus diuron
along with a little bit of Envoke to clean up
morning glory. “There’s not one pigweed
plant per acre left where we ran that system,”
On an adjoining test plot, Culpepper followed the same standard herbicide system
going over the top but left out the layby
application. In the test plot without the layby,
he had what would equate to 1,400 Palmer
amaranth plants per acre, which may not necessarily look like a lot when you ride by on the
road. But think about it, he said.
“Half of those plants are females. Those
females are going to produce upwards of
a half a million seed per plant. If for some
reason one survived those Roundup-Dicam-
ba applications we made, we really ought to
be concerned. If it’s resistant or is tolerant to
dicamba, just one of them, and produces that
progeny, here we go. In three years, we could
lose this chemistry,” he warned.
Last year, Culpepper surveyed about 400
cotton growers and of those about 40 percent
were still using layby applications as part of
their weed management program. Of course
getting that percentage higher would be
good, he said.
At the Sunbelt Ag Expo farm, Culpepper
created a pigweed jungle, so to speak, where
pigweeds towered more than eight feet tall.
Cotton growers can create their own
pigweed jungles, too, he said, by letting poor
management decisions linger unchecked in
fields. This patch of pigweeds served a productive purpose, though.
“It’ll only take two to three years to accomplish this goal if you try hard or make really
bad management decisions. So, when we’re
doing research, we want to challenge all
programs to the nth degree. … I can come
in here, and I can challenge the best weed
management programs,” said Culpepper.
Across the narrow road from the pigweed
jungle, set a 6-acre field of perfectly weed-
free cotton, lending proof that regardless
of how a neighbor does or doesn’t manage
pigweed, a prudent grower can keep his fields
clean. It costs money, time and cooperative
weather patterns, but it can be done — for
Over the last decade, Georgia cotton
farmers “have done a phenomenal job” overcoming resistant pigweed by adapting proven
agronomic practices, adjusting as needed to
maintain a viable cotton industry, he said.
Cotton growers across the region have done
equally well, and the effort on this can’t be
praised enough. Unfortunately, there’s a
warning that can’t be said enough, either.
COT TON GROWERS CAN’T REST.
“I know we can’t necessarily get (layby appli-
cation) on every acre, but 99 percent would
be wonderful. Right. But we all know where
our problem fields are. We know the fields
that have the most Palmer Amaranth. We
know just from experience. That’s where we
want to start the focus,” he said. “The ability
to use different chemistry that’s very effective
on emerged (pigweed) and residual control
with that ability to get good coverage under
the cotton. That full coverage is critical and
essential for long-term sustainability.”
Sunbelt Expo’s “Pigweed Jungle” important
proving ground for herbicide programs
FOCUS ON THE FARM
At the Sunbelt Ag Expo farm, Dr. Stanley Culpepper, UGA Extension weed specialist, created a pigweed
jungle, where pigweeds towered more than eight feet tall. And it’s OK.