Soybeans Today January 1998
Researchers Aim for Redvine Control
By Rich Maples
A team of University of Arkansas Division of Agriculture researchers is looking at
tillage and herbicide options for controlling the states No. 1 perennial vine
problem, redvine.
U of A weed scientist Dr. Dick Oliver, agronomist Dr. Terry Keisling and graduate
student Tate Castillo have put in 50-foot by 50-foot plots on Jimmy Fletchers farm
near Keiser to compare four approaches to tillage and four herbicide treatments. The
on-going study is being funded by the Arkansas Soybean Promotion Board.
"We put in tillage treatments in the fall of 1996," says Oliver.
"Were looking at four tillage levels: no-till, conventional tillage, use of a
moldboard plow and use of a hyperbolic subsoiler.
"Across each of the tillage plots, we put in four herbicide treatments. One
treatment had no herbicide. We just evaluated the tillage. In two treatments, dicamba
(Banvel) was applied at a rate of 2 pounds per acre. In one of the treatments, the dicamba
was broadcast. The second dicamba treatment involved spot spraying with a backpack
sprayer."
The fourth herbicide treatment, two applications of Roundup on the Group IV
Roundup-Ready soybeans planted in 1997, were done during the growing season. The Roundup
applications were made at the V2 stage of growth and then about three weeks later at the
V6 stage.
V2 is when theres one fully expanded trifoliate leaf with a second leaf just
separated, which is usually 10-14 days after emergence. The V6 stage is when there are
five fully expanded trifoliate leaves with a sixth leaf just separated.
Oliver noted that the backpack sprayer used to apply dicamba in the fall of 1996 was
replaced during the fall of 97 with a new Detect sprayer that automatically turns on
its nozzles when it senses green mass.
"We didnt have the new sprayer in 96, so we simulated how it works
with the backpack sprayer," said Oliver. "We spot sprayed to see if we could cut
down on the cost of controlling redvine with dicamba. Its expensive to broadcast the
herbicide."
He said spot treating can be as effective as broadcast spraying because redvine
generally grows in clumps and not across the entire field.
With the exception of the Roundup applications, all of the tillage and herbicide
treatments were done in the fall. The dicamba treatments were made prior to harvest, but
after the plants reached physiological maturity. The leaves and pods had turned yellow.
"Up at Keiser, in Northeast Arkansas, if you harvest your soybeans before you
apply the herbicide, you wont get enough regrowth of the vines to get good
control," explained Oliver.
"Our past experience shows that Roundup, like the dicamba, needs to be applied in
the fall, when the vine is translocating down. You want to get control of those
underground stems."
The first year of the project produced some excellent results. "We knew 15 years
ago when we did work with dicamba that it was outstanding for redvine," said Oliver.
"In this test, both our spot and broadcast treatments with dicamba gave us 98-100
percent control. Whether this treatment holds off the redvine next year remains to be
seen.
"We rated the effectiveness of Roundup throughout the growing season and found
that Roundup alone gave about 80 percent control. It knocked out the tips of the terminals
and stopped the vine from climbing, but we dont know if the weed will come back next
year."
Oliver said use of the moldboard plow gave about 90 percent control of the redvine.
"By plowing the ground, youre cutting off those underground stems."
The two other tillage treatments--conventional and subsoil--gave only 30 percent
control of the redvine. "We just broke off the vines, and they regenerated
quickly," he said.
One of the unique features of the redvine control study is the use of aerial
photographs and the Global Positioning System, or GPS, to map where the vines were located
at the beginning of the project.
"Over the next two or three years, we can use the map to tell us where the vines
have moved or if weve controlled them," said Oliver.
Information on soybean weed control is available at your county Cooperative Extension
Service office.
Soybeans Today January 1998
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