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Pigweed Control
Dr. Tom Barber, University of Arkansas Extension Weed Specialist
has been fighting pigweed for three years and discusses
some of what he has learned.
Photo by John LaRose Jr.
Specialist Offers Tips For Overcoming Palmer Amaranth
BETTY VALLE GEGG-NAEGER
MidAmerica Farmer Grower
LONOKE, ARK.
After fighting pigweed for three years beginning in 2015 in Northeast Arkansas, Dr. Tom Barber, University of Arkansas Extension Weed Specialist, discussed some of what he has learned in a presentation at the National Conservation Systems Cotton & Rice Conference recently.
“PPO-resistant Palmer amaranth (pigweed) has spread throughout many counties in Northeast Arkansas, West Tennessee and the Bootheel of Missouri,” he said. “Sampling throughout Northeast Arkansas has shown there is approximately a 50 percent or better chance that PPO-resistance is present in producers’ fields in that region.”
The first step is knowing you have a problem with PPO-resistance. The second is to develop a herbicide program that utilizes two effective modes of action PRE or at planting. However, regardless of the technology planted, starting off on the right foot with multiple PRE herbicides will set the season up for success.
“We recommend Gramoxone at planting plus two residuals,” Barber said.
The problem isn’t solved at that point. A second residual 21 days after the PRE application will continue to provide a level of protection.
Northeast Arkansas is a hotbed for the pest. During the years of study, it was found that gene mutations have made it even more aggressive. Melathion was added to Flexstar to help control it.
In 2017, a natural population of pigweed was found in Marion and a 16 oz. treatment of Reflex was used. That controlled some of it.
“The 2.5 oz rate is critical,” Barber said. “I don’t even want to talk residual unless it’s at least two ounces. We also got some activity out of Dual. However, nothing is 100 percent.”
Barber continued discussing the performance of various products, adding “We’re getting a little help from Valor.”
“Any of these products look good, but when you start adding residuals to these they look better,” he added.
Other methods of control are cleaning your equipment, narrowing the rows, cover crops of corn and rice, early planting and harvest weed seed control. Some of his suggestions were hopeful:
“Planting narrower rows can get you to canopy quicker.”
“My conclusion is ‘load up on residuals,’ a single mode of action doesn’t work.”
“Regardless of the system, we can do a good job.”
“Even though it’s a pigweed nightmare in that field, we can still clean it up. It goes back to timeliness and working around the weather.”
Some comments were less hopeful:
“There is a good chance you can spend a lot of money on these residuals and they won’t get activated.”
“You can have the cleanest property, never had a pigweed problem, but get a flood and you have a pigweed problem.” ∆
BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower
Note: To watch full presentation from the 2018 NCSCRC Conference go to our website www.mafg.net.
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