Dicamba shortage threatens Tennessee
Dicamba is a great burndown herbicide and usually gets Tennessee fields off to a clean start. The availability of the tried-and-true herbicide will be limited, but farmers have options.
“A number of folks from different retailers have stated that they have been allocated only about 20% to 25% of all the dicamba they sold last year,” says Larry Steckel, a weed specialist with the University of Tennessee Extension.
The problem is supply, he says, noting overseas suppliers decided to shut down production. “Apparently this problem cuts across companies, as even Latigo, a premix of dicamba and 2,4-D marketed by Helena, will be in short supply,” he says.
• Overseas suppliers halting dicamba production limits availability in Tennessee.
• Dicamba is the go-to herbicide against Tennessee’s horseweed problem.
• Tennessee weed specialist offers “Plan B” for horseweed control.
In Tennessee, dicamba-based programs are the go-to burndown choice and have been the backbone to horseweed control for more than a decade. “It now looks like for many acres, we will have to go with a Plan B,” Steckel says.
Other options for horseweed burndown are 2,4-D, Sharpen, Verdict, Gramoxone and Liberty, he says.
2,4-D can be about as effective as dicamba on horseweed if the rate is high enough. But Steckel says he has never had good control with rates less than 32 ounces per acre. Even at this rate, control can be inconsistent if the horseweed was well established from the previous fall.
For established horseweed in soybeans, a tank mixture of 1 ounce of Sharpen per acre with a pint of 2,4-D can be a more consistent option. The plant-back to soybeans from a 2,4-D application is seven days at the pint-per-acre rate and 15 days for 32 ounces per acre. The plant-back to cotton, regardless of rate, is 30 days.
Sharpen and the premix of Sharpen and Outlook, or Verdict, can be effective horseweed burndown options.
“Utilized in a tankmix with glyphosate, we have found horseweed control with Verdict,” Steckel says. “The three-way premix of glyphosate plus Sharpen with 1 pint of 2,4-D has been a very consistent control option for horseweed.”
Easy on the Liberty
Gramoxone, or paraquat, can also be an early preplant burndown for horseweed, but it is more inconsistent than the options mentioned above.
“I really like it applied right behind the planter to help finish off any horseweed that may be recovering from the early burndown, and to make sure no Palmer amaranth is emerged before the crop. Gramoxone control of horseweed and pigweed can be improved if tank-mixed with metribuzin in soybeans and Cotoran or Caparol before cotton,” Steckel says.
Liberty can be an effective burndown option for horseweed, but Steckel doesn’t recommend it. Under cool spring conditions, Liberty will not provide good horseweed control. It isn’t as economical as other choices, either. Also, if Liberty is used as a burndown, there may be a shortage of it for the more needed in-crop application later in the summer.
Dicamba will be in short supply in 2013. It’s the top herbicide for horseweed in Tennessee, but farmers do have viable options if done right.
Photo courtesy of Larry Steckel, UT
This article published in the April, 2013 edition of SOUTHERN FARMER.