In the Tank

Dicamba Glyphosate Tank Mixes Approved

Pam Smith , Crops Technology Editor
Recent approvals will allow Illinois farmer Kirk Martin to combine certain glyphosate herbicides into the tank as he sprays dicamba-tolerant soybeans. (DTN photo by Pamela Smith)

DECATUR, Ill. (DTN) -- Kirk Martin went through the winter with his fingers crossed and several weed control contingency plans in mind. The Mason City, Illinois, farmer has been looking forward to having dicamba available to clean up increasingly stubborn populations of marestail and waterhemp. However, he also wanted the convenience of glyphosate in that tank.

"I definitely did not want to make two separate post trips to get dicamba and glyphosate down. We're evaluating every trip across the field in this economy. We also prefer to have multiple herbicides working simultaneously as a resistance-management tool. While Roundup has some challenges, it is cheap and we are used to throwing it in to clean up some grasses," said Martin.

Martin's tank-mix wish has come with several glyphosate tank-mixes that are now available for use with the new Roundup Ready 2 Xtend technology. "Not to get greedy, but now I'd like to see Fusilade approved. I like it to clean up volunteer corn where I'm growing seed beans and doing it in one post pass would be a nice option."

EPA initially registered the new dicamba formulations with no tank-mix partners. Instead, the agency granted a "living label" to Engenia, FeXapan and XtendiMax. Each active ingredient, adjuvant, drift-reduction agent and nozzle being considered for use with these new dicamba formulations must endure wind tunnel testing to prove that it does not adversely affect spray drift properties. Dicamba herbicide manufacturers BASF, DuPont and Monsanto update a special website as approvals are granted.

In addition to other potential tank-mix partners, 12 glyphosate products have been approved for use with BASF's Engenia. The Engenia website, www.engeniatankmix.com, details each specific tank mix along with the recommended nozzle in a recipe-like format. Some adjuvants are recommended, depending on tank-mix combination.

Last week Monsanto announced that several potassium salt formulations of glyphosate had received approval for tank mixing with XtendiMax with VaporGrip. Examples of potassium salt formulations include Roundup PowerMax, Roundup PowerMax II, Roundup WeatherMax, Honcho K6 and Abundit Edge. These products carry a maximum use rate of 32 fluid ounces per acre per application when tank mixed with XtendiMax.

While there are positive aspects to the additional tank-mix news, Purdue University weed scientist Bryan Young said that growers need to carefully follow the approvals listed on the websites. Use of generic glyphosate formulations that have not been approved violate the label and the law. Specific drift-reduction adjuvants must also be used when tank mixing XtendiMax with the glyphosate products. Three approved drift control agents are currently listed at www.xtendimaxapplicationrequirements.com.

Monsanto continues to pursue a dicamba and glyphosate premix. Monsanto spokesperson Kyel Richard told DTN the company is hopeful Roundup Xtend with VaporGrip will be approved in coming months and the company is preparing for a full launch in 2018.

DuPont's FeXapan herbicide plus VaporGrip Technology has yet to list any tank-mix partners at www.fexapanapplicationrequirements.dupont.com. The appropriate paperwork to add tank-mix partners and nozzles has been filed with EPA, and the company said it anticipates adding them to the website shortly.

Getting clean early and staying clean is Martin's master weed control plan in soybeans. The seed beans he grows are dicamba-tolerant and raised for Monsanto.

Fall burndown applications are helping corral winter annuals, including marestail. He's already starting to see a few breaks this spring with the early warmup. Now that he has some tank-mix partners, he'll use Valor XLT as a foundation for his preemergence residual program and follow with a post application of XtendiMax plus a grass herbicide, depending on what's approved at that time. The trick will be keeping an eye open for waterhemp since that weed emerges fast and grows faster. The label for all three dicamba formulations recommends controlling weeds before they exceed 4 inches in height, and the cutoff for application is early bloom or R1 in soybeans.

Growers also need to check state approvals and restrictions. In Arkansas, for example, dicamba formulations based on the DGA-salt (including XtendiMax and FeXapan) can't be sprayed between April 15 and Sept. 15.

Young said mixing order for the new dicamba formulations shouldn't differ from what spray applicators are accustom to with other herbicides. "The main thing is timing," he said. "Spray small weeds and use the most restrictive label for weed size or crop growth stage."

Pamela Smith can be reached at Pamela.smith@dtn.com

Follow her on Twitter @PamSmithDTN

(AG)