Investigating Potential Antagonism of Select Max® Herbicide When Mixed with Warrant® Herbicide and Dicamba

2017 Trial Objective

• Warrant® Herbicide is often used postemergence (POST) in soybean to provide additional residual control of small-seeded broadleaves and grasses.
• Clethodim products (ACCase inhibitors), such as Select Max® Herbicide with Inside Technology™, are often tank-mixed with Warrant® Herbicide to provide volunteer corn control in soybean.
• With the widespread adoption of Roundup Ready 2 Xtend® soybeans, new dicamba products have also been tank-mixed with clethodim products.
• In the past few years, there have been instances regarding decreased volunteer corn control with these tank-mixes.
• The objective in 2017 was to evaluate volunteer corn control in soybean from tank mixes of Warrant® Herbicide and ACCase inhibitors.

Research Site Details

• Commercial glyphosate-resistant corn from the prior season (bin-run) was planted in the middle of the 30-inch soybean rows to establish a consistent volunteer corn stand.
• Plot size was 10 ft x 30 ft with three replications per location.
• Warrant® Herbicide was applied preemergence (PRE) to all treatments for control of other weeds.
• A factorial treatment design was utilized with two factors:

— POST herbicide treatment

— Application timing

• The seven POST herbicide treatments are listed in Table 1.
• Two application timings were chosen targeting 12- and 24-inch-tall volunteer corn, resulting in a total of 14 treatments.

Understanding the Results

• Overall, the control of volunteer corn increased when herbicide treatments were applied to 12-inch-tall volunteer corn compared to 24-inch-tall volunteer corn.
• Control of volunteer corn decreased when Warrant® Herbicide was tank-mixed with Select Max® Herbicide (Treatment 2) compared to Select Max® Herbicide alone (Treatment 1).
• The addition of crop oil concentrate (COC) to Warrant® Herbicide and Select Max® Herbicide (Treatment 3) overcame the reduced efficacy seen in Treatment 2 at both application timings, but was still not sufficient in achieving a standard of 90% control of volunteer corn at the later timing.
• Increasing the rate of Select Max® Herbicide (Treatment 4) overcame the decreased control from adding Warrant® Herbicide to the tank.
• Fusilade® DX Herbicide consistently provided among the highest level of volunteer corn control when tank-mixed with Warrant® Herbicide at both application timings with and without COC.

2018 Trial Objective

• To determine whether adding dicamba to Select Max® Herbicide affects volunteer corn control with and without Warrant® Herbicide.
• To test a 33% increase of the recommended rate of Select Max® Herbicide to maintain the desired level of volunteer corn control.

Research Site Details

• Similar to the 2017 study, commercial glyphosate-resistant corn from the prior season (bin-run) was planted to establish a consistent stand of volunteer corn at both locations.
• Warrant® Herbicide was applied as a blanket PRE to all treatments for control of other weeds.
• Eight combinations of a graminicide herbicide at varying rates (Select Max® Herbicide or Fusilade® DX Herbicide), Warrant® Herbicide (48 fl oz/acre), and XtendiMax® herbicide with VaporGrip® Technology (22 fl oz/acre) were utilized at two different application timings.
• The POST herbicide treatments are listed in Table 2.
• Two application timings were chosen targeting 12- and 24-inch-tall volunteer corn, resulting in a total of 16 treatments.

Understanding the Results

• The 24-inch-tall volunteer corn was more difficult to control than the 12-inch-tall volunteer corn.
• A 33% increase in the Select Max® Herbicide rate (Treatment 2) was not sufficient to overcome antagonism with Warrant® Herbicide when spraying volunteer corn at a 12-inch height.
• Using Select Max® Herbicide rates of 8 or 12 fl oz/acre at 12- and 24-inch-tall volunteer corn, respectively, when XtendiMax® herbicide with VaporGrip® Technology was a tank-mix partner (Treatment 3) provided equal control of volunteer corn compared to the suggested label rate of Select Max® Herbicide alone (Treatment 1) at both application timings.
• Volunteer corn control with Fusilade® DX Herbicide was among the highest at both application timings.

What Does This Mean for Your Farm?

• Using Warrant® Herbicide PRE and/or POST in soybeans can provide additional residual control of small-seeded broadleaves and grasses.
• XtendiMax® herbicide with VaporGrip® Technology is an excellent PRE and/or POST option in dicamba-tolerant soybeans for control of broadleaf weeds, particularly those that are resistant to glyphosate.
• Controlling small volunteer corn (12 inches or less) can provide more consistent performance from your POST herbicide application.
• Visit www.roundupreadyplus.com to learn more about potential incentives when utilizing Warrant® Herbicide or Select Max® Herbicide in a crop management solution.