- Dicamba-containing products for use in soybeans provide an additional tool to manage herbicide resistant weeds.
- Spraying small weeds with the proper adjuvants, nozzles and carrier volume provides the greatest level of efficacy on our hard-to-control weed species.
- An integrated weed management approach is still needed to successfully manage our hard-to-control and resistant weed species.
Since the launch of Roundup Ready Xtend soybeans we have observed great success in terms of weed control. The use of approved dicamba formulations in soybeans adds another great tool in the weed management tool belt to manage tough-to-control weeds such as waterhemp and marestail. While the federal label has been vacated as of February 6, 2024, in the United States, the EPA issued an Existing Stocks Order. This allows for the sale, distribution and application of products that were in the grower’s possession or in the channels of trade at the date of the court ruling. The labels still look the same as they did in 2023 except for an “End Date for Sale & Distribution,” which for the states of Illinois, Indiana and Iowa is May 13th and May 31st in Wisconsin. For other End Date for Sale and Distribution please see the last two pages of the EPA article linked here.
To steward this technology, it’s imperative that applications are optimized to their fullest potential so maximum weed control is possible. The following best management practices below have proved to be beneficial across the Midwest when applying Engenia®, Tavium® and Xtendimax® in Xtend® or XtendFlex® soybeans.
Best Management Practices
Nozzles and Carrier Volume: Nozzle selection can be an emotional and daunting task, factors that go into selecting the correct nozzle are droplet spectrum, desired application speed, pressure and gallons per acre, sprayer system (Pulse Width Modulation versus standard) and lastly approval lists. Approved nozzles provide ultra-course droplets to help mitigate particle drift. Ultra-coarse size droplets lessen overall coverage, therefore, increasing the carrier volume may contribute to greater efficacy of tough-to-control weeds along with volunteer corn. The lack of volunteer corn in the past was likely due to poor coverage in scenarios where clumps of plants existed. Increasing the carrier volume will result in more droplets to cover those clumps lessening the chance for escapes.
Adjuvants: Adjuvants are in integral part of any postemergence herbicide application, without the proper adjuvant control is often reduced. With the application of any approved dicamba formulation an approved drift reduction adjuvant (DRA) and volatility reduction adjuvant (VRA) are mandatory, however, do not forget about water conditioning adjuvants. Most of the water used for applications contains hard water cations like calcium, magnesium and iron which tie up weak acid herbicides like dicamba, often rendering the herbicide less effective. Water conditioning adjuvants on the market that do not contain ammonium sulfate and are approved should be added to the tank to mitigate hard water tie up of the herbicide so that weed control isn’t compromised. The addition of oil adjuvants is necessary with tank mix partners that may require oil adjuvants to maximize efficacy, but make sure that they are approved prior to mixing.
Other considerations
While many have experienced the benefits of the Xtend system, we cannot forget that the success of this technology relies on a program approach. To manage weeds in the short and long term, we must utilize preemergence herbicides because without one, management is likely to fail. When it comes to the POST emergence applications, include an overlapping residual to manage weeds through the establishment of the crop canopy. When we take this chemical approach, along with cultural and mechanical control measures, we can start clean and stay clean throughout the season.
With planting right around the corner, the 2024 crop will be going in the ground in a matter of a few weeks. We need to think about the best management practices such as the ones outlined above and make sure to capitalize on those as part of a total weed management plan. Contact your local Crop Specialist with any questions regarding dicamba application best management practices or to purchase dicamba-tolerant soybeans.