Early-season weed control sets fields up for a successful crop season by removing weed pressure to start with a clean slate. Since weed systems are less complex this early in the year, achieving efficacy is easier in early-season burndown applications. However, it’s still essential to ensure effectiveness, especially for weeds that can cause more problems later in the season. Burndown is all about setting up efficient weed control strategies that will last through harvest. Adjuvants play a crucial role in creating an optimum tank mix for effective burndown applications.
If a field is not cleared with burndown or tillage, weeds will continue to grow, developing harder stems and more growing points, making them more challenging to control. The larger weeds compete with and hinder the growth for newly planted crops. No-till fields can struggle with winter annuals that soak up moisture, like henbit or purple deadnettle, yellow rocket, or pennycress. This leaves soil drier to start and could lead to further challenges, especially in years with low rainfall.
While some winter annuals die off or are killed with tillage or a simple burndown application, others may linger into planting season or be resistant to specific actives. For example, Marestail (horseweed) can stick around into the summer and is one of the toughest to kill because of glyphosate resistance.
A hidden benefit to burndown applications is a jump on managing pests like Lepidoptera (corn borer) as well as soybean cyst nematode. Winter annual weeds can house these pests that attack crops once planted. Pests like soybean cyst nematode can also lead to diseases that can be very detrimental. Controlling weeds that harbor these other pest problems contributes to integrated pest management.
Pest on soybean plant
The primary active ingredients for burndown applications, glyphosate, 2,4-D, and dicamba, are commonly paired with saflufenicil to fight tougher weeds for a more complete kill. Gramoxone is also very effective as a burndown herbicide, but it is becoming more regulated and used less in the field.
Many active ingredient labels require or recommend adjuvants to enhance efficacy and overall effectiveness. Adjuvants can increase herbicide coverage and penetration, improve tank mix compatibility, and many other functionalities impacting application performance. Be sure to read the label of your active ingredients to ensure essential adjuvants are included in your tank mix.
Getting a complete kill is the main goal of a burndown application. By improving coverage of the active ingredient over the weed and increasing penetration into the weed, MSOs give active ingredients a leg up for any active ingredients that benefit from the addition of oil-based adjuvants.
Certain weeds like marestail can be hard to control without proper application. Sticker spreaders make applications more resistant to environmental factors that can impede an application. The sticker assists the spray in adhering to the target, while the spreader increases the droplet’s coverage area. This forms a protective layer that improves the performance of the pesticide over time.
Surfactants are particularly important to improve the effectiveness of glyphosate and decrease the risk of resistance. Surfactants increase efficacy by lowering the surface tension of spray droplets to enable the tank mix to spread evenly over the leaf surface.
Surfactants Explained
Mixing multiple active ingredients together can be tricky. Adding a compatibility agent can prevent issues if two products don’t get along. Jar tests are important to ensure a tank mix will work and help determine if a compatibility agent is needed.
Ensuring there is enough water conditioning agent to combat hard water is essential to application effectiveness. Since water hardiness varies by location, this is more important for applications in hard water regions.
Using a mix of adjuvants is key to ensuring an effective application. Rather than tank-mixing individual adjuvants, multifunctionals are easy-to-use products that provide multiple adjuvant functions. For example, MSO/water conditioner and NIS/water conditioner multifunctionals are great options for burndown applications since many burndown active ingredients recommend an MSO or NIS.
Not all active ingredients are created equally, and it is crucial to select the right adjuvant with your active ingredient. The use of spray adjuvants helps maximize the success of burndown herbicide applications by ensuring that the active ingredient reaches the targeted weeds. Many labels recommend or require certain adjuvants to help with common challenges faced when applying that herbicide. Be sure to check the label of your active ingredient to ensure your tank mix has the best chance of achieving a complete kill.
Burndown applications with glyphosate typically call for ammonium sulfate (AMS) and a surfactant. Surfactants improve leaf coverage and aid in leaf penetration. In hard water regions, using a water conditioner helps to ensure that tank mix water does not antagonize the active ingredients. Broadleaf-focused herbicides benefit from using oil-based activator adjuvants to penetrate leaf surfaces and get into the plant. The efficacy of the application is reduced if tank mix ingredients don’t play well together, but this can be solved with a compatibility agent.
Effective burndown applications start the season correctly and lay the foundation for a successful weed management program for the remainder of the year. Selecting the proper adjuvants with your burndown program can make the difference between a successful start of the season or crops competing with weeds and disappointing results at harvest.
Surfactants are widely used across the world – in fact, you probably use surfactants every day in soaps, detergents, toothpaste, cosmetics, and countless other applications. Surfactants are just as important in agriculture and turf and understanding how and when to use the right surfactant can make or break a successful application.
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Wielding his 35 years of experience, Mark Mahady provides insight on irrigation and water conservation, turf and soil moisture management, wetting agents, surfactants, and other related topics in this edition of Cutting-Edge Perspectives.
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With tightening EPA regulations and increased label restrictions on dicamba, Corteva’s Enlist One® and Enlist Duo® are seeing increased adoption. As more growers make the change, choosing the right adjuvants to use with Enlist One and Enlist Duo is key to ensuring optimum weed control.
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