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    Making herbicide effectiveness more predictable

    sprayer in early corn

    Herbicide active ingredient combinations and formulations continue to evolve in the quest to minimize the spread of herbicide-resistant weed seeds in corn and soybeans.

    One way is through the practice of premixing multiple active ingredients to produce new commercial herbicide products. The continued formulation improvements aim to reduce crop injury, extend residual control, increase tank-mix compatibility and extend rainfastness.

    Chemical formulators want to protect the crop from unintended consequences by making applications more predictable, but challenges can arise, including from uncertain weather patterns and herbicide label misunderstandings.

    “I think manufacturers try to have the optimal formulation right off the bat, but that can be a challenge because, eventually, the product will run into every possible environment,” said Aaron Hager, University of Illinois weed scientist. “But without a doubt, a lot of products now are easier and safer to handle than they were decades ago, even the older products that are formulated differently today.”

    A good example is Enclosa™ herbicide, the newest soybean herbicide from Corteva Agriscience. It’s the industry’s first liquid premix herbicide to combine cloransulam and encapsulated acetochlor. Combining these trusted active ingredients offers a simplified approach for growers.

    In addition to improved formulations, Hager says, herbicide labels have evolved to offer specific recommendations for various applications, tank mixes, adjuvants, use rates, precautions, user safety, environmental hazards and much more. These detailed recommendations help farmers and their advisers make more-informed, predictable application decisions.  

    Safener + encapsulation

    Numerous corn herbicide premix products are formulated with a safener to increase corn enzyme activity that detoxifies the herbicide within the plant. Then, encapsulation encloses active ingredients within microscopic polymer shells, preventing rapid absorption by the crop and halting early season injury.

    For example, Resicore® REV herbicide (containing clopyralid, mesotrione and acetochlor) contains an encapsulated acetochlor to improve crop safety and add longer residual control. This ZC formulation — meaning it suspends liquid microcapsules and solid particles together in the same jug — allows growers to apply it to corn up to 24 inches tall. Tank-mix compatibility is also enhanced to include fertility additives, such as ammonium thiosulfate (ATS) and UAN, as well as herbicides, such as glyphosate and atrazine.

    Tank-mix compatibility

    To help avoid unintended crop damage or reduced herbicide efficacy from incompatible tank mixes, herbicide formulators provide specific details on current labels. Hager recommends going a step further by using a jar test (mixing products in a small jar to observe any separation or reaction before adding to the spray tank) to check compatibility.

    Adding specific adjuvants to various herbicide combinations is recommended to help the chemistry blend and work optimally. Always check herbicide labels for specific instructions and follow the sequential order when adding individual products to the tank.

    It’s important to check water pH to hit pH targets for herbicides that require a specific pH, like glyphosate and other products. Water conditioning agents like AMS are often added to keep calcium cations from tying up glyphosate.

    Rainfastness

    For postemergence applications, most growers understand that applying four to six hours before rain or irrigation is usually a safe amount of time to get the herbicide into the weed under good growing conditions. Temperatures below 60 F may require a longer rain-free period to ensure adequate absorption before rain washes the herbicide off the weed.

    In the early days of glyphosate, the formulation didn’t contain any built-in additives, which caused issues due to lengthy six- to 12-hour rainfast intervals. “The company reformulated the product with different surfactants and reduced the rain-free period,” Hager said.

    Many herbicides today are rainfast within one to four hours, but always check the herbicide label.

    “Today, the different salts and surfactant loads that have been added to many formulations have provided a definite overall improvement, beyond rainfast capabilities,” he said.

    Application rates

    “The biggest thing that I think has always been a challenge to a herbicide is the application rate,” Hager said. “There’s always the temptation to cut a corner by shaving the herbicide rate. But if the lower rate fails, the growers know that they are responsible.”

    Deeper dive:

    Content provided by DTN/The Progressive Farmer

    Enclosa™ and Resicore® REV are not registered for sale or use in all states. Enclosa and Resicore REV are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.