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How Herbicide Half-life Impacts Weed Control

May 1, 2021
weeds growing in soybean rows

Shorter herbicide half-life equates to shorter residual weed control that can lead to a mess of weeds.

When we talk about effective weed management, we hear a lot about choosing herbicides with multiple active ingredients and different sites of action. Something we can overlook is half-life of a herbicide and the role that plays in length of residual control. The half-life of a herbicide describes the length of time it takes for 50% of the herbicide to break down and no longer be effective.

To be effective and crop safe, herbicides must have properties that result in most of the herbicide remaining near the surface. Since the majority of weed seedlings germinate in the upper inch of soil, movement out of this zone results in ineffective weed control.

Agronomy Service Representative Kevin Scholl shares the importance of herbicide half-life when it comes to weed control:

Key take-aways include:

  • Dual Magnum® herbicide:
    • Half-life: 48 days
    • Benefits: While an activating rain is required for any herbicide application, Dual Magnum offers longer soil residual activity to fight weeds like annual grass and small-seeded broadleaf weeds.
  • Outlook® herbicide:
    • Half-life: 29 days
    • Drawbacks: This herbicide can activate quickly but can also move out of the rooting zone quickly, so you could lose control of tough weeds like waterhemp that typically germinate in the top inch or so of soil.
  • Warrant® herbicide:
    • Half-life: 16 days
    • Drawbacks: This herbicide not only has a short half-life, it’s also encapsulated, which delays the release of the active ingredient. Both of these factors contribute to a short window of efficacy, which can lead to missed weed control in the top inch of soil.

The above herbicides contain 1 active ingredient which means half-life is a fairly defined number. When products contain multiple active ingredients with varying half-lives, it becomes difficult to assign to a specific number, but the combination of active ingredients help herbicides provide longer residual control. The following products contain multiple active ingredients and complementary sites of action to deliver consistent, longer-lasting management of tough weeds in corn and soybean fields.

  • For corn, Acuron® and Acuron Flexi corn herbicides contain multiple active ingredients (including Dual Magnum) that work in tandem to deliver broad-spectrum weed management with multiple effective sites of action. When applied preemergence and at full label rates, Acuron lets you discover 5-15 more bushels an acre than with any other herbicide because it manages tough, yield-robbing weeds better.*
  • For soybeans, Tavium® Plus VaporGrip® Technology herbicide for dicamba-tolerant soybeans contains built-in residual control (including Dual Magnum) to manage resistant weeds and maintain clean fields throughout the season. Use Tavium early post-emergence following Boundary® 6.5 EC , BroadAxe® XC or Prefix® soybean herbicides, which each contain 2 different sites of action. Tavium provides 3 weeks longer residual control than dicamba alone.

Wondering where you can get more information about your herbicides? Consult the product label for best practices on how to best manage weeds.

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*Acuron yield advantage range based on 2016 Syngenta and University trials comparing Acuron to Corvus®, Resicore®, SureStart® II and Verdict® applied preemergence and at full label rates. For more information on Acuron versus an individual product, ask your Syngenta representative.

Product performance assumes disease presence. Performance assessments are based upon results or analysis of public information, field observations and/or Syngenta evaluations. Trials reflect treatment rates commonly recommended in the marketplace.

The trademarks or service marks displayed or otherwise used herein are the property of a Syngenta Group Company. All other trademarks are the property of their respective owners.

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