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Seven Ways Preemergence Herbicides Protect Crops

March 19, 2020

Did you know that giant ragweed can reach a height of 15’ and Palmer amaranth can grow at a rate of 2 to 3” per day? With this magnitude and speed, it’s no wonder these weeds wreak havoc on corn and soybean yields. According to the Iowa State University Extension, preemergence herbicides are a recommended way to reduce weeds and protect against yield loss.

Preemergent herbicides impact crops in ways large and small, and with the right program, add up to a profitable harvest.

Here are 7 ways preemergence herbicides protect crops from yield loss and other damaging weed-related impacts:

  1. Burndown herbicides are the first line of defense against weeds each year. This may be even more crucial in 2020 after the challenges of delayed and prevented herbicide applications in 2019.
  2. Skipping a preemergence residual program makes it tougher to make timely post-emergent applications and exposes more weeds to post-emergent herbicides, increasing the potential for resistance.
  3. Marestail, giant ragweed, common lambsquarters and other Group 0 and Group 1 weeds are especially challenging to manage without preemergent herbicide applications, considering emergence can start as early as March.
  4. Early-emerging weeds are the most competitive weeds, and it’s crucial to control ALS-, PPO- and glyphosate-resistant weeds from the start.
  5. Timing is everything for early-season weed control, but that timing varies between crops as soybeans tend to have narrower application windows than corn.
  6. Preemergent residual herbicides provide a longer window for young corn and soybean plants to establish healthy root systems and strong stands free of competition from needy weeds.
  7. Season-long control of glyphosate-resistant weeds is possible when a preemergence herbicide with multiple effective sites of action is applied before an effective post-emergence herbicide.

This chart shows weed dormancy periods

To achieve preemergent control, there are several herbicides we recommend. First, start with a burndown application. With fast-acting results in as little as 48 hours, Gramoxone® SL 3.0 herbicide delivers convenient, flexible and dependable burndown of emerged grass and broadleaf weeds in corn and soybeans.

In soybeans, season-long weed control can be achieved with a preemergence application of Boundary® 6.5 EC, BroadAxe® XC or Prefix® herbicides followed by Tavium® Plus VaporGrip® Technology, the market’s first premix residual dicamba herbicide approved for use in dicamba-tolerant soybeans. In corn, Acuron® herbicide controls 70-plus grass and broadleaf weeds, and by doing so helps growers find an extra 5-15 bushels an acre*.

Weed resistance management in 2020 doesn’t start at planting; it starts with the herbicide decisions you’re making now.

See how weed resistance has spread across the US in the last 50 years, and learn more about how to keep tough weeds from jeopardizing your profits.

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©2020 Syngenta. 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.


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

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