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Pre-Emergence Herbicides for Early-Season Weed Management

May 15, 2018
This agronomic image shows weeds from 1 inch to 4 inches.

Apply your pre-emergence herbicide before weeds reach 4” tall.

It’s no secret that annual weeds like waterhemp, Palmer amaranth, marestail and giant ragweed can significantly decrease soybean yields if left unmanaged. However, there are multiple strategies for managing weeds early in the season to prevent them from competing with your soybeans for sunlight and nutrients.

One of the most effective early-season management strategies is applying a pre-emergence herbicide.The University of Wisconsin says a pre-emergence herbicide application can help keep your fields clean during the initial establishment of the crop and promote full yield potential at the end of the season.

The best time to make your pre-emergence application is:

  • Before weeds reach 4” tall
  • Before the soybean seeds germinate, up to 3 days after planting if seedlings have not broken the soil surface
  • Within 7 to 10 days of rainfall of less than 2”
  • When temperatures are mild and not too cool
  • Not during periods of excessive soil moisture

The University of Nebraska says that choosing a pre-emergence herbicide containing multiple sites of action (SOAs) is particularly important for fields where herbicide-resistant weeds are present or suspected. The university also conducted a study that demonstrated season-long control of glyphosate-resistant common waterhemp when a pre-emergence herbicide with multiple SOAs was applied and followed by a post-emergence herbicide.

To manage weeds in soybeans, we recommend starting with Boundary® 6.5 EC, BroadAxe® XC or Prefix® herbicides, each containing 2 effective SOAs. For continued weed management throughout the season, we recommend following Boundary 6.5 EC or BroadAxe XC with Flexstar® GT 3.5 herbicide. Applying a post-emergence herbicide can help keep your fields clean and delay the onset of weed resistance to help maximize your soybean yield potential this season and in the future.

For more tips on how to win the battle against resistant weeds, visit ResistanceFighter.com.

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