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Help Delay Resistance by Diversifying Herbicide Chemistries

September 30, 2019
This agronomic image shows morningglory

There are no confirmed cases of herbicide resistance in morningglory to date, though the weed can be difficult to control.

As a grower, you are a steward of the land. The decisions you make now will impact the viability of your farm and its potential to produce successful harvests down the road. Herbicide resistance poses a threat to crops and the tools needed to maintain profitable operations.

A successful herbicide program focuses on these main areas:

  • Stopping weeds from emerging.
  • Killing any emerged weeds in fields, before they go to seed.
  • Protecting herbicides so they can be as effective as possible, for as long as possible.

Weed scientists and experts recommend diversifying herbicide chemistries to preserve their efficacy and best manage weeds. Diversifying chemistries means using multiple effective sites of action, and is more than just rotating herbicides season to season.

The fewer sites of action you use, the easier it is for resistance to develop in a field. Our research has found that using only 1 site of action in a herbicide program can create resistance in as little as 2 years of repeated use. It’s also been the fastest path to resistance for many species of weeds.

Researchers from the University of Nebraska-Lincoln found that tank mixing products where resistance has been seen won’t make them any more effective. For example, if fields have shown resistance to glyphosate, then using glyphosate as part of a tank-mix program won’t serve as a viable site of action.

This Take Action chart illustrates the sites of action for the most popular corn and soybean herbicides. Programs with 4 sites of action can prolong resistance for up to 2 decades, compared to those with only a single site of action.

Soybean Programs

A successful, diverse program for soybean growers is a preemergence application of Boundary® 6.5 EC, BroadAxe® XC or Prefix® herbicides. Boundary 6.5 EC and BroadAxe XC can be followed by Flexstar® GT 3.5 herbicide for post-emergence control. Dicamba-tolerant soybeans can be treated with Tavium® Plus VaporGrip® Technology herbicide in 2020. Tavium is the first premix residual dicamba herbicide, providing 3 weeks longer residual than dicamba alone. It can be applied following Boundary 6.5 EC, BroadAxe XC or Prefix.

Corn Programs

Acuron® or Acuron Flexi corn herbicides followed by Halex® GT with either atrazine or dicamba will provide growers with 4 or 5 sites of action to defend against tough weeds. Be sure to read and follow label instructions when using these herbicides.

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