Relentlessly Dedicated To You
< Back to Agronomy

Are weeds damaging your glyphosate-tolerant fields?

Agronomy Bulletin 82 ─ Glyphosate Tolerance

Defeat glyphosate-resistant weeds such as ragweed with a three-pronged management program.

Situation

Glyphosate-tolerant corn and soybean systems have become commonplace. But more than a decade after the introduction of glyphosate-tolerant crops, weed control has again become a major problem in nearly every crop-producing state. Many weeds have become more difficult to control and herbicide application rates have spiked. Learn to effectively balance your management approach.

Factors to Consider

  • Herbicides
  • Tillage
  • Crop rotation
Defeat hard-to-control weeds such as morning glory with a three-pronged management program.

Action Plan

  1. Consider applying both preemergence and postemergence herbicides. For effective control, begin attacking weeds with a foundation herbicide that offers multiple modes of action. For example, SureStart® herbicide, for use in corn crops, contains three modes of action to control weeds. Growers have the flexibility with SureStart to apply any time from preplant up to postemergence, and it can be tank-mixed with glyphosate, atrazine or 2,4-D. Six weeks of residual control can keep weed pressure down in corn and extend the post glyphosate spray window. In soybean fields, Sonic® herbicide offers two unique modes of action to control against hard-to-control and resistant weeds. Early scouting is still an important practice for controlling weeds as they are smaller (2 to 4 inches tall), so postemergence herbicides are most effective. As always, follow label instructions, carefully considering weed size recommendations.
  2. Decrease tillage when possible. Glyphosate-tolerant systems have allowed growers to adopt conservation tillage practices, which they prefer to continue for many reasons. However, some growers are moving back to conventional tillage because of weed control issues. Instead of tilling, consider postemergence herbicides with multiple modes of action to defend against annual weeds with a long germination window, such as giant ragweed and waterhemp. Postemergence herbicides with multiple modes of action are exceptional tools for growers looking to diminish the need for cultivation, which subsequently reduces fuel and labor costs and promotes environmental conservation.
  3. Manage crop rotation. Growing a single crop for several years and relying on a single-mode-of-action herbicide can lead to hard-to-control, resistant weeds. While you rotate crops, also rotate herbicides with different modes of action to help battle hard-to-control or resistant weeds. For example, as you rotate crops, use a preemergence corn herbicide one year followed by a preemergence soybean herbicide with a different mode of action the following year.

Summary

Follow a herbicide application program that uses multiple modes of action, leveraging a preemergence residual herbicide followed by a postemergence application when weeds are between 2 and 4 inches tall for the opportunity to obtain weed control with those weed infestations that have become a yield-limiting factor in your operation. For more information, contact your Mycogen Seeds customer agronomist or trusted agronomic adviser.

Published on Thursday, August 01, 2013