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Early detection can prevent damage from troublesome weed.

Agronomy Bulletin 104 ─ Palmer Amaranth Control

Situation

Palmer amaranth is a resilient weed with increasing herbicide resistance and territorial expansion that could harm your crops. Through identification and precaution, you can maintain your plant health and yield potentials.

Factors to Consider

  • Weed identification
  • Growth development
  • Treatment selection
Mature Palmer amaranth has hairless, diamond-shaped leaves that may have a white chevron pattern. Plants are dioecious (single gender), and the female develops a prickly, long seed head.

Action Plan

  1. Identify the opponent. Palmer amaranth, or Amaranthus palmeri, is an aggressive, fast-spreading weed that is highly competitive with corn, soybeans and cotton. Identifying Palmer amaranth is important because it’s the largest and most destructive of its weed relatives (redroot pigweed and waterhemp). Distinguishing characteristics include leaf shape and length, stem hairs and seedhead shape.
  2. Analyze growth stage. For best control, detect Palmer amaranth early. It can cause up to a 91 percent reduction in corn yields and up to a 79 percent reduction in soybean yields in extreme cases. It emerges late May through early June and sets seeds by mid-July. One plant is capable of growing 2 inches to 3 inches per day and producing nearly 500,000 seeds at maturity. It thrives in hot, dry conditions. For proper management, treat plants before they reach 4 inches high.
  3. Choose correct treatment. Strong herbicide resistance to many treatments such as glyphosate and ALS inhibitors has been documented. Using clean soil, rotating crops and following an effective herbicide program can be successful. A two-pass system of preemergence and postemergence application has shown effectiveness. If escapes are present, hand-weed before the weed reaches reproductive maturity.

Summary

Palmer amaranth is a highly competitive weed species that can hurt your crop’s yield and economic value. Early detection and appropriate action against Palmer amaranth is critical for effective control of your operation. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

Resources

Published on Friday, October 10, 2014