Control palmer amaranth and waterhemp in crops

By Blake Jackson

Palmer amaranth and waterhemp are problematic weeds that can significantly impact soybean and corn production.

Scouting for these weeds and taking proactive measures can help limit their spread and reduce future management challenges.

Key identification characteristics of Palmer amaranth and waterhemp include the presence of male and female plants, hairless stems, and unique floral structures. If you notice infestations, roguing, hand removal, or mowing can be effective in controlling small populations.

However, populations that have gone undetected for more than a year are likely widespread and may require more intensive management.

Palmer amaranth and waterhemp produce a large number of seeds, which are easily dispersed by combine harvest.

To prevent further weed seed spread, implement the following best management practices:

• Scout fields before harvest: Identify fields with herbicide-resistant weed infestations.
• Harvest infested fields last: Harvest fields with herbicide-resistant weeds after clean fields to minimize cross-contamination.
• Clean equipment: Thoroughly clean combines and other equipment before entering fields with herbicide-resistant weeds.
• Deep clean combines: Use an air compressor to remove weed seeds from the combine, including the rock trap, grain auger, and tailings processor.
• Follow the Straw Bale Methodology: For more thorough cleaning, follow the Straw Bale Methodology when moving between fields with herbicide-resistant weeds or at the end of the year.

Even plants that pass through the cutter bar at harvest can still survive and produce seeds. Consider applying post-harvest herbicides like 2,4-D, dicamba, or paraquat to control regrowth and prevent additional seed production.

By implementing these practices, you can effectively prevent the spread of Palmer amaranth and waterhemp, reducing the need for more labor-intensive and costly management strategies in the future.

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