KTIC Radio Extension Corner: Control Waterhemp Early in Soybeans

Waterhemp in soybeans

Waterhemp growing fast in no-till soybean fields.

Listen to this morning’s extension corner:

This is Dr. Nathan Mueller, your local agronomist with Nebraska Extension for Dodge and Washington counties. Besides marestail, waterhemp is one of the most challenging weeds to control in soybeans. This past week, we saw some waterhemp plants grow as much as 8 inches. Most soybean fields have been planted and some postemergence herbicide programs are already being sprayed. Let’s discuss options for controlling both emerged waterhemp and providing residual control.

Delaying control of waterhemp early in the season can cost you yield based on your row spacing. The critical weed free period in soybeans starts at V1 or one trifoliolate leaf in 30” rows, V2 in 15” rows, and V3 in 7.5” rows. Additionally, there are numerous glyphosate-resistant waterhemp populations across Dodge and Washington counties, so another mode of action needs to be used to control emerged waterhemp.  ALS herbicides such as FirstRate and PPO herbicides such as Flexstar need to be tank mixed with glyphosate for more effective postemergence control. Because of the potential for both ALS and Glyphosate cross-resistant populations in our area, PPO herbicides are likely a better choice. Target height for spraying waterhemp is less than 4 inches with PPO herbicides with a higher carrier volume of at least 15 gallons per acre.

To improve residual control of waterhemp, add a soil applied Group 15 herbicide such as Dual, Zidua, Outlook, or Warrant to your tank mix to keep the field clean until it canopies. Be aware on the growth stage restriction differences between these Group 15 herbicides.  Dual and Zidua can be applied up to the V3 or 3rd trifoliolate leaf stage, Outlook up to V5, and Warrant up to full bloom. Premix formulations do exist including both PPO and Group 15 herbicides such as Warrant Ultra, Anthem, and Prefix.

In summary, get an early jump on controlling waterhemp in soybeans fields to protect yield and improve control. For more information on controlling waterhemp, call me at 727-2775 or visit our local website at croptechcafe.org. Know your crop, know your tech, know your bottom line. This is Dr. Nathan Mueller, your local agronomist for Nebraska Extension on KTIC radio.

Additional information on controlling waterhemp, location of herbicide-resistant populations, and herbicide mode of action:

Soil residual herbicide options after soybean emergence

Glyphosate-resistant waterhemp populations in Dodge and Washington counties

Herbicide Classification by Mode of Action Table

KTIC Radio Extension Corner: Control Waterhemp Early in Soybeans
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