Herbicide-resistant waterhemp continues to spread and is problematic for many North Dakota soybean farmers. Herbicide-resistant Palmer amaranth continues to be introduced into new areas in the state and will need to be controlled in soybean fields. Enlist E3 and Xtendflex soybean offer the ability to use glufosinate and either 2,4-D or dicamba postemergence to control glyphosate-resistant pigweeds. Commercially, there are escapes of waterhemp after an initial glufosinate or 2,4-D application each year for-various reasons, such as environmental conditions, or high weed density. Subsequent respray applications are typically used in these situations to control weed escapes. This project will evaluate the optimal order of application of glufosinate and 2,4.-D, or gluosinate and dicamba, as well as the optimal respray interval for control of glyphosate resistant waterhemp and palmer amaranth following initial application.

1. Determine the optimal respray interval for glufosinate, 2,4-D, and dicamba, followed by either glufosinate, 2 4-D, or dicamba applied at intervals of 7, 14, or 21 days after initial application.
2. Determine the optimal order of application for glufosinate and 2,4-D (i.e. E3 soybean) and glufosinate and dicamba (i.e. Xtendflex soybean).

1. Manuscript submitted to. a scientific journal (after a 'second year of research).
2. Results will be shared at Extension meetings and scientific meetings.
3. Trials will be on display at Weed Science Field Days that are open to the public.

Updated December 1, 2022:

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This project will evaluate the optimal herbicide sequence and respray intervals for control of waterhemp and Palmer amaranth inE3 and Xtendflex soybean. Result should help guide-the best time to scout for pigweed escapes from post emergence applications and the best time to apply a follow-up, treatment. The results should also help determine if 2,4-D or dicamba is more efficacious on waterhemp and Palmer amaranth to help guide soybean technology planting decisions on acres where either weed is the driver weed species. All of these results will be important to help reduce the amount of seed production and risk for development of herbicide resistance in order to prolong the amount of time that these soybean technologies are useful for controlling herbicide-resistant pigweeds.