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Stop the Cycle of Weed Seed Production

March 15, 2021
Syngenta agronomist Dean Grossnickle in Orient, IA, measures a female waterhemp plant, which can produce around 100,000 seeds.

Syngenta agronomist Dean Grossnickle in Orient, IA, measures a female waterhemp plant, which can produce around 100,000 seeds.

One way to manage tough weeds like waterhemp and Palmer amaranth is to keep them from going to seed. Once these weeds go to seed, weather, machinery, livestock and wild animals spread them further, causing additional hurdles for your crop to overcome. Below are some key seed production stats to keep in mind as you manage weeds in your soybean fields.


  • Can produce around 100,000 seeds per plant, and the seeds can survive in the soil for 7 – 10 years.
  • Can grow as much as 1” per day and up to 4’ to 5’ in height, with some weeds reaching up to 12’.
  • Season-long competition by waterhemp (more than 20 waterhemp plants per square foot) can reduce yield by 44% in soybeans.

Palmer amaranth:

  • Capable of producing up to 500,000 seeds per plant, Palmer amaranth remains viable in the seed bank for up to 6 years.
  • Thrives in reduced-, minimum- and no-till systems because it germinates close to the soil surface.
  • Aggressively competes with soybeans, growing up to 3” per day and reaching up to 8’ in height.
  • When allowed to compete throughout the growing season, it can create yield losses up to 79% in soybeans.

Watch as Dean Grossnickle, Syngenta agronomy service representative in IA, shows us what 100,000 waterhemp seeds look like and why it is important to make a management plan now.

To stop the cycle of weed seed production, choose pre- and post-emergence herbicides that manage a broad spectrum of weeds with multiple effective sites of action. Consider a burndown of Gramoxone® SL 3.0 herbicide followed by a preemergence herbicide, such as Boundary® 6.5 EC, BroadAxe® XC or Prefix®. Each of these soybean herbicides contain 2 different effective sites of action for season-long residual activity. For dicamba-tolerant soybeans, consider an early post-emergence application of Tavium® Plus VaporGrip® Technology herbicide. Tavium contains both contact control and built-in residual control to manage resistant weeds and maintain clean fields throughout the season. Tavium provides 3 weeks longer residual control than dicamba alone.

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Product performance assumes disease presence. Performance assessments are based upon results or analysis of public information, field observations and/or Syngenta evaluations.