The Agronomists, Ep 50: Mike Cowbrough and Tammy Jones on shifting weed spectrums


Every selection tool shifts the weed spectrum, and that includes farmer-controlled decisions such as tillage, crop rotation, and seeding rate. It also includes non-farmer controlled selection tools, such as wet or dry weather cycles.

To unpack what we can learn from shifting weed patterns, we go to Mike Cowbrough, weed specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs, and Tammy Jones, technical sales agronomist-Manitoba with Corteva.

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  • Weeds are adaptive — especially to weather. Exhibit A: lamb’s-quarters
  • First clip: Dr. Peter Sikkema and Bern Tobin on knowing the weed spectrum
  • Weed stage and weed size matter for control options (weed size can be tricky)
  • Certain weeds thrive in hot, dry conditions, such as kochia, red root pigweed. Some prefer cooler temperatures, such as wild oats
  • Mike drops a truth bomb: knowing how weeds adapt is important, but so what? What are you going to do about it? Scout, understand, use the whole spectrum of options for control
  • Why is chicory a weed here but not in Australia/New Zealand?
  • Tillage is also a selection tool. Downey brome doesn’t like it. But other weeds get worse with increased tillage (ie. horsetail)
  • Second clip: The Weed Zapper! Part of this episode of the Sharp Edge episode
  • Seed destructor technology is coming online as well
  • No one technology is perfect, even though glyphosate was pretty close at the outset
  • Using all the tools, when appropriate, keeps you ahead of the shifting weed spectrums
  • The zapper and seed destructors are about targeting weed-seed return to impact next year’s (and for years) weed spectrum, but, yes, the yield loss has already happened

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