The Agronomists, Ep 38: Tammy Jones and Rob Miller talk pre- and post-harvest weed control

(Kara Oosterhuis/RealAgriculture)

It’s evolving into a rather odd year for pre-harvest weed control in parts of Western Canada as a return of some moisture has meant sprouting swaths, and monster weeds. In Ontario, an accelerated season means plenty of farmers are making the dry-down decision on edible beans this week.

From pre-harvest weed control, to swapping to a desiccant, and on to post-harvest decisions, this episode of The Agronomists gets answers from Rob Miller, with BASF, and Tammy Jones, of Corteva.

Catch a new episode of The Agronomists every Monday night at 8 pm E!


  • We get a crop update from both Miller (near Guelph, Ont.) and Jones (near Carman, Man.)
  • To spray or not to spray? Desiccant, that is. If you’re thinking in terms of your edible beans, check out our latest Edible Bean School episode
  • Canola sprouting in the pod? Swathed canola re-flowering? We have expletives for that
  • Clip #1: Soybean School: Pre-harvest burndown options for a fast-moving crop
  • Check with your processor for allowed product use
  • The difference between dry-down (desiccant) versus weed control
  • Spraying a four foot tall weed right now is not weed management, it’s now considered dry-down
  • Are there a lot of “escaped” weeds? Consider that they might be resistant
  • The debate to leave glyphosate in the tank mix
  • Pre-harvest interval — go with the herbicide in the tank mix with the longest PHI
  • PHI for canola: time between spraying and cutting, not spraying and putting it in the bin
  • Clip #2: Wheat School: Making the right choice for fall weed control
  • Don’t rely solely on spring control, a pre-harvest pass is a good idea in some circumstances
  • Winter annuals? Weeds that can germinate in the fall?
  • The fall window can be a great way to get ahead of spring — lots of opportunities, but challenges as well
  • Winter does take care of some weeds for us, but some thrive and need that vernalization
  • Some weeds become a small target for herbicide after the combine goes through
  • Even spread of chaff matters; use open falls wisely
  • When to spray out regrowth versus just leaving it for the frost, especially in a year when moisture is limited
  • Snirt (snow plus dirt) is not good
  • Bare soil is undesirable, so consider planting something (if you’re in the east), Miller recommends oats
  • Kochia after harvest, regrowth, seed production… Go Jones Go
  • Grazing? Watch out for nitrates
  • Kochia seed doesn’t last in the seedbank for very long, most of it germinates the next year. Lamb’s-quarters of redroot pigweed, or even waterhemp, have more durable seed coats
  • Back to frost for a second, it depends on the weed
  • Clip #3, which we didn’t actually get to during the show: Weed control in a dry year and the risk of carryover
  • Herbicide carryover: rainfall in-season plus soil texture (clay particles will bind pesticide molecules, higher OM means higher microbial biomass, which process said pesticide molecules)

Wake up with RealAgriculture

Subscribe to our daily newsletters to keep you up-to-date with our latest coverage every morning.

Wake up with RealAgriculture