The Agronomists, Ep 27: Mike Cowbrough and Tammy Jones on hard-to-control weeds


From fleabane, to wild oats, to kochia and Palmer amaranth, which weed is the toughest to kill on the farm?

For this episode of The Agronomists, host Lyndsey Smith is joined by Mike Cowbrough, weed specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs, and Tammy Jones, technical sales agronomist with Corteva AgriScience, to cover integrated weed management.

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


  • Wild parsnip, will sheep eat it? Uh, Lyndsey, have your sheep eaten wild parsnip before? Toxicity issue is of phytophotodermatitis
  • Young and succulent is the key to some cases of grazing success
  • Integrated weed management, we’re not just talking about herbicides. Timing, depending on the weed species, spring applications or in-crop applications might not be the best time. Canada thistle is a good example of this
  • Death by a thousand cuts, a lot of tiny hammers, rotation is one of these
  • Other weeds that are better controlled in the fall: dandelion. Know thy enemy
  • Sometimes you need herbicides to whittle down the population to a level that’s more manageable, where integrated approaches will work much better
  • Canopy closure photos. Placement of fertilizer and base fertility. Get the crop ahead of the weeds
  • Why is horsetail (Equisetum spp) such a pain? Shoot material issues, getting product into the plant itself. A lot of root reserve. Soil will influence your dominate your weed species
  • Clip 1:  Palmer amaranth in the U.S.
  • Best pre-emerge treatment on soybeans if you’re worried about group 9 resistance? Can’t predict what weed will be Group 9 resistant. Waterhemp might be one to watch. Identify the most abundant species in each field. Resistance is ultimately a numbers game
  • Active ingredients that are utilized in Ontario may never be a reality for western Canada. Always read the label and make sure you’ve got the right active
  • Some of the tough weeds like waterhemp are probably multiple resistant anyways
  • What makes a weed so hard to kill or so susceptible to resistance?
  • Scouting is critical. Take pictures. But please take well-lit, clear photos
  • Selection pressure. However many times a weed is exposed to a management practice
  • Good kochia control in dusty, dry conditions? Group 2 resistance. Some Group 9 resistance. Some herbicides require soil moisture for plant uptake
  • You can’t commercialize kochia for the Christmas season
  • *Australia enters the chat. Evening primrose is an issue for some down there, and it does exist in Canada, but isn’t a weed of concern
  • Human transfer of weed seeds. Mike counted and identified the species in the the bottom of his boot once (there are photos)
  • Clip 2: Glyphosate resistant Canada fleabane
  • In the east, the challenge in soybeans is managing Canada fleabane before planting. There’s value in having cereals in the rotation to control it. There are good pre-plant options; the tools exist it’s just a matter of implementing them before the fleabane gets out of control
  • How close is the west to having Group 9 resistant wild oats?
  • What other things can the west be doing other than rotating crops and herbicides? Weed seed destructor. Patch management by silage. Altering seeding date. Panicle clipping. Livestock
  • WEED MANAGEMENT LASAGNE –layers and meat!

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Other Episodes

The Agronomists (view all)Season 2 (2021) Episode 25

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