The Agronomists, Ep 7: Breanne Tidemann and Andrew Reid on resistant weed management

(Kara Oosterhuis/RealAgriculture)

Herbicide resistant weeds lurk on millions of acres of Canadian farm land. There’s no one way to manage resistant weeds or to delay resistance, but there are plenty of little hammers to use. That’s the subject of this episode of The Agronomists!

Join host Shaun Haney in discussion with Breanne Tidemann, research scientist at AAFC Lacombe, and Andrew Reid, technical marketing specialist for herbicides with BASF Canada, for this entertaining and informative discussion on herbicide resistance.

The Agronomists goes every Monday evening at 8 pm E — Live on Youtube, Facebook, Twitter and Twitch


  • Both our guests tonight are self-professed “weed nerds”
  • Don’t let your eyes glaze over when people talk about herbicide resistance. It’s not a new subject, but once you have herbicide resistance on your farm, you’ll regret not paying attention. The problem is spreading, too.
  • Lack of performance, is it due to herbicide resistance?
  • Like getting a body part caught in a zipper, funny until it happens to you
  • Weeds that are resistant to herbicide groups: kochia, Palmer amaranth (three or four-way resistance).
  • Stacked resistance: dicamba, glyphosate, Groups 2, 5, 27, 14
  • Why is Palmer amaranth falling so disastrously down that resistance slope? 100,000 seeds from one plant, lots of mutations, the more plants you are selecting with that herbicide the more likely you’ll have resistance, more genetically diverse
  • Group 27 was brought to market in the 80s, it’s been several decades since the last active ingredients were introduced
  • Things work so well, until they don’t
  • Don’t cut rates, it’ll cause its own set of problems
  • Franck Dayan, Colorado State University Clip (Don’t miss rewatching this one it’s got a good checklist of questions to review for determining herbicide resistance in a field)
  • Kochia, lots of seeds, genetically diverse, mutations happen, growing less competitive crops in areas where kochia is difficult to manage
  • “Catch it in the ditch” strategy? Watch for kochia patterns… they’ll tell you a lot
  • Vectors of spread: wind, water, equipment, BIRDS, those damn waterfowl, COWS
  • Evolution of resistance. Can you find the same species beside each other, one alive, one dead?
  • Herbicide traits, do they match the weeds you need to manage? What else am I doing within my crop rotation to manage herbicide resistance?
  • Herbicide tolerance in terms of breeding for management is limited. Using multiple modes of action will delay herbicide resistant weeds, but it’s not going to stop it
  • “Nature bats last” and “We’ve found all the low-hanging fruit”
  • Development of products and narrowing down an effective molecule is lengthy and expensive
  • Herbicides are part of the solution, but not on their own
  • Rock paper scissors. Other management practices: crop rotation, harvest weed seed control, including a silage crop, adequate crop competition, other forms of mechanical control
  • Rob Gulden, University of Manitoba, Resistance Management School episode
  • Increasing the seeding rate means more competition against the weed, it’s a proven concept
  • Interactions with other pests, so many factors come into play
  • Intercropping or cover crop mixes to increase the competition, you don’t want the intercrop or cover crop to start behaving like a weed against your cash crop
  • Harrington seed destructor, pulverizes chaff into dust, and any weed seeds along with it
  • Weeds will PREVAIL, they’ll adapt to anything, dominant species will change, populations, biotypes, evolving their growth habits
  • Shaun’s scared
  • “Weed scientists have job security, and the more tools you can put into place, the better you’ll be at war”
  • Agronomists, scout post-application, and that doesn’t mean scouting from the sprayer when you’re applying fungicide, don’t wait too long, mark those weed patches, try and determine why, monitor that area next year
  • Collect samples pre-harvest to send away for resistance testing, be aware of when that weed will mature, but you need mature seeds to test
  • Mike Cowbrough — collecting seeds for resistance testing

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