Ontario Diagnostic Day 1: Controlling waterhemp and fleabane, plus avoiding herbicide injury in soybean

Dr. Peter Sikkema, University of Guelph.

The annual Ontario field crop diagnostic days held at Ridgetown, Elora, and Winchester will again go virtual in 2021.

The organizing committees of these three highly successful in-field education and learning events are again partnering with crop researchers and extension, along with support from RealAgriculture and a host of sponsors to bring you a series of eight Ontario Diagnostic Days episodes.

We would like to thank the following sponsoring organizations: The Grain Farmers of Ontario, AGRIS Co-operative, BASF, Bayer/DeKalb, Corteva/Pioneer, Great Lakes Grain, Maizex Seeds, The Mosaic Company, PRIDE Seeds, RealAgriculture, and Syngenta.

The virtual video series gives the OMAFRA field crop team, research colleagues from the University of Guelph, and industry agronomists an opportunity to deliver diagnostic insights in a new way, sharing what attendees have come to expect from Diagnostic Days at Ridgetown, Elora, and Winchester. As part of the offering, continuing education credits (CEU) will also be available.

Check out this first episode featuring University of Guelph weed scientist Dr. Peter Sikkema, and OMAFRA weed management specialist Mike Cowbrough. Host Shaun Haney and Sikkema discuss the dramatic spread of waterhemp across Ontario and control options for growers, while  Cowbrough offers tips on how growers can manage soil-applied herbicides and avoid injury in soybeans. (More about the series after the player. You’ll see a full summary of the episode is below.)

The series kicks off with this one-hour episode on Tuesday, July 19. A new episode will then be published every two weeks, on Tuesdays at 9 am Eastern, through to November 2, 2021. Each episode will highlight a general field crop agronomic theme and will be available here on RealAgriculture for viewing, as well as the OMAFRA Field Crop News website. All episodes will also be available in our main podcast feed.

Historically, these in-person diagnostic days have provided some of the best opportunities for certified crop advisors (CCAs) to acquire a broad range of CEUs.

Certified crop advisors will be able to collect eight CEUs by registering for the event here. Registration is required for processing CEU credit requests and can be done up to December 1, 2021. Directions for applying for CEUs will be provided during each episode.

The videos are free and registration is not required for Grain Farmers of Ontario members, media, and those not seeking CEU credits.

Registration Fees  — Only required if applying for CEU Credits

·      $100 (plus HST) for eight CEU credits. A receipt/confirmation email will be provided.

There’s a saying regarding field tours: “Your mind can only absorb what your feet can endure.” We sincerely hope that by offering these one-hour field tour stops, at home, you can save yourself some sunscreen, bug spray, and tired soles.

Segment #1: Managing glyphosate resistant waterhemp

  • Dr. Peter Sikkema, Weed Management Professor, University of Guelph
  • Glyphosate resistant waterhemp confirmed in 2014 at Lambton County, seven seasons since, now found from Essex to Leeds-Grenville 700 km
  • Now resistant to Groups 2, 5, 9, and 14
  • Clip #1 — How did we get here? Waterhemp has evolved in the last 20 years, quickly. How did it get here? No one knows for sure, but genetics came all the way from Missouri
  • Check out the weed density in those plots!
  • Management options? Deploy a two-pass system: put down your soil-applied, and come back in post-emerge to manage escapes, for example
  • A three-product system can achieve nearly 100 per cent control
  • The key: manage “escapes” or misses (impacted by emergence, rainfall, etc.)
  • How close are we to not having a herbicide option? Long-term crop and weed management programs, and reduce over-reliance on a single mode of action

SEGMENT #2: Managing soil-applied herbicide injury in soybeans, Groups 14 and 15

  • Mike Cowbrough, OMAFRA Weed Management Specialist
  • How large of an issue is herbicide injury? It’s seen every year, and always with other factors at play (untimely rain, compaction, carryover)
  • Increased uptake of herbicide at emergence can kill the plant, but axillary buds often take over
  • Mixing of products can increase the risk, too. Some leaf distortion is possible and that will stay
  • Penalty to top growth
  • Mitigate the risk? Consider soil type (lower OM, coarse texture would be worse). There are other options, but limited
  • We got used to zero crop injury, and we need to remember that not all crop injury equates to yield loss

SEGMENT #3: Glyphosate-resistant Canada fleabane control in winter wheat

  • Back to Dr. Peter Sikkema, Weed Management Professor, University of Guelph
  • Let’s try and quantify the size of the problem: Stretches from end to end of the primary agriculture producing area of southern Ontario
  • The range in yield loss in winter wheat is much lower vs. other crops, and that’s all about emergence timing
  • It can be a summer or winter annual. Winter annual type is more competitive with winter wheat, but spring-germinated fleabane is less competitive against the already-growing wheat crop
  • Options? Infinity. Now, InfinityFX. Pixxaro M, Lontrel.
  • Timing of control: all four herbicides were applied in the spring, or in the fall, or both spring and fall. Only once? Go in in the spring, but early.
  • Cover crops play a role too. After winter wheat harvest, cover that field for a 95 per cent reduction in Canada fleabane in the following corn crop
  • Why is yield loss with winter wheat less? The emergence pattern! Fall seeded crop. It works!
  • How far will fleabane travel and should you talk to your neighbours about their issue? It gets carried on wind, mind
  • Usually the seed lands 100 m of mother plant


  • How do you determine resistant populations? Send it for testing
  • But consider/assume escaped fleabane is glyphosate resistant
  • Perennial sow thistle problems. How do you manage for a cover crop and fall application? There is a window after harvest with annuals, but perennials need to be controlled later
  • Fleabane matures in late August to September — very little seed at wheat harvest. BUT it will re-grow
  • How much late-emerge fleabane and waterhemp this season is surprising to Sikkema. Later rain has led to more weed flushes and soil-applied herbicides have run out
  • Grassy weeds above the canopy — identify and make a plan (Italian or annual ryegrass in winter wheat, bluegrass, cheatgrass)

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