Ontario Diagnostic Day 3: Controlling resistant fleabane and waterhemp, plus herbicide carryover risk


It’s time for Day 3 of the virtual Ontario Diagnostic Days!

This week, we’re joined by Dr. Peter Sikkema with the University of Guelph, and Mike Cowbrough, weed specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs. This episode focuses on weed management, specifically on glyphosate resistant Canada fleabane and waterhemp, and the risk of herbicide carryover and how to identify it, and much more!

Ontario Diagnostic Days are brought to you by OMAFRA, University of Guelph and the Ontario Soil and Crop Improvement Association with sponsorship support from the following  organizations: The Grain Farmers of Ontario, Agris Co-operative, BASF, Bayer/Dekalb, Corteva/Pioneer, Great Lakes Grain, The Mosaic Company, RealAgriculture, and Syngenta.


  • We started with University of Guelph weed scientist Dr. Peter Sikkemma. Peter will take us through a series of Glyphosate resistant Canada fleabane research plots, and discuss the best products and strategies to control this yield-robbing weed in both corn and soybeans.
  • Our next guest is OMAFRA weed management specialist Mike Cowbrough.  Mike will walk us through a crop injury scenario where soybeans can be affected by carryover from the previous year’s corn herbicide.
  • We’ll then rejoin Peter Sikkema at one of his waterhemp research locations in Essex county. In just six years Glyphosate resistant waterhemp has spread to 13 counties in Ontario. Peter will identify recommended herbicides and management strategies to tackle this troublesome weed.
  • Mike Cowbrough will wrap up the episode with a look at 2,4-D injury in soybeans — how to identify it… and how to avoid it.

The virtual video series gives the OMAFRA field crop team and research colleagues from the University of Guelph an opportunity to deliver diagnostic insights in a new way, sharing what attendees have come to expect from Diagnostic Days.

The virtual diagnostic series was launched after COVID-19 forced the cancellation of the popular Diagnostic Days held each July at Ridgetown, Elora, and Winchester, Ont.

The series consists of eight, one-hour episodes. A new episode is published every two weeks, Wednesdays at 9 am Eastern through to October 21, 2020. 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 are able to collect eight CEUs by registering for the event at: https://bdc.ridgetownc.com/useservices/conferencemanagement/southwest-crop-diagnostic-days/.

Registration is required for processing CEU credit requests and can be done up to December 1, 2020. A CEU code will be provided on screen at various points 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 (includes HST) for eight CEU credits. A receipt/confirmation email will be provided.

The next Diagnostic Day tackles insect and disease management, and will be published August 26, 2020.

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