Guest post: Resistant Weed Testing Is Available for Horticulture Growers

May 14, 2019

by Kristen Obeid, OMAFRA Weed Management Specialist

Herbicide resistant weeds are not unique anymore, they are the norm.  When I ask growers how many believe they have herbicide resistant weeds on their farm, more than 70 per cent of the hands in the room go up.  Then I ask – how many people have tested their suspected populations?  And not a single hand goes up.  I always wonder why?  In the past testing a weed for herbicide resistance could take up to a year, now we can do it in under 2 weeks and the service will be free, at least for the foreseeable future.  So, there is absolutely no excuse not to get your weeds tested.

Why is it so important to get your weeds tested?  It’s simple, the number and distribution of herbicide resistant weeds in Canada is increasing rapidly in all crops and the cases of multiple resistances (weed biotypes resistant to more than one group of herbicides) are becoming more common.  Currently, there are 12 genetic quick tests that can be used to determine target site resistance in specific weeds to specific groups of herbicides and more are in development.  These tests can be completed in under 2 weeks.  Having diagnostic tests available to quickly confirm the presence of herbicide resistant weeds will improve the timeliness of management and prevent the spread, which will increase the life time of current herbicides for as long as possible.

Our only defense against herbicide resistant weed species is to scout for and test suspected populations, as soon as, possible.

If you would like to get you suspected herbicide resistant weeds tested.  Please contact me.  Kristen Obeid, OMAFRA Weed Management Specialist for Horticulture Crops on twitter @WeedProfesh, by email: or text or cell 519-965-0107

This work is being completed by a large team that includes AAFC weed scientists: Dr. Martin Laforest, Dr. Robert Nurse, Dr. Eric Page, Dr. Marie-Josée Simard, AAFC technicians: Brahim Soufiane, Kerry Bosveld, Sydney Meloche, MAPAQ Pest Diagnostic Lab, Antoine Dionne and Kristen Obeid, OMAFRA