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Herbicide Resistance in Canada A good bad example
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erbicide resistance refers to a weed’s ability to successfully survive and reproduce after exposure to a lethal dose of herbicide. Although the situation at home is more optimistic than other areas of the world, Canadian farmers only have to look south of the border to see what the future will look like if we don’t start managing the problem properly. According to a survey of American growers conducted in 2012, almost half (49%) confirmed they had glyphosate resistant weeds in 2012* and the numbers continue to grow. Conversely, Canadian growers are just starting to notice the development of glyphosate resistance, a reassuring sign that it’s not too late, but a definite wake up call to change our ways. In addition to glyphosate resistance, Canada currently has over 50 other weed biotypes with resistance to one or more herbicide groups: Why should we care? Not only do resistant weeds take more money and time to manage, the loss of your old herbicide’s effectiveness leaves you with fewer tools to work with. However, the real concern is to protect the economic viability of your operation for the future. Following your herbicide application, resistant biotypes remain in crop and freely compete for available resources that would otherwise be dedicated to your desired crop.
In all cases, this results in decreased yield potential. The problem is then compounded once these resistant weeds propagate (go to seed), leading to an even worse situation the following year. Unmanaged, herbicide resistance can very quickly result in total crop loss and the inability to successfully sustain a farming operation. On the move Herbicide resistance usually spreads from one field to the next through three major routes: pollen, seeds and vegetative structures. However, we often forget that the genetic potential for resistance is always present in every weed population and only requires the repeated use of a single mode of action to manifest itself in our fields. Thus, we need to employ management strategies that will protect our farms from both foreign field invaders and internal uprisings. Integrated Management Systems Developing a concrete resistance management strategy is paramount to combatting resistance. Despite the various factors that create and further contribute to the development of herbicide resistance, employing a simple integrated weed management system can effectively delay the onset of resistance and preserve your most valuable weed management tools and the sustainability of your operation.
Source: 2012 Agri-Marketing, Glyphosate Resistant Weeds in US Crops
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FARM FORUM / SPRING 2014
Resistant weed management strategies 1. P ERIMETER WEED MANAGEMENT Leave a 1m wide weed-free zone around your cropping fields (so new weeds can’t propagate and expand throughout your fields). 2. SCOUT OFTEN Scout often and take note of individual weed response to all applications (pre-emergent, post-emergent and pre-harvest). 3. CROP ROTATION Rotate crops as often as possible to utilize the unique modes of action available within the crop. 4. TIME FERTILIZATION Time and place fertilizer to benefit your crop, not weeds. 5. REMOVE ALL WEEDS Make sure you remove all weeds before they set seed – even if you have to pull by hand. Remember the old English proverb: One year seeding, seven years weeding. 6. TARGET PROBLEM WEEDS Systematically target problem weeds and respond quickly to changing weed populations. 7. OUTCOMPETE WEEDS Decrease your row spacing and increase seeding rates to maximize crop competitiveness and minimize time to crop canopy closure. 8. HERBICIDE EFFECTIVENESS Maximize your herbicide’s effectiveness: • Match selection of herbicide(s) with your most difficult weeds • Use full-labelled rates • Include the best tank mixes and adjuvant(s) • Use correct spray volume (follow label directions) • Use correct nozzle spacing and droplet size • Don’t spray at excess travel speeds, follow label directions • Apply during the best weather conditions (warm, humid, and sunny conditions with minimal wind) • Maximize rain-fastness intervals • Time of day (herbicides are most effective when sprayed between 8:00am and 9:00pm) For more information about herbicide resistance and effective management strategies visit MixItUp.ca