Optimal spray timing: Right place at the right time


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Once fields have been seeded, it is time to establish your timeline for next steps to ensure you are providing the right support to your crop at the right time. Andrew Chisholm, Trait and Trait Launch Manager at Bayer, shares three key reminders for farmers to maximize crop yield in TruFlex™ canola with Roundup Ready® Technology hybrids.


Identifying the right time to spray is key to minimizing the occurrence of key weeds of concern in canola – including dandelions, wild buckwheat, foxtail barley and wild oats. Chisholm speaks to the versatility of Roundup® – in which the labelled application options offer two application timings:

Option 1 (sequential): First application of Roundup WeatherMAX® at 0.67 L/ac. between cotyledon and two-leaf followed by a second application of 0.67 L/ac. up to first flower* (if required).

Option 2 (single): One in-crop application of Roundup WeatherMAX at 1.33 L/acre (cotyledon to 6-leaf).

While the single application timing can support farmers who experience delays or poor spring weather, Chisholm emphasizes that the best way to support your TruFlex canola and experience the full benefits of the system is to ensure you are using the correct spray rate whenever possible.

“Keeping your fields clean during the critical weed-free period is where you really start to make your yield,” he says. “If you get a second flush, to control weeds before the crop canopies over, you can apply a second 0.67 litre rate up until first flower* and have clean fields for harvest.”


The TruFlex canola system offers application flexibility based on weed spectrum and growing conditions. Compared to previous technology, farmers can go in with a higher spray rate of 0.67 L/ac. in TruFlex canola, which means better weed control, control of tougher weeds and no crop safety issues. This also means cleaner fields with easier harvestability and greater yield potential.

The TruFlex canola system is labelled for 51 weed species, a marked increase from the 27 weed species controlled by Roundup Ready® canola.


It’s important to take environmental factors into consideration when determining timing to spray. According to Chisholm, in areas of Western Canada with higher precipitation this spring, the slow start means more weeds will germinate to compete with the canola. He believes it is essential to spray soon after cotyledon emergence to protect against damage from weeds as they emerge in higher quantities than in 2021.

When possible, choosing the sequential rate opens doors for increased control with a wider application window. After an initial application, growers potentially have 10 to 14 extra in-crop spray days. Chisholm believes flexibility is important, particularly in canola with the unpredictability in spring weather to take the pressure off that exists in a narrow spray-timing window.

Late spray timing is only available when using the sequential rate. “Making a second application is about cleaning up any weeds that escaped,” says Chisholm. “It is the best way to set yourself up for a more enjoyable harvest and maximizing the yield potential of your crops.”

For more information about TruFlex canola with Roundup Ready Technology, visit traits.bayer.ca/en/canola/truflex-canola.

*First flower is when 50% of the plants in the field have no more than one flower.
Bayer is a member of Excellence Through Stewardship® (ETS). Bayer products are commercialized in accordance with ETS Product Launch Stewardship Guidance, and in compliance with Bayer’s Policy for Commercialization of Biotechnology-Derived Plant Products in Commodity Crops. These products have been approved for import into key export markets with functioning regulatory systems. Any crop or material produced from these products can only be exported to, or used, processed or sold in countries where all necessary regulatory approvals have been granted. It is a violation of national and international law to move material containing biotech traits across boundaries into nations where import is not permitted. Growers should talk to their grain handler or product purchaser to confirm their buying position for these products. Excellence Through Stewardship® is a registered trademark of Excellence Through Stewardship.
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Roundup Ready® Technology contains genes that confer tolerance to glyphosate. Glyphosate will kill crops that are not tolerant to glyphosate. Bayer, Bayer Cross, Roundup®, Roundup Ready®, Roundup WeatherMAX® and TruFlex™ are trademarks of Bayer Group. Used under license. Bayer is a member of Crop Life Canada. ©2022 Bayer Group. All rights reserved.
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