Technical Bulletin

Benefits of a Pre-harvest Application in Canola

Benefits of a Pre-harvest Application in Canola

A pre-harvest application of Roundup Transorb® HC or Roundup WeatherMAX® herbicide tank-mixed with Heat® LQ herbicide in canola can help growers address many challenges at harvest.


Perennial Weed Control

Perennial weeds are formidable crop competitors, consuming moisture and nutrients from your fields throughout the season. This is especially true in years where pre-seed burndown may not have occured due to slow weed growth in the spring, or in cases where the crop may not have had the ability to out-compete weeds throughout the season. 

Pre-harvest is the best time to control Canada thistle, quackgrass, perennial sow thistle, dandelion, toadflax and milkweed.

Ensure proper weed staging; dandelions should be at the bud to bloom stage and Canada thistle at bud or beyond. In all cases, the leaves of the target weeds should be green and actively growing at the time of application. 


Straight Cut Benefits

For producers looking to use a dessicant in Genuity® Roundup Ready® canola, a pre-harvest application of Roundup Transorb HC or Roundup WeatherMAX herbicide tank-mixed with Heat LQ can provide enhanced drydown while providing perennial weed control.

For more information on the use of Heat LQ at pre-harvest, visit


Crop Staging is Critical

Physiological maturity is the key for timing a pre-harvest glyphosate application. Physiological maturity is reached once seed moisture content is less than 30%. At this stage, the canola pods are green to yellow and most seeds have turned from green to yellow or brown.  


Application Rate

The ONLY registered pre-harvest rate of Roundup Transorb HC or Roundup WeatherMAX herbicide is 0.67 L/ac.

An application greater than 0.67 litres per acre risks exceeding the MRL (maximum residue limit) which can result in lost market options, both domestic and export. MRLs are established by Health Canada as part of the assessment process prior to the registration of a pesticide and are regulated by the Pest Control Products Act1

Spray on label to ensure you do not exceed the MRL. 

For more information on preharvest applications, or to download our Preharvest Staging App, visit For technical support, contact Monsanto’s CustomCare® line at 1-800-667-4944.  

 Source: 1Health Canada (2012). Maximum Residue Limits for Pesticides. Verified (July 25, 2014)

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ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Roundup Ready® crops contain genes that confer tolerance to glyphosate, the active ingredient in Roundup® brand agricultural herbicides. Roundup® brand agricultural herbicides will kill crops that are not tolerant to glyphosate.Tank mixtures: The applicable labeling for each product must be in the possession of the user at the time of application. Follow applicable use instructions, including application rates, precautions and restrictions of each product used in the tank mixture. Monsanto has not tested all tank mix product formulations for compatibility or performance other than specifically listed by brand name.Always predetermine the compatibility of tank mixtures by mixing small proportional quantities in advance. CustomCare and Design®, CustomCare®, Genuity®, Monsanto and Vine Design®, Roundup Ready®, Roundup Transorb®, Roundup WeatherMAX®, Roundup® and Transorb® are registered trademarks of Monsanto Technology LLC, Monsanto Canada ULC licensee. All other trademarks are the property of their respective owners. ©2015 Monsanto Canada ULC.