Diagnosing glyphosate damage in canola

Glyphosate is a systemic knockdown herbicide that is used extensively for brown fallow, summer weed or pre-seeding weed control, or selective weed control in glyphosate resistant crops.


Emerging leaves are distorted and discoloured; leaf blades become cupped and crinkly
The growing point then whole plant dies
Stunted and reddened plants
Spray drift near flowering causes flowering spike death and multiple shoots from the stem that also die back

What to look for


  • Limp discoloured plants that may slowly die.
  • Direct spray damage is uniformly distributed but varies with spray coverage on overlaps or boom turns.
  • Spray drift damage is worse near the source.


  • Vegetative plants develop yellow-red-purple leaves and may slowly die.
  • Emerging leaves are distorted and discoloured and leaf blades become cupped and crinkly.
  • The leaf blade develops blotchy purple-yellow interveinal discolouration that is initially worse towards leaf margins, and uniformly purple undersides.
  • Petioles become increasingly twisted as symptoms worsen.
  • Spray drift after head emergence causes leaf purpling, and death of the flowering spike. Plants may repeatedly send up flowering side branches that then slowly die.

What else could it be

Condition Similarities Differences
Diagnosing group B herbicide damage in canola Discoloured distorted young plants with distorted or dying growing point. Plant death or multiple growing points. Flowering spike death. Group B herbicides are much more damaging in trace amounts and as soil residues; young plants have more yellow than purple colours; surviving plants after bud formation have shortened internodes giving pods a bunchy appearance.
Diagnosing calcium deficiency in canola Flowering head death No leaf symptoms and plants usually recover

Where to go for expert help

Page last updated: Tuesday, 27 May 2014 - 5:12pm