Diagnosing group C herbicide damage in canola
A range of group C herbicides are registered for use in triazine tolerant (TT) varieties, but other varieties are susceptible to both pre and post emergent applications.
What to look for
- Pale and/or scorched plants.
- Direct spray damage is uniformly distributed but varies with spray coverage on overlaps or boom turns
- Residue affected plants will be worse on soils that are wetter, sandier, lower in organic matter or more alkaline.
Paddock
- Plants emerge normally but paleness then death of the oldest leaf occurs. Necrosis on leaves progresses in from the leaf edges to the veins.
Plant
What else could it be
| Condition | Similarities | Differences |
|---|---|---|
| Diagnosing potassium deficiency in canola | Older leaf necrosis from edges | Plants have puckered leaves and seedlings rarely show these symptoms. Damage varies according to soil type |
Where did it come from?
Wet conditions
Herbicide treated soil
Low organic matter
- These herbicides are more active in moist soil. More damage is likely after heavy rainfall, particularly in shallow duplex soils that are more easily waterlogged.
- Situations where the herbicide is close to seed. This includes shallow sowing or heavy rain washing herbicide into furrows in ridged seedbeds.
- Topsoils with low adsorption capacity such as sands with low organic matter.
How can it be monitored?
- It is important to observe withholding periods for these herbicides to avoid damage to following crops.
- Take care when spraying not to spray non-tolerant varieties.
See also
Further information
Page last updated: Wednesday, 4 February 2015 - 11:24am