Diagnosing group B herbicide damage in field peas

Sulfonlyureas, imidazolamines and sulfonamides are systemic herbicides that are used for pre and/or post emergent grass and/or broadleaf weed control in cereals and are mostly highly toxic to peas. Damage can be caused by soil residue or spray contact. Imazamox and imazathapyr are used for post emergent broadleaf weed control in peas.

 

Affected plants are stunted with reduced root systems
Chlorotic new growth that becomes necrotic
Excessive new shoots form to compensate for growing point death

What to look for

    Paddock

  • Residual herbicide damage shows as stunted plants with pale to yellow new leaves.
  • Residual damage is more likely on more alkaline (sulphonylureas) or acidic (imis) soils
  • Spray tank contamination causes similar damage that is more uniformly distributed but varies with spray coverage on overlaps or boom turns.
  • Spray drift damage is usually worse near the source, with similar symptoms

    Plant

  • Soil residual herbicide damaged plants germinate normally but are stunted with pale to yellow new leaves. Red colours may develop on leaf edges/underside, stems and tendrils.
  • Discoloured areas develop brown necrotic spots and the plant slowly dies.
  • Plants are severely stunted with shortened stems, tendrils and petioles.
  • Excessive new shoots form to compensate for growing point death.
  • Seedling lateral roots are severely stunted.
  • Plants sprayed at later growth stages develop similar symptoms to new growth, and may take weeks to die.

Where did it come from?

  • Chemical breakdown in soil is inhibited by high pH for sulfonylureas and low pH for imidazolinones.
  • Stressed plants are less able to metabolise herbicides and therefore more susceptible to damage. Stressors include drought, cold, wet weather, waterlogging, deep sowing, frost, nutrient deficiency and soil compaction.

How can it be monitored?

  • It is important to observe withholding periods for these herbicides to avoid damage to following crops.

Further information

Pulse Australia [1]

Links
[1] http://www.pulseaus.com.au/

Source URL: https://www.agric.wa.gov.au/mycrop/diagnosing-group-b-herbicide-damage-field-peas
This print version was generated at 11:25pm on the 29th of April, 2024.
The original document was last revised at Wed, 13/05/2015 - 1:51pm

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Important disclaimer

The Chief Executive Officer of the Department of Primary Industries and Regional Development and the State of Western Australia accept no liability whatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.