Diagnosing group B herbicide damage in narrow-leafed lupins

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 highly toxic to lupins. Damage can be caused by soil residue or spray contact.

Discoloured leaflets develop brown necrotic spots on the edge and tips then slowly die
Seedling lateral roots are severely stunted
Sulfonylurea drift damage
Sulfonylureas are more persistent on alkaline soils
Sulfonylureas (SUs) Imidazolinones (IMIs)
Chemical name Example trade name Chemical name Example trade name

Triasulfuron

Logran®

Imazapyr

Arsenal®

Chlorsulfuron

Glean®

Imazapic

Flame®

Sulfosulfuron

Monza®

Imazamox

Raptor®

Metsulfuron

Hussar®

Imazethapyr

Spinnaker®

Iodosulfuron

Ally®

Imazapic+Imazapyr

Intervix®

Mesosulfuron

Atlantis®

Imazapic+Imazapyr +MCPA

On duty®

Sulfonamides    

Fumetsulam

Broadstrike®

   

Metosulam

Eclipse®

   

Furasulam

Conclude®

   

Pyroxulam

Crusader®

   

 

What to look for

    Paddock

  • Residual herbicide damage shows as stunted plants with 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 emerging leaves are yellow and plants are stunted.
  • Discoloured leaflets develop brown necrotic spots on the edge and tips then slowly die.
  • Plants are severely stunted and slowly die.
  • Seedling lateral roots are severely stunted.
  • Plants sprayed at later growth stages develop similar symptoms to new growth, and may take weeks to die. These plants are also often more affected by brown spot.

What else could it be

Condition Similarities Differences
Diagnosing sulphur deficiency in narrow-leafed lupins Pale small new leaves Plant growth not affected
Diagnosing iron deficiency in narrow-leafed lupins Pale small new leaves Plant growth not affected
Diagnosing zinc deficiency in narrow-leafed lupins Stunted plants with pale new leaves Plants do not die back as severely and roots are not affected.

Where does it occur?

  • 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.

Where to go for expert help

Page last updated: Thursday, 5 February 2015 - 9:54am