Diagnosing Group A herbicide damage in cereals

These are post-emergent grass contol herbicides used for annual ryegrass and/or wild oat control in wheat and barley or non-selective grass control in broadleaf crops.

Barley plant death from Fusilade® spray drift from neighbouring lupin paddock
Plants form new tillers to compensate for growing point and tiller death
The dying growing point is easily detached
Most common symptoms light coloured lesions on sprayed leaves
Oat plants show orange red leaves and usually die

 Symptoms appear 7 - 10 days after spray application and are slow to appear. Symptoms are generally mild to moderate with registered wheat and barley herbicides, but severe with broadleaf crop grasskillers.

Chemical name Example trade name Chemical name Example trade name
Fops Dims
Clodinafop-propargyl

Topik®

 Tralkoxydim

Achieve®
Diclofop-methyl

Hoegrass®

 Clethodim

Select®
Fenoxaprop-p-ethyl

Wildcat®

 Tepraloxydim

Aramo®
Diclofop-methyl fenoxaprop-p-ethyl

Tristar®

    
Fluazifop

®Fusilade

    
Haloxyfop

Verdict®

    
Quizalfop

Targa®

    
Propaquizafop

Correct®

    

 

What to look for

    Paddock

  • Directly sprayed areas are uniformly pale.
  • Wind drift damage from grass selective herbicides is worst on paddock edges, temperature inversion drift occurs in low lying areas.

    Plant

  • Symptoms in order of severity are:
  • Mostly temporary yellowing with wilting and yellowing of newly-formed leaves.
  • Pale to yellow necrotic droplet spots on sprayed leaves.
  • Leaf blade pinched and white where droplets lodge at the junction of the leaf blade and the new leaf.
  • Inhibition of root growth that may induce trace element deficiency.
  • Inhibition of shoot growth and young leaves easily pulled from the crown.
  • Shoot and tiller discolouration and death, progressing to death of the whole plant.

What else could it be

Condition Similarities Differences
Diagnosing abiotic leaf spots in cereals Leaf spots Damage correlates with a spray event
Diagnosing copper deficiency in wheat Growing point death Group A affected emerging leaves can be easily pulled out of the stem

Where did it come from?

Time of herbicide application
Time of herbicide application
  • Damage by registered wheat and barley herbicides is ​exacerbated by:
  • Herbicide applied at the incorrect growth stage.
  • Low water rates.
  • Adjuvants that are not recommended.
  • Frost prior to or after application.
  • Broadleaf grasskiller damage could be caused by mistaken herbicide choice, wind drift from an adjoining paddock, or sprayer contamination.

Management strategies

Time of herbicide application
Time of herbicide application
  • There are no treatment options, plants either die or completely recover. As a precaution, spray when the risk of drift is low or when environmental conditions are safe.

See also

Herbicides
Factors affecting herbicide performance

Further information

HerbiGuide
GRDC Incrop-Herbicide-Use
APVMA registered products database

Topics

Page last updated: Friday, 29 May 2015 - 2:09pm