Diagnosing net type net blotch

Net-type net blotch is a stubble-borne fungal foliar disease occurring more frequently in the medium and high rainfall areas of the WA wheatbelt. It can reduce grain yield and quality.

Dark brown spots that elongate and produce dark brown net-type streaks
Streaks form larger yellow edged  blotches, often with straight sides
Net pattern lesions with yellow edges
Older leaves rapidly wither and die

What to look for


  • Blotched, yellowing and dead leaves generally evenly distributed across the paddock.


  • Small dark brown spots that elongate and produce fine dark brown streaks along and across the leaf blades and leaf sheaths, creating a distinctive net-like pattern. Lesions may also form larger elongated blotches, often with straight sides.
  • The area surrounding the spots frequently goes yellow and severely affected leaves wither rapidly.
  • Older leaves are affected first and more severely.
  • In severe cases heads are infected.
  • Severe leaf or head infection can result in shrivelled grain.

What else could it be

Condition Similarities Differences
Diagnosing spot type net blotch Brown spots. Similarities only occur during the early stages of infection. Spots expand into net-pattern lesions (Net-type net blotch).
Diagnosing physiological leaf spot in barley Brown spots. Similarities only occur during the early stages of infection. Spots expand into net-pattern lesions (Net-type net blotch).
Diagnosing boron toxicity in barley Brown spots. Spots expand into net-pattern lesions (Net-type net blotch).

Where did it come from?

Contaminated seed
Contaminated seed
Green bridge
Green bridge
  • The fungus is carried from season to season on infected barley and wild grass residues. Regrowth barley or infected seed can act as an initial source of infection.
  • Early in the season, wind-blown spores may spread over long distances to infect early unprotected sown crops.
  • After initial infection spores are produced on leaves when conditions are moist, then spread from leaf to leaf by wind. Serious disease results when there is frequent rainfall and a dense canopy that retains moisture on the leaves for a longer period of time. Drying spring conditions slow the cycle of infection.
  • Potassium deficient crops are more susceptible to leaf disease.

Management strategies

Resistant varieties
Resistant varieties
Stubble management
Stubble management
Seed treatment
Seed treatment
Spraying foliar
Spraying foliar
Green bridge control
Green bridge control
  • Avoid cropping barley on barley in medium to high rainfall areas.
  • Avoid growing highly susceptible varieties.
  • Reduce stubble residue carry-over as much as possible.
  • Appropriate seed dressings may be effective against seed borne infection but is ineffective against an infection coming from airborne spores.
  • Certain foliar fungicides containing triazole and/or strobilurin are effective in net-type net blotch control, check label registrations.
  • Treat for potassium deficiency if economic.
  • Control barley grass.

Where to go for expert help

DDLS Seed Testing and Certification
+61 (0)8 9368 3721
Page last updated: Thursday, 16 April 2015 - 10:11am