Diagnosing spot type net blotch

Spot-type net blotch is a stubble-borne fungal foliar disease occurring more frequently in the medium and high rainfall areas of the West Australian (WA) wheatbelt. Up to 44% yield loss under severe disease pressure and increased screenings have been recorded. Spot-type net blotch differs from spot blotch, a leaf disease occurring in the eastern states of Australia. Spot blotch has not been identified in WA.

First signs are dark spots with yellow edges
Spots elongate and join together,leaves turn yellow and die back from tips
Typical spot
Disease progresses from older leaves

What to look for

    Paddock

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

    Plant

  • Oval dark brown spots with yellow edges that occur first and more severely on older leaves.
  • As spots age they elongate and join together causing blotch symptoms.
  • With severe infection, the leaves turn yellow and die back from the tips.
  • Symptoms can vary with varietal resistance.
  • Shrivelled grain with severe infection.

Where did it come from?

Green bridge
Green bridge
  • The fungus is carried from season to season on infected barley and wild grass residues, regrowth barley or infected seed that acts as an initial source of infection.
  • Early in the season, wind-blown spores spread over long distances to infect early unprotected sown crops.
  • Spores released from initial infection are spread from leaf to leaf by rain splash, so serious disease is seen 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
Spraying fungicide
Spraying fungicide
Grass weed control
Grass weed 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.
  • Foliar fungicides containing triazole and strobilurin are effective in spot-type net blotch control.
  • Treat for potassium deficiency if economically viable to do so.
  • Control barley grass.
Source URL: https://www.agric.wa.gov.au/mycrop/diagnosing-spot-type-net-blotch
This print version was generated at 10:04pm on the 7th of May, 2024.
The original document was last revised at Mon, 09/11/2015 - 2:37pm

Error

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.