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.
What to look for
Paddock
Blotched, yellowing and dead leaves generally evenly distributed across the paddock.
Plant
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.
Where did it come from?
Contaminated seed
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
Stubble management
Seed treatment
Spraying foliar
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.
