Scald (Rhynchosporium secalis) has been found in a paddock of Hindmarsh barley, sown on fallow at Kinnabulla (north-west of Birchip). The crop was at GS31-32 when scald was discovered and was certainly not a thick or heavy crop.
The infection, although still in the early stages, was most noticeable on the crop’s upper canopy and was not presenting in hotspots, but uniformly across the whole paddock. Neighbouring paddocks were at similar growth stages and not infected.
Scald can spread by air and in stubble, infecting susceptible varieties. Growers should be aware that even though Hindmarsh was resistant to the scald strain three to four years ago, because there has been an increase in the area sown to Hindmarsh in recent years, the level of inoculum has increased so that now Hindmarsh is more susceptible to scald infections. The disease rating for scald in Hindmarsh has recently been updated from resistant to susceptible to very susceptible. BCG first reported scald in Hindmarsh barley when hot spots were discovered in a trial sown at Lubeck in 2010.
The disease can very quickly defoliate plant leaves, reducing the green area that contributes to yield. Early sown paddocks are at greatest risk and in the southern Mallee scald has accounted for yield losses of up to 30 per cent with an even greater impact in wetter years but less when it is dryer.
Identifying scald
Scald usually occurs where water accumulates, typically at the base of leaves, but it can spread up the leaves. Initially, lesions on the leaves present as grey/green patches which become bleached with brown borders around the plant ages.
Disease spores are spread by rain splash and survive on residual barley and barley grasses, although the disease can also be seed borne. Three days of leaf wetness is typically required for the disease to spread.
Control
Up-front fungicide treatments may help and early control is best. Common azole fungicide can easily control the disease, but again, early control is essential.
Key action
Check Hindmarsh paddocks regularly if you are at all worried about the disease. If you are planning to spray the paddock with a broadleaf herbicide, it may be a good idea to add a fungicide in as a preventative, however there is no guarantee that the infection will occur in your paddock. BCG recommends Mallee farmers adopt a wait and see approach while Wimmera farmers should be on the front foot.
An article on Management of scald in barley using seed, fertiliser and foliar fungicides can be found in the 2010 Season Research Results (pp. 133-135).Â
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