Leaf scald

Description

Initial signs of leaf scald infection are the development of water-soaked lesions on the leaf and sheath. Lesions are oval or irregular shaped, grey-green in colour which change to a straw colour with a dark brown edge. Leaves may appear blotched and yellow lesions can merge, causing the whole leaf to wither and die. The infection may spread onto all parts of the plant other than the upper stem.

Leaf scald is a stubble and seed-borne disease, surviving from one season to the next on barley stubble, barley grass and infected seed. Spores are released from the stubble during early opening rains, infecting newly sown barley plants. Initially, ‘hot spots’ of infection appear when plants are tillering, soon spreading via rainfall from plant to plant. Severe infections can occur particularly during spring when crop canopies are dense, and conditions are wet and warm (15 – 20 °C). Often crops with high levels of applied nitrogen can cause infections to be more severe.

Control

An integrated approach to managing leaf scald should be employed, rather than focusing on control. Where possible, plant resistant varieties and particularly avoid planting susceptible varieties in high rainfall regions. The fungal pathogen R. secalis is highly variable and consequently able to overcome genetic resistances quickly so growers should continually review the most current varietal disease resistance ratings. 

Aim to reduce carryover inoculum by grazing, burning or cultivating stubble and by controlling volunteer barley and barley grass.  Plant disease-free seed, avoid planting barley consecutively in the same paddock and, if possible, leave a two-year break between crops. Early sown crops can be more severely infected, therefore avoid early sowing of susceptible varieties, particularly in high rainfall areas.

Seed and fertiliser treatments provide suppression of leaf scald during seedling development, delaying early infections. Monitor crops for symptoms and apply foliar fungicides from mid-tillering (earlier if no seed treatment has been used) if infection levels warrant crop protection. Often two applications may be required to minimise grain yield and quality reductions under heavy infection. Prosaro^®and Aviator^® XPro^® have both protective and curative properties, and both are registered for the control of leaf scald in barley.

References

Department of Primary Industries and Regional Development (DPIRD) (2015), ‘Diagnosing barley scald’, https://www.agric.wa.gov.au/mycrop/diagnosing-barley-scald

McLean, M (2012), ‘Scald of barley’, Agriculture Victoria, http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/grains-pulses-and-cereals/scald-of-barley