Scald of Barley
Note Number: AG0765
Published: April 2007
Updated: May 2009
This Agnote provides Victorian grain growers with information on the management of scald of barley.
Scald in Victoria
Scald is often widespread in Victorian barley crops in most seasons, but its severity varies greatly from crop to crop. Scald is more likely to be a problem when infected trash remains from a previous barley crop, or when infected barley grass is present. Scald can be managed using an integrated approach that includes growing resistant varieties, avoiding early sowing, using seed dressings and not sowing into infected crop residues.
What to look for 
The first signs of scald are the appearance of water-soaked lesions on the leaf blades and sheaths. Lesions are ovate to irregular in shape, and change from a grey-green colour to a final straw colour with a distinctive brown margin (Figure 1). In severe infections, lesions coalesce, and the pathogen may virtually defoliate the whole plant (Figure 2).
The size and colour of the lesions and their presence on the older leaves distinguishes scald from numerous other leaf blotches, which may be seen on barley after heading.
All of the above-ground parts of the plant except the upper stem can be infected. Heads and grain can be infected when rain falls after ear emergence.
The symptoms of scald may be confused with similar symptoms caused by other diseases, herbicide damage or nutrient deficiency or toxicity. Paddock history and the pattern of symptoms through the paddock should be considered to eliminate other factors which could cause scald-like symptoms.
Economic Importance
In Victoria scald has caused average annual yield losses of 10-20%, with individual losses as high as 45% in susceptible varieties. In recent years, however, scald has been less important because of later sowing and the widespread use of effective seed treatments.
Disease cycle
The scald fungus (Rhynchosporium secalis) survives from one crop to the next predominantly on barley stubble and on barley grass. Though considered less important, the fungus can also survive on seed from heavily infected crops.
Early in the season, following the opening rains, spores are released from the stubble to infect early sown crops. The disease is usually first observed in isolated patches when plants are tillering. Further spread of the disease, within the crop, is by splash dispersal of the spores from one plant to another, and from old leaves to young leaves moving infection higher up the plant.
Serious damage is common in years of frequent rain, especially in the spring. By the end of the growing season the disease is usually evenly distributed within the crop.
The scald pathogen is highly variable and able to change, which means that it often overcomes (or breaks down) the resistance in commercial varieties. It is therefore important to regularly consult a current Cereal Disease Guide (AG1160) to determine if previously resistant varieties have maintained their resistance.
Management
Scald can be effectively controlled using an integrated approach encompassing resistant varieties, cultural practices, time of sowing, seed treatment and foliar fungicides.
Resistant varieties
Resistant varieties are the simplest and most economical means of managing scald (Table 1). Since the scald pathogen is known to overcome resistance it is important to consult current information when selecting varieties.
Table 1 Disease reaction of barley varieties to scald (Cereal Disease Guide AG1160)
| Variety | Disease reaction |
| Baudin | S-VS |
| Buloke | MS |
| Commander | S |
| Flagship | MS |
| Fleet | MR-MS |
| Gairdner | S-VS |
| Hindmarsh | MR |
| Keel | MS |
| Schooner | MS |
| Sloop | S |
| SloopVic | S |
| Yarra | S-VS |
R = resistant; MR = moderately resistant; MS = moderately susceptible; S = susceptible and VS = very susceptible.
Cultural practices
Destroying infected stubble and barley grass by grazing, burning or cultivation reduces the carry-over of the fungus between crops. Rotations involving consecutive barley crops should be avoided. The use of clean seed is advisable when heads have been infected.
Time of sowing
Delayed sowing can help reduce the severity of scald as later sown crops often escape infection from the early spore release.
Seed treatment
Seed treatments that suppress early scald infection are an essential part of effective scald management. They should be used every year in susceptible varieties. In addition, effective scald seed treatments also give suppression of early powdery mildew infections.
Foliar fungicides
There are a range of effective foliar fungicides available that will give disease suppression for up to 3-4 weeks. See Cereal Foliar Fungicides (AG1190). Fungicides should be applied before the disease defoliates the plant.
Further References
More detailed information can be obtained from the DPI Information Note Series
- Cereal Diseases Guide (AG1160)
- Cereal Foliar Fungicides (AG1190)
Wallwork H (2000) Cereal Leaf and Stem Diseases.
Acknowledgements
This agnote was developed by Grant Hollaway April 2006 and was reviewed by Frank Henry, Farm Services Victoria - BioSciences Research, May 2009. Financial support by the GRDC is gratefully acknowledged.
Contact/Services available from DPI
DPI Field Crops Pathology, Grains Innovation Park, 110 Natimuk Rd, Horsham 3400. Tel (03) 5362 2111, or the DPI Customer Service Centre 136 186.
