There is no one solution to controlling disease in barley crops, however, developing an integrated disease management approach can help to reduce the risk according to Western Austrlia Department of Agriculture plant pathologist Kith Jayasena.

Speaking at the Department’s Agribusiness Crop Updates next week, Dr Jayasena said the 2004 season was characterised by a wet winter and a dry spring, which resulted in the emergence of several barley diseases.

“These included powdery mildew and net blotches over winter and loose smut, powdery mildew and leaf rust during spring,” he said.

“Depending on the weather conditions most of the diseases seen in 2004 will occur again in 2005. One of the diseases of most concern is loose smut.”

Dr Jayasena said loose smut disease caused yield losses that were directly related to the percentage of infected heads. For example a 10 per cent infection in the crop generally results in a 10 per cent yield reduction. 

“First sign of the loose smut disease is when the infected heads emerge from the flag leaf as a mass of dark brown powdery spores,” he said.

“These spores are blown off in the wind leaving inconspicuous bare stalks that may be the only sign of the disease late in the season.”

Dr Jayasena said to reduce the emergence of loose smut growers should always use healthy and clean seed.

“Where possible seeds should be treated with the appropriate fungicide prior to sowing,” he said.

He said barley should not be grown year after year in high-risk disease prone environments to lower the risk of establishment of early stubble borne disease such as net blotches and scald.

“Crops should be monitored regularly to detect early disease infections of powdery mildew, especially if fungicide has not been applied at seeding or with fertilizer,” Dr Jayasena said.

“Growers should also limit the number of self-sown barley volunteers over summer, as these contribute to early disease outbreaks of leaf rust and powdery mildew.

”In low to medium rainfall regions, seed dressing fungicides should be used for early disease protection from powdery mildew.

“An additional foliar spray may be needed for late protection from powdery mildew, rust, scald and net blotches depending on weather conditions.

 “In high rainfall regions, for early protection from scald, leaf rust and powdery mildew, fungicide in-furrow is recommended, in addition to a smuticide.

“One or two foliar sprays may be needed to control leaf diseases in spring depending on disease pressure and weather conditions.”

Dr Jayasena said barley grown in potassium (K) marginal soil in the high rainfall regions is more prone to spot-type net blotch and powdery mildew. An application of K can help the plant to resist disease infection.

For more information on barley disease control, copies of Farmnote No. 64/2001 Managing barley leaf diseases are available from Department offices, or visit www.agric.wa.gov.au and search for ‘barley leaf diseases’.

Mr Jayasena will also be speaking at Ravensthorpe Update on 10 March and in Esperance on 11 March.

The Grains Research and Development Corporation is a major supporter of the Department’s Agribusiness and Regional Crop Updates.