The disease outlook for cereal crops on the South Coast and the impact of disease in 2004 will be presented to growers at the Regional Crop Updates at Ravensthorpe on 10 March, Esperance on 11 March and Katanning on 18 March.

Department of Agriculture, Western Australia plant pathologist Kith Jayasena said wheat stripe rust and barley leaf rust were prominent in south eastern crops in 2004 and steps should be taken to reduce the risk in 2005.

Dr Jayasena said growers could minimise the impact of rust by taking an integrated crop management approach.

“By encompassing green bridge management, variety choice, seed dressing or in-furrow fungicides, crop monitoring and foliar fungicides, the impact of stripe rust can be reduced,” he said.

“The first step is to destroy self sown cereals at young stages well in advance of seeding associated with the wet autumn conditions.”

Dr Jayasena said using wheat varieties with some resistance (intermediate or better) would reduce stripe rust infection in the cropping season and reduce green bridge carry-over next season.

“Varieties that are very susceptible to stripe rust should be avoided as they greatly increase the development of the disease, thus increasing the overall epidemic and yield loss,” Dr Jayasena said.

“When green bridge situations develop, growers can minimise risk of early stripe rust infection on very susceptible to moderately resistant wheat varieties with early season fungicide, particularly when sowing early.

“The need for fungicide protection later in the season will be considerably lower for varieties with adult plant resistance to stripe rust, as resistance increases after heading.”

Dr Jayasena said for barley leaf rust, research in 2004 confirmed that applying foliar fungicides during later crop development was more beneficial than using a long acting seeding fungicide during early development.

He said the research examined four barley varieties and two advanced lines - Baudin, Gairdner, Hamelin, Stirling, WABAR2175 and WI3586-1747, grown at Gibson under five fungicide regimes. 

“Some powdery mildew occurred but leaf rust became severe and continued to develop late into the season.  A significant yield response of 0.7 t/ha was observed with the application of foliar fungicide, consistent across all varieties,” Dr Jayasena said. 

Dr Jayasena said the 2004 season was characterised by a wet winter and a dry spring, which also resulted in the emergence of powdery mildew and net blotches over winter, and loose smut and powdery mildew during spring.

“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,” he said.

“To reduce the emergence of loose smut, growers should always use healthy and clean seed and where possible seeds should be treated with the appropriate fungicide prior to sowing.

”In high rainfall regions, optimum control of barley loose smut and powdery mildew can involve a standard smuticide on seed and one or two foliar sprays to control leaf diseases in spring depending on disease pressure and weather conditions.” 

In Baudin, a seed dressing effective for loose smut is highly recommended given the high levels of infection present in this variety.  In extreme cases of loose smut infection (> 5% heads affected) new seed may be required 

Dr Jayasena said crop rotation and adequate crop nutrition also remained a key feature of minimising disease impacts for sustainable cropping systems in WesternAustralia.