Western Australian wheat growers are advised to avoid or reduce intended sowings of high rust-risk varieties with 2006 shaping up as a danger year for stripe rust and possibly stem rust in some areas.

Department of Agriculture principal plant pathologist Robert Loughman (photo) said rust outbreaks had a history of following wet summers like 2005/06.

Dr Loughman said the risk of rust outbreaks was high in many areas but highest in the Great Southern, eastern wheatbelt and Esperance areas.

“Continued survival of self sown wheat across extensive areas of Western Australia has heightened concerns about potential for rust in wheat this year,” Dr Loughman said. 

“In the final lead up to sowing, growers should check their intended varieties and reduce plantings of varieties with very high rust risk such as Westonia, Bonnie Rock, Brookton, H45 and Harrismith.

“Research has shown that these varieties rev-up rust epidemics by producing high loads of the rusty coloured fungus spores that spread onto other varieties.”

Department of Agriculture research in 2005 identified that stripe rust on susceptible varieties such as Westonia could progress from barely detectable to 100 per cent infection in just 4-5 weeks.

“This provides growers with little opportunity to implement control strategies in a year when fungicides and spray contractors could be in high demand,” Dr Loughman said.

Dr Loughman said the most susceptible varieties also experienced the highest yield losses, as high as 90 per cent if rusts such as stripe or stem rust were not controlled with fungicide.

“The amount of fungicide required to control rust on very susceptible varieties is also higher than other varieties, making them more expensive to manage if rust develops,” he said.

“Growers can use long acting seed dressing or in-furrow fungicides to reduce rust risk in 2006.This is essential if retaining varieties for 2006 that are very susceptible to stripe rust.

“However, fungicides don’t prevent these varieties carrying rust over summer if green-bridge conditions develop again in 2006/07.”

Dr Loughman said by de-emphaising the most susceptible varieties, growers could help reduce both the in-season and the between-season rust risk in future.

Further information on varieties, regional rust risk and management are available at www.agric.wa.gov.au/cropdisease or contact your local Department of Agriculture or agronomist service. 

Variety resistance of 10 popular wheat varieties (2 = very susceptible; 8 = very resistant).  In 2006 growers are advised to avoid or minimise varieties with stripe or stem rust ratings of 2 or 3 in regions where self sown cereal presents a rust risk for 2006.

*        PBR variety

/        indicate the response to main and alternate strains of stem rust existing in W.A.

-        indicate range observed under different pressures and environments.