WA growers warned: don't be complacent about leaf rust

WA's relative geographic isolation has given its wheat growers a reprieve from breakdowns in rust resistance in the varieties Janz, Nyabing and Datatine.

However, they have been warned that virulence to the leaf rust resistance gene Lr24 could occur in the future, caused by a similar change in the local rust population to that experienced in SA, or simply thanks to wind transport across the Nullarbor.

The warning comes from AGWEST Senior Plant Pathologist Rob Loughman, who said that although WA's isolation from other wheat-growing regions meant changes in rust populations in the east did not automatically flow onto WA, it was always possible.

"The positive news for WA growers is that varieties possessing Lr24 resistance, such as Janz, Nyabing and Datatine, will continue to be effective here, at least for the time being.

"Additionally, the change has not affected varieties with other resistance, such as Camm, which still provides effective leaf rust resistance in both the west and the east."

Dr Loughman urged WA growers not to be complacent, saying the SA report flagged the need for a range of rust management strategies, including a broad base of resistance.

Management advice

As an immediate strategy, growers should kill self-sown summer cereal volunteers as soon as they develop with herbicides or heavy grazing. This helps reduce carryover of rust spores and also reduces the risk of early infection next season.

In the autumn, when potential rust risk is identified, seed treatment and spraying fungicides could help reduce losses in rust-susceptible varieties.

"In the medium to longer term, the challenge for plant breeders and pathologists is to develop replacement varieties with other forms of resistance," Dr Loughman said.

Cultivars that possess Lr24 and may be affected by the new pathotype include: Anlace, Babbler, Cunningham, Datatine, Giles, Goroke, Janz, Krichauff, Lang, Mira, Mulgara, Nyabing, Perouse, Petrie, Sunsoft, Sunpict, Swift, Tasman and Worrakatta.

Wheat crops of cultivars with Lr24 sown in 2001 should be closely monitored for leaf rust. If found, samples should be sent to the Australian Cereal Rust Survey, University of Sydney, Plant Breeding Institute Cobbitty, Private Bag 11, Camden NSW 2570.

Contact: Dr Rob Loughman 08 9368 3691, Dr Robert Park 02 9351 8806