Stripe rust has been confirmed for the first time this season in susceptible wheat varieties on a property near Miling and in a Department of Agriculture, Western Australia disease nursery trial at Manjimup.

Department plant pathologist Geoff Thomas said leaf rust of wheat, barley and oats had also been confirmed in crops at several sites throughout the wheatbelt over the past two weeks.

Wheat leaf rust was found at Brookton, barley leaf rust at Gnowangerup, Badgingarra, Mullewa and Moonyoonooka and oat leaf rust at Mount Barker and from Kamballup to Green Range.

MrThomas said the stripe rust became apparent as hotspots in susceptible varieties grown close to where stripe rust was present in 2004. Neither site was protected with a fungicide at seeding.

“As expected, the long dry summer greatly reduced opportunities for early rust diseases this season due to the lack of significant summer regrowth,” Mr Thomas said.

“However, heavy autumn rains through much of the wheatbelt resulted in extensive cereal regrowth and this potentially provided many sites for rust to build up.

“The widespread nature of these recent rust finds in wheat and barley indicate that infection which started earlier in the year is just becoming visible within crops.”

Mr Thomas said the initial reports should act as a warning for growers to be alert for rust in their crops, particularly in areas close to where rust had already been identified.

He said active monitoring of crops would help to identify rust early so that fungicides could be applied before the disease had time to progress and cause large yield losses.

“Stripe rust will initially be present as isolated lesions on a few leaves in the canopy. As infection develops, hotspots will become apparent within the crop before infection develops rapidly throughout the crop,” Mr Thomas said.

Factors which increase the rust risk include the use of susceptible varieties, early sown crops, proximity to early emerged wheat regrowth, presence of stripe rust in 2004, not having used upfront seed dressing or in-furrow fungicides and proximity to other infected crops this season. Crops which meet these criteria should be closely monitored for rust.

“While the first finds of rust are much later this year than in 2004, there is still potential for yield loss, particularly in susceptible varieties, later sown crops or longer season environments,” Mr Thomas said.

“Where stripe rust is detected in crops with resistance ratings of 5 or less, they should be protected as soon as possible with a fungicide spray, including crops yet to reach the flag leaf emergence stage. However, trial work with stripe rust in 2004 showed that spraying a crop after it had finished flowering was not economic. “


Mr Thomas said as the season progressed and became drier and warmer, potential losses from new infections of stripe rust would decrease and the return from fungicide application would also decrease, particularly in more resistant varieties.

Any finds of cereal rust should be submitted to the Department of Agriculture’s Agwest Plant Laboratories as a contribution to an Australia wide initiative to monitor strains of rust, which are constantly evolving to challenge grain varieties.