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Stem Rust Outbreak Threatens Southern Cereal Crops

24 October 2011

AUSTRALIA - Stem rust inoculum levels in late spring and early summer have southern growers on crop monitoring duty as the damaging pathogen takes hold across the high rainfall grain zone.

For the first time in more than 30 years stem rust inoculum is present across south eastern Australia. The last stem rust epidemic in Australia was in 1973 and was restricted to south eastern Australia. At the end of the season the damage bill was estimated at $300 million.

Professor Robert Park, University of Sydney’s Plant Breeding Institute, Cobbitty, NSW and Grains Research and Development Corporation (GRDC) cereal rust research chair has urged growers to monitor crops closely for signs of stem rust.

“Stem rust is a very damaging disease, it can cause total crop failure,” Prof Park said.

“At this time it is widespread in south eastern Australia and if you are growing a variety that is susceptible or moderately susceptible to stem rust then you should be monitoring your crops regularly.”

He said growers who suspect they have found stem rust should contact their local agronomist or regional pathologist for confirmation of the pathogen.

“The next decision will be whether to use chemical intervention and there are currently five fungicide active combinations that are registered in wheat to control stem rust and these are also registered for control of stripe rust.

“These chemicals include propiconazole, tebuconazole, OperaTM ProsaroTM and Tilt ExtraTM.

“It can sometimes be difficult to tell rust pathogens apart so confirmation is important.”

Stem rust can be distinguished from stripe rust in that it infects the true stem of the plant, Prof Park said.

“It also does infect all above-ground parts of the plant so it can be found on the leaves and ears of wheat.

“It produces large, red-brown pustules and masses of spores that are distributed by the wind – the same way as leaf and stripe rust spores.”

Prof Park said that stem rust is currently widespread across eastern Australia.

“This is the first time we have seen this for 30 years and is a result of the wet summer of 2010/11,” he said.

“That allowed for a significant green bridging of inoculum allowing stem rust to survive.”

Growers growing varieties rated moderately susceptible to susceptible such as Yitpi and Wyalkatchem are advised to monitor crops.

PBI work shows there is just one stem rust pathotype present south eastern Australia.

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