Western Australia
July 28, 2015

Growers in Western Australia’s southern cropping regions are encouraged to be on their guard against barley leaf rust, with research revealing a heightened risk of crop infection this season.

Department of Agriculture and Food (DAFWA) researcher Kith Jayasena said each of nine spore traps in the lower Great Southern region had detected barley leaf rust spores and conditions were also conducive to the disease in the Esperance region.

Dr Jayasena, who is conducting spore trap experiments under a project funded by the Grains Research and Development Corporation (GRDC), said growers should monitor crops and spray infected crops early.

He said some barley varieties currently grown in WA were more prone to leaf rust following a breakdown of resistance detected in 2013.

“Action needs to be taken promptly against barley leaf rust because, once established, it is very difficult to control,” Dr Jayasena said.

“At the first sign of barley leaf rust, growers should immediately spray appropriate fungicides on barley varieties that are rated susceptible to very susceptible.

“If growers have sown moderately resistant varieties, they can wait until infection is at a level of 5 per cent or until flag leaf emergence.

“Fungicides can be applied to these moderately resistant crops at the same time as any post-emergent herbicides that might be required.

“A follow-up spray four weeks later may be necessary.”

Dr Jayasena said factors which had heightened the risk of barley leaf rust this year included:

• Significant areas of barley regrowth from last year’s crops, which had allowed barley leaf rust to carry over from last season
• Intermittent rainfall between January and April favouring the survival of this ‘green bridge’
• A reluctance by some growers to control barley regrowth, in order to provide sheep feed

Dr Jayasena said the new barley leaf rust pathotype (5457 P-) was identified in WA in 2013 in WA’s southern cropping districts, and had resulted in reduced resistance to leaf rust in several varieties known to carry the Rph3 resistance gene in WA.

“This new pathotype means that in barley leaf rust-prone areas such as the South Coast, Bass is likely to require careful management of leaf rust, comparable to existing susceptible varieties,” he said.

A list of registered foliar fungicides is available by searching ‘registered foliar fungicides’ on the DAFWA website www.agric.wa.gov.au.

Dr Jayasena said that in addition to barley leaf rust, other barley diseases growers should look out for this year included net blotch, scald and powdery mildew.

The spore trap experiments being conducted by Dr Jayasena aim to finetune recommendations to growers about the optimum timing of foliar fungicide application in any given season.

They are part of a GRDC funded project which aims to reduce costs and losses attributed to crop diseases in WA.

Information about barley leaf rust is available in a GRDC Hot Topic at www.grdc.com.au/BarleyLeafRust.

Information on developing a rust management strategy can be found on the Rust Bust website www.rustbust.com.au, which includes a ‘Rust Bust Management Checklist’, or in the GRDC Cereal Fungicides Fact Sheet at www.grdc.com.au/GRDC-FS-CerealFungicides.

If rust is detected on crops, samples should be sent to the University of Sydney Plant Breeding Institute for pathotype analysis.

Rusted plant samples can be mailed in paper envelopes (not plastic wrapping or plastic-lined packages) to the Australia Cereal Rust Survey Plant Breeding Institute, Private Bag 4011, Narellan, NSW, 2567. 
 

Website: http://www.grdc.com.au

Published: July 28, 2015