Oxford barley infected with leaf rust this season. Photo by Kith Jayasena, DAFWA.
Growers in Western Australia’s Great Southern and south coastal regions are encouraged to check barley crops for leaf rust and to spray infections early because the disease is difficult to manage if left unchecked.
They are also advised that, despite having a relatively durable form of resistance, the feed variety Oxford is behaving unusually this season – a high pressure year for barley leaf rust - and fungicides should be applied pre-emptively to it.
Department of Agriculture and Food (DAFWA) researcher Kith Jayasena conducts research under a Grains Research and Development Corporation (GRDC)-funded project which aims to reduce costs and diseases attributed to crop diseases in WA.
“Seasonal conditions and large amounts of regrowth barley – which has facilitated disease carry-over from 2015 – has fostered this year’s development of barley leaf rust which can reduce grain yields by more than 30 per cent when infections are severe,” he said.
Dr Jayasena said Oxford carried the adult plant resistance (APR) gene Rph20 which tended to be effective at the adult plant stage.
“Research has shown that a number of APR barley varieties, such as Westminster and GrangeR, can be grown without fungicides in leaf rust-prone environments,” he said.
“However, Oxford is behaving differently this season and, despite many crops being at a relatively advanced stage, is becoming widely infected with leaf rust.”
Dr Jayasena said this was possibly due to the effect of temperature which was known to influence the expression of APR.
“I recommend that Oxford should this year be treated like a susceptible variety and be sprayed with fungicide pre-emptively because we don’t know when its resistance genes will be activated,” he said.
“Fungicides can be applied at the same time as any post-emergent herbicides that might be required and a follow-up spray four weeks later may be necessary.
“However, growers should always apply fungicides in accordance with product label directions including specific instructions for timings, withholding periods and spray compatibilities.”
Details of registered foliar fungicides for barley leaf rust are available on the Australian Pesticides and Veterinary Medicines Authority’s Public Chemical Registration Information System Search (PubCRIS) database, accessible via this link.
Information about managing barley leaf rust is available by searching the DAFWA website, accessible via this link.
Information on developing a rust management strategy can be found on the Rust Bust website, accessible via this link.
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 Australian Cereal Rust Survey Plant Breeding Institute (PBI), Private Bag 4011, Narellan, NSW, 2567.
The GRDC-funded annual surveys of rust variability carried out at the PBI continue to form the basis of all genetically-based cereal rust control efforts in Australia.
Genetic resistance to rust in wheat and barley delivers significant benefits to Australian grain growers, estimated at $1.1 billion annually, and remains the basis of rust control, especially in wheat.
Kith Jayasena, DAFWA
08 9892 8477
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code