Barley leaf rust
- South Stirlings
Stuart Witham (Landmark) found leaf rust in early tillering Oxford barley at Gairdner last week. The paddock will be monitored for further development of disease.
Monica Field (Farm and General EOPP) has reported leaf rust in early sown (seeded in March) Hindmarsh (mixed in with Urambie winter barley) in Dalyup. Trace infections have been found on less than five plants. The Hindmarsh is pushing out a flag leaf and Urambie is tillering. This paddock will not be sprayed as it is to be grazed for a 2-3 week period.
Esperance based DAFWA Plant Pathologist Andrea Hills says there was volunteer barley in some southern barley growing regions leading into this season and there were reports of leaf rust on barley volunteers from the South Stirlings area.
Early sown crops emerging into slightly warmer autumn conditions were at risk from early disease incursion arising from inoculum hosted on green volunteers.
Leaf rust develops rapidly in moist conditions when temperatures are between 15-22°C.
Oxford is ranked as susceptible as a seedling and resistant as an adult, therefore under early disease pressure we might expect to see seedling/tillering infection but with effective adult plant resistance (APR) the infection should diminish as the plant grows.
However if the infection continues to progress at this early stage then it may need control prior to the APR becoming fully effective.
Hindmarsh and other varieties that are susceptible to leaf rust as a seedling and adult plant will need close monitoring and infected crops may need fungicide intervention (or heavy grazing) if leaf rust continues to develop.
Managing rust in susceptible varieties can be difficult if the disease has been allowed to become severe.
Andrea says that cooler winter temperatures (below 15°C) may slow the development of leaf rust slightly but infected crops need to be closely monitored.
If rust continues to develop within the canopy then fungicide protection may be required before the disease becomes too severe. It is highly likely that in susceptible varieties this will require follow-up applications later in the season. The closer the first fungicide application can be to late-tillering/early stem extension, the greater chance there is of not needing multiple follow-up sprays.
It is important that samples of all rusts are sent for pathotype testing. Infected leaf samples should be mailed in paper envelopes (do not use plastic wrapping or plastic lined packages) along with your details and collection information (location, variety etcetera) directly to the Australian Cereal Rust Survey, Plant Breeding Institute, Private Bag 4011, Narellan NSW 2567. Free reply paid envelopes can be ordered from the University of Sydney.
For further details see the University of Sydney's Cereal Rust website and How to prepare and send samples for dispatch to the Australian Cereal Rust Survey.
For more information visit the DAFWA's Diagnosing barley leaf rust page.