By Professor Robert Park and Dr Colin Wellings, University of Sydney Plant Breeding Institute, Cobbitty (Dr Wellings is on secondment from NSW Primary Industries.)
With the 2004 season well under way, reports of rust in cereal crops have already been made from many locations in the western and eastern cereal-growing regions.
Stripe rust was reported from WA in late July at separate locations at Merredin (east) and Esperance (southeast), and has since spread through central, southern and even the northern zones. Reports of stripe rust in eastern Australia have indicated that, as in the west, the disease began in widely separated locations with first reports in early August from Grenfell (southern NSW), Millicent (SA) and Bellata (northern NSW). Over the following four weeks, stripe rust was found in all regions of eastern Australia with the exception of Queensland. The first rust samples from the east have been shown to be the WA pathotype that caused major problems for growers in 2003.
A crop of Kelalac wheat was sprayed for leaf rust at Lake Bolac in Victoria in early August, and a recent but unconfirmed report was received in mid-September of leaf rust in a crop of Lang at Walgett (western NSW). Leaf rust has also been identified in WA.
Of potential concern are recent unconfirmed reports of stem rust in crops of Yitpi and Camm on the western margin of the Eyre Peninsula (SA). Yitpi will be vulnerable to most stem rust pathotypes and, given the increasing area sown to this variety in areas such as the Mallee, monitoring will be important.
Stem rust has been rare in wheat crops in eastern Australia for much of the past 20 to 30 years, and if these reports are authenticated, this disease could rapidly become important.
Growers in all regions are advised to inspect crops for signs of rust infection now. Early detection and correct identification are vital if chemical control is to be considered.
In particular, the wheat cultivars Camm and Yitpi (stem rust) and H45 (stripe rust), and the barley cultivars Keel and Baudin (leaf rust) should be monitored closely.
The GRDC has information on identifying rust diseases on its website (www.grdc.com.au), and also has available several publications that include photographs of the rust diseases (the "Back Pocket Guide" series).
One of the easiest ways of initially diagnosing rust diseases is to rub the affected plant part with a white tissue. Rusts produce massive quantities of brown-yellow coloured spores that will produce a tell-tale rusty colour on the tissue if rust is present. These spore masses are usually more noticeable at early morning in the field, or on stems collected and stored in a bucket of water overnight.
Samples of suspected rust-infected cereals can also be sent for diagnosis and pathotype analysis to the Australian Cereal Rust Control Program. Ideally, samples should comprise several well-infected leaves and should be packaged in paper envelopes only and posted without delay.
For more information:
Australian Cereal Rust Control Program, 02 9351 8826, firstname.lastname@example.org
Australian Cereal Rust Survey PMB 11, Camden, NSW
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