The season’s first occurrence of wheat leaf rust has been reported through the Western Australia Department of Agriculture’s ‘PestFax’ cropping pest alert system.

Agronomist Rick Maddin has reported  finding wheat leaf rust at a trace level on a crop of Eradu wheat growing near Brookton.

Department of Agriculture plant pathologist Dr Robert Loughman said Eradu was a variety known to be susceptible to leaf rust although it was not among the most susceptible varieties.

“With the onset of milder temperatures which favour rust growth, more reports of rust finds in wheat crops are a possibility,” said Dr Loughman.

“From this time of the season onwards we encourage growers to inspect crops for the first signs of rusts and to review management strategies according to the susceptibility of the variety.”

Leaf rust in wheat appears as brown to orange dusty pustules, circular to oval in shape and mainly found scattered on the upper surfaces of leaves.

Colour depends on the freshness of the pustule. Because most of the spores are formed overnight, the pustules are best observed in the morning.

Inspect the most susceptible and earliest sown crops carefully over a wide area of the paddock, and examine leaves at the top and bottom of the canopy for scattered light infections.

Samples can be sent to AGWEST Plant Laboratories for positive identification.

Where rust is noticed on leaves or stems, send six to 10 leaves or stems for disease confirmation, to AGWEST Plant Laboratories, Department of Agriculture, Locked Bag 4, Bentley Delivery Centre WA 6983.

Crops prone to infection are those with a crop variety testing resistance rating from 2 to 5.

These varieties should be inspected at seven to 10 day intervals, particularly if seeding fungicide treatments registered to control rust diseases have not been used.

The detection of other finds will determine if the outbreak is localised or more widespread.

Yield loss depends on the disease resistance of the variety and how early the onset of the disease in the crop.

Rust disease can be controlled effectively and economically if fungicide is applied shortly after infection commences, but follow-up application will probably be required in long season environments or on very susceptible varieties.

For further information on rust management, including fungicides, see Farmnote 43/2005 ‘Managing stripe rust and leaf rust of wheat’.