The disease has been reported in crops from Dalby to Moree and at least one crop has been severely infected.

Agri-science Queensland principal plant pathologist Greg Platz said conditions had been favourable for barely leaf rust and its effects could hit growers hard.

“Grain yields could be down by more than 30 per cent in a severely infected crop with significant quality downgrading at harvest,” Mr Platz said.

“The frequent wet periods we are having and the expectation of rising temperatures in spring mean inspections should be continued throughout the growing season.”

Mr Platz said most current commercial barley varieties were susceptible to the disease, particularly Grout, Kaputar and Binalong.

“Detection of significant leaf rust in the lower canopy of a crop would suggest a fungicide spray is required immediately and a second spray might be needed four to six weeks later,” he said.

“There are several fungicides registered for control of barley leaf rust and most will also be effective against other barley diseases.

“A ground rig application is likely to cost around $13 per hectare and growers should be specific with their application.

“For maximum effect, fungicide should be applied on the last three leaves formed, including the flag leaf, before obvious signs of disease are visible on those leaves.

“Once plants have produced their flag leaves, a single spray should be all that is required to control the disease.”

Mr Platz said while most of the infection was likely to be on the lower canopy at this stage, the rust could move up the plants to cover all leaves, leaf sheaths and awns.

“Leaf rust appears as small (0.5 to 1mm) brown pustules on the leaves and at low levels of infection the pustules are difficult to detect,” he said.

“The most conspicuous indicator will be small green spots on the yellow leaves at the base of the plant.

“If leaf rust levels are low, spraying may be delayed but the obligation to continue monitoring those crops should not be neglected.”

* For more information visit the DEEDI website and choose ‘Agriculture’ or contact an Agri-Science officer by calling 13 25 23.