Dry summer conditions have greatly reduced opportunities for wheat rust diseases, which are expected to have a much lower impact this year compared to 2004.

Each year around St Patrick’s day, the Department of Agriculture, Western Australia provides a regional assessment of potential rust risk based on the prevalence of summer rain and subsequent green cereal re-growth.

Department plant pathologist Geoff Thomas said stem, stripe and leaf rust needed living host plants to survive and the greatest yield impacts occurred when early infections developed from over summer build up – the so called ‘green-bridge’ high risk scenario.

“Rainfall in the period December to February has been average to well below average throughout all areas of the Western Australian wheatbelt,” Mr Thomas said.

“With few opportunities for wheat re-growth, green bridge sites are largely absent.

“This lack of green-bridge reduces the ability of all rusts to survive through the harsh summer conditions.”

The lack of significant summer rain has reduced overall risk significantly throughout the wheatbelt and as a result, rust risk for 2005 is expected to be less than that observed in 2003 and 2004.

While the potential for rust outbreaks exist every season, a dry summer normally results in fewer and later rusts outbreaks and without significant occurrence of summer re-growth in 2004/05, the build up of rust will be slowed.

Mr Thomas said the Department would provide a further rust risk assessment if unusual regional rainfall occurred and the risk changed.

“While growers in many areas are reliant on good early rains, ongoing dry conditions may reduce the requirement for costly management of wheat re-growth prior to the onset of mainstream cropping,” he said.