The welcome news from Gordon Murray at Dubbo was that wheat stripe rust will be beaten, as it was 20 years ago. The less welcome news was that victory would take a lot of thought, planning and industry collaboration.

The Wagga Wagga based pathologist with the New South Wales Department of Primary Industries (NSWDPI) told the recent Grains Research Update for Advisers in Dubbo a whole-of-industry approach was likely to be needed to coordinate the complex range of measures needed to control the current strain of stripe rust.

More than 140 advisers and leading farmers attended the two-day Dubbo Update, which was supported by the Grains Research and Development Corporation (GRDC) and the New South Wales and Queensland DPIs.

Dr Murray said two factors were associated with the severity of the wheat stripe rust epidemic in 2004:

• widespread occurrence of the new “Western Australia” pathotype in eastern Australia, reducing the resistance of a range of commonly grown varieties, and

• more importantly, the epidemic starting early in the season.

“The more advanced the growth stage of a wheat crop when stripe rust appears, the less impact the disease has on yield,” Dr Murray said. 

“So delaying the onset of stripe rust within a crop is the key to significantly reducing the risk of yield loss to this disease in 2005.

“Stripe rust needs to infect living wheat plants to survive, so volunteer wheat – which acts as a green bridge for the rust to survive over summer – should be destroyed well ahead of the establishment of early sown wheat crops in a district – ideally at least two weeks before early sowing of grazing wheat crops.

“Used on an area-wide basis, controlling the green bridge would delay the onset of stripe rust across a district, dramatically reducing early season pressure, decreasing potential yield loss and making in-crop management more flexible.”

Dr Murray said application of fungicides to the seed or fertiliser at sowing would continue the strategy of destroying the green bridge, keeping the level of stripe rust in autumn and early winter to the absolute minimum.

Stripe rust would not produce sufficient spores to create a major epidemic until later in the winter or spring, when adult plant resistance in many varieties would provide good control.

However, growers also had to remember that high nitrogen status in a wheat crop appeared to exacerbate the severity of stripe rust by delaying the expression of adult plant resistance.

“In the short term we should be ready for another early epidemic, because many people have wheat varieties that are susceptible, even very susceptible ones that we should be getting out of the system,” Dr Murray told the Dubbo Update.

“In the medium term we need an integrated approach to fungicide and varietal management system and in the longer term need to be prepared for stripe rust to change.

“And there is no best control system. We have to choose the measures that are best for individual paddocks.”