Wheat yellow rust (From Gazette & Herald)

Wheat yellow rust

SIGNIFICANT outbreaks of yellow rust (Puccinia striiformis) will occur in wheat crops next year, predicts Nickerson senior wheat breeder Bill Angus.

"There is more yellow rust in crops now than I can remember for a very long time," says Mr Angus. "The disease is cyclical, and we expect to see raised levels every five to ten years - so the threat is not new.

"However, what is particularly worrying this time is how vulnerable many of the popular varieties are to this disease. In 2001-2002, 20pc of the wheat crop was down to yellow rust-susceptible varieties, and this year this figure has leapt up to 50pc. Yellow rust-susceptible varieties will have to be managed very carefully to achieve their full potential, and to avoid spreading the disease to neighbouring fields and beyond."

Yellow rust epidemics, which can cut yields by up to 50pc in untreated, highly-susceptible varieties, usually begin in early May - depending on the temperature and how much inoculum is present in the juvenile crops. Once the first pustules are spotted in a susceptible variety, the crop needs to be sprayed straight away.

"As we approach T2, farmers need to be walking their crops extensively, to see what level of disease is lurking," said Mr Angus. "Septoria is a big problem already, and growers should seek the advice of their agro-chemical specialists to help them through the rest of this season."

When it comes to deciding which varieties to sow in the autumn, Mr Angus believes that growers in high-risk areas should grow wheats they know won't succumb to yellow rust.

Updated: 12:08 Wednesday, May 26, 2004