"The summer months will be a critical period for minimising rust in the expanded Australian wheat industry," Jeff Arney said today. Mr Arney is Chairman of the National Rust Forum Working Group, which is convened by the Grains Council of Australia.
According to expert advice received by the Group, rainfall in the next two months will make favourable conditions for stem rust to develop in 1999 wheat crops.
While stem rust found in 1998 Victorian and South Australian long-season wheats was at low levels and crop losses should be minimal, the wide geographical spread of infection increases the likelihood of inoculum carryover into 1999. The possibility of a wet summer on the 'La Nino' pattern compounds the risk.
To support later crop health, farmers will need to maintain a weed-free summer fallow, as regrowth of wheat and barley will host rust pustules to infect the 1999 sowing.
The events of 1998 point to heightened vulnerability unless many growers change to different varieties in 1999. In addition to known rust-prone cultivars, the red wheat Paterson proved to be susceptible to stem rust.
Among the long-season wheats, available evidence points to the advisability of a switch from Declic, Lawson, More and Paterson to Gordon and the new variety Brennan in 1999. The suggestion that Gordon produces lower yields becomes of minor importance if a serious rust epidemic occurs. In that event, Gordon and newer varieties such as Brennan should provide good returns instead of a substantial or total loss with more susceptible wheats.
If Gordon or Brennan is not on sale locally in sufficient quantity, the Declic variety might offer an advantage through having a shorter season due to earlier maturity.
In cases where the local environment is favourable, milling wheats might be a viable alternative and seed suppliers should be consulted for rust-resistant varieties.
Mr Arney warned that the whole industry would be significantly disadvantaged if rust-susceptible varieties including Declic, More, Lawson, and Paterson were allowed to oversummer and contribute to a 'green bridge' between cropping seasons, which could give the infection a chance to survive. Self-sown wheat and barley, are potential summer carriers of stem rust highly damaging to the next season's crops.
"The message is clear: get rid of unseasonal vegetative growth through summer and switch to resistant varieties for 1999 plantings," Mr Arney said. "Growers, in cooperation with distributors, must take responsibility for safeguarding the health of their long- season wheats and protecting the crops of their neighbours and of farmers in the traditional dryland areas."
National Rust Forum Working Group