Disease alert: deploy the two Rs

The dramatic losses in wheat and barley in the northern region in 1998 reminded everyone of the impact of disease. Nearly $250 million loss may be the outcome of a once-in-a-hundred-year rainfall, but some level of disease takes a toll everywhere in Australia in most years.

Research and delivery of plant breeding and management practices have minimised higher direct losses in most years.

Every region has its own challenges such as yellow spot and crown rot in the North, nematodes in the South, and Septoria blotch in the West. But when considering any disease, there are two basic management approaches within the reach of every grower.

Rotate crops

Given a steady diet of their favourite crops, diseases will build up. To avoid this, breaking the cycle is a long-used and necessary part of crop planning. Rotating crops such as cereals and legumes, or wheat and barley, is a key contributor to sustainable cropping.

Within rotational practice, growers are increasingly adopting minimum tillage and stubble retention. These can alter the relative importance of diseases, and the potential for disease carry-over on straw. Farmers may want to keep a flexible attitude to occasional cultivation and stubble burning to combat disease carry-over on stubble, always weighing up the erosion risk.

Resistant varieties

Australian farmers have been investing in disease resistance since the days of Farrer. All cereal programs have an objective of delivering cultivars that are robust enough to withstand the challenges of disease. However, this is not a static process. Breeders and pathologists recognise that diseases change in importance depending on the conditions experienced in a season, and with changes in the disease organism itself. At the farm level, the main message is: know the resistance levels of your varieties and how best to use them in rotations.