Diagnosing stem rust of wheat

• Stem rust requires living plants on which to grow and reproduce, so to infect crops during the season it must survive over summer by infecting volunteer cereals or grass hosts, known as the 'green bridge.' Wheat stem rust can infect wheat, durum wheat, barley, triticale, and some grasses including barley grass.
• A high level of stem rust in the previous season increases the chance of carryover into the next season.
• Stem rust development and spread is favoured by warm (18 - 30°) humid conditions and an epidemic is more likely if the spring is suitably wet. The latent period (the approximate time taken for an infection to result in new spores) of stem rust is 7 - 10 days under these optimal temperature conditions.
• Stem rust spreads rapidly within and between wheat crops. Spores can be blown by wind over very large distances from infected crops or cereal regrowth. Spores can also be carried on clothing. Thoroughly wash potentially contaminated clothes and shoes before visiting crops and consider farm biosecurity measures to minimise likelihood of visitors introducing spores to your property.
• To identify any stripe rust pathotypes that are new to WA, growers and consultants are encouraged to send rust samples to the Australian cereal rust control program at the University of Sydney.

• Avoid sowing susceptible varieties. Use resistant or intermediate varieties wherever possible.
• Destroy greenbridge (volunteer wheat and barley, triticale and grass weeds) at least four weeks prior to seeding.
• Foliar fungicide applications are most effective when applied as soon as rust appears. Use a registered fungicide at a registered rate.

To assist in assessing the economic risk and financial costs associated with various treatment strategies go to MyEconomicTool [1]

There may be other economic and financial implications that need to be considered when choosing a management option. These may include:

• Assess the risk of stem rust occurring.
• Understand the potential yield losses associated with infection.
• Assess the costs and benefits of taking preventative action.

• Compare the costs, benefits and risks of each management option against doing nothing.
• Consider risk and associated costs or savings of delaying treatment.
• Consider the potential risk of re-infection and costs of further treatment.
• Ignore all previous treatment costs in assessing current management options.
• Undertake a 'what if' scenario analysis to see what impact changing variables, such as grain price and season, have on the economic outcome.

• Consider longer term consequences of not adequately treating stem rust.

View these economic considerations in more detail. [2]