Geoff Thomas from DAFWA discusses rusts in wheat crops including leaf rust, stripe rust and stem rust.
Reports of rust have most commonly been related to an autumn green bridge continuing into the cropping season.
Favorable conditions for rust infection and spread is warm dry days (with breeze for spores to spread) with damp, humid evenings (for germination and penetration of spores).
Optimum temperatures for infection and growth of rusts are:
- Stripe rust: 12-20C (dormant >23C)
- Leaf rust: 15-25C
- Stem Rust: 20-35C (most common later in season during grain fill)
Crops should be monitored regularly to catch epidemics early.
When rust is spreading and conditions are favorable, fungicides can be used for control before it reaches damaging levels. Delays in fungicide application can result in yield and grain quality losses.
Spraying for stem rust can be economical at much later growth stages than other diseases (post flowering into grain fill) as it usually occurs later in the season due to the temperatures required.
To limit rust carryover next year, manage the green bridge prior to the start of the cropping season to ensure all rust is removed 3-4 weeks prior to the start of the season.
Adding variety diversity can also help with managing the disease risk on your property.
Geoff also discusses results from field trials looking at responses to fungicide application at various times and provides information regarding the best time to apply fungicide for stem rust.
Rust Pathotyping through Australian Cereal Rust Survey – samples can be sent to University of Sydney