Senior plant pathologist – cereals at the Victorian Department of Economic Development, Jobs, Transport & Resources, Dr Grant Hollaway, explains some of the risks facing growers and tips to best manage rust. He also explains some of the research work he and his team are doing, as well as the important work of the Rust Bust Click here to watch.
Rust Bust Management Checklist
By planning ahead to manage rust it is possible to minimise its cost to your business. It is important that growers choose a strategy that is appropriate to their situation, and follow it during the growing season.
This checklist outlines a simple rust management strategy.
1) Have you controlled the green bridge?
In the 4-6 weeks before seeding, there should be no ‘green bridge’ in and around paddocks to be sown. Remove green material by grazing, burning, cultivation, and/or herbicides. The green bridge is rust susceptible living plants or volunteers (mostly wheat, and to a lesser extent barley, triticale and barley grass) that grow in paddocks during summer/autumn. The more susceptible volunteer wheat plants growing during summer and autumn, the greater the risk of a rust epidemic. Rust does not survive on seed, stubble or soil.
Susceptibility of the volunteer wheat plants over summer influences the quantity of inoculum generated by the green bridge. If most varieties in a district are resistant there will be considerably less inoculum than if the majority of plants are susceptible or very susceptible.
It is critical that all volunteer wheat plants are removed either by spraying, cultivation or heavy grazing in the four week period leading up to sowing.
Particular care should be taken to destroy plants around sheds and silos, as rust often survives on these plants.
2) Have you considered alternate varieties to S and VS?
Growers should, wherever possible, select varieties with sufficient rust resistance to suit their individual risk situation. Select varieties with the highest levels of rust resistance possible, keeping in mind other agronomic and disease traits of the variety.
While it is generally agreed that S and VS varieties are best avoided, if growers do select them a rust management plan is a must.
The actual disease response that occurs in the field will depend on many factors, including the amount of inoculum carry over, the timing of the rust outbreak in the crop, seasonal conditions and the pathotypes (races/strains) of rust occurring in a region.
For MS-VS varieties: It is highly recommended that these cereal varieties should be protected throughout the entire growing season.
- Rust management options, depending on the current seasonal risk in your region, include:
- Fungicide with rust activity applied as a seed dressing.
- Fungicide amended fertiliser (coated or granulated with fertiliser) or liquid fungicide applied in furrow at sowing.
- Foliar fungicide.
For MR-MS varieties: One or more of the following rust management options should be considered at sowing, especially in seasons of high rust risk:
- Fungicide with rust activity applied to seed or fertiliser (coated or granulated with fertiliser).
- Fungicide amended fertiliser (coated or granulated with fertiliser).
- Foliar fungicide.
For R or MR varieties:
- For MR varieties or higher, additional rust management (listed above) at sowing is unnecessary.
3) Are you monitoring crops at every growth stage?
It is critical to monitor all crops for the presence of rust, particularly during spring. This can be done by either visually assessing the thicker patches in a crop or by walking in a W shape through the paddock to ensure a representative sample of the crop. It is suggested wheat growers collect five plants at ten different locations.
Inspect the lower parts of the plant, the stem and the leaves for rust symptoms.
If a fungicide has been applied, monitoring must start in the week before the protection period is expected to end.
- For MS-S to VS varieties:These will require continual monitoring, even if there has been protection applied at sowing. Growers cannot afford to miss the early detection of a rust outbreak as epidemics can be explosive in susceptible varieties. Growers will have to consider in their budgeting seedling protection and up to three foliar sprays to achieve yield potential in highly susceptible varieties. In these varieties, a fungicide spray must be applied either before, or soon after, the detection of rust in the canopy. If stripe or leaf rust first appears after ear emergence then a fungicide spray may not be required, depending on the seasonal outlook. However varieties MS to VS will need stem rust protection until early grain fill.
- For MR-MS and MS varieties: Foliar sprays must be considered for these varieties if disease begins early (before second node) and if chemical protection was not applied at sowing. Post-emergence herbicide applications can include a tank-mixed fungicide to reduce application costs and provide early protection against rust. Follow-up spraying to protect flag leaves may be valuable in high disease pressure seasons. Fungicides are not expected to give economic protection after heading in the MR-MS and MS varieties for stripe rust and leaf rust. However, stem rust is a late season disease and these varieties may benefit from post-heading fungicide protection if disease pressure remains high.
- For R or MR varieties: Although resistant varieties should be fine throughout the season and not require fungicide support, it is wise to continue monitoring because pathogen change is a possible scenario.
4) Have you talked to your neighbour?
Rust management is a group effort. To deliver an effective rust management strategy, growers must communicate with their neighbours. Here’s why:
- It only takes one neighbour or others in the district using S and VS with no control for a rust outbreak to occur.
- Growing S and VS varieties increases inoculum levels and the vulnerability of other less susceptible varieties being used in the vicinity.
- Fungicide treatments will be most effective when adopted across a region as they will greatly reduce the inoculum levels in a district.
Rusts are caused by parasitic fungi which reproduce and thrive on green plant tissue. The fungus releases airborne spores which are spread readily by the wind over large areas in a short time.
Rust spores can also spread on clothing, footwear and machinery. If a rust spore comes in contact with susceptible plant tissue, it penetrates and infects individual plant cells.
Biosecurity is vital in managing rust. Stop the spread of rust disease by being responsible. The GRDC has published “Rust diseases of grain crops – biosecurity brochure” to outline simple steps you can take to reduce the possibility of spreading rust. Click on the image below to view the brochure.
Additional tips for busting rust can be found on the following pages: