Act now to manage rust
GroundCover™ Issue: 29
WA wheat growers are advised to take account of widespread rust this season and the risk of disease carry-over when planning for next year's crop.
Growers and scientists alike are assessing losses from the 1999 rust epidemic. Wheat leaf rust occurred throughout WA's wheat-growing areas this year, and late stem rust was widely reported in many southern and central areas.
Fungicide use was extensive, and yield losses from leaf rust were measured at 30 per cent in some cases. Sporadic losses from stem rust exceeded these levels.
Frost and hail damage in 1999 also have the potential to add to the ongoing rust problem by increasing the amount of seed not collected at harvest. With summer rain this will result in abundant cereal volunteers.
High rainfall last summer produced widespread volunteer cereal plants which carried rust and caused this season's epidemic. Summer rainfall scenarios like this have a 20 per cent chance of occurring in any year.
With abundant rust spores in all wheat-growing areas, now is the time to minimise controllable risks for the 2000 cropping season.
Key management strategies for rust prevention
Destroy the green bridge
Green paddocks are a major liability. Self-sown summer and autumn cereal volunteers, the green bridge, should be killed with herbicides or heavy grazing as soon as they develop and well before sowing. This will reduce the amount of local carry-over of rust spores and reduce the risk of early infection. Graingrowers need to be active in their summer and autumn weed management.
Sow resistant varieties
If we're having a wet summer it will be important to use rust-resistant varieties. Recommended varieties combining stem and leaf rust resistance for WA include Camm, Carnamah, Cunderdin, Datatine, Janz, Nyabing, Wilgoyne, Krichauff and Goldmark. Brookton and Perenjori also combine stem rust resistance with intermediate resistance to leaf rust.
Budget for fungicide use
The strategic use of a seed-dressing fungicide can provide early protection against leaf rust in susceptible varieties. Where potential rust risk exists, use Real seed treatment in autumn costing around $12/100 kg seed. Protection will last for up to eight weeks. Fungicide crop sprays (applied at early head emergence and costing $15-25/ha) were widely used in 1999, and help reduce losses in susceptible varieties.
Time of sowing
Early-sown crops carrying rust through winter show rapid development of the disease in spring, increasing yield losses and making it difficult to manage. April sowings of susceptible varieties can lead to early rust developing on young crops before winter, and should be avoided.
Destroy the green bridge
Use resistant varieties Budget for fungicides
Consider time of sowing
Contact: Dr Robert Loughman 08 9368 3691