Wet winter conditions have been ideal for foliar diseases to develop in barley crops across most of Victoria. Reports of spot form and net form of net blotch and scald have been common in susceptible varieties in the Wimmera and Mallee regions, prompting growers to consider if fungicides are warranted to prevent losses to grain yield and quality should the wet conditions continue.
It is NOW time to inspect your barley crops for disease with a view to timely foliar fungicide applications by following these simple steps:
- Review current disease ratings for your varieties
- Inspect crops at tillering to early stem elongation for diseases and to determine if levels are above 10% leaf area affected.
- Plan for timely fungicide application if warranted (see below – Fungicide Timings)
Inspect crops at mid tillering to early stem elongation (Z25-31). If foliar diseases such as the net blotches and scald are easy to find, low in the canopy on most plants and cover greater than 10% of leaf area in susceptible varieties, then fungicide application should be considered:
Crops rated S, SVS or VS
If yield potential is greater than 3 t/ha, then there is a good chance of economic gains from fungicide application when disease is present. Extensive testing has shown that there are two very effective fungicide strategies for all foliar diseases of barley in the low to medium rainfall zones. Foliar fungicide applications at both Z31-2 (early stem elongation – first node) and Z39-49 (flag leaf emergence on the main stem – booting), or Systiva® applied to seed, followed by Z39-49 (flag leaf emergence to booting) have proved to be the best strategies. If there are continued wet conditions following the first fungicide application, it is preferable for the second application to be applied no later than four weeks later. There are still likely to be significant gains from the first fungicide application after early stem elongation during a good season, especially in the medium and high rainfall zones. Should conditions turn dry during spring, then the application of the second fungicide should be reviewed as its benefits will be reduced, making the earlier application at Z31 more important. Should yield potential be greater than 5 t/ha, then both foliar fungicide applications are essential as losses can be as great as 1 t/ha. In the high rainfall zone, fungicides will give their best returns when applied to the more important upper leaves. Leaves produced at tillering are less important than leaves produced at Z31 and Z39-49.
Crops rated MRMS, MS, and MSS, where disease is present
Crops rated as moderately susceptible are less likely to have significant yield loss from foliar diseases. In general, there will only be benefits from fungicide application where yield potential is greater than 4 t/ha. Monitor these crops and apply fungicides if there are favourable, wet conditions during spring. The same fungicide strategies are applicable to these varieties as discussed above for the susceptible varieties.
To extend the life of fungicides growers should:
- follow label directions for use and adhere to MRLs
- not apply the same fungicide active to a crop more than once per season
- use fungicide mixtures where possible
- avoid unnecessary fungicide use
Further information is available in the GRDC Update papers listed below:
Nick Poole (FAR Australia)
Hugh Wallwork (SARDI)