Are early fungicide applications effective for yellow spot and septoria nodorum blotch in the low rainfall zone 2014 trial report

Page last updated: Wednesday, 25 July 2018 - 11:34am

Previous research in high rainfall zones or above average seasons has shown that in cases where leaf spot disease levels are high very early, fungicide application at or before first node (Z31) is effective at reducing disease levels and increasing yield in wheat. This trial at Mullewa in 2014 is investigating if the same results will be obtained in lower rainfall environments.

Background

Recent trends in cereal production have been towards increasing areas sown to wheat after wheat.

Stubble-borne leaf diseases such as yellow spot are a higher risk in a continuous wheat system.

In the past, control strategies for yellow spot have been modelled after the rust diseases with controls aimed at reducing losses in the last stages of crop growth, that is, at or after flag leaf emergence.

In wheat on wheat situations in Western Australia, growers are tending to apply foliar fungicides earlier than ever before, applying them at the same time as herbicides at 3-5 leaf stage or early tillering.

Previous research in high rainfall zones or above average seasons has shown that in cases where leaf spot disease levels are high very early, fungicide application at these early stages is effective at reducing disease levels and increasing yield.

This trial in 2014 will investigate if the same results will be obtained in a lower rainfall environment.

Aim

To assess the efficacy of foliar fungicide application prior to stem extension for control of yellow spot or septoria (stagonospora) nodorum in wheat in low rainfall zones.

Trial details

Table 1 Trial details
Property DPIRD Mullewa Research Annex, Ardingly South Rd, Mullewa
Crop/variety Wheat - Zippy
Paddock rotation 2011 – wheat, 2012 - wheat, 2013 - wheat
Treatments
  1. Unsprayed
  2. Sprayed at Z31
  3. Sprayed at Z31 + 1 follow up spray at Z39
  4. Sprayed at Z39
Replicates Four

Z31 fungicide application applied on 25 June 2014. Treatment 2 received Prosaro® at 300mL/ha, treatment 3 received Prosaro® at 150mL/ha.

Z39 fungicide application applied on 14 July 2014. Treatment 3 received Prosaro® at 150mL/ha, treatment 4 received Prosaro® at 300mL/ha

Results

Septoria nodorum and yellow spot symptoms were present at low levels when trial was established in July at first node on 25 June 2014 with on average 11% disease on the top four leaves.

Disease continued but progressed slowly due to lack of rain. Diease assessment on 14 July 2014 (Z39) showed that the plots that had received the Z31 (first node) spray had half the disease levels of the nil (unsprayed) plots - average 7% on top four leaves versus 14% on top four leaves in the nil plots.

On 14 August 2014 (Z65, flowering) disease levels were signifiantly lower in fungicide treated plots (Table 2).

Table 2 Average leaf area diseased (%) on top two leaves of sampled tillers in the fungicide treatments at Z65 growth stage
Fungicide treatment % average leaf area diseased on top two leaves at Z65
1. Unsprayed (nil fungicide) 38
2. Prosaro® at 300mL/ha at Z31 21
3. Prosaro® at 150mL/ha at Z31 and Prosaro® at 150mL/ha at Z39 16
4. Prosaro® at 300mL/ha at Z39 20
LSD (5%) 4.7

The trial will be harvested and grain yield, quality results and trial conclusions provided when available.

Yellow spot symptoms on a wheat leaf
Yellow spot symptoms in the trial as observed on the flag leaf of an unsprayed plot in the trial on 14 August 2014 during crop flowering

Acknowledgements

This trial is part of the GRDC funded project DAW00229 Improving growers surveillance, management, epidemiology knowledge and tools to manage crop disease.

Contact information

+61 (0)8 9956 8504

Authors

Ciara Beard
Anne Smith