‘Timing of fungicide application is becoming more critical’

Septoria is the most destructive disease of Irish winter wheat crops and in the absence of commercially-viable, highly-resistant varieties, fungicides will continue to be relied upon to control diseases in Irish wheat.

Speaking at Teagasc’s Crops and Cultivation open day in Oak Park last week, Dr. Steven Kildea explained the importance of building a suitable fungicide programme and the timing of its application.

“In Ireland, we do have yellow rust every so often and we will have other diseases such as eyespot, fusarium, powdery mildew and take-all.

“But when we’re talking about a fungicide programme, we want to make sure that we target the diseases that are going to cost us the most. And in all years, this will be septoria,” Kildea said.

‘The why, when and what’

Kildea added that farmers need to know when they should apply fungicide, what fungicide to use and why they are using it.

Septoria attacks the foliage, reducing green leaf area and the ability of the plant to capture sunlight. This indirectly reduces its yield potential.

Kildea explained how the timing of applications is now becoming more and more critical as we start to lose efficacy in some products.

Research carried out by Kildea over the last number of years looked at four-spray fungicide programmes. This was carried out in order to determine what aspect of a programme is protecting the stem, upper canopy, ear and consequently the yield from disease.

Leaving out the flag-leaf spray led to a serious reduction in wheat yield, highlighting the importance of the upper canopy for yield potential.

The second-most important application was found to be the earlier application – the T1.

“As we lose the efficacy of certain products, T1 will become more important and we have seen it becoming more important in the last two years,” Kildea added.

In the trials where there was just septoria present, dropping the ear spray (specifically for fusarium) didn’t have a major impact on yield.

However, Kildea added that if there was fusarium present, yield would have dropped by over 1.5t/ha without the timely application of the ear spray.

Another interesting finding was in relation to the T0 applied. If a good fungicide programme followed, there was no impact on yield if this was dropped out.

For high disease pressure, Kildea recommended the following fungicide programme:
  • End of tillering: Multi-site (if you include a T0);
  • Third leaf emerged: SDHI/Azole mix with a multi-site;
  • Flag leaf emerged: SDHI/Azole mix with a multi-site;
  • Start of flowering: Azole mix.

If a location is prone to high disease pressure, Kildea added that it’s important to select the most resistant variety available; delay planting as late as possible; and ensure the crop is sprayed when required.

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