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United Kingdom - Statement on SDHI fungicides and resistance risk in cereals issued by FRAG-UK


United Kingdom
December 16, 2015

Following reports of laboratory and field isolates of septoria tritici with reduced sensitivities to SDHI fungicides, a statement has been issued by Fungicide Resistance Action Group-UK (FRAG-UK).

What has been detected?

To date, many mutations which confer a change in sensitivity to SDHI fungicides have been detected in the field and from laboratory mutation studies. Not all of these mutations affect field performance. 

The laboratory 

There have been several examples of laboratory mutants of cereal pathogens showing reduced sensitivity to SDHIs. In 2012, extensive monitoring detected two septoria isolates (France and UK) and two isolates of net blotch (Germany) with sensitivities outside the baseline range. In 2013, isolates of net blotch with mutations conferring reduced sensitivity to SDHI fungicides were commonly detected throughout Europe including the UK. In 2014, more of these isolates were reported and additional mutations were found. 

The field 

In November 2015, Rothamsted Research reported low frequencies of septoria isolates with reduced SDHI sensitivity in UK field populations. In December 2015, Teagasc in the Republic of Ireland confirmed the detection of field isolates of septoria with reduced sensitivity to the SDHIs. Some of these isolates had a mutation (C-H152R) in the SDHI target site which had not previously been detected in field isolates. 

What are the implications for management? 

Field performance from SDHIs is still anticipated to be good in 2016. However, strong stewardship is needed to prevent a rapid increase in the frequency of isolates with reduced sensitivity to SDHIs in the septoria population. 

In view of these detections, it is crucial that fungicide programmes on wheat and barley adhere strictly to the guidelines on resistance management detailed in the full FRAG-UK statement.                                                         

Fungicide performance trials 

Dr Paul Gosling, AHDB Research Manager, said: “AHDB supports the resistance action groups in their effort to provide evidence-based, independent and practical information on resistance management.

“FRAG-UK’s statement follows the release of our latest fungicide performance data at our Agronomists’ Conference last week.

“Our trials show that SDHIs remain the most active chemistry against septoria when applied in protectant situations.

“However, the new information on SDHI sensitivity, once again, shows why it is critical to adopt best resistance management practices.”


For further information on the latest fungicide performance results, see the press release:

Latest fungicide performance data unveiled amid fresh resistance management warnings

The 2015 AHDB Cereals & Oilseeds Agronomists' Conference included an in-depth analysis of the strengths and weaknesses of a range of fungicides.

Taking place on 8 December, Dr Jonathan Blake Senior Research Scientist ADAS provided an in-depth analysis of the performance of fungicides trialled in the AHDB fungicide performance programme.

Shifts in sensitivity of pathogen populations were also presented at the event. In particular, delegates were provided with new information on SDHI sensitivity. 

Watch the video

Using fungicides effectively in wheat, barley and oilseed rape

Jonathan Blake - Senior Research Scientist, ADAS

Fungicide rewards

Dr Blake presented data extracted from the AHDB Recommended Lists trials which revealed the continued good yield response to fungicides.

For example, for wheat – based on a 14-year period (2002–15) – the average treatment benefit was 1.97t/ha.

Septoria solutions

One of the main discussion points was the control of septoria tritici which was still not fully controlled on farm in 2015.

Dr Blake said that, on average, 50% of wheat crops are infected with septoria in mid-late June and it was inevitable that the disease would ‘bulk up’ and impact on yield.

In terms of control, fungicide performance trials showed that SDHIs remained the most active chemistry when applied in protectant situations.

Jonathan Blake

SDHI efficacy warnings

Delegates were also informed of a recent development, by Teagasc in Ireland, where septoria isolates with reduced sensitivity to SDHIs had been detected.

Commenting on this finding, Dr Blake said it represented a ‘step-change in sensitivity but what size that step is, we just don’t know’.

‘As the less sensitive isolates are at a low frequency in Ireland, and, as its fitness is unknown, it could disappear altogether’.

However, with this development so close to home, delegates were told it reinforced the need for SDHI stewardship.

Dr Blake said ‘if you can avoid using an SDHI, avoid it’.

Delegates were advised to use different modes of action and embrace varietal resistance.

The AHDB fungicide performance trials show that multi-site products remain valuable as protectants and, along with azoles, can help to play an important role in resistance management and ‘protect the efficacy of SDHIs for as long as possible’.

Data for Librax (fluxapyroxad and metconazole), which was trialled for the first time in 2015, looked as effective as other SDHI/azoles.

The main conclusions from the current trials, along with performance curves, are available from the disease management section of the AHDB Cereals & Oilseeds website.

All conference presentations and videos can be viewed at cereals.ahdb.org.uk/agconf

The main conference findings will be presented over the next few weeks as a series of news items on the AHDB Cereals & Oilseeds website. 

Following the reports of laboratory and field isolates of septoria tritici with reduced sensitivities to SDHI fungicides, a statement has been issued by Fungicide Resistance Action Group-UK (FRAG-UK). This can also be viewed on the AHDB Cereals & Oilseeds website.

Agronomists’ Conference 2016 

A provisional booking for the Agronomists’ Conference 2016 has been made for Thursday 8 De



More news from: AHDB - Agriculture and Horticulture Development Board


Website: http://cereals.ahdb.org.uk/

Published: December 16, 2015

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