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Getting the balance right

Barley disease control

Welcome to ADAMA’s updated barley disease information page where you’ll find an introduction to the control of ramularia and rhynchosporium in winter and spring sown crops.

Getting the balance right

For 2022 we’re focusing on how to ensure your spring fungicide programme delivers in three key ways:

  1. Efficacy of disease control
  2. Resistance management
  3. Return on investment

Throughout the spring we’ll be looking back at some of the lessons learned last year and making recommendations for how to use a diverse range of single and multi-site fungicides – including ARIZONA (500 g/L folpet) – to maximise disease control, future-proof the efficacy of ‘at-risk’ chemistries and secure a return on investment through improved crop performance.

Disease control - getting the balance right

Disease resistance

While the current range of cereal fungicide chemistries is more effective against barley diseases than it is versus wheat infections, barley fungicide resistance is increasing and continues to be detected.

Against ramularia, the efficacy of prothioconazole has declined significantly in recent years, while strobilurins are already largely ineffective. Likewise, the field performance of strobilurins versus net blotch is variable with SDHI sensitivity shifts also confirmed.

Sensitivity shifts have reduced the efficacy of SDHI fungicides, with their efficacy now variable at best. This is hampering protection against ramularia, as is the erosion in efficacy of prothioconazole and increasing levels of strobilurin resistance. Meanwhile, Revysol (mefentrifluconazole) is active against ramularia and net blotch with no sensitivity shifts detected to date.

This places the multi-site group of fungicides at the forefront of the barley disease arsenal, although active ingredients such as folpet will only provide contact protection.

Barley fungicide field performance

Azole resistance

  • Rhynchosporium: the performance of the azole group of fungicides has been in decline for a number of years although prothioconazole and mefentrifluconazole performance remains good and stable.
  • Net Blotch: despite the existence of sensitivity shifts for a number of years, the azole group remains relatively stable, with prothioconazole and mefentrifluconazole giving good levels of protection.
  • Ramularia: reduced sensitivity has been seen across the azole group (with the exception of mefentrifluconazole), with prothioconazole field performance issues first reported in 2016 in Germany and in the UK since 2017. The ability to control ramularia infections with prothioconazole has been significantly reduced. Whilst mefentrifluconazole is active against ramularia it should be noted that higher rates are required to achieve satisfactory levels of control.  This azole product is at risk to resistance and therefore the addition of folpet will improve efficacy against ramularia and help to prolong the effective life of mefentrifluconazole against this challenging disease.

Strobilurin erosion

  • Rhynchosporium: strobilurin performance is variable thanks to G143A resistance which is found at a very low frequency. Field performance concerns first became evident in 2017.  Whilst efficacy has reduced, the best performing strobilurins continue to contribute to programmes.
  • Net Blotch: the F129L mutation, which confers partial resistance, was first detected in 2004. Field performance has been in decline in the subsequent years with performance now variable at best.
  • Ramularia: monitoring shows that the G143A mutation now affects almost 100% of the UK ramularia population, therefore rendering strobilurins ineffective.

SDHI setbacks

  • Rhynchosporium: despite a ‘moderate’ risk of resistance, the SDHI group of fungicides remains stable at present and works well in mixtures with other actives.
  • Net Blotch: isolates with reduced sensitivity to SDHI chemistries were first recorded in the UK in 2013.  Several additional mutations have subsequently been detected since 2014. The reduced field performance of SDHI in UK trials was confirmed in 2016. Further resistance development is considered to be medium to high.
  • Ramularia: disease mutations associated with a decreased sensitivity to SDHIs have been detected across Northern Europe, with field performance issues confirmed in UK since 2017. Currently, SDHIs provide variable efficacy against ramularia at best.

Cyprodinil activity

As a unique mode of action belonging to the anilino-pyrimidine group of chemicals, cyprodinil is a useful addition to the barley arsenal as it increases the diversity of modes of action and reduces the potential for further resistance to single site chemistries to develop.

  • Rhynchosporium & net blotch: performance is stable with no evidence of any sensitivity shifts or erosion in efficacy.
  • Ramularia: while only providing relatively low levels of activity against ramularia, its performance remains stable.

 

Mult-site modes of action

In contrast to single site modes of action (azoles, SDHIs and strobilurins), multi-site fungicides such as folpet have no known resistance issues and, despite being less effective than some of the more robust single sites, remain vital to the sustained protection of cereal crops: not just in terms of reducing the threat of disease, but also by protecting partner products with which they should be used in mixture.

In barley, ARIZONA (500 g/L folpet) provides contact protection against rhynchosporium and ramularia by acting on multiple bio-chemical pathways which makes it less susceptible to resistance. New trials data from ADAMA shows that it delivers the following benefits:

  • Added efficacy against ramularia
  • Maintains green leaf area and delivers yield benefits for a viable return on investment
Folpet mode of action

A valuable tool for managing resistance

Folpet is recognised by the Fungicides Resistance Action Group (FRAG-UK) as a valuable tool for managing resistance thanks to its ability to provide added levels and spectrum of disease control which can protect and prolong the lifespan of medium to high resistance risk fungicides like SDHIs.

FRAG UK

Protecting crop quality and yield

In order to maximise the yield potential of barley, fungicide programmes should be designed to maximise the crop’s green area index by reducing the effect of disease on tiller numbers early in the season and to keep the entire plant as green as possible for as long as possible.

A well-timed T1 spray (typically GS 30-32 in winter barley or GS 25-30 in spring barley) is key to protecting the crop at tillering/stem extension and should be followed by a subsequent treatment at T2 (typically GS 39-49) to provide continued protection.

Barley crop

Winter barley use recommendations

For ramularia protection, T2 is the key timing for including ARIZONA in any scenario, with a two-spray approach giving the best results:

Option 1: to deliver improved ramularia protection particularly where disease builds early in the growing cycle following a wet spring:

T1: 0.75-1.0L/ha (GS30/31)

T2: 1.0-1.5L/ha (GS39/49)

Option 2: to deliver improved ramularia protection and application flexibility by applying the first split with a PGR application

T1.5: 0.75-1.0L prod/ha (GS37)

T2: 1.0-1.5L prod/ha (GS39/49)

Option 3: to provide ongoing protection in scenarios where the canopy is extended

T2: 1.0-1.5L prod/ha (GS39/49)

T3: 1.0-1.5L prod/ha (T2 + 7-10 days, but before GS59)Maximum total dose 3.0L per crop

Maximum total dose 3.0L per crop

Ramularia on winter barley

Spring barley use recommendations

For ramularia protection, T2 is the key timing for including ARIZONA in any scenario, with a two-spray approach giving the best results:

T1: 0.75-1.0L prod/ha (GS25/31)

T2: 1.0-1.5L prod/ha (GS39/49)

Maximum total dose 3.0L per crop

ARIZONA Spring Barley Recommendations

Future-proofing disease control in barley

In order to protect the current armoury of single site barley fungicides, growers should implement the following tactics:

1. Integrate a range of cultural controls to minimise the threat

  • Consider disease resistance ratings when selecting which barley variety to grow
  • Delay drilling to reduce the crop’s exposure to disease
  • Reduce the disease threat by using cultivation and establishment methods which remove volunteers and bury trash and debris from the previous crop
  • Avoid using seed from affected crops as this can act as a host and source of infection

2. Keep ahead of the disease

  • Use disease forecasting tools to predict when crops are at risk from infection so that fungicides can be applied at the optimum timing to provide maximum protection – thereby avoiding the need for curative activity
  • Spray applications must be timed accurately to protect key leaves, so that infections are unable to establish. This means using a stacked and sequenced programme of effective single site products together with multi-site fungicides to provide a strong protective effect.

3. Create a diverse fungicide programme

  • Use a mixture of compatible fungicides of different modes of action (including a multi-site) in a stacked and sequenced approach to prevent the over-use and over-exposure of any single active ingredient to the threat of disease resistance and sensitivity shifts.
  • Use the minimum effective dose of each fungicide to control the pathogen(s) being targeted and to reduce the risk of resistance developing.

4. Maximise the use of multi-site chemistry

ARIZONA (500 g/L folpet) should be included in the tank mix at T1 and T2 to protect the crop against rhynchosporium and ramularia at tillering and beyond. The most effective timing for ramularia control with folpet is T2 (GS39-49) but results have shown improved efficacy from an additional earlier timing at T1.