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Australia - Fungicides – protecting yields in the fight against foliar diseases


Australia
July 30, 2013

Key points:
  • Fungicides are an integral component of the in-season management of a range of cereal diseases.
  • Yield responses to fungicide application are maximised by using appropriate products at the most effective rate and at the appropriate stage of the disease cycle and crop development.
  • Fungal pathogen (eg. powdery mildew) resistance to fungicides is widespread in WA.
  • There are few new active fungicide ingredients registered for use in cereals.
  • Fungicide use should be strategic and based on correct disease identification.
  • Disease levels, especially for yellow spot and spot type net blotch, may have been lower than expected in many grainbelt areas this year due to the prolonged dry spell in May and June.
  • But it is worth monitoring cereal crops for disease incidence to achieve best use of fungicides.
  • Any cases of fungicide failure should be reported to the Australian Centre for Necrotrophic Fungal Pathogens (ACNFP) at Curtin University.

Managing cereal fungicide use:

Effective and economic fungicide plans should have strategies for spraying if:
  • Disease threatens key plant parts (flag-1 to flag-2);
  • Varieties are moderately susceptible (MS) or susceptible (S) to very susceptible (VS); or
  • There are early signs of disease, especially for MS and MR varieties before resistance kicks-in.
Timing of application and using recommended label rates are critical, depending on disease pressure and growth stage of the crop - along with a carrier water volume of 70-80 litres.

Monitor crops regularly to protect against early infection and keep abreast of disease incidence across the State during the growing season through the Department of Agriculture and Food WA’s (DAFWA) PestFax report.

GRDC has released a new ‘Managing Cereal Fungicide Use’ fact sheet that outlines strategies to determine if and when a fungicide is needed.

It provides information about identifying fungal diseases, diagnosis, fungicide modes of action, timing of applications, economics of using fungicides, resistance and stewardship.

The fact sheet was included in the May/June 2013 edition of Ground Cover and is available at:
www.grdc.com.au/GRDC-FS-CerealFungicides

Tips for fungicide use in WA in season 2013:


Barley leaf diseases

Powdery Mildew
  • Risk of infection is high in very susceptible (VS) Baudin, especially in south coastal and Esperance areas.
  • Other varieties, including Vlamingh and Gairdner, are also susceptible to this disease.
  • There have been widespread reports of barley powdery mildew infection made to the PestFax service from across the southern grainbelt.
  • These reports involve several varieties, including Baudin, Bass, Vlamingh, Gairdner and Urambie.
  • Avoid using compromised triazole fungicides, such as tebuconazole or triadimefon, flutriafol or triadimenol-based products for powdery mildew control.
  • These fungicides should also be avoided or limited when controlling other diseases, such as spot type net blotch, to prevent the build-up of resistant powdery mildew populations.
  • Avoid strobilurin-based products in crops with heavy infestations.
  • Treat susceptible crops with cyproconazole, strobilurin, prothioconazole or epoxiconazole-based products or mixtures registered for this use when powdery mildew is at less than 5 per cent infection levels.
  • If necessary, spray again three to four weeks later – depending on disease pressure and environmental conditions.
  • Timing of fungicide application will depend on the time of disease onset and susceptibility of the variety.
  • A permit for Prosper® (spiroxamine) has been issued for powdery mildew in WA until 2016, which provides an alternative mode of action.
  • Addition of potassium to deficient crops has been shown to reduce the impact of powdery mildew.
  • Send any powdery mildew infected samples from barley varieties to the ACNFP, which is monitoring any mutations or changes in powdery mildew fungus and its response to fungicides.
Barley leaf rust
  • This disease was widespread in south coast and lower Great Southern crops in 2012 and risk in these areas is high this year.
  • To date this season there have been reports from across south coastal areas, including on: Hindmarsh barley (at Wellstead and Beaumont); Baudin (North Wellstead); and in volunteer crops in the South Stirlings.
  • Several varieties, including Buloke, Vlamingh and Gardiner, are also susceptible.
  • During June, high levels of leaf rust fungus were found in fungal spore traps in the Wellstead area.
  • This disease is difficult to control once established.
  • Prevention is best achieved by using newer generation fungicides - such as those containing cyproconazole or prothioconazole – or strobilurin or epoxiconazole-based products or mixtures.
  • Use of spray adjuvants can be effective to boost fungicidal activity on Baudin crops – for example, Uptake®/Hasten®/Adigor® - at recommended label rates (0.5-2 per cent ) with lower rates of the fungicides Prosaro® (prothioconazole + tebuconazole) or Amistar Xtra® (azoxystrobin + cyproconazole).
  • Use fungicides at full rates as soon as infection is spotted (ideally before 5 per cent infection) - around Z30 to Z32 is ideal.
  • A second spray may be needed two-four weeks later (based on crop monitoring and label recommendations).
  • Research shows if early infection occurs on susceptible varieties (many are), yield losses can be as high as 30 per cent and grain quality issues (especially high screenings) can occur.
Spot type net blotch
  • This is appearing across widespread areas on susceptible varieties, particularly on barley-barley rotations.•    Infection risk is high when susceptible varieties are grown in stubble from susceptible varieties. Rain will determine further spread of disease in-crop.
  • Moderate and high disease pressure is a threat to grain yield and quality and losses in susceptible varieties can be high.
  • Spore traps in the South Stirlings area continually detect net blotch asexual conidia spores in the region and the risk this year is moderate.
  • Triazole-based products, such as propiconazole, prothioconazole and strobilurin-based products and mixtures, are most effective against this disease.
  • But choosing a fungicide should depend on the spectrum of diseases in the crop.
  • Adding potassium to deficient crops has been shown to reduce the impact of net blotch.
Wheat leaf diseases

Wheat leaf spot diseases
  •  Some advanced crops (tillering) in the eastern wheatbelt are showing symptoms of wheat leaf spot diseases, such as Yipti (rated S to VS to yellow spot).
  • Yellow spot and Septoria nodorum blotch have similar symptoms, so correct diagnosis is important.
  • Spots appear irregularly or in oval shapes and are initially small and yellow before enlarging to form brown dead centres with yellow edges.
  • Both diseases can severely restrict yield and impact on grain quality.
  • Wet spring weather drives infection and when this occurs, fungicides to control diseases in the upper canopy can be a profitable investment.
  • Research has shown it can be profitable to apply fungicides when there is high disease pressure in early crop growth stages (at or before early stem elongation – ie first node or Z31), especially when susceptible varieties are sown on wheat stubble and there is good yield potential.
  • A follow-up spray at flag leaf emergence (Z39) may be required.
  • Applications prior to first node – ie seedling and tillering – can reduce early infection, but often provide shorter duration of disease protection.
  • Profitable responses to fungicides applied at flag leaf (Z39) in trials were more likely in: well-grown crops where disease was moving rapidly from lower leaves to upper canopy leaves; and in areas where there was a good chance of 100mm of rainfall in the two months after flag leaf emergence.
Rust
  • Risk of wheat leaf rust and stripe rust in all grain production regions is low this year due to minimal occurrences of these diseases last year.
  • There is a risk of wheat stem rust on the south coast and in the Esperance region.
  • Crop monitoring is recommended across all areas, especially for susceptible varieties such as Yipti, Westonia, Arrino and Calingiri.
  • Several cases of wheat stem rust were reported in the South Coast and Esperance regions in 2012.
  • One case of wheat stripe rust was found in the Great Southern last year and risk is low.
  • Little fungicide intervention was needed.
  • There were no reports of wheat stem or stripe rust in the central or northern wheatbelt regions in 2012 and no reports of wheat leaf rust or oat rust.
  • In recent years, any wheat rust incidences have occurred mainly in susceptible or very susceptible varieties – such as Yitpi (stem rust) and Clearfield Stl or Stilletto (leaf rust).
  • Spraying for stem rust can still be cost effective at much later growing stages than for other diseases.
  • Optimal single spray timing for stem rust is around Z55-Z59, but with earlier disease onset or if the disease is severe, it may need to be treated earlier.
Powdery mildew
  • Wheat powdery mildew risk is considered low across the wheatbelt due to minimal disease incidence in 2012.
  • There have been no reports of resistance to fungicides in Australia to date, although this has been described in other countries, and there is a risk of resistance developing if poor anti-resistance strategies are followed.

Research efforts

GRDC funds projects in WA through DAFWA and the ACNFP investigating best use of fungicides as part of integrated management strategies.

Projects at the ACNFP aim to address fungicide failure in important WA crops.
The ‘Fungicide Resistance Benchmarking’ project analyses the efficacy of solo compounds in currently registered mixtures.

It aims to identify combinations in which one of the fungicide partners is at risk due to mutations in the pathogen population.

A ‘New Actives’ project is also underway to study the efficacy of unregistered chemicals to allow the registration of successful compounds to complement current fungicides available to growers.

DAFWA has several projects investigating the biology of grain crop diseases and use of fungicides, variety resistance and cultural approaches to limit the impact of a range of cereal diseases.

GRDC Project Codes: CUR0010; CUR00015, CUR00016, DAW00190, DAW00210

Useful resources:
To send disease samples to the ACNFP, post to:
Harry Zhang, ACNFP, Department of Environment and Agriculture, Building 311, Curtin University, Bentley WA, 6845;
or contact:
fran.lopezruiz@curtin.edu.au or simon.ellwood@curtin.edu.au
WA disease incidence maps and to register to receive Pestfax newsletters: 
pestfax@agric.wa.gov.au
GRDC Managing Cereal Fungicide Use fact sheet (May/June edition of Ground Cover):
www.grdc.com.au/GRDC-FS-CerealFungicides
GRDC cereal diseases resource hub:
www.grdc.com.au/diseaselinks
GRDC Wheat and Barley Leaf Symptoms Back Pocket Guide:
www.grdc.com.au/GRDC-FS-WheatBarleyLeafSymptoms
GRDC Fact Sheet: Barley Powdery Mildew:
www.grdc.com.au/GRDC-FS-BarleyPowderyMildew
GRDC Ground Cover TV: Adult Plant Resistance, Fungicide Resistance:
www.grdc.com.au/GCTV9
DAFWA disease publications:
www.agric.wa.gov.au/cropdisease; http://www.agric.wa.gov.au/objtwr/imported_assets/content/pw/ph/dis/managing_barley_powdery_mildew_in_2013.pdf
DAFWA cereal disease diagnosis: 08 9368 3721 or
www.agric.wa.gov.au/agwestplantlabs


Disclaimer
Any recommendations, suggestions or opinions contained in this publication do not necessarily represent the policy or views of the Grains Research and Development Corporation.
No person should act on the basis of the contents of this publication without first obtaining specific, independent, professional advice.
The Corporation and contributors to this publication may identify products by proprietary or trade names to help readers identify particular types of products.
We do not endorse or recommend the products of any manufacturer referred to. Other products may perform as well as or better than those specifically referred to.
The GRDC will not be liable for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information in this publication.
CAUTION: RESEARCH ON UNREGISTERED PESTICIDE USE
Any research with unregistered pesticides or of unregistered products reported in this document does not constitute a recommendation for that particular use by the authors or the
authors’ organisations.
All pesticide applications must accord with the currently registered label for that particular pesticide, crop, pest and region.



More solutions from: GRDC (Grains Research & Development Corporation)


Website: http://www.grdc.com.au

Published: July 30, 2013

 

 

 

 

 

 

 

 

 

 


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