Look out for rusts and other foliar diseases in your crops
Weather conditions in many areas this year have been conducive to disease. Diseases can cause significant yield or quality losses.
Monitoring crops is crucial in spring. It is recommended to walk through crops every week or fortnight as early disease detection makes control easier.
Leaf diseases
Wheat
Yellow spot and stagonospora (septoria) nodorum
Of particular concern at present is that the disease can move from leaf lesions to the upper canopy and then infect heads, a condition called glume blotch.
The risk is higher in susceptible varieties, continuous wheat crops (particularly early sown crops) and higher rainfall environments.
Fungicide application is best aimed at reducing disease impact on upper canopy leaves before head infection and is not likely to be economic after crop has finished flowering.
Powdery Mildew will still be an issue in dense crops of susceptible varieties this season.
If there is ongoing mild weather, powdery mildew may continue in susceptible crops.
However warm spring weather (over 22°C) and drying winds are likely to cause it to disappear.
Very susceptible to susceptible varieties (eg. Scepter, Zen, Corack, Trojan, Wyalkatchem) face the greatest risk.
Varieties such as Mace and Calingiri (moderately susceptible to susceptible) can also suffer severe infection.
Applying fungicides to limit the progress of infection into the upper canopy and heads is recommended in the more susceptible varieties before the crop has finished flowering.
Although it should be noted that responses from a single fungicide in trials have varied from <5% to up to 15% yield increase.
In the case that favourable conditions continue, a second fungicide application may be required if the disease symptoms return after 2-3 weeks, but generally, spraying after crop flowering is not economic.
A period of warmer, drying weather can rapidly reduce progress of infection, limiting the response to fungicide.
Stem rust is better adapted to warmer conditions (15-30°C) than leaf or stripe rusts, and is usually detected later in the season (mid-late spring).
Crops can be at risk until well into grain fill, therefore it is important to monitor for this disease during spring.
Stem rust can cause losses of 10-50% and increased screenings depending on the disease resistance of the variety.
This can be higher when it occurs in early spring on susceptible varieties and is not controlled.
It is vital to monitor susceptible varieties (e.g. Yitpi, Calingiri, Ninja) and apply fungicide early in the disease progress.
Managing the infection once it becomes severe is extremely difficult.
Fungicide application can be worthwhile up until dough grain fill stage, so long as there is at least 4 weeks of the season remaining.
Mace, Scepter and other moderately resistant rated varieties can also show some symptoms of infection but disease should not develop rapidly and it will generally have minimal yield losses
Leaf rust has been found near Esperance this year.
Monitor susceptible crops (eg. Scepter, Mace, Wyalkatchem, Emu Rock, Corack, Stiletto, Calingiri, Westonia, Carnamah, Yitpi and more) for infection.
Remember some varieties have changed disease ratings since the establishment of new leaf rust pathotypes.
Significant yield losses are possible and fungicide application early in the disease cycle can be beneficial, particularly in susceptible varieties.
It is less likely that responses to sprays during and after flowering will be economic, unless the crop is reaching these growth stages very early in the season or is affected by stem rust.
Barley
Leaf rust
Leaf rust is commonly found in barley crops along the south coast, as is the case this season.
It was regularly seen in the central wheatbelt in 2017 and has reached the northern wheatbelt on occasion.
The varieties Bass and Compass are the most susceptible to leaf rust.
For more information on this and other barley diseases please see Managing barley leaf diseases.
Spot-type and net-type net blotch
This disease can be managed with foliar fungicides but care must be taken in choosing an active ingredient that is effective, after recent identification of fungicide resistance in both diseases.
For more information see managing net-type net blotch in barley Western Australia
Similarly, due to resistance, not all fungicide active ingredients are effective against barley powdery mildew so check recommendations at management of barley powdery mildew.
Oats
Septoria avenae blotch
This disease causes light or dark brown to black blotches and lesions on leaves and stems of susceptible oat varieties.
The fungus can be associated with dark discolouration of the grain when unseasonably late rain occurs. Fungicide management trials have shown significant yield responses in seasons which support disease development into the upper canopy.
Leaf and stem rust
These both occur in oats, varieties vary in their susceptibility to these diseases.
Further information on managing these diseases is available at Oats: Leaf diseases.
Lupins
Sclerotinia stem and collar rot
Sclerontinia stem rot (caused by Sclerotinia sclerotiorum may be a problem in dense lupin crops in some areas as well as sclerotinia collar rot (caused by Sclerotinia minor).
Anthracnose
Antracnose has been found in volunteer blue lupins already this season. For further information on managing sclerotinia and anthracnose or other diseases see Lupin foliar diseases.
Canola
Sclerotinia stem rot is expected to be widespread in the northern wheatbelt.
It could also be an issue in some central areas and other pockets where is it wet enough.
Late spraying, up until 50% flowering, can be economical when continuing humid conditions and temperatures below 25°C have been forecast.
Continued wet conditions generally prolong the spore release and extend the flowering window.
Fungicide spray is unlikely to eradicate an already established infection but may prevent any subsequent infections occurring via infected petals.
It is important to comply with the withholding periods of fungicides.
At this time of year Blackleg can cause upper canopy infection including lesions on pods.
Diagnosis is important for planning for seed (may need new seed) and paddock allocations next year.
Fungicide management
Application of fungicide sprays can reduce the impact of many of the diseases outlined above, however yield responses and positive economic benefits from fungicide application are never guaranteed.
Factors that will favour fungicide application include;
- the presence of disease
- more susceptible varieties
- weather favourable for disease development and crop growth (rainfall and/or humid conditions), and
- good yield potential.
Good responses from fungicide applications at this time of year are more likely in early sown crops and in higher rainfall environments.
Remember, fungicides are best used as ‘protectants’ rather than ‘eradicants’, that is, stopping disease progress by protecting uninfected leaves rather than trying to eliminate a severe infection already present.
Fungicides will only protect the leaves that are out at the time of application.
Later germinating plants that do not have all their leaves out at time of application may harbour disease and be a source of ongoing infection, if not controlled by a second fungicide application.
Disease development, yield impact and potential fungicide responses are usually greatest in more susceptible varieties.
Further information
Lists of fungicides registered for cereals, canola and lupins in WA are available on the DPIRD website.
Check your wheat or barley variety guide for the disease status of varieties or online for the most up to date ratings. Oat variety disease ratings available on the oat page.
MyCrop is an interactive tool that brings crop diagnostics to the paddock. A free app is available to assist with diagnosing crop problems including diseases. The app is available from the Google Play Store and the Apple iTunes Store.
Pestfax and the Pestfax reporter app are available to report disease finds and get updates on what is being found around the wheatbelt.
Crop disease management pages are available in one central location. (https://www.agric.wa.gov.au/cropdisease)
Please send cereal rust samples in paper envelopes, not plastic wrapping or plastic lined packages, to:
University of Sydney
Australian Rust Survey
Reply Paid 88076
Narellan NSW 2567
Please note the location, variety, date and contact details of the sender.
You can obtain the sampling instructions, posting details and further information on the new pathotype finds from Australian Cereal Rust Control Program website.
Alternatively, you can deliver samples to your nearest Department of Primary Industries and Regional Development office to be forwarded for testing.
If you are having difficulty controlling diseases in your crop/s and suspect fungicide resistance developing please contact:
Centre for Crop and Disease Management
Fungicide Resistance Group
Curtin University
Perth on +61 (0)8 9266 1204 or frg@curtin.edu.au
Request further information and a sample tube so you can submit plant samples.
The group is interested in barley net blotches, wheat yellow spot and powdery mildew, botrytis (grey mould), ascochytas in pulses and blackleg in canola.
For more information contact Plant Pathologists, Geoff Thomas (South Perth) +61 (0)8 9368 3262, Ciara Beard (Geraldton) +61 (0)8 9956 8504, Kith Jayasena (Albany) +61 (0)8 9892 8477 or Andrea Hills (Esperance) +61 (0)8 9083 1144.