How to use fungicides effectively
Effective fungicide use depends on the following areas:
Correct diagnosis of a fungal disease
Fungicides are effective only on diseases that are caused by fungi. Sometimes plant symptoms resemble those caused by pathogens but they are actually caused by nonpathogens, such as nutrient deficiencies or toxicities and adverse weather conditions. A disease diagnosis service is provided by DDLS - Plant pathology services. PestFacts WA provides useful up to date information on diseases present throughout the wheatbelt each season. Further information on both of these services is available via the links under the 'See Also' section of this page. The My Crop pages describe the symptoms of sclerotinia stem rot and blackleg, downy mildew, turnip mosaic virus, damping off, white leaf spot, alternaria black spot, beet western yellow virus, cauliflower mosaic virus and clubroot. Foliar fungicides are currently only registered for the control of black leg (stem canker and upper canopy infection), sclerotinia stem rot and white leaf spot but there may be other management strategies you can use to manage other diseases.
Variety resistance ratings and disease forecasts
For both blackleg stem canker and blackleg UCI, growers need to consider their varietal resistance levels before they spray as it may not be economical to spray varieties with high blackleg resistance level.
Blackleg resistance data for WA canola varieties is available in the latest WA Crop Sowing Guide or the GRDC Blackleg Management Guide. The most current resistance ratings are also in the BlacklegCM decision support tool.
Canola blackleg spore maturity forecasts are available on the Crop diseases: forecasts and management page.
Appropriate selection of a fungicide from available registered products
Once you have correctly identified the disease, refer to the table provided under 'Documents' on the right (or bottom of screen if on a mobile) for registered active ingredients in WA. For details on which products or trade names contain a specific active ingredient search the online PubCRIS database or Infopest (subscription required) or contact your agronomist or chemical provider. Foliar fungicides are currently only registered for the control of blackleg (stem canker and upper canopy infection), sclerotinia stem rot and white leaf spot.
There are now some foliar fungicides registered for use for blackleg upper canopy infection (UCI). Fungicides applied during the bloom stage (before 50% bloom) may reduce UCI. Registered products should be applied at similar times to the fungicides used for Sclerotinia control. These fungicide applications for UCI are likely to be more economical in higher yielding crops. Use the UCI BlacklegCM decision support tool when considering the value of a fungicide application.
DPIRD, along with national collaborators, has developed canola disease decision support tools to assist growers and agronomists.
- BlacklegCM decision support tool can be downloaded from Apple or Google Play stores and used to help you decide which blackleg crown canker treatments are economical under your circumstances.
- UCI BlacklegCM decision support tool can be downloaded from Apple or Google Play stores and used to help you decide whether a fungicide application at early flowering is likely to be economical for upper canopy blackleg management under your circumstances.
- SclerotiniaCM decision support tool can be downloaded from Apple or Google Play stores to aid in decision making about the economics of foliar fungicide application for managing sclerotinia stem rot in your specific paddock.
It is vital that product labels are read before application to identify: that the chemical is registered for use on the crop and for the spectrum of diseases present, the withholding period and any specific application instructions. Be careful of tank mixes with other products. In some instances fungicide sprays need to be mixed with an adjuvant (refer to label).
Correct timing of fungicide application
Most of the information on optimal application timing is available on fungicide product labels. Fungicides are better applied before or in the initial stages of a disease outbreak so being aware of your disease risk and routine crop monitoring is needed for timely application of fungicide. Follow-up fungicide application may be needed to extend protection in some situations. Refer to specific disease management pages on this site for recommended application timings, such as Managing sclerotinia stem rot in canola, and the GRDC Blackleg Management Guide, external link available on the right (or bottom of this page if you're on a mobile phone). Through the BlacklegCM decision support tool, UCI Blackleg CM decision support tool, and SclerotiniaCM decision support tool you can run different scenarios to estimate the most likely financial return of different fungicide application timings in a given season. A guide to canola bloom stages is shown below.
Reduce the risk of fungicide resistance developing
Fungicide resistance develops from misuse of fungicides and poor disease management practices. There are currently barley powdery mildew and net blotch populations resistant to some fungicides in WA so this is a very real threat that we are facing. You can reduce the risk of fungicide resistance developing by growing varieties less susceptible to disease (where available), supported by integrated disease management in conjunction with strategic and responsible use of fungicides (eg rotating and mixing fungicides with different modes of action). For more information on how fungicide resistance develops, where it is occurring, and what you can do to avoid the risk of it developing in your crops go to the Australian Fungicide Resistance Extension Network (AFREN) webpage.
Disclaimer: Mention of trade names does not imply endorsement or preference of any company’s product by Department of Primary Industries and Regional Development and any omission of a trade name is unintentional. Recommendations are current at the time this page was prepared.