How to use fungicides effectively
Effective fungicide use depends on the following areas.
Variety resistance ratings
Disease resistance ratings for WA cereal varieties are available in the latest WA Crop Sowing Guide.
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 non-pathogens, such as nutrient deficiencies or toxicities and adverse weather conditions. A disease diagnosis service is provided by DPIRD Diagnostic Laboratory Services (DDLS). PestFax provides useful up to date information on diseases present throughout the wheatbelt each season.
Decision support tools
DPIRD along with national collaborators has developed the StripeRustWM app to assist growers and agronomists.
StripeRustCM app can be downloaded from Apple or Google Play stores to aid in decision making about the economics of foliar fungicide application for managing wheat stripe rust in your specific paddock.
Appropriate selection of a fungicide from available registered products
Once you have correctly identified the disease, refer to the tables provided under 'Documents' on the right for registered active ingredients in WA. For details on which products or trade names contain a specific active ingredient search the online PubCRIS database (free) or Infopest (subscription required) or contact your agronomist or chemical provider.
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 in the initial stages of a disease outbreak so 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 via the Crop disease: forecasts and management page for recommended application timings.
Optimal application of fungicide
Apply fungicide to the plant surface by using correct application methods including correct choice of volume of water and nozzles to manipulate the droplet size. These are often described on product labels. In general, cereal crops will require a spray volume between 70L/ha and 100L/ha in case of ground spray and, for aerial spraying, 20L/ha is adequate. However, in high disease situations, higher spray volumes will be beneficial to penetrate into the lower parts of the canopy.
For fungicides to effectively reach their target, they need to be applied using medium sized droplets (100-300 micrometres). Historical research by DPIRD has found that ground and aerial application methods are equally effective in controlling disease in cereal crops. When choosing an application method, consider timeliness and cost of application (including potential crop damage).
Further information on application methods including water volumes, adjuvants and spray quality see GRDC publication Foliar applications of fungicides and insecticides.
How to prevent or delay fungicide resistance
Responsible use of fungicides is key to delaying the development of fungicide resistance. Fungicide resistance occurs when populations of a pathogen develop which are no longer controlled adequately by fungicide application. This usually occurs as a response to repeated use of a single fungicide active ingredient. It can also occur through repeated use of closely related fungicide active ingredients using a similar mode of action. Fungicide resistance has been identified in barley powdery mildew and barley net blotches in WA.
The following methods are good resistance management practice:
- Rotating fungicides to prevent over-use of any one product or chemical activity group. As a general rule, avoid using the same chemical /mode of action more than necessary and follow label instructions. To help growers in this area, all fungicide products sold in Australia are classified according to the chemical activity group (mode of action) of their active constituent. The activity group is indicated by a number code or letter/number combination on the product label (for a complete list of all chemical activity groups see the fungicide activity group table on the Croplife Australia website). Don't forget that at seeding, fungicides need to be counted as well (that is, fungicide seed dressings or in-furrow fungicides applied on fertiliser).
- Ensuring that fungicides are working optimally by applying them in the most effective and appropriate manner. Before applying fungicide, ensure a disease is actually present. When applying fungicide adhere to disease threshold levels, target applications to control early disease stages and follow label recommendations, rates and coverage. Always use the label rates according to the manufacturers recommendations.
- Use fungicides in conjunction with other tools such as cultural practices and/or growing more resistant varieties so fewer or less frequent fungicide applications are required.
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.
Tables of registered foliar fungicides for use on wheat, barley and oat crops in WA are updated each year and are available under 'Documents' on the top right hand side of this page.
These are a guide only and product labels should be read carefully before application. To help us keep these tables updated please contact Ciara Beard with any new registration information.
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.