Fungicides available for Australian grain crops and their modes of action

Date:02-09-2024

Fungicides play a critical role in safeguarding Australian grain crops, ensuring healthy yields and maintaining food security. As one of the world’s leading exporters of grains such as wheat and barley, Australia relies on effective fungicide strategies to combat fungal diseases that can devastate crops.

Fungal diseases such as rusts and net blotches can quickly spread and decimate entire fields. In a country where climate variability is a constant challenge, timely and effective disease management is essential.

This is where correct fungicide application along with best disease management practices are vital to support a successful yield for the grower and ensure the longevity of fungal chemistries.

Understanding the mode of action of fungicides is key to managing fungicide resistant disease causing pathogens

Photo: Dr Anna-Sheree Krige, CCDM and AFREN

Fungicides work through various modes of action (MoA) to combat fungal pathogens. These MoA determine how the fungicide interacts with the fungal pathogen and ultimately prevents or manages the disease. Understanding MoA is crucial for growers and agronomists when selecting and applying fungicides effectively.

Fungicides are categorised according to their MoA and assigned to an internationally determined group number. When a fungal pathogen develops resistance to a particular fungicide, it often puts all other fungicides belonging to the same MoA group at risk of reduced effectiveness, or the development of resistance.

Globally, more than 200 fungicides are approved for the management of fungal pathogens in agriculture, classified into 57 different MoA groups. However, in the context of Australian grain crop protection, only a limited number of these MoA groups are registered, and a select few dominate the market (Tables 1 and 2).

This limited availability of fungicide groups increases the risk of fungicide resistance emergence because growers have very few alternatives to rotate with, which would otherwise help mitigate the selection pressure on these fungicide MoA groups.

While fungicides are invaluable tools in grain crop protection, their overuse or improper application can lead to the development of resistance in fungal populations.

How can we prevent the emergence of fungicide resistance? Simple: stop the fungus from adapting to the treatments applied. This can be achieved by regularly changing the types of fungicide chemistries used, or mixing fungicides from different MoA groups.

Properly implemented fungicide rotations are crucial when incorporating fungicides with specific MoAs into disease management programs. It is essential to strictly adhere to fungicide labels and ensure that certain fungicide chemistries are not excessively employed to maintain their long-term effectiveness.

To combat resistance, GRDC supports the operation of the Australian Fungicide Resistance Extension Network. This network provides information and support for growers and advisers to manage fungicide resistance. AFREN strongly encourages growers to implement the AFREN Fungicide Resistance Five integrated disease management (IDM) strategies.

1. Avoid susceptible crop varieties

2. Rotate crops – use time and distance to reduce disease carry-over

3. Use non-chemical control methods to reduce disease pressure

4. Spray only if necessary and apply strategically

5. Rotate and mix fungicides/mode of action groups

Additional information

Fungicides are approved based on factors such as state/territory, crop, target pathogen, formulation and application rate. Up-to-date details regarding registered fungicides and their applications can be accessed through the APVMA website at apvma.gov.au.

The mentioned risk of resistance development is determined through global observations and evaluations conducted by the international Fungicide Resistance Action Committee (FRAC). For further insights, refer to the FRAC website at frac.info. For an overview of MoAs as it relates to the Australian grains industry, visit AFREN.com.au and under the Resources tab locate the Fungicide Resistance Management in Australian Grain Crops Guide.