Turf Fungicide Mode of Action Table

This turfgrass blog discusses Turf fungicide resistance and in particular fungicide mode of action groups. Fungicide resistance is the ability of fungae to survive exposure to fungicides that would normally kill or inhibit their growth. This can occur when fungal cells develop genetic mutations that allow them to tolerate the fungicide. These resistant cells are able to survive and reproduce and over time, the proportion of resistant cells in a population can increase, making it more difficult to control the fungus with the fungicide. This fungicide mode of action table is to help delay the onset of fungicide resistance.

Turf fungicides are commonly used to control diseases such as dollar spot, brown patch, and fairy ring. The same principles of disease control apply to both professional turf managers and home lawn owners. However, the overuse or improper use of fungicides can lead to fungicide resistance in fungal populations.

By rotating fungicides with different fungicide mode of action groups, using fungicides in combination, and using cultural practices to reduce fungal populations you can manage this. Cultural practices include irrigation management, fertilization, mowing, and aeration.

Fungicide Rotation.

You can use a strategy of fungicide rotation to manage fungicide resistance. This is when you use different fungicide mode of action groups to prevent the build-up of resistance in fungal populations. The IGFH Guide to Australian Turf pesticides goes into more detail on this topic but the following is a summary.

Fungicides have different modes of action, which refers to the way in which they kill or inhibit the growth of fungal pathogens. So for example azoxystrobin fungicide mode of action differs from that of chlorothalonil.

By rotating fungicides with different modes of action, the likelihood of a fungal population developing resistance to a single fungicide is reduced. You can achieve this by alternating between fungicides with different modes of action during a single season, or by using fungicides with different modes of action in successive seasons.

Fungicide rotation can be used in combination with other resistance management strategies, such as using combination fungicides like Lexicon Intrinsic and cultural practices to reduce fungal populations. It’s important to keep track of the fungicides that you use and the timing of their application to ensure that rotation is effective.

Fungicide resistance can develop quickly, so use fungicides responsibly and in rotation with other products and management practices. It’s also important to monitor for resistance and to adjust management strategies accordingly.

Australian turf fungicide mode of action table.

 

To get the best out of the Australian turf fungicide mode of action table, follow these steps:
 
 

1.  Understand what this table is for:

The turf fungicide mode of action table provides information about different groups or classes of fungicides. It helps turf managers, turf agronomists, and lawn owners select and rotate fungicides to prevent or manage fungal diseases.
 
 

2.  Identify the columns:

Familiarize yourself with the table’s column headings. Each column provides information about these turf fungicides and their properties.

 

3.  What does each column mean?

Here’s what each column represents:

    • FRAC Resistance Group: Fungicides are put into Groups or classes based on their modes of action;
    • Fungicide active ingredient: What is actually in it;
    • Product name: Lists some examples of common turf fungicides;
    • Mode of Action: Describes the specific process that the fungicide affects in the target organism.
    • Diseases controlled: Specifies the fungal diseases that you can use the turf fungicides for in Australia.

 

4.  Determine target disease:

Identify the fungal disease you are dealing with. This useful turf disease guide helps with this.

 

5.  Choose the appropriate group or class:

Look for the group or class of fungicides that are effective against your target disease. Cross-reference the fungicide group or class with the target disease column to find suitable options.

 

6.  Rotate fungicides:

It is crucial to rotate fungicides with different modes of action to prevent fungal resistance. Refer to the mode of action column to select a fungicide from a different group or class for future applications.

 

7.  Follow the label:

Once you have identified a suitable fungicide, read the product label and follow the manufacturer’s application rates, timing, and safety precautions. This advice also relates to whether it is legal to use a specific fungicide in a home lawn situation.

 

8.  Monitor and assess efficacy:

After applying the fungicide, monitor the treated turf for disease control and evaluate how well your selected fungicide works. If necessary, consult with local turf agronomists or sports turf consultants for further guidance.

Turf fungicide resistance table with FRAC classifications

Fungicide Resistance management plan for turf.

Turf diseases vary in how susceptible they are to resistance. High risk turfgrass diseases include dollar spot; grey leaf spot, anthracnose and Pythium blight.
 
 
 
In the US dollar spot resistance to Iprodione and the DMI fungicides was first seen in 1980’s and 1990’s. Resistance was first reported to boscalid in 2018.
 
 
Resistance is also seen with anthracnose (azoxystrobin and thiophanate methyl;  gray leaf spot (azoxystrobin and theoretical cross resistance to all QoI/strobilurin’s , and possibly thiophanate-methyl) and Pythium blight targeted by metalaxyl and mefenoxam.
 
 
Preventive applications of fungicides are most effective when you use different FRAC groups (i.e., modes of action) to deal with high risk diseases such as dollar spot, gray leaf spot and anthracnose.
 
 
Curative sprays should include two different modes of action (see FRAC Codes).
 
 
You should use these along with with low risk (i.e., multi-site activity) fungicides which may be a weak control option when you use them alone but are invaluable to manage resistance. Options include Squadron, Secure and Pistol Fungicide.

Single Site or Multi-site?

 

Single site turf fungicides are at a medium to high risk of developing resistance. Being single-site means they act at a specific point in the pathogen.

Multi-site fungicides are mostly contacts such as Squadron Weatherace and have many different target sites. This means there is less of a risk as more changes are required in the pathogen for resistance to occur.

Rotate.

 

Do not use site specific fungicides from the same group more than twice in a row. This also applies if your are using premix combination fungicides such as QualiPro Enclave.

In an ideal situation aim to use multisite fungicides as often as possible, as they have low to no risk for resistance.

Interestingly, CropLife has published the following resistance guidelines specific to turfgrass.

  • Groups classed as medium to high risk for fungicide resistance development; Groups 1, 2, 4, 7 (N3), 11 and 21. Rotate these to reduce the development of resistance.

 

  • Do not apply consecutive sprays from the same activity group, unless mixed with a registered fungicide from a different mode of action group with no known resistance.

 

  • Group N3 nematicides are also classified as Group 7 fungicides, so avoid consecutive applications even if targeting different pests/pathogens.

 

  • If consecutive sprays are applied from a high-risk fungicide group (i.e. Group 1, 2, 4, 7, 11 or 21) you must follow these by at least the same number of applications of fungicide(s) from a different group(s) before the same high-risk fungicide is used again.

Apply the correct rates.

 

On so many occasions we have seen turf managers change the rates of application as it “didn’t work last time”. This is a big no no. Stick to the label rates.

Practice integrated disease management (IPM).

 

Don’t just say you do it. Actually do do it! IPM practices will break any disease cycle. Increasing air flow, reducing turf stress and using resistant cultivars of bentgrass or ryegrass can save you a lot of money in the long term. I would also consider products such as salicylic acid into any IPM plan as these will also counter any resistance issues. The turf pigment and grass colorant Vertmax Duo contains this.

Senior Turf Agronomist at Gilba Solutions Pty Ltd | 0499975819 | Website | + posts

After Graduating from Newcastle University with an Hons Degree in Soil Science in 1988, Jerry then worked for the Sports Turf Research Institute (STRI) as a turf agronomist before emigrating to Australia in 1993.

He followed this by gaining a Grad Dip in Business Management from UTS. He has worked in a number of management roles for companies as diverse as Samsung Australia, Arthur Yates and Paton Fertilizers.

He has always had a strong affinity with the Australian sports turf industry and as a result he established Gilba Solutions as an independent sports turf consultancy in 1993. Jerry has written over 100 articles and two books on a wide range of topics such as Turf Pesticides and Nutrition which have been published in Australia and overseas.