NovaChem > Industry News > 2023 > Fungicide actives: love them or lose them

Fungicide actives: love them or lose them

Published on 21/11/2023

FAR cereal researcher Jo Drummond says it’s vital to choose the right fungicide mode-of-action (or mix), and only apply them if you are sure they are needed.
“To prolong the life of our at-risk fungicide
groups, we need to up our resistance management game. Ongoing control of Septoria tritici blotch (STB), which is caused by the pathogen Zy-moseptoria tritici (Zt), is of particular concern.

“Effective management of STB relies on
the use of DMI – triazole (Group 3) and SDHI (Group 7) fungicides, with support from the multi-site fungicide folpet (Group M4) and QiI (Group 21) fungicide fenpicoxamid. If STB develops resistance to these active ingredients, it will be very difficult to manage.”

With this in mind, fungicide sensitivity was
monitored in Zt populations in wheat crops across New Zealand in the 2020-21 and2021-22 seasons. Sensitivity shifts were detected in both SDHIs and DMIs.

Here’s what you need to know...

DMI fungicides

The biggest sensitivity shifts were identi
fied in DMI (Group 3) fungicides, especially prothioconazole and epoxiconazole. As sensitivity shifts to the DMIs appear to be driven by the number of applications, you should think carefully about the value of each application, particularly if applied very early or very late.

Managing DMIs

• Mix DMIs with fungicides with different
modes of action in repeat spray programmes

 • Alternate your DMI base between fun
gicide applications within and between seasons. E.g. if you have used prothioconazole (including as part of a ‘stacked’ product) at GS 32 (T1), use a mefenitrifluconazole or epoxiconazole based product at GS 39 (T2).
• Use at appropriate doses to ensure effec
tive disease control.
SDHI – Group 7 Fungicides

There continue to be small sensitivity shifts
in the SDHI fungicides, but they remain stable. Shifts are most obvious in fluxapyroxad (Adexar®, Imtrex®and Revystar®) which has been on the market longer than benzovindiflupyr (Elatus Plus) and isoflucpyram (Caley®Iblon® and Vimoy®Iblon®).

However, all three active ingredients are
showing similar trends, meaning that continued efficacy is reliant on careful management.
Managing SDHIs:

• Apply SDHIs in a balanced mixture with at
least one fungicide with comparable efficacy against the target pathogens from an alternative mode of action group.

• Limit the number of applications as stat
ed on each product label (some products can be used twice, others only once).

• Alternate SDHI active ingredients both
within and between seasons.

• Alternate your mixing partner – utilise all
the tools at your disposal.

Fenpicoxamid (Group 21) and Folpet (Group

All Zt isolates showed high sensitivity to
fenpicoxamid (QiI – Group 31) and the multi-site (Group M4) fungicide folpet. However, the development of resistance still remains a risk. Folpet’s value continues to be as a mixing partner with other fungicides.

For more information contact jo.drummond@

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