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Dual use of azoles as fungicides and antimycotics

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Challenges posed by the development of resistance and EU recommendations

Aug. 2025. The dual use of azoles as both fungicides and antimycotics can, among other things, promote the development of resistance in the fungus Aspergillus fumigatus, which can make it more difficult to treat infections in immunocompromised individuals. A comprehensive EU analysis confirms the link between agricultural use of azoles and reduced medical efficacy. To counteract this, EU authorities recommend stricter approval procedures, the development of new active substances that do not exhibit cross-resistance, and the responsible use and disposal of active substances.

We provide you with a concise overview of the causes of resistance development and the EU's recommendations, and explain how we can support you with precise analyses as your competent laboratory analysis partner.

Impact of dual azole use on the development of resistance in Aspergillus fumigatus

Between 2010 and 2021, a total of around 120,000 tonnes of azoles were used, over 119,000 tonnes of which were used for plant protection. In January 2025, the European Chemicals Agency (ECHA), the European Food Safety Authority (EFSA), the European Centre for Disease Prevention and Control (ECDC), the European Environment Agency (EEA), the European Medicines Agency (EMA), and the Joint Research Center (JRC) of the European Commission published a joint study which comprehensively analysed the impact of the non-medical use of azoles as fungicides in agriculture on the development of resistance in the fungus Aspergillus fumigatus.

According to the study, the intensive use of azole fungicides in EU agriculture exerts strong selection pressure, promoting the development of resistant fungal strains such as Aspergillus fumigatus. The development of resistance poses a growing challenge as Aspergillus fumigatus can primarily infect immunocompromised patients and complicates medical treatment with azole antifungals.

EU recommendations for minimising the development of resistance to azoles

To ensure the long-term effectiveness of medical azole antifungals, the following measures are recommend by EU agencies:

 

  • Integration of new specific requirements into the approval and authorisation procedures for azole fungicides.
  • Promoting research and development of new fungicides with innovative modes of action that do not promote cross-resistance to medical antifungals.
  • Adherence to good agricultural practices, proper storage of organic waste, and responsible use and disposal of azole-containing products.
  • Introduction of effective waste management for wood treated with azole-based biocides.
  • Collection of further data on the use of azole-based fungicides and antimycotics.
  • Further development of technical guidelines and risk assessment methods to support regulatory decisions.
  • Conducting further research to reduce existing uncertainties.

The dual use of azoles in medicine and agriculture poses a complex challenge requiring a holistic One Health strategy. Coordinated measures at the regulatory, agricultural, and medical levels can reduce the selection pressure on fungal populations and ensure the long-term effectiveness of important azole antifungals.

Mechanism of action of azoles

Azoles are a key class of active substances that play an important role in both human medicine and agriculture. They are five-membered, nitrogen-containing aromatic heterocycles and inhibit the biosynthesis of ergosterol, an essential component of the fungal cell membrane. This effectively prevents the growth of fungi. The mechanism of action is the same for azole fungicides used in agriculture to control fungi and in azole antimycotics used to treat invasive fungal infections in humans.

Examples of use in agriculture

The azole fungicides difenoconazole and tebuconazole belong to the group of systemically acting triazoles and are used in agriculture. In particular, they are used to combat fungal diseases such as Septoria leaf spot, Fusarium species, brown rust and leaf and glume blight in cereal cultivation.

Other relevant azole active ingredient groups include imidazoles (e.g., imazalil and prochloraz). These have a local-systemic effect with limited distribution and are mainly used in post-harvest treatments and for special crops.

Contact us

We support you in the analysis of azoles and other pesticides and advise you on your individual questions so that you can comply with EU recommendations. Our multi-analysis pesticide screenings (Quechers method) cover a wide range of azoles relevant to agriculture.

For further information or personalised advice, please contact your personal account manager at any time or contact our expert Ayman Farhod Naeem directly.

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