Prevention of resistant fungi can be approached from several angles

Chemical and biological solutions should go hand in hand in order to prevent development of resistance in pathogenic fungi. Using variety mixes can be part of the strategy – but cannot stand alone.

2018.03.02 | Janne Hansen

A combination of various measures can and should be used to control fungi in crops, such as septoria in wheat. Photo: Lise Nistrup Jørgensen

The Danish media have recently run a story about resistant fungal diseases in weakened patients and a possible correlation to agriculture’s use of fungicides. This can be a serious issue so it is therefore necessary to arm yourself with facts – and create new knowledge about the subject. 

Resistance against measures that are used to fight infections caused by bacteria or fungi, and that occurs when these measures have been used frequently or exclusively, is a familiar phenomenon in the health and agricultural sectors. 

The currently debated fungus, Aspergillus fumigatus, is ubiquitous in our surroundings and can be exposed to triazoles in connection with applications to prevent harmful fungi in the field, pressure treated wood, textiles, building materials and paint. The fungus can be difficult to manage when a patient is treated repeatedly with a triazole or if a patient is infected with a fungus that is already resistant. 

The issue poses some questions: How serious is the problem in Denmark, where does the resistance in Denmark come from, and what can be done to prevent further development of resistant pathogenic fungi? 

Variety mixes cannot stand alone

Researchers from the Department of Agroecology at Aarhus University are investigating fungi that infect plants and various methods to control these phytopathogenic fungi. A common method to prevent fungal infection in cereals is to treat the crop with fungicides, including triazoles. 

This solution cannot, however, stand alone, not least because the fungi develop resistance against the fungicides. The researchers are therefore looking at other possibilities. One method being investigated at by PhD student Rose Kristoffersen from the Department of Agroecology is if variety mixes can be used as a supplementary solution. By sowing a mixture of varieties in the field instead of just one variety, it might be possible to reduce the crop’s vulnerability to fungal infection.   

- We have good indications that variety mixes can be included as part of an anti-resistance strategy. However, in most of the trials I have looked at, triazoles were necessary to control fungi in order to ensure against yield loss. The project is still in its early days, but in most cases there were significantly higher yields when the crops were treated with fungicides, says Rose Kristoffersen. 

The preliminary results indicate that it is possible to arrest development of resistance in fungi if the farmer: 


  • reduces the number of sprayings by, among other things, including resistant varieties
  • only treats when necessary
  • uses fungicides with various modes of action
  • uses adjusted and not too high dosages


- It would be nice if we could find methods so that fungicides could be omitted without any problems, but we cannot at the present, says Rose Kristoffersen.  

- In the meantime, chemical and biological solutions can go hand in hand, for example as part of integrated pest management (IPM). 

Read more here:

Does agricultural use of azole fungicides contribute to resistance in the human pathogen Aspergillus fumigatus? 

Azole-Resistant Invasive Aspergillosis: Relationship to Agriculture 

Environmental study of azole-resistant Aspergillus fumigatus and other aspergilli in Austria, Denmark, and Spain 

For more information please contact

PhD student Rose Kristoffersen, Department of Agroecology, email:, mobile: +45 2621 8664 

Senior Researcher Lise Nistrup Jørgensen, Department of Agroecology, email:, telephone: +45 8715 8234, mobile: +45 2228 3352

Agro, Crops, DCA