(Reviewed January 2024)
Phytophthora infestans is classified by FRAC as a medium risk pathogen. Long-term experience with CAA fungicides demonstrates that the resistance risk of Phytophthora infestans to this fungicide group is low to moderate. For effective resistance management a precautionary strategy has to be implemented.
- Apply CAA fungicides preferably in a preventive manner.
- Apply a maximum of 50% of the total number of intended applications for late blight control.
- Apply CAA fungicides always at recommended dose rates.
- Apply CAA fungicides using not more than 2 consecutive applications.
- Apply CAA fungicides preferably in mixtures with effective partners belonging to different modes of action.
- Alternation with fungicides having other modes of action is recommended in spray programs.
- Good agricultural practices must be considered to reduce source of inoculum, disease pressure and resistance risk, e.g. consider to plant resistant varieties and refer to disease prediction models.
In regions with reported cases of resistance:
- CAA fungicides must be used in mixtures, with not more than 2 consecutive applications.
- In case mixtures cannot be applied for regulatory reasons, apply CAA fungicide in strict alternation.
For more detailed product recommendations refer to the use guidelines published by the respective CAA manufacturers.