Irlanda: Concern about fungicide resistance in potato blight strain

This was the key message given to over 60 potato stakeholders in attendance at the workshop, which was organised to address concerns over the recent emergence and spread of fungicide resistance through the European late blight population.

Potato late blight, caused by phytphthora infestans and synonymous with Irish potato production, continues to be the most destructive disease of potato.

Fortunately, the development of disease control strategies, including the application of fungicides, has curtailed the impact the disease now has on crops, both in Ireland and throughout Europe.

Unfortunately, the vulnerability of these strategies to the disease has recently been exposed following the emergence of strains of P. infestans with resistance to two key groups of fungicides used for its control. 

Late potato blight

At the start of the workshop, Dr. David Cooke from the James Hutton Institute in Scotland provided an overview of how the European late blight population has been changing in recent seasons, including the emergence of fungicide resistant strains, to the CAA and OSBPI fungicides.

The detection of a strain of late blight known as EU_43_A1 in a research plot at Teagasc Crops Research Centre at Oak Park, Co. Carlow in late autumn of 2023 was confirmed by Dr. Steven Kildea.

The sample found was resistant to one of the fungicide groups in question.

Commenting on its detection, Dr. Kildea said: “This detection signified the presence of EU_43_A1 in the Irish late blight population and the onus is now on the entire industry to ensure all precautions to minimise its potential impact on late blight control are adhered to.”

To provide an overview of what the potential impact to the sector if precautions are not taken, Dr. Geert Kessel of Wageningen University and Research (WUR) in the Netherlands described the impact these strains had on the control of late blight in the Netherlands in 2023.

He also provided recommendations on how to tackle the disease, emphasising the need to ensure fungicides are mixed, and alternated across fungicide programmes.

These recommendations were further stressed by Dr. Faye Ritchie, from ADAS in England, who presented findings from research trials that demonstrated how such programmes disrupted the selection for fungicide resistance strains of late blight.

Reflecting on how the wider European late blight population has changed and the detection of fungicide resistance in the Irish population, Shay Phelan, Teagasc potato crops specialist said: “We have the benefit of the lessons learned in other countries across Europe to help us be better equipped to control these newer strains in Ireland.”