Given its role in The Great Famine, blight is etched into the Irish psyche and remains the most serious disease of potatoes in modern times.
Despite advances in fungicides, varieties and forecasting, there is still no means of eradicating an outbreak of blight in a potato crop, meaning that prevention is key.
According to Teagasc, €5 million is spent annually on fungicides to mitigate against the disease.
Blight forecast
Potato blight is caused by a fungal-like organism called Phytophthora infestans.
The pathogen thrives in humid weather spreading rapidly on the foliage of potatoes and tomatoes, causing the leaves to decay and the crop to be infected
A vital tool in that arsenal to combat blight is the blight forecast provided to the public by Met Éireann.
The specialised forecast can be traced back to the 1950s, when the so-called “Irish rules” were developed by Austin Bourke who was a director of the national meteorological service.
Padraig Flattery, meteorologist with Met Éireann, told Agriland that these rules used meteorological data and field experiments to forecast “blight like conditions”.
“They developed these rules to say that if humidity was at 90% and if temperature was over 10°C and that happened for a period of 12 hours, then blight conditions are present and there’s a higher likelihood that blight will happen in a field or in an area,” he said.
New blight rules
The rules remained in use up to 2019, when Mladen Cucak carried out his PhD studies on potato blight forecasting through field trials with Stephen Kildea at Teagasc Oak Park.
The study is among the research on integrated pest management (IPM) being carried out by Teagasc as part of efforts to reduce fungicide use.
The European Union is aiming to reduce by 50% the use and risk of chemical pesticides by 2030, in line with the EU’s Farm to Fork and biodiversity strategies.
The field trials led to the development of the “New Irish Rules”, which reduced the threshold for relative humidity from 90% to 88% and the initial sporulation period, or the time it takes the fungus to develop, from 12 hours to 10 hours.
The new method is now used by Met Éireann to produce 3-day, 4-day and 5-day forecast spatial maps for the island of Ireland which illustrate the blight risk at five different risk levels from very low (green) to very high (red).
“If a weather front is coming in and it’s warm and moist, you can see that track across the country and it shows the risk of blight in different counties and in different areas.
“So previously we might just have had a county-level advisory, but since some counties in Ireland are quite big, and there’s quite a lot of spread, and it might be different weather in the east of the county to the west of the county, we find that these maps are much more spatially relevant now.
“So hopefully it will help people to monitor and adapt the amount of fungicide that they spray on their crops to reduce it and to save them money in the long run. It should hopefully improve the outcomes for blight as well,” Flattery said.
Spraying
Klara Finkele, meteorologist with Met Éireann, added that there are other maps, known as meteograms, which provide hourly data, that can also help farmers with their decision making around their spraying cycles.
“They may not be able to adjust the time they spray, but they can adjust the amount they spray,” she said.
The Met Éireann meteograms provide “point forecasts” for multiple areas around the country covering temperature, relative humidity, rainfall and the blight risk for the coming days.
“Just like you would look at any other weather map in the morning to see what the weather will be for the day, it’s exactly the same thing for the blight,” Finkele advised.
Research
Met Éireann is collaborating with Teagasc on research on fungal toxins and diseases, which are all weather related.
A pilot project with Dublin City University (DCU) is underway involving an automatic laser-based instrument being placed on the roof of Met Éireann headquarters in Glasnevin, Dublin.
The “SwissensPoleno Jupiter” has the ability to automatically detect funguses and pollen.
There are plans to add up to five more of these instruments in order to develop “a fungal/pollen observation network”.
“This will look more into funguses in general for human health and plant health,” Finkele said.
It is hoped that the project being led by Dr. David O’Connor, a pollen expert in DCU, will improve the blight forecast based on “actual real data”.
Another instrument for blight will also be trialled by Dr. O’Connor in fields in Teagasc Oak Park.