Blight prevention remains an ever-present challenge for the Irish potato industry. Growers spend millions of euro each year protecting their crops from the disease.

But the ongoing use of fungicides puts the potato sector centre stage within the debate on how to best wean production agriculture off these chemical-based prevention strategies.

Depending on the year, commercially grown potato crops could receive up to 15 anti-blight fungicide sprays in a growing season.

Blight is a weather-related disease of potato crops. So it should not come as a surprise to learn that Met Éireann is playing a central role in the development of new blight control strategies.

Met Éireann and blight prevention

The organisation’s Dr. Klara Finkele took part in a recent episode of Teagasc’s Tillage Edge podcast to discuss these matters.

She confirmed that Met Éireann has been providing farmers across the island of Ireland with a blight prediction service for the past 60 or more years.

However, field studies which investigated the occurrence of blight under different weather conditions, found that the so-called ‘Irish rules’ were not as accurate as they could be.

The old model being overly conservative, missing the onset of outbreaks and failing to warn of blight outbreaks when they occurred.

These failings led to the model being recently updated to reflect the latest science.

The new method reduces the threshold for relative humidity from 90% to 88% and the initial (sporulation) period from 12 hours to 10 hours; the analysis also showed temperature thresholds for blight epidemics could be changed from 10° to 12°.

Though risk estimation has increased compared to the previous rules, estimated chemical usage is still lower compared to standard grower’s practice. The new methodology is now referred to as the ‘New Irish Rules’.

“These changes were agreed courtesy of a joint Teagasc: Met Éireann research project,” confirmed Finkele.

“Met Éireann subsequently introduces the new rules in line with the results of the research work that has been undertaken.”

Teagasc potato specialist Dr. Stephen Kildea explained that the development of late blight prediction models had been an obvious priority for the potato industry for some time, adding:

“The original prediction service was extremely conservative in nature, and would have only flagged-up high blight pressure situations.

“But it was missing other periods when blight could have caused considerable damage to potato crops.

“By adding in new variables and tweaking a number of the existing parameters, we now have a blight forecasting service that is more fit for purpose under Irish conditions.”

According to Kildea, the research undertaken to come up with the new blight prediction model included Teagasc field trials, which also factored-in issues such as varietal resistance.

Significantly, this work has indicated that the ‘New Irish Rules’ can significantly reduce the total amount of fungicides applied while controlling the disease.