More than 175 years after Ireland has recovered from the ravages of the terrible Great Famine, scientists warn that same microbe, Phytophthora Infestans, continues to pose a serious biotic threat to global potato crops, with intensive fungicide programs rigorously implemented for its control, on an annual basis.

“It is probably a more aggressive, more virulent and more difficult pathogen to control than it was back then,” explains Dr. Steven Kildea, senior research officer with Teagasc Crops, Environment and Land Use Program, and author of a new report on the microbe, recognizing the 175th anniversary of its arrival in Ireland.

According to the Irish Examiner, while fungal, bacterial, and viral pathogens continue to shape global societies, the scientist says there are few plant-specific pathogens that can be regarded as having impacted the world throughout the 19th and 20th centuries in the way Phytophthora Infestans has.

“As a pathogen it is not native to the majority of the world and when you introduce it, it can basically run amok,” he points out.

The battle to control the microbe, also known as late blight, is virtually an ongoing ‘arms race’ — both between the pathogen and the plant, and between the pathogen, the farmer and modern science.

What happens, Kildea explains, is that when scientists and farmers put a particular layer of control in place, a strain of this pathogen eventually adapts — and jumps the hurdle. Another element of this ongoing battle, he says, lies in developing resistant varieties of potato so that the plant itself could prevent the pathogen from taking hold. This has to be done in a way that was acceptable to the consumer, he explained, which was where modern breeding programs came in.

The third element in the battle against late blight is the environment — although the Irish climate is inevitably conducive to the disease, as Ireland was exposed to westerly winds, lots of moisture and mild weather.

“Knowing this, we target our infection prevention measures, which means farmers target their pesticides based on when the infection is predicted to occur — it is about preventative measures being implemented on the basis of knowledge about the weather.”

These three elements are the cornerstones in the battle to control this formidable pathogen, Kildea concludes.