US-based scientists have compiled the first-ever maps detailing how potato blight first hit North America in the mid-19th century before crossing the Atlantic Ocean and causing the Great Hunger in Ireland between 1845 and 1852. 

Researchers at North Carolina State University led by Professor Jean Ristaino have concluded that potato blight was first reported in five different US states - New York, Pennsylvania, New Jersey, Delaware, and Connecticut - in 1843, two years before the beginning of the Great Hunger. 

The study found that the disease had spread to a further six states by 1844, including Vermont, Ohio, Massachusetts, Rhode Island, Maine, and New Hampshire.

It also spread to the Canadian province of Nova Scotia in the same year before spreading to Michigan, Illinois, Maryland, Indiana, and New Brunswick in Canada in 1845. 

The study, which was published in Scientific Reports on Thursday, reported that blight caused crop losses of between 33% and 50% in North America between 1843 and 1845. 

"Since the fungus-like plant pathogen was unknown to science at the time, the cause and source of the disease as well as remedies for control were widely discussed in agricultural reports, newspapers, and government pamphlets," the researchers noted in the study. 

"We have created the first accurate maps of the 1843–1845 outbreaks of potato late blight in the US. Our text analytics has also revealed information on theories of the cause and methods of control." 

The research team proposed a number of potential causes of the outbreak of potato blight in the mid-19th century, including insects, weather conditions, poor-quality potato varieties, and a fungus. However, they debated whether the fungus caused or was created by the emergence of potato blight. 

The authors of the report additionally proposed a number of potential treatments for blight, including calcium oxide (lime), sulfur, copper sulfate (bluestone copper), and salt.

The study concluded that infected potato tubers from France, Colombia, or Nova Scotia were possible sources of the disease in the US. 

Researchers searched keyword terms such as "potato rot" and "potato disease" to map the spread of potato blight in mid-19th-century North America, using historic farm reports, news accounts, and US Patent Office agricultural records to document how the pathogen spread. 

First reports of the disease surfaced in Ireland and Scotland in 1845. In Ireland, where many peasants depended on potatoes as their primary source of food, blight caused mass starvation and the death of over one million people between 1845 and 1852, with around two million people leaving Ireland in the decade after the Great Hunger began. 

Meanwhile, researchers analyzed tweets from 2012 to 2022 to learn more about the modern spread of the disease by using common and scientific names for the pathogen. 

"The social media mining was interesting because we found that most people talking about this disease are scientists in developed countries promoting their own work on Twitter (now X)," Professor Ristaino said. 

"It was also interesting to note that states where the disease appeared all those many years ago still have the disease now." 

Ristaino added that the tools used in the study will help future researchers to "explore and map unstructured text to track and visualize pandemics".