Pennsylvania Could Face a Potato Shortage

Your favorite potato chip might be at risk, as new potato diseases have been identified in Pennsylvania.

Several species of bacteria that had not been seen before in the state, as well as one that had not ever been found in the U.S., were detected in potatoes across 26 fields in Pennsylvania, according to new research in the journal Systematic and Applied Microbiology.

If these diseases were to spread across the state and cause crops to fail, it could be disastrous: Pennsylvania is the home of several chip companies, including Martin's Potato Chips, Utz and Snyder's of Hanover.

"In 2014-2016 there were unusually high potato losses across the U.S. due to blackleg and soft rot of potato. Because Pennsylvania potatoes are important for fresh market and potato snack products, we wanted to determine who—which bacteria—[had] done it," study author Carolee Bull, a professor of plant pathology at Penn State, told Newsweek.

"We sampled diseased potatoes from Pennsylvania, isolated bacteria, and identified bacteria from a particular group—soft rot Pectobacteria—that have been shown to cause or have been associated with soft rot and blackleg.

"The key results are that many more species of potential pathogens from this group are now known to be present in Pennsylvania and associated with these diseases—soft rot and blackleg—in Pennsylvania potato production. This research means that disease management strategies will need to consider the broad diversity of pathogens to be effective."

These new species of bacteria were found by researchers in the stems and tubers of potatoes suffering from black leg or soft rot, which manifests as lesions, rotting tubers, and wilting. These diseases are caused by several bacteria, usually Pectobacterium species and Dickeya species, and can result in huge crop losses.

The researchers found that of 456 bacterial samples collected from the fields, there were six species of Pectobacterium and one strain of Dickeya that had not been previously seen in Pennsylvania, and even one Pectobacterium species never before seen in the U.S.

"In this survey, P. actinidiae, P. brasiliense, P. polonicum, P. polaris, P. punjabense, P. parmentieri, and P. versatile were identified from Pennsylvania for the first time. Importantly, the presence of P. actinidiae in Pennsylvania represents the first report of this organism in the U.S. As expected, P. carotorvorum and D. dianthicola were also isolated," the authors wrote in the paper.

It comes after Maine saw a smaller crop this year, harvesting 700 million fewer pounds of potatoes than in 2022 because of unusually high amounts of rain. In the past few years, both Maine and New York have seen reduced potato crop harvests.

"We don't know whether the organisms weren't here before or were distinguishable before. For some, they may have just been considered pectobacterium carotovorum prior to our having the tools to distinguish them from that species," Bull said.

"We now have more tools to differentiate organisms at finer levels and many new species have been described in the last few years. For example, although P. parmentieri was only recently distinguished or described as a new species it has been in the U.S. since before it was distinguished as a new species.

"Previous research has shown that infested potatoes, water, equipment and storage facilities can serve as inoculum sources for the pathogens to initiate disease. These could be sources of introduction in the past or future.

"The organism we are most concerned about is Dickeya solani, which is not documented in the U.S. but caused severe losses in Europe. There are quarantine regulations in place to prevent the spread of this organism from Europe.

"We will continue to monitor blackleg and soft rot from potatoes in Pennsylvania for this pathogen. This pathogen has not been found in any survey in the U.S. either reported in the literature or as far as I am aware," Bull said.

D. solani has been associated with severe disease outbreaks in Europe, but has not yet been identified in the U.S.

Potato pathogens have been catastrophic in the past, most notably during the 1845-52 Irish Potato Famine, which was caused by an infestation of the fungus Phytophthora infestans, also known as the potato blight. This led to around one million people dying, and over a million more emigrating from Ireland, many of whom went to North America.

Bull hopes that these findings will help potato growers to know which bacterial species grow on which potato variety, and further research into how potato diseases grow and spread, thereby helping efforts to manage them.

"In addition to surveillance, these insights could also help us better understand disease epidemiology," Bull said in a statement. "For example, the pathogens may have different optimum temperatures for growing or for producing these symptoms in the potatoes. So, the severity of the disease may change depending on different climate conditions."

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about potatoes? Let us know via science@newsweek.com.

Update 1/24/24 11:29 a.m. ET: This article was updated with comment from Carolee Bull.