Stem rust (Puccinia graminis) is back. The first confirmed case of the disease in 60 or so years was discovered on a single wheat plant in Suffolk, England, in 2013. It might not sound like much, but stem rust is a crop disease that has plagued farmers since the time of Aristotle with severe crop failure and famine.
“Resistant wheat varieties have not been developed. We hope that our study will serve as an alarm call to the industry, that an old enemy may be about to return,” Dan Bebber, a senior lecturer in biosciences at the University of Exeter, said in a statement.
Stem rust is a fungal infection that forms scaly red – and fatal – pustules on the plant’s stem.
Genetic tests carried out by researchers at the University of Exeter and published in Nature show that the strain in the UK comes from the Digalu race of fungus. This is the same strain culpable for the 2013 outbreaks of stem rust in Ethiopia and parts of Western Europe, including Germany, Sweden, and Denmark.
Most worrying is the fact that more than 80 percent of UK wheat strains are vulnerable to the infection and changes in the climate could be making it more virulent.
One thing to blame for stem rust’s return is the barberry. The hedgerow shrub was taken down in England when people started realizing that wheat crops close to the plant were more likely to contract the disease. But barberries have been growing in popularity recently as a result of efforts to protect an endangered species of moth – the barberry carpet moth.
The last confirmed case of stem rust in the UK was in 1955 but archaeological evidence shows the disease has existed since 1300 BCE or earlier. In ancient Rome, farmers sacrificed red animals (dogs, foxes, and cows) to the rust god every spring to protect their crops from the fungus. Later, stem rust was brought to the Americas by the early settlers. In the 1950s, North America saw a major epidemic that destroyed up to 40 percent of wheat crops.
With wheat and barberry making up roughly 25 percent of the world’s food supply, experts worry a similarly devastating disaster could be on the horizon.
For now, at least, the disease appears to be contained.
“The discovery of stem rust in Suffolk has so far been an isolated one-off occurrence in 2013; however, with global temperatures set to rise by another 1 or 2°C [1.8-3.6°F] over the next century, stem rust could extend its geographic range,” explained Paul Fenwick, a cereal pathologist at Limagrain UK Ltd and paper co-author.
“Therefore, there is the potential for stem rust to become an ever-increasing threat across Europe and so research, such as this, will help to underpin breeding for resistance in the future.”