A devastating fungus is spreading rapidly across the world

NC State researchers have found that blueberry powdery mildew has spread globally in two forms, costing the industry up to $530 million a year. A new tool now helps farmers identify and manage the disease.

A new study of

” data-gt-translate-attributes=”({“attribute=”” tabindex=”0″ role=”link”>North Carolina State University traced the global spread of a fungus that causes powdery mildew of blueberry plants, a disease that reduces crop yields and increases the need for fungicides. These results could help blueberry growers better predict, monitor and manage the spread of powdery mildew.

Research reveals that over the past 12 years, the fungus Erysiphe vaccinii has expanded from its original range in the eastern United States to several continents.

“We are watching this global spread happening right now, in real time,” said Michael Bradshaw, assistant professor of plant pathology at NC State and corresponding author of a paper describing the research.

The nature of powdery mildew

As its name suggests, powdery mildew disease causes a white powdery substance that coats host plants, stealing nutrients and delaying

” data-gt-translate-attributes=”({“attribute=”” tabindex=”0″ role=”link”>photosynthesis while keeping the host alive. Different

” data-gt-translate-attributes=”({“attribute=”” tabindex=”0″ role=”link”>species of this fungus affect different plants; wheat, hops, grapes and strawberries, among other plants, have been seriously affected by powdery mildew.

“There are other closely related powdery mildews that affect plants like wild berries or eucalyptus, but these are genetically different from those that spread worldwide on blueberries,” Bradshaw said.

In the study, Bradshaw and colleagues examined the leaves of historical and modern plants plagued by powdery mildew. The collection includes 173 samples from North America, Europe, Africa and Asia; one sample analyzed in a North American herbarium was collected more than 150 years ago, while the foreign samples were all collected within the last five years. In this study, powdery mildew was first observed outside of North America on a farm in Portugal in 2012, as noted by a Bradshaw co-author who was employed by a large small-scale company. fruits.

The researchers performed genetic testing on the fungal samples to trace the history and spread of powdery mildew. Interestingly, none of the ancient specimens have the same genetic makeup, or genotype, as the specimens currently distributed throughout the world.

Two distinct global strains

The study showed that the disease originated in the eastern United States and spread globally in two different introductions. A strain of E. vaccinii found its way to China, Mexico and California, while a different strain turned up in Morocco, Peru and Portugal. Bradshaw believes humans are responsible for the spread when nursery plants move to foreign shores.

“It’s a difficult organism to control,” Bradshaw said. “If you send plant material across the world, you’re probably spreading this fungus with it.”

Interestingly, the study also showed that E. vaccinii the fungus found in blueberries in other countries appears to reproduce only asexually; both sexual versions of the fungus are not necessary for reproduction, whereas the fungus reproduces sexually and asexually in the United States.

The study also collaborated with a large company and farmers to provide an estimate of the global cost of powdery mildew on blueberries, reflecting the cost of spraying fungicide to prevent or reduce powdery mildew. The study estimates the annual cost of the global blueberry industry to be between $47 million and $530 million.

Warning for vulnerable growing regions

Finally, the study provides early warning signals for important blueberry-producing areas, such as the U.S. Pacific Northwest. The conditions are ripe for powdery mildew to take hold and spread, but the disease has not yet found its way there.

“The spread of the disease could also be influenced by agricultural conditions,” Bradshaw said. “Some areas that grow blueberries in tunnels or enclosed areas appear to have worse disease outcomes than areas that grow blueberries outdoors without any cover, such as in North Carolina.”

Bradshaw added that the researchers used a useful tool that can help identify E. vaccinii strains to help farmers and other researchers.

“It is difficult to identify the fungus that causes powdery mildew in blueberries, so we enter our data into a public database developed at NC State by a co-author, Ignazio Carbone. This platform allows growers to enter their data and know what specific strain is in their fields,” Bradshaw said. “This is important because understanding genetics can warn farmers about what strain they have, whether it is resistant to fungicides and how the disease spreads, as well as the virulence of particular strains.”

Reference: “Emerging fungal disease spreads across the world and affects the blueberry industry” by Michael Bradshaw, Kelly Ivors, Janet C. Broome, Ignazio Carbone, Uwe Braun, Shirley Yang, Emma Meng, Brooke Warres, William O . Cline, Swarnalatha Moparthi, Alejandro K. Llanos, Walter Apaza, Miao Liu, Julie Carey, Mehdi El Ghazouani, Rita Carvalho, Marianne Elliott, David Boufford, Tiaan Coetzee, Johan de Wet, James K. Mitchell, Luis Quijada, JamJan Meeboon, Susumu Takamatsu, Uma Crouch, Scott LaGreca and Donald H. Pfister, January 8, 2025, New plant scientist.
DOI: 10.1111/nph.20351

The document appears in New phytologist. Funding was provided by the National Science Foundation under grant numbers 2315953, 2200038, 2031955, and 2308472. The work was also supported by the Novo Nordisk Foundation under grant numbers NNF19SA0059360 and NNF19SA0035476.