Attention Blueberry Growers: Global Spread of Powdery Mildew Poses Threat

A recent study conducted by scientists from North Carolina State University has raised significant alarms regarding the global spread of powdery mildew, a fungal disease that poses a severe threat to blueberry production worldwide. The research primarily focuses on the pathogen Erysiphe vaccinii, known for its devastating impact on blueberry plants by reducing crop yields and increasing reliance on fungicide applications. With findings that span over a decade, this study marks a crucial step in understanding the dynamics of this emerging disease and presents vital insights for blueberry growers.

The study reveals that Erysiphe vaccinii, once limited to the eastern United States, has rapidly expanded its geographical reach to various global regions, including Europe, Africa, and Asia, over the past 12 years. Michael Bradshaw, an assistant professor of plant pathology at NC State and the corresponding author of this research, expressed his concerns about this ongoing expansion. He stated, “We’re watching this global spread happen right now, in real time.” This statement conveys the urgency with which the scientific community must address the implications of the fungus’s proliferation.

As the study indicates, powdery mildew manifests as a distinctive white, powdery coating on plants, which not only deprives them of essential nutrients but also hinders their ability to photosynthesize. This results in diminished vitality and productivity for affected crops. While various species of powdery mildew affect a wide range of plants, such as wheat, grapes, and strawberries, E. vaccinii has become a particular focus due to its targeted disruption of blueberry cultivation.

In examining the history of this pathogen, Bradshaw and his colleagues analyzed 173 samples of infected leaves from diverse regions, including North America and Europe, as well as modern specimens collected from around the globe. Notably, the researchers discovered that the fungus was first observed outside North America in Portugal in 2012. This alarming finding was corroborated by a co-author who had previously worked with a major berry production company. The implications of such discoveries underscore the growing trend of agricultural diseases transcending geographical barriers.

The research team employed genetic testing on the fungal samples they collected to trace the evolutionary history and spread of the disease. Intriguingly, none of the historical samples exhibited the same genetic composition as the current specimens, emphasizing the dynamic nature of this pathogen’s evolution. The findings revealed that the disease likely initiated two separate introductions, one reaching regions like China, Mexico, and California, while the other impacted Morocco, Peru, and Portugal. Bradshaw proposes that the introduction of these strains can be largely attributed to human activity, particularly through the international movement of infected nursery plants.

In addition to addressing the disease’s geographic spread, this study also explored the reproductive mechanisms of E. vaccinii. The results indicated that the strain affecting blueberries in other nations appears to reproduce only through asexual means, circumventing sexual reproduction altogether. In contrast, the American variants exhibit both sexual and asexual reproduction. This adaptation may contribute to the pathogen’s aggressive spread, establishing it definitively in new areas with minimal hindrance.

Moreover, the researchers worked alongside agricultural professionals and a significant blueberry company to calculate the financial impacts of powdery mildew on the global blueberry industry. Their estimates suggest that the economic burden incurred from fungicide applications and crop loss ranges from $47 million to an astounding $530 million annually. This substantial cost highlights the urgent need for effective management strategies to combat this burgeoning threat.

Bradshaw noted that the environmental conditions in certain regions, such as the U.S. Pacific Northwest, present potential risks for the spread of powdery mildew, even as it has not yet been reported in that area. The study warns that rising temperatures and agricultural practices, such as growing blueberries in tunnels or greenhouses, could exacerbate the risk, creating conducive environments for the disease to establish itself and proliferate further.

In response to the complexities associated with identifying various strains of E. vaccinii, the researchers have developed a valuable tool that can assist both farmers and scientists in the field. They have contributed their data to a publicly accessible database created at NC State by co-author Ignazio Carbone. This platform allows growers to enter their own data to accurately determine which specific strain of powdery mildew they are dealing with, offering critical insights into potential genetic resistance to fungicides as well as the virulence associated with different strains.

As this study emerges as a formidable warning signal to blueberry producers worldwide, it serves as a clarion call to prioritize research efforts focused on this fungal threat. The development of effective management practices, alongside enhanced identification and monitoring tools, will be essential to shield the blueberry industry from the extensive ramifications posed by Erysiphe vaccinii. The findings from this research will be published in the journal New Phytologist, promising to influence future discussions and strategies in agricultural disease management.

The ongoing battle against agricultural diseases like powdery mildew can only be won through collaborative efforts in research, innovation, and education. By remaining vigilant and proactive, growers and scientists alike can work together to mitigate the spread and impact of this serious fungal threat, safeguarding blueberry production for future generations.

A comprehensive understanding of the genetic diversity within Erysiphe vaccinii, alongside an appreciation of its historical spread, enhances our ability to anticipate and combat future incursions. As efforts to manage powdery mildew continue, the scientific community’s commitment to collaboration and information-sharing will remain indispensable. The research conducted by Michael Bradshaw and his team offers a foundational platform on which further research will build, ensuring that agricultural practices evolve in step with the challenges posed by emerging plant diseases.

This study’s findings underscore the intricate relationship between plant pathogens, human activity, and environmental conditions, drawing attention to the myriad ways in which they intersect. Effective responses to E. vaccinii will require a multifaceted approach, including heightened awareness of the potential risks associated with plant movement and the evolution of new management techniques tailored to address this evolving threat.

The discovery of new haplotypes and their implications for understanding the pathogen’s spread and resistance will remain a focal point of ongoing research, promoting a better understanding of the threats faced by blueberry producers worldwide. As the blueberry industry strives to stabilize and recover from the effects of powdery mildew, the integration of scientific insights and practical strategies into agricultural practices will be essential.

With the challenges posed by Erysiphe vaccinii detailed in this study, it is clear that understanding the genetics of pathogens and their environmental interactions is key to sustaining agricultural productivity. The future of blueberry cultivation depends on a comprehensive approach that anticipates and prepares for potential threats, ensuring that growers can maintain healthy, fruitful crops in an increasingly complex global landscape.

Subject of Research: Fungal disease affecting blueberry cultivation
Article Title: An emerging fungal disease is spreading across the globe and affecting the blueberry industry
News Publication Date: January 8, 2025
Web References: http://dx.doi.org/10.1111/nph.20351
References: New Phytologist, DOI: 10.1111/nph.20351
Image Credits: Michael Bradshaw, NC State University

Keywords: Powdery mildew, Erysiphe vaccinii, blueberry production, fungal disease, global spread, plant pathology.