Disease attacking blueberry plants is spreading around the world

Picture a charming blueberry farm, where vibrant bushes brim with richly colored fruit and sunlit leaves shimmer in the light. Yet, a change is on the horizon.

Blueberry plants are now under threat, with their vibrant appearance dulled and growth stunted by a powdery white substance.

The culprit is a fungus called Erysiphe vaccinii, which is responsible for the disease known as powdery mildew.

A recent study from North Carolina State University reveals the alarming global spread of Erysiphe vaccinii in blueberries.

Powdery mildew reduces yield and increases fungicide reliance. It is currently impacting blueberry production on multiple continents.

Global spread of fungal blueberry disease

According to the study, the fungus has spread globally over the past 12 years, after originating in the eastern United States.

“We’re watching this global spread happen right now, in real time,” said Michael Bradshaw, assistant professor of plant pathology at NC State.

The fungus responsible for powdery mildew creates a white, powdery layer on the surface of infected plants.

This coating not only disrupts the plant’s ability to absorb sunlight for photosynthesis but also steals essential nutrients from the plant’s tissues.

As a result, the plant’s growth is stunted, and its overall health declines – making it weaker and less productive.

“There are other closely related powdery mildews that affect plants like wild berries or eucalyptus, but these are genetically different from the ones spreading across the world on blueberries,” noted Bradshaw.

Tracking the spread of powdery mildew

The researchers examined 173 samples of infected blueberry leaves to study the spread of powdery mildew disease. These samples included both historic specimens from herbariums (some collected over 150 years ago) and more recent samples from various countries.

Through genetic testing, the team discovered that the strains causing the current outbreaks are entirely new and different from those found in the older specimens. They identified two distinct introductions of the fungus into the global blueberry-growing regions.

One strain spread to China, Mexico, and California and the other strain was found in Morocco, Peru, and Portugal.

Bradshaw suggested that humans likely played a major role in the spread of the fungus by transporting infected nursery plants across borders.

“If you’re sending plant material across the world, you’re likely spreading this fungus with it,” he stated. This highlights how the global plant trade can inadvertently introduce harmful pathogens to new regions.

Impact of the disease on blueberries

Powdery mildew has a significant economic impact on the blueberry industry, costing between $47 million and $530 million every year.

These costs stem primarily from the increased use of fungicides needed to prevent or manage the disease, as well as from potential losses in crop yield.

The study also identifies regions like the U.S. Pacific Northwest as being particularly vulnerable to future outbreaks. This area has environmental conditions that are ideal for the disease to thrive, such as the right combination of temperature and humidity, yet the fungus has not yet been reported there.

Proactive monitoring and management are urgently needed to prevent the disease from taking hold in such high-risk regions.

Bradshaw noted that agricultural practices could influence disease severity. “Some areas that grow blueberries in tunnels, or enclosed areas, seem to have worse disease outcomes than areas that grow blueberries outdoors without any covering, like in North Carolina,” he said.

Helping farmers manage powdery mildew

To help farmers manage powdery mildew more effectively, the researchers developed a public database designed to identify different strains of the fungus. Growers can use this tool to input data about the fungus affecting their crops and determine which specific strain is present in their fields.

This information is crucial because it helps farmers understand the characteristics of the strain they are dealing with, including its level of virulence (how damaging it can be) and whether it is resistant to commonly used fungicides.

By knowing these details, farmers can make more informed decisions about how to control the disease and protect their crops.

“Understanding the genetics can warn farmers about which strain they have, whether it is resistant to fungicides, and how the disease is spreading,” Bradshaw explained.

This research highlights the urgent need to address powdery mildew’s global spread. By improving monitoring and control strategies, the study offers hope for safeguarding the blueberry industry from this emerging disease.

The research was supported by the National Science Foundation (NSF) and Novo Nordisk Foundation.

The findings are published in the journal New Phytologist.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–