Virginia Tech researchers study a natural approach as they continue the battle against the devastating disease, boxwood blight.

Imagine if boxwood had a natural ally to help them grow strong while guarding against this destructive disease. Plant pathologist Ping Kong and her colleagues at the Hampton Roads Agricultural Research and Extension Center (AREC) are investigating Pseudomonas eucalypticola 1021Bp, a beneficial bacterium that may be the game-changer boxwood needs.

Boxwood blight, first identified in the 1990s, has caused widespread devastation to landscapes across Europe, Asia, and North America. By 2020, this fast-spreading disease had reached 30 U.S. states, severely impacting boxwood production, the nation’s top evergreen ornamental shrub crop.

While fungicides are commonly used to manage disease, they can pose risks to human health and the environment, underscoring the urgent need for safer, more sustainable solutions.

The Problem

Boxwood has been a staple of American landscapes since 1653. However, boxwood blight is a highly contagious and aggressive disease threatening the existence of this plant species.

The Study

To determine the effectiveness of Pseudomonas eucalypticola 1021Bp in promoting plant growth and controlling boxwood blight, researchers conducted detailed experiments in both the lab and greenhouse.

  • Lab Studies: The team collected 1021Bp from healthy boxwood leaves and tested its ability to stop harmful fungi. They evaluated the bacteria’s effects on five fungal pathogens, including Calonectria pseudonaviculata, the fungus responsible for boxwood blight. Researchers also studied how 1021Bp supports plant growth by analyzing traits like nitrogen fixation, phosphate solubilization, and production of growth-enhancing compounds.

  • Greenhouse Tests: Boxwood plants were treated with 1021Bp in the greenhouse and then exposed to the blight-causing fungus under controlled environments. Treated plants showed significantly less disease and better overall health, demonstrating the bacteria’s potential as a powerful natural protectant.

The Results: A Triple Threat 

Kong and her team uncovered three key benefits of Pseudomonas eucalypticola 1021Bp.

  1. Encourages Plant Growth: 1021Bp produces substances that enrich the soil with nutrients and help plants absorb essential resources, promoting healthier growth.

  2. Fights Fungal Infection: In lab tests, 1021Bp successfully inhibited the growth of five major fungal pathogens, including the one that causes boxwood blight, by producing specialized antifungal chemicals.

  3. Controls Boxwood Blight: In greenhouse studies plants treated with 1021Bp were significantly less likely to develop boxwood blight. This highlights the bacteria’s effectiveness as a natural, eco-friendly alternative to chemical fungicides.

Implications for Growers

The discovery of Pseudomonas eucalypticola 1021Bp opens the door to safer and more sustainable methods for managing boxwood blight. 

In addition to 1021Bp, Kong’s biocontrol project has identified over a dozen beneficial bacteria, known as boxwood endophytes, with similar traits for disease control. 

A few of these have already shown success in real-world field tests, demonstrating their potential to effectively protect boxwoods.

By harnessing this naturally occurring bacteria, researchers hope to protect boxwood while reducing reliance on synthetic chemicals. With further study, 1021Bp could become an essential tool for gardeners and landscapers, ensuring the longevity of this beloved plant in landscapes worldwide.