Xylella fastidiosa is a bacterium that has become a growing concern for agriculture, landscape trees, and plant health in Missouri. This pathogen is responsible for a variety of plant diseases, including bacterial leaf scorch (BLS), Pierce's disease, and Phony Peach Disease, and has been making its way through the state, affecting trees such as red mulberry, red maple, oak, and grapevines. The bacterium is transmitted by insects and causes severe damage to plants, making early detection and management crucial.

What is Xylella fastidiosa?

Xylella fastidiosa is a gram-negative bacterium that infects the xylem vessels of plants, disrupting the movement of water and nutrients. This leads to symptoms like leaf scorch, dieback, and stunted growth. The pathogen is most commonly spread by xylem-feeding insects such as leafhoppers and spittlebugs, which transport the bacterium from one plant to another.

Historically, Xylella fastidiosa was limited to warmer climates, but recent research and studies show that it is expanding its range, reaching new regions, including Missouri. The bacterium is known to cause several plant diseases, each with its own symptoms and impacts on different tree species. For Missouri, this means a heightened risk to both urban forestry and agriculture, particularly with species like oak, sycamore, red mulberry, and grapevines.

The Spread of Xylella fastidiosa in Missouri

Xylella fastidiosa has been detected in several regions of Missouri, signaling the pathogen's growing presence in the state. Its spread into Missouri is particularly concerning because the state was not previously associated with this bacterium. The emergence of bacterial leaf scorch (BLS) in trees like red mulberry and red maple, as well as the detection of Pierce’s disease in grapevines, underscores the increasing vulnerability of Missouri's plant life to this pathogen.

Proof of Presence and Findings:

Several studies confirm the presence of Xylella fastidiosa in Missouri, especially in urban and agricultural areas:

1.      Study 1: The presence of Xylella fastidiosa in Missouri was first reported in the 2000s, with particular findings in trees such as red mulberry and red maple. This study highlights the spread of bacterial leaf scorch in these trees, which is a significant concern for both urban forestry and landscape management in Missouri. (Sherald, J. L., and S. J. Kostka. "Bacterial Leaf Scorch of Landscape Trees Caused by Xylella fastidiosa." Journal of Arboriculture, 18(2), March 1992: 57-63).

2.      Study 2: In 2009, researchers confirmed the presence of Xylella fastidiosa in various counties in Missouri, including St. Louis and Boone. These findings indicated that the pathogen was spreading into the Midwest, reaching areas that were previously unaffected. (Starbuck, Christopher J. "Bacterial Leaf Scorch in the Midwest and Plains States." Missouri Environment and Garden News, University of Missouri, January 1, 2010. Accessed April 24, 2025).

3.      Study 3: A study in Missouri vineyards showed the first confirmed case of Pierce’s disease caused by Xylella fastidiosa. In 2013, a vineyard in central Missouri reported vine deaths that were later attributed to the pathogen, marking a turning point for Missouri's grapevine growers. (Jones, Linda. "Controlling PD in Texas and Missouri: Researchers Present Latest Information About Pierce's Disease in Grapevines." Wines & Vines, September 1, 2014).

4.      Study 4: Research into Phony Peach Disease and Plum Leaf Scald found that Xylella fastidiosa had infected peach orchards in Missouri, with the potential for devastating economic losses. These diseases, while not as widespread as in other regions, are a growing concern for Missouri's agricultural industry. ("Phony Peach Disease Xylella fastidiosa," Summerfruit NZ, December 2022).

5.      Study 5: The impact of Xylella fastidiosa on oak trees in Missouri is becoming more prominent, with bacterial leaf scorch reported as a major contributor to tree health decline. Oak wilt has traditionally been a larger concern, but BLS is now emerging as an equally damaging factor. (Mathias Precision Tree Service. "Why Oak Trees Are Dying in Missouri and How to Help." Accessed April 2025).

Table: Summary of Xylella fastidiosa Presence in Missouri

Study	Location/Region	Affected Trees	Disease	Year of Detection
Study 1: Sherald and Kostka	Urban Missouri	Red mulberry, Red maple	Bacterial Leaf Scorch	1992
Study 2: Starbuck	St. Louis, St. Charles, Boone	Oak, Sycamore, Red maple	Bacterial Leaf Scorch	2009
Study 3: Jones	Central Missouri	Grape vines	Pierce’s Disease	2013
Study 4: Summerfruit NZ	Southeastern Missouri	Peaches, Plums	Phony Peach Disease	2022
Study 5: Mathias Precision Tree Service	Missouri Statewide	Oak Trees	Bacterial Leaf Scorch	2025

Impact of Xylella fastidiosa on Missouri Agriculture and Forestry

Xylella fastidiosa's growing presence in Missouri poses significant risks to both the forestry and agricultural sectors. In urban areas, landscape trees such as red mulberry, red maple, and sycamore could face decline due to bacterial leaf scorch, leading to a decrease in urban canopy and the loss of vital ecosystem services such as air purification and shade. The economic impact could be far-reaching, as Missouri’s ornamental tree industry and urban forestry initiatives rely on the health of these trees.

In agricultural areas, the detection of Pierce’s disease in grapevines is particularly concerning for Missouri’s wine industry. Grapevines infected with Xylella fastidiosa often die within two years, devastating vineyards and leading to significant financial losses. Peach and plum orchards are also at risk, as Phony Peach Disease can cause long-term damage to fruit production, making infected trees economically unviable.

Diagnosis and Management of Xylella fastidiosa

One of the challenges with managing Xylella fastidiosa is its elusive nature. The bacterium does not grow well on standard culture media, making it difficult to detect using traditional methods. However, improved diagnostic tools such as enzyme-linked immunosorbent assays (ELISA) and polymerase chain reaction (PCR) are now available, making it easier to confirm the presence of the pathogen in affected plants.

Management Strategies:

·         Pruning and Tree Care: Infected trees may require early intervention, including pruning and the removal of infected branches. However, pruning alone is not sufficient to manage the spread of the pathogen, especially since it spreads systemically.

·         Antibiotics and Injections: Some therapeutic approaches, such as injections of antibiotics like oxytetracycline, have shown promise in alleviating symptoms temporarily. However, these methods do not cure the disease.

·         Vector Control: Managing insect vectors like leafhoppers is crucial in preventing the spread of Xylella fastidiosa. However, controlling these insects is difficult due to their mobility and the fact that they can spread the disease over long distances.

Conclusion: Navigating the Threat of Xylella fastidiosa in Missouri

The growing presence of Xylella fastidiosa in Missouri is a cause for concern for both urban and agricultural communities. The pathogen’s spread across various regions in the state and its impact on tree health underscore the need for effective diagnostic tools, management strategies, and awareness campaigns. Early detection is key to preventing further damage, and ongoing research is essential to understanding the pathogen’s behavior and potential solutions.

As Missouri continues to face challenges related to this emerging threat, it is crucial for farmers, arborists, and residents to stay informed about Xylella fastidiosa. By embracing the latest research and implementing proactive measures, Missouri can mitigate the risks associated with this bacterium and protect its valuable tree populations for generations to come.

 

References:

1.      Sherald, J. L., and S. J. Kostka. "Bacterial Leaf Scorch of Landscape Trees Caused by Xylella fastidiosa." Journal of Arboriculture, 18(2), March 1992: 57-63.

2.      Starbuck, Christopher J. "Bacterial Leaf Scorch in the Midwest and Plains States." Missouri Environment and Garden News, University of Missouri, January 1, 2010. Accessed April 24, 2025.

3.      Jones, Linda. "Controlling PD in Texas and Missouri: Researchers Present Latest Information About Pierce's Disease in Grapevines." Wines & Vines, September 1, 2014.

4.      "Phony Peach Disease Xylella fastidiosa," Summerfruit NZ, December 2022.

5.      Mathias Precision Tree Service. "Why Oak Trees Are Dying in Missouri and How to Help." Accessed April 2025. https://mathiasprecision.com.