Xylella Fastidiosa

Plant diseases are a big deal in agriculture and natural landscapes, especially when they start affecting major crops or native trees. One such problem that Georgia is facing is Xylella fastidiosa, a harmful bacterium that spreads through plant xylem tissues. It blocks the water flow inside plants, causing leaf scorch, defoliation, and even death in some cases.

This post covers the latest and most thorough research on Xylella fastidiosa in Georgia, taken from seven scientific studies. These studies focus on blueberries, pecans, oaks, elms, and even hickory trees. They give us clear evidence that this disease is spreading and is a real problem for farmers, researchers, and conservationists in Georgia.

 

What is Xylella fastidiosa?

Xylella fastidiosa (Xf) is a type of bacteria that lives inside the water vessels (xylem) of plants. It’s mainly spread by small insects like sharpshooters that feed on plant sap. Once inside a plant, the bacteria multiply and block the flow of water, leading to symptoms like leaf burn, stunted growth, and eventually, plant death.

This bacterium is not new to science, but its effects are being seen in more plant species and more regions, especially throughout Georgia.

 

Summary Table: Presence of Xylella fastidiosa in Georgia

Study	Year	Plant Affected	Region in Georgia	Outcome
1	2021-2022	SHB Blueberries	South Georgia	Xf confirmed in blueberries. Genetically diverse from NC strains.
2	2006-2007	SHB Blueberries	Southern Georgia	Xf confirmed by Koch’s postulates. High impact on 'FL86-19' cultivar.
3	2006	Red Oak	Griffin, Georgia	Xf subsp. multiplex (Griffin-1) sequenced. First confirmation in oak.
4	2004-2009	Blueberries	South Georgia	Xf identified as cause of new disease in blueberries. Severe symptoms.
5	2023	Southern Shagbark Hickory	Byron, Georgia	First report of Xf in hickory. Confirmed subsp. multiplex.
6	2018	Pecans	Southwest & Central GA	Xf widespread in pecan orchards. Cape Fear most affected.
7	2019	American Elm	Pulaski County	First report in elm trees in Georgia. Confirmed via PCR and ELISA.

Study Highlights

1. Blueberries in North Carolina and Georgia

Funded by SRSFC Project #2021 R-03, this study by Oliver, Cline, and Ali confirmed Xf in southern highbush (SHB) blueberries in Georgia and North Carolina. Xf was especially common in cultivars like 'Rebel' and 'O’Neal'. Georgia strains were found to be genetically different from North Carolina strains, suggesting local evolution and multiple origins. (Oliver et al., 2021)

2. First Major Discovery in Blueberries

Back in 2006, Dr. C.J. Chang and team confirmed the presence of Xf in blueberries by fulfilling Koch's postulates. This confirmed it as a new disease, primarily affecting the SHB cultivar FL86-19. Insect vectors like the glassy-winged sharpshooter were identified as the main source of spread. (Chang et al., 2007)

3. Red Oak Trees in Griffin

The Griffin-1 strain was isolated from a red oak in 2006. It belongs to the Xf subsp. multiplex group and was sequenced to better understand its genetic identity. The sequencing revealed 2,903 ORFs and provided vital information on how this pathogen behaves in hardwood trees. (Chen et al., 2013)

4. Confirming Bacterial Leaf Scorch in Blueberries

A 2009 study published in HortScience once again confirmed Xf as the main cause of a new leaf scorch disease in southern highbush blueberries. Through ELISA, bacterial isolation, and inoculation tests, the researchers confirmed that even root tissues were infected. The bacterium also survived Georgia’s mild winters. (Chang et al., 2009)

5. Hickory Trees and New Concerns

In 2023, leaf scorch symptoms in Southern Shagbark Hickory at the USDA-ARS station in Byron, GA, were confirmed to be caused by Xf subsp. multiplex. The pathogen was verified through PCR and next-gen sequencing. This is the first documented case of Xf in hickory in Georgia. (Bock et al., 2025)

6. Widespread Infection in Pecans

Georgia is the biggest pecan-producing state in the U.S., and this makes the finding of Xf even more serious. A 2018 study tested 91 pecan trees across different counties, confirming infections in over 60% of sampled trees. The Cape Fear cultivar was the most symptomatic. (Bock et al., 2018)

7. American Elms Affected

In 2019, bacterial leaf scorch symptoms were seen in American elm trees at a nursery in Pulaski County. PCR and ELISA tests confirmed the presence of Xf. Though only one tree was affected, this finding points to the spread of Xf into ornamental trees, not just crops. (Ali et al., 2020)

 

Proof of Presence: From Research to Reality

Multiple scientific studies prove the presence of Xylella fastidiosa in Georgia. For example:

·         "Researchers confirmed the presence of Xf in blueberries in Georgia using Koch’s postulates and DNA testing" (Chang et al., 2007).

·         "The draft genome sequence of Griffin-1 confirms the identity of the Xf subsp. multiplex from red oak in Griffin, GA" (Chen et al., 2013).

·         "Real-time PCR confirmed Xf infection in pecan trees from multiple Georgia counties" (Bock et al., 2018).

Each of these statements provides concrete evidence of the pathogen’s presence across the state and different hosts.

 

What This Means for Georgia

The growing number of Xf cases in Georgia points to one fact: this is not an isolated problem. It’s a statewide issue that could continue to affect many more crops and trees if not addressed. From blueberries to pecans and oaks to elms, Xf has shown it can adapt to different hosts.

Current management options are limited. The best practices involve:

·         Removing infected plants

·         Managing insect vectors

·         Avoiding propagation of infected material

·         Developing and planting resistant cultivars

These practices are hard to maintain across large areas, especially with mild winters and overlapping plant hosts.

 

Final Thoughts

Xylella fastidiosa in Georgia is a serious and growing concern. Its impact is being felt across agriculture and forestry, with multiple plant species now confirmed as hosts. Through these 7 detailed studies, we now have clear proof of its presence and effect.

If you're a grower, researcher, or policy maker in Georgia, this is your signal to take it seriously. More research, surveillance, and collaboration are needed to keep the state’s plants healthy and productive.

 

References

·         Oliver, J. E., Cline, B., & Ali, E. (2021). Assessing the Impact of Xylella fastidiosa in Southern Highbush Blueberry Plants in North Carolina and Georgia. SRSFC Project #2021 R-03. University of Georgia.

·         Chang, C. J., Brannen, P. M., Krewer, G., Boland, B., & Donaldson, R. (2007). Bacterial leaf scorch of blueberry: A new disease caused by Xylella fastidiosa. Phytopathology, 97(7), S20.

·         Chen, J., Huang, H., Chang, C. J., & Stenger, D. C. (2013). Draft Genome Sequence of Xylella fastidiosa subsp. multiplex Strain Griffin-1 from Quercus rubra in Georgia. Genome Announcements, 1(5), e00756-13.

·         Chang, C. J., Donaldson, R., Brannen, P., Krewer, G., & Boland, R. (2009). Bacterial Leaf Scorch, a New Blueberry Disease Caused by Xylella fastidiosa. HortScience, 44(2), 413–417.

·         Bock, C. H., Hotchkiss, M. H., Hilton, A., Chen, C., & Chen, J. (2025). First Report of Xylella fastidiosa subsp. multiplex Infecting Southern Shagbark Hickory in Georgia, USA. Plant Disease, 109(7), 711.

·         Bock, C. H., Oliver, J. E., Chen, C., et al. (2018). Pecan Bacterial Leaf Scorch, Caused by Xylella fastidiosa, Is Endemic in Georgia Pecan Orchards. Plant Health Progress, 19(4), 284–287.

·         Ali, M. E., Hudson, O., Waliullah, S., et al. (2020). First Report of Bacterial Leaf Scorch Disease of American Elm Caused by Xylella fastidiosa in Georgia, USA. Plant Disease. https://doi.org/10.1094/PDIS-11-19-2367-PDN