Xylella Fastidiosa: Bacterial Leaf Scorch Causes, Symptoms and Treatment

05/09/2018
Bacterial Leaf Scorch

Because bacterial leaf scorch symptoms look similar to those caused by abiotic stressors like nutritional deficiency and other blights, it was not recognized as a pathogen until the 1980s. Though it’s often overlooked or misdiagnosed, this disease is essentially a death sentence for residential trees.

What Is Bacterial Leaf Scorch?

This tree affliction is caused by the spread of xylella fastidiosa bacteria via insect that feed on xylem, including:

  • Sharpshooters
  • Treehoppers
  • Leafhoppers
  • Spittlebugs

As these insects eat the terminal shoots of a susceptible host tree, they transmit bacteria to the tree. As the bacteria travels, it clogs the xylem vessels, multiplying and infecting other parts of the tree. The disease can also be spread from one tree to another through root grafts.

Bacterial leaf scorch kills deciduous trees by restricting the leaves’ access to water, leading to scorch development. There’s a long list of susceptible trees, including:

  • Oaks (red, pin, bur, white, willow and 12 other species)
  • Sycamore
  • American elm
  • Maples (red and sugar)
  • Mulberry
  • Sweet gum
  • Almond

Symptoms of Bacterial Leaf Scorch

The severity of symptoms varies, and symptoms often won’t present themselves until the tree is close to death. Early in the season, leaves appear to develop normally. Symptom expression typically begins in June and July and progresses as the season goes on in the following way:

  • Necrosis along leaf edges spreads toward the veins in an irregular pattern
  • Green tissue separates from reddish-brown necrotic tissue, creating a yellow band or halo
  • Symptoms reappear in the same limbs yearly as the disease eventually spreads
  • The tree exhibits an overall decline in health

In most afflicted trees, death occurs in five to 10 years. Those exposed to more abiotic stressors may die more quickly, so it’s important to watch for and combat the infection sooner rather than later.

Bacterial leaf scorch can be mistaken for several other maladies, some of them treatable. The only way to confirm the diagnosis is through laboratory analysis. Testing should be conducted during late summer or early fall when the bacteria count is at its highest level.

How to Treat Bacterial Leaf Scorch

Unfortunately, there is no known cure for bacterial leaf scorch, but there are several management practices that can help extend the longevity of infected trees.

Maintain Plant Vigor

Hiring a professional arborist is the best way to keep susceptible trees healthy and thriving. Professional-grade care can help trees resist further decay and survive longer if they become contaminated.

Practice Good Sanitation

Limbs that have succumbed to bacterial leaf scorch should be continually removed. Between pruning cuts, tools should be disinfected with a 10 percent bleach solution to prevent further spreading the infection.

Plant Resistant Species

If you’ve had a tree die from bacterial leaf scorch, avoid planting another highly susceptible tree in the same area.

Antibiotic Injections

Injections of oxytetracycline in the root flare during spring can reduce bacteria levels and delay symptoms by a few weeks. These injections will need to be reapplied each year. If you are considering injecting your trees with this antibiotic, you should contact a certified arborist.

Tree Replacement

Overall, the best treatment method for afflicted trees is removal and replacement with a tree that isn’t susceptible to bacterial leaf scorch. To prevent future infections, take care to water the new tree regularly, apply mulch periodically and prune trees correctly so good branch structure is established when the tree is young.

Discussing your options with a certified arborist is the best way to make the right decision and ensure the health and longevity of your plants.

Residential Tree Preservation in Georgia

Improve the health of your trees by arming them against illness with help from an experienced arborist at Gunnison Tree Specialists. Since 1999, we have provided prompt and professional residential tree care services to the greater Atlanta area, including:

  • Tree removal
  • Stump removal
  • Pruning
  • Insect and disease management
  • Emergency services
  • Risk assessments
  • Tree preservation

Contact us online today or call 404-386-3333 for your FREE quote!

05/09/2018

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