Bacterial Canker: Atlanta Diagnosis & Treatment Guide

What Is Bacterial Canker?

Bacterial canker is a disease caused by Pseudomonas syringae bacteria (most commonly the pathovar syringae) that infect the bark, branches, twigs, leaves, and blossoms of trees, most often Prunus species like cherry, plum, and peach. The bacteria enter through wounds, leaf scars, or frost cracks and form sunken, oozing lesions (cankers) that can girdle and kill limbs.

How to Recognize It

• Sunken or cracked areas on the bark of branches and trunks, sometimes with an amber or gummy ooze (a symptom called gummosis).
• Dieback of twigs and small branches, often most obvious in spring when buds fail to leaf out.
• Small, dark, water-soaked spots on leaves that may dry out and drop, leaving a "shothole" appearance.
• Dead or blackened flower clusters and young shoots (sometimes called blossom blast).
• Buds that turn brown and die before opening in spring.
• A sour or fermented smell near the canker on some hosts.

Symptoms are most visible in spring as buds fail and cankers begin to ooze. The bacteria become active again in fall during leaf drop, infecting fresh leaf scars and moving into dormant buds where they overwinter. Cool, wet weather and frost injury greatly increase infection.

Why It Matters for Atlanta Trees

Bacterial canker is considered serious because there is no highly effective cure once a tree is infected, and cankers that girdle the main trunk or major scaffold limbs can kill the tree or cause large limbs to fail. In Atlanta landscapes, the disease shows up most often on flowering cherries (including Yoshino and Kwanzan), ornamental and fruiting plums, peach and nectarine, cherry laurel, and other Prunus species used in residential plantings, where weakened limbs over driveways, walkways, or homes can become a human safety hazard if left in place.

General Prevention

• Keep trees vigorous with deep, infrequent watering during dry spells and a 2 to 4 inch layer of mulch (kept off the trunk), since stressed trees are far more susceptible.
• Prune only in dry weather during summer after the worst infection periods have passed, never during wet spring or fall conditions when bacteria are active.
• Avoid wounding the bark with mowers, string trimmers, or aggressive pruning cuts, since wounds and frost cracks are the main entry points.
• Choose planting sites with good drainage and air movement, and protect young trunks from winter sunscald and frost injury.

What NOT to Do

• Do not self-diagnose. Many tree problems look alike, and treating the wrong one wastes time and can harm the tree.
• Do not apply fungicides, insecticides, or other chemicals without an arborist's specific recommendation. Wrong product or wrong timing makes things worse.
• Do not prune symptomatic limbs during wet spring or fall weather, and do not move from cut to cut without sanitizing your tools, because both practices can spread the bacteria into healthy wood.

Related Services

For most diagnosis and treatment questions, the right starting point is one of our services:

• ISA-Certified Arborist Services: diagnosis, consultation, second opinion
• Plant Health Care (PHC): ongoing tree health management
• TRAQ Tree Risk Assessment: when the tree may be a safety hazard

Sources

This page summarizes general information from: University of Georgia Extension (CAES Peaches), UGA Extension, Bartow County, and Michigan State University Extension.