Botryosphaeria Canker: Atlanta Diagnosis & Management Guide

What Is Botryosphaeria Canker?

Botryosphaeria canker is a fungal disease caused by Botryosphaeria dothidea and related species, an opportunistic fungal pathogen complex. The fungus enters trees and shrubs through wounds, pruning cuts, or natural openings in the bark and forms sunken, dead patches (cankers) that can girdle and kill branches or whole limbs.

How to Recognize It

• Rust colored, yellowing, or browning branches on an otherwise healthy looking tree
• Sunken, cracked, dark brown or black areas in the bark, often centered on an old wound or pruning cut
• Wood beneath the bark looks blackened or dark brown when scratched
• Wilting leaves and tip dieback that progress from the branch tip inward
• Dead bark that peels or flakes off the cankered area
• Scattered dead branches in the canopy while the rest of the tree still looks green

The fungus overwinters in dead bark and infected tissue, then becomes active in spring as spores spread by wind and splashing water. Visible decline most often shows up during and after summer heat or drought, when stressed trees can no longer wall off the infection.

Why It Matters for Atlanta Trees

Botryosphaeria is an opportunistic pathogen, meaning it usually attacks trees already weakened by drought, heat, freeze damage, or wounds. On a healthy tree it may cause only minor branch dieback, but on stressed or repeatedly wounded trees it can girdle limbs, kill major branches, and eventually take the tree down. Dead and dying limbs over a home, driveway, or play area also become a falling-limb hazard, so early identification matters for both tree health and personal safety. In metro Atlanta, the disease shows up regularly on Leyland cypress, flowering dogwood, redbud, azalea, rhododendron, oak, crabapple, sweetgum, tulip poplar, and beech, all of which are common in local landscapes.

General Prevention

• Keep trees watered during summer drought and into early fall, with deep, less frequent soakings rather than light daily sprinkling.
• Mulch in a wide, flat ring (around 2 to 3 inches deep) out past the lowest branches, and keep mulch pulled back off the trunk.
• Avoid wounding the trunk and roots with mowers, string trimmers, or careless pruning, since the fungus enters through wounds.
• Prune out dead and clearly cankered branches during dry weather in late winter while the tree is dormant, and disinfect pruning tools between cuts.

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 in wet weather or without sanitizing your tools between cuts, because the fungus spreads readily on contaminated blades and through splashing water.

Related Services

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

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

Sources

This page summarizes general information from: UGA Cooperative Extension, Virginia Cooperative Extension (Virginia Tech), and Penn State Extension.