Quick Facts
- General yellowing and wilting
- Mushrooms or conks at tree base
- Dark or water-soaked bark near soil line
- Sparse canopy and reduced growth
What Is Phytophthora Root Rot?
Phytophthora root rot is a soil-borne disease caused by water mold organisms in the genus Phytophthora (including P. cinnamomi, P. cactorum, P. citricola, and P. citrophthora) that attack a tree's roots and the lower trunk, or crown. The pathogen thrives in saturated, poorly drained soils and rots the fine feeder roots, which starves the canopy of water and nutrients and can ultimately kill the tree.
How to Recognize It
- Foliage looks dull green, yellow, or sometimes reddish or purplish, often starting with the oldest leaves.
- Wilting that gets worse in warm weather even when the soil is moist.
- Thinning canopy, smaller new leaves, branch dieback, and overall loss of vigor.
- Darkened, sunken bark or oozing sap near the base of the trunk where it meets the soil.
- Roots that are soft, brown, and decayed when examined, rather than firm and white inside.
- Trees in low spots or poorly drained areas of the yard tend to show symptoms first.
Infection is favored by warm, wet soils, so disease activity typically picks up in spring and early summer and again during humid late summer in Georgia. Canopy symptoms often become most visible during the first prolonged heat or drought stretch after a wet period, when damaged roots can no longer supply enough water.
Why It Matters for Atlanta Trees
UGA Extension describes root rots as among the most damaging diseases in Georgia landscapes. A tree can decline slowly over several years or, in severe cases, collapse in a single season. Because the damage is hidden below ground until the canopy shows symptoms, early detection matters: once large portions of the root system or lower trunk are infected, recovery is unlikely and the tree may become a structural hazard that can fall.
Many of the trees and shrubs that fill Atlanta yards are on the susceptible list, including Leyland cypress, dogwood, azalea and rhododendron, cherry, peach and other stone fruits, boxwood, white pine, Fraser fir, Japanese maple, and hemlock. With the region's clay soils and summer thunderstorms, drainage problems are common, and these species can be especially vulnerable in low-lying or chronically wet parts of a property.
Why this needs an ISA-certified arborist
Phytophthora root rot looks very similar to drought stress, mechanical root damage, girdling roots, and other root diseases like Armillaria, so an accurate diagnosis usually requires a trained eye and sometimes laboratory testing of root or soil samples. An ISA-certified arborist can examine the root flare and crown, assess drainage and site conditions, rule out look-alike problems, and judge whether the tree can be saved or has become a fall hazard that needs removal.
Suspect Phytophthora Root Rot on your tree? Schedule a free on-site visit from EastLake's ISA-certified arborists at request a free estimate or call 404-850-1174.
General Prevention
- Plant in well-drained soil and avoid low spots where water pools. Do not plant trees deeper than they grew in the nursery, and keep the root flare visible at the soil surface.
- Water deeply but not constantly. Soaker hoses or drip irrigation aimed at the root zone (not the trunk) are better than frequent shallow watering, and established trees usually need less water than people assume.
- Mulch in a wide, shallow ring (two to four inches deep), but pull mulch back several inches from the trunk. Mulch piled against the bark holds moisture against the crown and invites infection.
- Avoid moving soil, mulch, or plants from an area with known root rot into healthy parts of the yard, and clean tools between sites. The pathogen spreads in contaminated soil and water.
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 add more water, more soil, or more mulch around a struggling tree in hopes of helping it. With Phytophthora, the problem is usually too much moisture against the roots and crown, so piling on amendments or watering more often tends to accelerate decline.
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: UGA Extension (Common Landscape Diseases in Georgia), UGA Extension (Diseases of Leyland Cypress in the Landscape), NC State Extension, and UC Statewide IPM Program.