Quick Facts
- White powdery coating on leaves
- Leaf curling and distortion
- Stunted new growth
- Premature leaf drop
What Is Powdery Mildew?
Powdery mildew is a fungal disease caused by a closely related group of fungi in the order Erysiphales. It produces a distinctive white to grayish powdery coating on leaves, young shoots, and flowers of many ornamental trees and shrubs.
How to Recognize It
- White to grayish powdery patches on the upper surfaces of leaves, young shoots, and sometimes flowers
- Yellowing, browning, or curling of affected leaves
- Distorted, stunted, or dwarfed new growth
- Premature leaf drop on heavily infected branches
- Blemished, deformed, or aborted flowers on flowering trees like dogwood and crape myrtle
- Slowed overall growth and reduced vigor, especially on young trees
In Georgia, powdery mildew is typically present on ornamentals from May through October, with the heaviest activity in May and June. It is favored by warm, humid days followed by cool nights, and is worst on plants growing in shade with poor air circulation.
Why It Matters for Atlanta Trees
Powdery mildew is rarely lethal to established trees, but heavy or repeated infections can weaken young trees, cause premature leaf drop, and disfigure flowering species. Because the fungus overwinters in bud scales, it can return more aggressively each year if conditions favor it, which matters in Atlanta where flowering dogwood, crape myrtle, oak, sycamore, saucer magnolia, crabapple, lilac, euonymus, and bigleaf hydrangea are all common landscape hosts.
Why this needs an ISA-certified arborist
Several tree problems (downy mildew, leaf scorch, early-stage anthracnose, and certain insect damage) can be mistaken for powdery mildew, and treating the wrong issue wastes time while the tree declines. An ISA-certified arborist can confirm the diagnosis on site, judge whether the infection is cosmetic or threatens a young or stressed tree, and recommend the right cultural or, if warranted, chemical response for that specific species.
Suspect powdery mildew 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 susceptible species (dogwood, crape myrtle, lilac) in spots with good morning sun and open air movement, not in still, shaded pockets.
- Maintain proper spacing between trees and shrubs so foliage can dry quickly after rain or dew.
- Prune selectively during the dormant season to open the canopy, improve light penetration, and increase air circulation. Avoid severe pruning during an active infection, because it can disperse spores.
- Rake up and dispose of fallen leaves and other plant debris from beneath affected trees to reduce overwintering fungal inoculum.
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 shoots without sanitizing your tools between cuts. Powdery mildew spores spread easily on contaminated blades, and unsanitized pruning during an active infection can move the problem to healthy parts of the tree.
Related Services
For most diagnosis and treatment questions, the right starting point is one of our services:
- ISA-Certified Arborist Services for diagnosis, consultation, and second opinions
- 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 (Dougherty County Horticulture), UGA CAES Field Report, and University of Maryland Extension.