Quick Facts
- Dark olive-green to black lesions on leaves
- Lesions on nut shucks
- Premature nut drop
- Reduced nut quality and size
What Is Pecan Scab?
Pecan scab is a fungal disease of pecan trees caused by Venturia effusa, also known by the synonym Fusicladium effusum. It attacks leaves, twigs, and the green shucks around developing nuts, and it is the most economically damaging disease of pecan in the southeastern United States.
How to Recognize It
- Small black or olive-colored spots on leaves, often only 1 to 8 millimeters across, that may merge into larger blotches
- Black, sunken lesions on the green shucks (outer husks) of developing pecans
- Premature leaf drop, especially on the lower and inner canopy
- Small, poorly filled nuts and difficulty shelling at harvest
- Early nut drop before the crop matures
- Lesions also visible on young twigs and leaf stems
Infections typically begin in spring as new leaves and shoots emerge, and pressure builds through the warm, humid Atlanta summer. Hot, wet weather and extended periods of leaf wetness drive the worst outbreaks, with damage to nuts becoming obvious from midsummer into early fall.
Why It Matters for Atlanta Trees
On susceptible pecan varieties, scab can cause yield losses of 50 to 100 percent in a bad year, and repeated heavy infections weaken the tree over time. While scab itself rarely kills a mature pecan outright, the resulting stress, defoliation, and limb dieback can contribute to declining tree health and structural problems that become a safety concern on the large pecans (Carya illinoinensis) common in older Atlanta neighborhoods, where yard trees often tower 50 feet or more above the home.
Why this needs an ISA-certified arborist
Pecan scab looks similar to several other leaf and shuck problems, including anthracnose, downy spot, and certain insect injuries, and accurate diagnosis matters because treatment options and timing differ. Mature pecans in Atlanta yards are often 50 feet or taller, so meaningful intervention and any structural pruning to improve airflow require the equipment, training, and risk assessment of an ISA-certified arborist.
Suspect Pecan Scab 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
- Rake and remove fallen leaves, shucks, and twigs during late fall and winter, since the fungus overwinters in this debris and reinfects the tree the following spring
- Improve airflow and sunlight through the canopy with proper structural pruning so leaves dry faster after rain and dew
- Avoid overhead watering of pecans and keep irrigation off the foliage
- When planting a new pecan, choose a site with good air movement and full sun, and ask an arborist about scab-resistant cultivars suited to Georgia
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 without sanitizing your tools between cuts. Unsanitized blades can spread the fungus from one part of the canopy to another, and improper cuts on a tall pecan create new entry points for disease and decay.
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 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: University of Georgia Extension (Lincoln County), UGA Pecan Extension, and North Carolina State University Cooperative Extension (Robeson County).