Sooty Blotch and Flyspeck Make for Ugly Apples

The time for apple harvest in Kentucky has arrived, bringing with it the possibility of less than perfect looking apples. Sooty blotch and/or flyspeck are one of many causes for blemished, ugly apples. The two fungal diseases occur together as a complex that is often called "sooty blotch/fly speck." Sanitation, cultural practices, and fungicides all play roles in disease management.

Sooty Blotch and Flyspeck Facts

Symptoms of sooty blotch include black-brown to olive-colored irregular blotches. Fungal reproductive structures (pycnidia) may be visible in darker spots. Flyspeck symptoms appear as sharp, black, shiny dots grouped into clusters. These black dots are fungal reproductive structures (pseudothecia). Sooty blotch and flyspeck may occur independently, but they usually develop together.

Infection may occur during summer or throughout fall.

Both pathogens overwinter on fallen fruit, dried fruit (mummies), and in crevices in bark and dead wood. Pathogens are superficial and are restricted to fruit surfaces. The flesh of the fruit is not affected.

Sooty blotch is caused by the fungus Geastrumia polystigmatis, and flyspeck is caused by the fungus Zygophiali jamaicensis.

Management Options

• Remove and discard diseased fruit to help reduce inoculum.
• At the end of the season, remove fruit from the ground, as well as cankers and dead wood that could harbor fungi.
• Homeowners and small scale growers can bag apples to prevent disease onset (ENTFACT-218).
• Homeowners can apply fungicides that contain captan or mancozeb beginning soon after petal fall and continuing every 10 to 14 days until harvest. Always follow label directions.
• Commercial growers should refer to ID-232 for fungicide recommendations.

Additional information available online or through your local Extension office include:

• Apple Fruit Diseases Appearing at Harvest (PPFS-FR-T-2)
• Fruit, Orchard, and Vineyard Sanitation (PPFS-GEN-05)
• Backyard Apple Disease & Pest Management Using Cultural Practices (with Low Spray, No Spray, & Organic Options) (PPFS-FR-T-21)
• Simplified Backyard Apple Spray Guides (PPFS-FR-T-18)
• Effectiveness of Fungicides for Management of Apple Diseases (PPFS-FR-T-15)
• Commercial Fruit Pest Management Guide (ID-232)
• Bagging Apples: Alternative Pest Management for Hobbyists (ENTFACT-218)