Sooty Blotch & 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 & Flyspeck Facts

  • Symptoms of sooty blotch include black-brown to olive-colored irregular blotches (Figure 1, black arrow). Fungal reproductive structures (pycnidia) may be visible in darker spots.
  • Flyspeck symptoms appear as sharp, black, shiny dots grouped into clusters (Figure 1, red arrow). These black dots are fungal reproductive structures (pseudothecia).
  • Sooty blotch and flyspeck may occur independently, but they usually develop together (Figure 1).
  • 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.
Figure 1: Sooty blotch (black arrow) and flyspeck (red arrow) often occur on the same fruit (Photo: Kimberly Leonberger, UK)

Figure 1: Sooty blotch (black arrow) and flyspeck (red arrow) often occur on the same fruit (Photo: Kimberly Leonberger, UK)

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

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

 

By Kimberly Leonberger, Extension Associate and Nicole Ward Gauthier, Extension Plant Pathologist

 

Posted in Fruit