The Rotten Truth about Bitter Rot

While fruit rots have a variety of causes, the most common fungal fruit rot of apple in Kentucky is bitter rot. The disease results in rotten, inedible fruit. Fungicides are available for management; however, sanitation is critical for disease prevention.

Bitter Rot Facts

  • Symptoms include small, slightly sunken lesions that eventually develop a bull’s-eye pattern (Figure 1). Cutting into infected fruit reveals an internal rot with a V-shaped pattern (Figure 2).
  • Symptoms may not appear immediately after infection and may take several months to become visible.
  • Initial infection begins as early as bloom and may continue through harvest.
  • The pathogen overwinters in fallen fruit, dried fruit (mummies), and in crevices in bark and dead wood.
  • Caused by multiple species of the fungus Colletotrichum.

Figure 1:   Sunken lesions with bull’s-eye appearance are symptoms of bitter rot on apple. (Photo: Nicole Ward Gauthier, UK)

Figure 2: Internal V-shaped rot in apple caused by bitter rot. (Photo: Nicole Ward Gauthier, UK)

Management Options

  • Remove and discard diseased fruit immediately.
  • At the end of the season, remove fruit from the ground, as well as cankers and dead wood that could harbor fungi.
  • Plant cultivars that are less susceptible to bitter rot, including Rome Beauty, Winesap, and Red or Yellow Delicious.
  • 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 when utilizing fungicides.

Additional Information

  • Apple Fruit Diseases Appearing at Harvest (PPFS-FR-T-02)
  • Fruit, Orchard, and Vineyard Sanitation (PPFS-GEN-05)
  • Backyard Apple Disease & Pest Management Using Cultural Practices (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)

 

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

 

Posted in Fruit