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.
- 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.
- 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