Apple Bitter Rot Season is Upon Us

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 begin as small, slightly sunken lesions that enlarge and eventually develop a bull’s-eye pattern. Cutting into infected fruit reveals an internal rot with a V-shaped pattern.
• · 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.
• · Fruit infected in the field can develop symptoms in storage and shorten shelf-life.
• · The fungal pathogen overwinters in fallen fruit, dried fruit (mummies), and in crevices in bark and dead wood.
• · Bitter rot is caused by multiple species of the fungus Colletotrichum.

Management Options

• · Remove and discard diseased fruit immediately.
• · At the end of the season, remove fallen fruit from the ground and prune out cankers and dead wood that may harbor fungi.
• · Plant cultivars that are less susceptible to bitter rot. Information on cultivar susceptibility can be found in the publication Disease Susceptibility & Resistance of Common Apple Cultivars (PPFS-FR-T-28).
• · Fungicide recommendations for commercial orchards can be found in the Commercial Fruit Pest Management Guide ID-232.
• · Homeowners should consult the Backyard Apple & Pear Disease, Pest, and Cultural Practices Calendar (PPFS-FR-T-21) for fungicide information or contact a county Extension agent for additional information and recommendations regarding fungicides.   

Additional Information

• · Bitter Rot of Apple (PPFS-FR-T-24)
• · Fruit Diseases of Apple (PPFS-FR-T-2)
• · Sanitation Practices for Disease Management in Commercial Specialty Crop Production (PPFS-GEN-05)
• · Backyard Apple & Pear Disease, Pest, and Cultural Practices Calendar (PPFS-FR-T-21)
• · IPM Scouting Guide for Common Problems of Apple (ID-219)
• · Midwest Fruit Pest Management Guide (ID-232)

By Kimberly Leonberger, Plant Pathology Extension Associate, and Nicole Gauthier, Plant Pathology Extension Specialist. The University of Kentucky is an Equal Opportunity Provider.