Botrytis Bunch Rot
Botrytis cinerea
2 host plants · Fungal
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Botrytis bunch rot causes fruit clusters to decay and become moldy, particularly in grape vines grown in cool, damp regions. You see brown rot spreading through berry bunches in wet spring weather. California grapes are particularly susceptible. Manage by improving air circulation through pruning, avoiding overhead irrigation, and removing infected fruit promptly.
Reduce moisture around affected tissue by improving drainage and air circulation. Remove rotted material cleanly and dispose of it away from the planting area. Avoid wounding healthy tissue during cleanup, as fresh wounds create new entry points. If the problem keeps returning, evaluate whether the site is too wet or poorly drained for the species you are growing.
Quick Reference
Management
Full bloom period (primary risk); fruit development through veraison (color change) in cool, wet seasons; post-harvest storage in cool, humid conditions.
4-6 hours continuous leaf wetness at 60-77°F (15-25°C); optimum 65-73°F. Tight berry clusters slow fruit drying and sustain high humidity. Rain or overhead irrigation during bloom and fruit development promotes infection. Cool, wet springs and early summers strongly favor disease. # Source: PNW Plant Disease Management Handbook
Cultural Controls
- Space plantings and prune to provide good air circulation and reduce humidity.
- Avoid overhead watering and practices that cause prolonged canopy wetness.
- Prevent injury to fruit, which facilitates disease development.
- Remove and destroy mummified fruit and infected plant debris.
- Do not compost diseased materials.