Grape: Botrytis bunch rot (Gray mold)
categories: Grape Grape Diseases Small Fruits
revision date: 2022-12-06 12:00
Biology
This fruit rot is caused by a fungus which also causes disease in strawberries, raspberries, and many other plants. In grapes, the disease is typically limited to fruit. Infection may occur throughout the season and in storage. Early-season infections often occur through the flower. A characteristic, fuzzy, gray-brown coating of fungal growth develops on the young fruit, which may later dry into infected mummies. Later infections may develop as a result of rain during harvest, causing a condition known as “slip-skin”. Brownish patches develop on the fruit and the skin separates from the flesh. After harvest, storage rot may cause a brown, soft rot of the fruit. The fungus overwinters on old cluster stems, canes, or mummified, diseased fruit. Disease development is favored by tight fruit clusters, dense foliage, and cool, moist conditions.
Management Options
Use Integrated Pest Management (IPM) for successful plant problem management.
Non-chemical Management
Select non-chemical management options as your first choice!
- Space plantings and prune to provide good air circulation and reduce humidity.
- Avoid overhead watering and other practices which cause moist conditions in the canopy.
- Prevent injury to the fruit, which can facilitate disease development.
- Clean up plant debris, including mummified fruit. Destroy or discard (do not compost) diseased materials.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- Apply at beginning of fruit set after bloom is gone.
- Make 2 or 3 additional applications at 10- to 14- day intervals up to 3 weeks prior to harvest or when weather dries.
- Copper products offer only slight control.
Approved Pesticides
Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.