Cause Sclerotinia sclerotiorum, a fungus. This is a widespread but relatively unimportant disease of cucumbers grown in the field but has caused severe losses of vines and fruit in greenhouses.
Symptoms Occurs primarily as a stem blight or fruit rot. Older vines are affected most often. After a white cottony mold develops, the stem dries and withers and small, black sclerotia appear in rotting tissues. Affected cucumber fruit are watery, soft, and later develop sclerotia.
Cultural control
- In the field, practice crop rotation and do not follow snap bean, potato or tomato crops.
- When possible, plow deeply to bury sclerotia.
- Remove and destroy infected vines and fruit in the garden or greenhouse.
Chemical control
- Botran 75 W at 1.3 lb/100 gal water. For greenhouse crops only; not registered in Oregon. May apply up to 1 day before harvest. 12-hr reentry.
- Fontelis at 16 fl oz/A on 7- to 14-day intervals. Do not make more than two (2) sequential applications before alternating to a labeled fungicide with a different mode of action (non-Group 7). Preharvest interval is 1 day. 12-hr reentry.
- OSO 5% SC at 3.75 to 13 fl oz/A on 7- to 14-day intervals. Can be applied the day of harvest. 4-hr reentry. O