See:
Greenhouse Plants, Ornamental - Gray Mold
Cause Botrytis cinerea, a fungus. The disease is favored by warm and moist conditions. Can survive in dead plant debris and is ubiquitous in most Pacific Northwest production areas.
Symptoms Twigs die back, and a gray, fungal growth develops on dead tissue. A stem rot has also been observed by the OSU Plant Clinic.
Cultural control
- Keep foliage as dry as possible.
- Space plants for good air circulation.
Chemical control No products are specifically registered for daphne, but it is legal to try products like Cleary's 3336 or Decree on a small scale to check for phytotoxicity before wide scale use. Best when used with cultural controls.
Reference Fillinger, S., and Elad, Y. (ed.). 2016. Botrytis-the Fungus, the Pathogen and Its Management in Agricultural Systems. Switzerland: Springer International Publishing.