See:
Greenhouse Plants, Ornamental - Gray Mold
Cause Botrytis cinerea, a fungus commonly found on ornamentals, greenhouse plants and flowers, vegetables, and small fruits. The fungus colonizes dead, dying, and wounded plant parts. From these infections it can attack healthy tissues. A moist, humid environment is ideal for pathogen sporulation and spread. Spore dispersal is stimulated by changes in relative humidity. Conidia may come from many sources. Flower petals are most susceptible at any stage of development. Leaf blights can start when infected floral tissue falls on healthy leaves.
Symptoms Grayish to brown necrotic spots develop at the leaf margin and gradually involve the entire leaf. A twig dieback and flower blight also can occur. Small black sclerotia develop in the blighted flowers and occasionally on leaves.
Cultural control
- Space plants for adequate air circulation.
- Avoid overhead irrigation or apply such that plants are not wet for extended periods of time.
- Plant in full sun.
- Rake and destroy fallen leaves.
- Remove and destroy infected leaves and shoots. Collect infected tissues carefully to avoid spreading the disease.
Chemical control Best used with cultural controls. Tank-mix and/or alternate products with different modes of action to prevent building up resistant fungi. Limit the use of any one group during crop production.
- Astun at 10 to 17 fl oz/100 gal water. Group 7 fungicide. 12-hr reentry.
- Broadform at 4 to 8 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Chipco 26019 FLO at 1 to 2.5 quarts/100 gal water. Group 2 fungicide. 12-hr reentry.
- Orkestra at 8 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Pageant at 12 to 18 oz/100 gal water. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. 12-hr reentry.
- Phyton 27 at 1.3 to 2.5 oz/10 gal water. Group M1 fungicide. 48-hr reentry.
Reference Rizzo, C. F., Smith, E. M. and Fretz, T. A. 1979. An Evaluation of Fungicides on Container-Grown Woody Ornamentals During Winter Storage Under Microfoam. In, Ornamental Plants--1979 A Summary of Research. Ohio Ag Research and Development Center. Research Circular 246:44-45.