See:
Greenhouse Plants, Ornamental - Gray Mold
Cause Botrytis cinerea, a fungus favored by warm, wet greenhouse conditions. Senescent leaves and spent flowers are often infected. There are few references about Botrytis on this plant but it does show up on host lists.
Symptoms Leaves, especially those near the soil surface, rot and become covered with gray fungal growth as do fading flowers. A stem collapse or crown rot can also occur.
Cultural control
- Heat and ventilate to maintain low humidity.
- Remove dead and dying plant tissue from the greenhouse.
Chemical control Best when used with cultural controls. Tank-mix and/or alternate products from different groups with different modes of action to prevent the buildup of resistant fungi. Minimize the use of any one group during the growing season.
- Astun at 10 to 17 fl oz/100 gal water. Group 7 fungicide. 12-hr reentry.
- Decree 50 WDG at 0.75 to 1.5 lb/100 gal water. Group 17 fungicide. 12-hr reentry.
- Spirato GHN at 2 to 4 fl oz/100 gal water. Use with oils or adjuvants may cause plant damage. Group 12 fungicide. 12-hr reentry.
- Terraguard SC at 4 to 8 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
Biological control
- Prestop (Gliocladium catenulatum strain J1446) at 0.33 oz/5 gal water. Do not use with other products in the tank. 4-hr reentry. O
Reference Elad, Y., Pertot, I., Prado, A.M.C., and Stewart, A. 2016. Plant hosts of Botrytis spp. In Botrytis-the fungus, the pathogen and its management in agricultural systems (pp. 413-486). Springer, Cham.