Rhizopus Blight -- Rhizopus stolonifer
Host:crossandra, Euphorbia milii (Crown-of-Thorns), poinsettia, Gerbera, vinca.
Symptoms: This disease affects the flowers, leaves and stems of the plant. A mass of white mycelium completely covers the flowers and is quickly followed by the formation of black sporangia dotting the tissue. The mycelium then spreads from the flowers into the stems and crown, causing a mushy, brown rot to occur, which eventually may kill the plant, especially during propagation/rooting phases.
Conditions Favoring Disease: Rhizopus blight is favored by temperatures between 70° and 90°F and often occurs on stressed plants.
How Pathogen Survives/Disperses: Spores are borne at the apex of long sporangiophores and are disseminated by wind and water. The fungus can survive in plant debris.
Photo and write up provided by Syngenta Professional Products