Myrothecium Leaf Spot -- Myrothecium roridum
Host:begonia, dieffenbachia, gloxinia, New Guinea impatiens, philodendron, spathiphyllum, pansy
Symptoms: Symptoms of Myrothecium leaf spot for the majority of host plants include spots anywhere on leaves. The spots initially appear water-soaked and are dark brown to black in color. Irregularly shaped black sporodochia can form with a white fringe of mycelium. These spore structures appear in concentric rings within the necrotic areas on the lower surface of the leaf.
Conditions Favoring Disease: This disease occurs during conditions with temperatures between 70° and 81°F, moisture on leaves and poor greenhouse sanitation. The fungus may invade plant tissue through open wounds most easily.
How Pathogen Survives/Disperses: The fungus survives in soil or plant debris. The optimum temperature for spore germination is 82°F.
Photo and write up provided by Syngenta Professional Products