Sporangia are deciduous and fall from the colony with a short stalk attached to the base of the sporangia. In water, sporangia release numerous swimming zoospores. Without sufficient water, sporangia germinate by producing germ tubes that penetrate the host. Zoospores are able to swim for many hours and are attracted to organic matter or host tissue. These zoospores encyst, germinate by forming a small germ tube, and penetrate the host.
Oospores are thick walled and can serve as survival structures in the absence of the host.
Both mating types were found in Hawaii although more isolates were of the A1 mating type. This pathogen produces sporangia on the surface of large leaf rots or blights. Advanced stem rots also have sporangia on the surface on the diseased tissue. These sporangia are splashed onto other parts of the plant or to other plants. Rain and overhead irrigation favors diseased spread in nurseries.