Before discussing these two diseases and their management, a brief introduction to the life cycle of this fungus would be helpful. There are four possible forms of infective structures produced by Phytophthora-sporangia, zoospores, oospores and chlamydospores. Water is required for germination of all spore types. The sporangia are vegetative structures that can germinate by a germ tube that produces new mycelium. They are attracted to amino acids and other chemicals given off by roots or succulent plant parts.
Oospores develop from the sexual combination of two fungi and serve as a fungus resting stage.
Though few in number, they are important because they combine the genetic material from two different fungi. Chlamydospores are vegetative cells, found within hyphae, that develop thick walls and also serve as resting structures. Both of these stages germinate through a germ tube that can develop into either mycelium or sporangia depending on the species. They can also withstand adverse environmental conditions. In order for this type of mobile spore to enter the plant, the leaves must be wet.