The diseases caused by these fungi are locally serious and usually root rots or diseases below the soil line. Only disease of above ground parts. Urophlyctis - Crown wart of Alfalfa , first found in South America now widespread in western USA, not serious. Life cycle handout. An example of these diseases.
Control is by quarantine, seed certification and resistance.
These fungi overwinter as resting spores and germinate with one zoospore which infect a root hair and forms a plasmodium which develops into a zoosporangium and releases lots of zoospores as secondary inoculum and fuse to dikaryotic zygote. Recover at night. Young plant may be killed. Typical knobby club like roots appear after several weeks and roots collapse and die. Not always the whole root.