These asexual structures are stimulated to form when soil water becomes abundant. Zoospores are formed inside these sporangia , released into the soil water and are attracted to feeder roots of susceptible plants. Chlamydospores are thick-walled, asexual structures produced by P. cinnamomi and are the chief means of survival in the soil. The fungi can also survive as hyphae in infected plant roots. Oospores are formed only when sexually compatible strains of the fungus fuse.
Oospores are also a means of survival in soil or infected roots.
Oospores are not common in North Carolina. Return to the top of the page Symptoms of Phytophthora Root Rot on Fraser Fir P. cinnamomi can cause damping off as seen for these seedlings in an inoculated pot and in a nursery bed. Root decay can occur in the nursery when seedlings are grown for more than one year in the bed. These seedlings are three years old. Wilting and necrosis on seedlings inoculated in pots in the greenhouse.