I. Phycomycete root rots a. Loser stems frequently are also rotted. In rare cases as with petunias only the lower stem is involved with the roots appearing healthy, similar to a collar rot in woody plants. Several species of Phytophthora.
Symptoms depend on host and speces ii.
Species of Pythium. Damping-off of young plants and seedlings and root pruning of older plants which limits productivity and performance. Become active and germinate when approached by a host root. Uninfested artificial mixes ii. Heat or fumigation to kill propagules iii.