Damping-off
is stimulated by exudates from roots of a susceptible host nearby. The oospores germinate and form so-called sporangia from which subsequently zoospores [...] usually only affect plants that are in a sub-optimal condition or suffer from stress, caused for example by too much water, too high or low temperatures [...] typical symptom of a Pythium infection is the easy stripping of the skin from the root cortex with a finger nail. Life cycle and appearance of Damping-off