i) Presence of virulent/aggressive isolate of a pathogen:

• For any epiphytotic, rapid cycle of infection is essential, and successful infection can be caused only by virulent isolates of the pathogen.

ii) High birth rate:

• The fungi that assume epiphytotic form invariably have the capacity to produce enormous quantity of spores that are adapted to long distance dissemination in a short time.

iii) Low death rate of the pathogen:

• Epiphytotics is attributed to low death rate of the pathogens in those in which the causal agent is systemic and protected by the plant tissues.

iv) Easy and rapid dispersal of the pathogen:

• The ability of a pathogen to cause epiphytotics is much more dependent on its dispersal rate.
• Ex: Fungal spores disseminated by wind, water, etc.
• Viruses disseminated by insect vectors
• Bacteria dispersed through rain splashes and water.

v) Adaptability of the pathogen:

• Most of the pathogens causing epiphytotics adapt themselves to various adverse conditions.