Therefore, Phytophthora root rot may occur on papaya at any age in poorly drained areas. Waterlogged conditions appear to weaken the defense mechanism of papaya roots against invasion by the pathogen. Mobility of zoospores of P. palmivora under such conditions also may contribute to the severity of the disease due to their attraction by papaya roots. Favorable temperature is also a contributing factor to the severity of Phytophthora diseases because of its effect on growth and sporulation of the pathogen. Rain splash is needed for liberation of sporangia of P. palmivora from the surface of infected fruit into the atmosphere and for projection of the soil inoculum into air.
Wind is required for dispersal of the inoculum once it reaches the air.
Therefore, wind-blown rain is essential for initiation of the primary infection and the development of epidemics in papaya orchards. Roots of papaya plants are protected by the virgin soil during the susceptible stage, and become resistant to the pathogen when they extend to the infested soil. Trees established with the virgin soil method in the replant fields produce fruit as abundantly as those growing in the first planting fields. The virgin soil method has the advantages of being relatively inexpensive, very effective and nonhazardous. Cultural practice is also important in the management of Phytophthora diseases of papaya.