However, chlamydospores produced in papaya juice at lower concentrations or in other kinds of fruit juice are mostly thin-walled. In the presence of nutrients, chlamydospores germinate by producing germ tubes that continue to grow and form mycelial masses. In water, chlamydospores germinate by producing short germ tubes, each with a sporangium at the tip. Sexual reproduction in P. palmivora requires the presence of opposite mating types known as A1 and A2. Both A1 and A2 isolates can produce oospores by selfing when stimulated by sex hormones produced by A2 and A1, respectively.
Light is inhibitory to oospore formation but stimulatory to oospore germination.
Although sporangia and zoospores may survive in soil for short periods, chlamydospores are the main survival structure for P. palmivora in nature. Oospores are capable of long-term survival but do not play a significant role in the disease cycle because sexual reproduction in P. palmivora requires the presence of opposite mating types, and the chance for this to occur in nature is very low. During rainy periods, chlamydospores in soil may germinate in water to produce sporangia and release zoospores. The impact of falling rain drops may splash zoospores into air in droplets. The zoospore-containing droplets may be further dispersed by wind and become the inoculum for infecting fruit and occasionally stems of papaya in the fields.