The disease in papaya is caused by the type p strain of
PRSV (Purcifill et al. 1984). Typical symptoms of PRSV
include mosaic and distorted leaves, stunted trees, drastically
reduced fruit yield, and small fruits with ringspotting
blemishes (Purcifull et al. 1984). Symptom expression is
highly influenced by environmental conditions. Symptoms
are more severely expressed during cooler months (Gonsalves
and Ishii 1980).
PRSV is sap transmissible and reported to be vectored
by many species of aphids, including Myzus persicae, Aphis
gossypii, A. craccivora, and A. maidis in a non-persistent
manner (Purcifull et al. 1984). This mode of transmission is
characterised by a short acquisition period followed by
rapid loss of infectivity (Purcifull et al. 1984). An entire
papaya orchard can become completely infected with PRSV
in three to four months (Gonsalves 1994, 1998). Losses up
to 70% have been reported in some regions (Barbosa and
Paguio 1982). Although transmission is widely shown to be
by aphid vectors, one study in the Philippines reported seed
transmission of PRSV (Bayot et al. 1990). Two of 1355
seedlings (0.15%) from fruit of an infected tree were reported
to develop symptoms of PRSV six weeks after emergence.