Seasonal development and life cycle
Tristeza virus is spread through budding and grafting or by aphids feeding on citrus. The melon aphid,
Aphis gossipyii, is the vector for all tristeza isolates found in California; it does not, however, transmit
all isolates equally well. Symptoms of tristeza become more apparent during the hot summer months, when
increased water needs cannot be met by the declining root system. Changes in virus virulence may occur
over time and affect the current tolerance of many cultivars.
and dark forms of melon aphids