Florida growers are familiar with the
Citrus
tristeza
virus
(CTV)-induced decline of trees on sour
orange and bitter sweet rootstocks, a disease that is
continuing to destroy the remaining trees on
susceptible rootstocks in Florida. Growers are less
familiar with the stem pitting disease caused by
certain CTV isolates. Unlike decline, CTV-SP is not
a bud union disorder and can affect sensitive scion
varieties regardless of the rootstock used. CTV-SP is
a debilitating disease on grapefruit and sweet orange,
and may take years after infection before trees show
obvious loss of vigor and yield. However, once
infected the effect is continuous and long-term
economic effects to the grower may be worse than
those from other CTV declines. Trees if lost to
decline can be replaced by trees on tolerant rootstocks
and production is restored in a few years. Currently,
there are no CTV-SP tolerant grapefruit and sweet
orange. Once CTV-SP is endemic in an area, replants
will soon become infected and the debilitation cycle
is repeated. Mild and decline-inducing isolates of CTV are already widespread in Florida, but isolates
that induce CTV-SP in grapefruit and sweet orange
are relatively rare. However, CTV-SP isolates are
widespread in Asia, Australia, South Africa, Brazil,
Columbia, and other areas. Florida also has the
brown citrus aphid vector capable of transmitting
CTV-SP. There is clearly a potential for the
introduction and natural spread of CTV-SP in
Florida.