Florida Agricultural Experiment Station


tion concerning the absolute cause of the disease is still far from
complete.
 DISTRIBUTION
 Dieback has long been known as a disease of citrus trees in
Florida. It was first reported by Fowler in 1875. (Florida,
its scenery, climate and history. Sydney Lanier, 1876. Appen-
dix, pp. 281-290.) It has probably been present in the State ever
since citrus trees have been grown under culture. It is not
known to affect trees growing in the wild.
 The disease is largely confined to trees growing on sandy
soils. While trees growing on clay soils are subject to it to some
extent, it often happens that the same soil treatments that induce
the disease in the trees on sandy soils fail to induce it in those on
clay soils. Consequently, the disease is not common in groves
planted on the heavier soils in the western part of the State, and
in other Gulf States.
 Altho the disease is probably most prevalent in Florida, it is
by no means confined here. It is found to a considerable extent
in California, and in many other parts of the world. It is re-
ported to be in Australia, the Philippines, Dutch Guinea, and
Italy. It probably exists to some extent in other countries, but
has not been recognized there as such.
 DISSEMINATION OF THE DISEASE
 Dieback seems to be neither infectious nor contagious. Ex-
 tensive experiments have been carried out to produce the disease
 by inoculation. The results have invariably been negative. Bud-
 ders in the nursery have been able to bud healthy trees with buds
 from dieback-affected trees. They state that the resultant growth
 showed dieback. It is very difficult to make such buds "take"
 on account of their lack of vitality.
 'The writer has repeatedly moved young trees that were se-
 verely affected with the disease, to new locations. The trees that
 lived showed no dieback, and made a normal growth.
 TREES SUSCEPTIBLE TO THE DISEASE
 Dieback affects practically all kinds and varieties of citrus
 that are grown commercially in Florida. It is a disease of the
 growing tissues and reaches its greatest development in the trees
 making rapid growth. Therefore, other conditions being equal,
 it is likely to be more prevalent in trees budded on stocks that
 give a rapid and rank growth. While it is somewhat more
 prevalent in trees budded on rough lemon stock, there is not