Bulletin 229, Diseases of Citrus in Florida


 Where groves are subject to wind whipping along the coast a
strip of the natural hammock or other forest should be main-
tained for protection. In case groves are established where there
is no forest growth suitable for a windbreak, or where this
growth has been cleared off, it is advisable to plant a windbreak
of suitable trees. Such a planting should not be too close to the
groves, however, since the roots will compete with those of the
outer row of citrus trees for moisture and plant food. When
such competition threatens to become a factor in grove manage-
ment, a root ditch may be dug between the windbreak and the
grove.
 LIGHTNING INJURY
 Lightning is occasionally a destructive agency in citrus groves,
especially in the ridge section of the state, and may cause in-
juries to trees that may easily be mistaken for the effects of
some parasitic diseases.
 The amount of injury that results when lightning strikes in
a grove is quite variable. The injury may be confined to a single
tree or it may extend to a number of surrounding trees. The
injury may vary all the way from the sudden death of the tree
to partial destruction of patches of bark on a few twigs or
branches. A trunk struck by lightning usually shows a strip
of dead bark extending downward from some one of the larger
limbs to the ground. The discharge usually runs out on one side
of the lateral roots or, in some cases, it may spread around the
base of the tree, killing the bark at this point. The dead bark
is soon invaded by fungi and bacteria, which cause it to decay
rapidly. Trees that have been severely injured rarely recover.
In case the struck tree was not killed outright, however, the
foliage turns yellow within a few weeks and the top starts to die.
In groves where cabbage palmetto trees occur the lightning
sometimes strikes the top of a palmetto, killing the bud, skipping
down the trunk, tearing up the surface more or less, and then
jumping to a nearby citrus tree.
 The injury from a stroke of lightning, however, rarely is con-
fined to the struck tree but may also manifest itself in the death
of twigs and branches on surrounding trees. Young shoots and
twigs may be injured in a very peculiar manner, which is so
characteristic that no one familiar with lightning injury can
mistake the trouble. The striking feature of this injury is the
characteristic spots or blotches which develop on the surface