Bulletin 229, Diseases of Citrus in Florida


like areas. In localities where loose sand occurs, the young
foliage, especially of the spring growth, is often scarred by wind-
blown sand.
 Even after the fruits have attained considerable size, the
rind may become variously scratched, scarred, punctured, and
even gashed as a result of swinging against thorns. Hard, cal-
lused areas resulting from repeated thorn scratches or partial
punctures (Fig. 89) and injuries from the stubs of twigs and
small branches are familiar to every grower. These injuries
commonly pave the way for the development of the withertip
fungus and other decay-producing organisms. In years of un-
usually high winds these blemishes may result in the culling of
many thousands of boxes of fruit.
 Injury to the trees themselves, as a rule, results only from
unusually strong or prolonged winds. Even moderate winds,
however, especially in hot weather, may cause a pronounced
wilting of the foliage, since the rate of transpiration of water
in such cases exceeds the rate of its absorption. During periods
of high winds, the trees exposed to the direct action of the wind
may have more or less of the fruit, foliage, and young shoots
whipped off. In case considerable well-developed fruit is borne,
breakage of the branches commonly occurs, especially where
they have been weakened internally by the inroads of wood-bor-
ing insects and decay-producing fungi. In tropical hurricanes,
where winds of extremely high velocity continue for two days
or more at a time, the foliage, shoots, and fruit are whipped off,
the bark may be skinned from many of the twigs and smaller
branches, shallow-rooted trees may be blown over, and the
branches on the exposed sides, tops, or even on entire trees may
be killed outright by salt spray or by the pronounced desiccation
of the tissues resulting from the high winds alone (Fig. 90).
The defoliation of the trees on the side exposed to the storm robs
them of a considerable portion of their bearing wood, which re-
quires time and judicious care to renew. Moreover, the violent
swaying of the trees results in a severe injury to the root sys-
tems, many of the smaller woody roots and fibrous feeding root-
lets which are so necessary in sustaining the proper growth of
the tree, being broken and pulled loose. Thus, it is not surpris-
ing that large numbers of trees are killed outright following a
hurricane and that an even greater number lapse into a chronic
decline. The damage from wind injury is most extensive in ex-