Bulletin 229, Diseases of Citrus in Florida


seems clearly evident that the disease can be spread by picking
crews and in pruning operations.
 CONTROL OF SCALY BARK
 Experiments by Fawcett and others have demonstrated that
scaly bark can be controlled and that fruit losses from nail-
head rust can be greatly diminished by a combination of pruning
and spraying. In some groves, pruning alone suffices. The
trees should be pruned of all dead wood and, as far as practicable,
of all badly diseased watersprouts and weakened branches be-
fore growth starts in the spring. This treatment alone will prove
beneficial in lessening the sources of infection. All prunings
should be burned and the tools used on the diseased trees should
be disinfected before they are used on trees free from the disease.
 After pruning, the trees should be given an application of bor-
deaux-oil emulsion early in February before they bloom. All
twigs and branches, as well as the main limbs, should be spray-
ed thoroughly, since the diseased spots are almost entirely lo-
cated on these parts. A second application of bordeaux-oil
emulsion should be made at some time between one and two
months after the bloom has shed. This treatment will suffice
for the control of scaly bark and nail-head rust under ordinary
conditions. Where the disease is exceptionally severe, however,
a third application of bordeaux-oil emulsion, made two months
after the second, will prove of value in protecting the fruit and
twigs against subsequent infections. In such case it may be ad-
visable to make one or two applications of bordeaux-oil emulsion
during the year following the treatment.
 WITHERTIP AND ANTHRACNOSE
 Caused by Colletotrichum gloeosporioides Penz. and
 Gloeosporium limetticolum Clausen
 Withertip and anthracnose have long been regarded as fre-
 quent sources of trouble in Florida citrus groves. Although
 most attention has been called to these diseases in Florida, es-
 pecially in the publication by Rolfs in 1904, the same troubles
 have been reported in nearly every citrus-growing country.
 Two forms of these diseases occur, namely, one which attacks
 the young growing tissues of the Key lime, and the more com-
 mon and widespread form which usually attacks only mature,
 weakened leaves, twigs, and fruit of oranges, lemons, grapefruit,
 and other citrus trees. The latter form of withertip may occur