Florida Agricultural Experiment Station


This requires extra spraying with insecticides to control the
insects, thus adding greatly to the necessary labor and expense
of disease control. The situation is further complicated by the
fact that oil emulsions often result in "shadowing" or burning
of the fruit and, if used too freely, exert certain injurious effects
upon the trees and delay the coloring and ripening of the fruit.
In spite of these drawbacks, however, a certain amount of spray-
ing will be necessary for proper disease control and the sooner
the citrus grower realizes this and plans to take care of this
work in a systematic manner the less trouble he will have with
diseases, especially those affecting the fruit and foliage.
 The number and frequency of spray applications will vary ac-
cording to the disease, growth conditions of the tree, and cli-
matic conditions. The efficiency of a single spray application may
not extend beyond from 10 to 14 days, even without rainfall,
since, where a rapid growth occurs, considerable new and un-
protected shoots may develop in a few days. To achieve the
best results, the fungicides should be applied often enough to
give complete protection to all exposed surfaces of susceptible
tissues throughout the entire period during which the parts
are liable to infection by the spores of the fungus in question.
 The spray should be applied in the form of a fine mist. This
gives a more uniform distribution of the liquid, resulting in a
thin film which covers the surface of the parts to be protected.
If the spray is supplied with a coarse mist it tends to collect in
drops and run off, resulting in a loss of material, an incomplete
covering of the surfaces and the likelihood of burning at the
places where the spray material is concentrated. A good power
sprayer should be provided, preferably one that will maintain
a pressure of from 250 to 300 pounds. The sprayer should be
properly cleaned after use and should be overhauled from time
to time to maintain it in proper working order.

 FUNGICIDES AND THEIR PREPARATION
 A fungicide is generally used as a preventive and, in order
to be effective, must be applied at the proper time, which is
usually before the disease is visible. A fungicide merely forms
a protective film on the surface of the susceptible parts and it
must be applied before the spores of the disease-producing fungi
have lodged on the surface or, if they have already lodged on
susceptible parts, before they germinate and infect the tissues.