Bulletin 229, Diseases of Citrus in Florida 17

In many cases, spraying after the disease manifests itself is
only a waste of time and material. The fungicide must contain
a poisonous principle of sufficient strength to kill the spores of
the fungus to be combatted and, at the same time, not injure
the tender growth on which it is used.
 The preparation and use of fungicides requires care and judg-
ment, as the efficiency of any spray solution will depend upon
proper preparation and the manner and timeliness of its appli-
cation. The discouraging results sometimes obtained from the
use of reliable fungicides are usually due to a carelessness or
lack of timeliness in applying, or to their improper preparation.
It should be remembered that a fungicide is used for a specific
purpose, under certain limited conditions. It is not a "cure-all"
and should not be applied indiscriminately against any and all
diseases that appear in the grove. A better understanding of
fungicides in general, including their preparation, uses, and
limitations will aid materially in obtaining satisfactory results
in the control of diseases in the grove.
 The standard fungicides for the control of citrus diseases are
bordeaux mixture and lime-sulphur solution. The former has
proved decidedly more effective than the latter for the control
of most citrus diseases. Other materials are sometimes used
as fungicides, but they are usually employed in special cases
and have not been found satisfactory for general use. The dry,
or dust, fungicides have been found to be less effective than the
liquid ones.
 BORDEAUX MIXTURE AND BORDEAUX-OIL EMULSION
 Bordeaux mixture is the best known and most widely used
fungicide. It is made from copper sulphate (bluestone), either
fresh quicklime (lump or stone lime) or fresh hydrated lime,
and water in certain definite proportions. Bordeaux mixture made
according to the 3-3-50 formula is generally considered to be
of standard strength for the control of citrus diseases in Florida.
Such a formula indicates that the bordeaux mixture is pre-
pared in the proportion of 3 pounds of copper sulphate and 3
pounds of quicklime to 50 gallons of water. On account of the
fact that insects may increase greatly following the use of bor-
deaux mixture in a grove, it is recommended that 1 percent of
oil in the form of an emulsion be used with it. Hence, we call the
spray bordeaux-oil emulsion and write the formula as 3-3-50-1.