Florida Agricultural Experiment Station


fed. In such groves extreme dryness of the soil is to be avoided
as much as possible by regular cultivation or mulching. If irri-
gation is possible, the water supply can easily be controlled.
Great care should be exercised in choosing the amount of fer-
tilizer to apply following a long period of drouth. If the previous
application was not well washed into the soil by rains, only a
light application should be made. A formula somewhat low in
ammonia will be preferable. If heavy rains follow so that the
trees may later show the need of ammonia, the application can
be supplemented by an application of a readily available source
of ammonia.
 Spruce Pineland.-Dieback is very common in trees planted
 on the loose dry soils of spruce pinelands (fig. 2). Such soils are
 deficient in humus and become extremely dry at times. It re-
 quires much care to grow trees successfully on this type of land.
 The practice should be such as to build up these soils. Cultivation
 should be shallow and be made only where necessary to conserve
 moisture. The space around the trees should be heavily mulched.
 Plowing should be avoided as much as possible. Leguminous
 crops should be grown between the trees, cut, and worked into
 the soil in the fall or winter. If these crops do not grow well,
 an application of a ton or two of stable manure to the acre can
 be made to advantage. This should be applied and worked into
 the soil a short time before the legumes are planted. It will also
 be well to inoculate the seed of the legumes before planting. The
 fertilizer applied should be largely from mineral sources; small
 amounts from organic sources would probably not be harmful.

 CURATIVE METHODS
 The curative methods which are employed in the control of
citrus dieback consist in the use of bluestone or copper sulphate
in various ways. It may be spread on the soil, placed beneath
the bark, or sprayed onto the tree in the form of bordeaux mix-
ture. While these methods are effective under certain condi-
tions they are not known to be effective under all conditions.
Therefore, to be safe it will be well when using these to use also
the preventive methods which have already been discussed.
 Bluestone on Soil.-The most popular method has been to
apply bluestone to the soil. But the price of the chemical has
recently become so great that its use in this manner is almost
prohibited. By this method the crystals are spread over and
worked into the soil in the same manner as fertilizer. The usual