Bulletin 229, Diseases of Citrus in Florida


soil moisture conditions, locations, rootstocks, and kinds of citrus
trees that come under cultivation. In regard to tillage and the
use of fertilizers, a grove in one locality or on one kind of root-
stock may require a method of treatment quite different from a
grove in some other locality or on a different rootstock. The
method of handling any grove must be determined largely by
the rootstock and local conditions which influence its develop-
ment.
 It should be kept in mind that a citrus tree requires a certain
amount of attention regularly and that a generous amount of
suitable plant food is necessary for good growth and productiv-
ity. Applications of fertilizer should be made at timely inter-
vals and should be in proportion to the size and condition of the
trees and the crops they have borne or are capable of bearing.
Applications of fertilizer cannot be withheld any great length
of time in groves on the average sandy soil without causing the
trees to become greatly weakened and die back rapidly. This
is especially true if the trees have been previously stimulated
to vigorous growth and fruit production.-
 The care of the grove, however, is not limited to a few cultural
operations each season or to the application of a certain amount
of fertilizer. Other factors of equal importance are the control
of diseases and insects which may attack and lower the grade
of the fruit or cause it to rot before it reaches the market. The
diseases of citrus trees that are caused by fungi and bacteria
are influenced to a large extent in their spread and development
by moisture and temperature. As a rule, they require warm,
moist conditions for their rapid development. Thus, groves lo-
cated in low, shady situations, especially where the trees are
closely crowded, will afford very favorable conditions for the de-
velopment and spread of a number of diseases. In such cases
the disease situation frequently can be greatly improved merely
by thinning out the trees to let in the sunlight and give better
aeration. However, by no means all of the tree and fruit troubles
are caused by fungi or bacteria, insect pests, or meteorological
conditions. Certain factors of site, including moisture-holding
capacity and soil reaction, and cultivation, fertilization, and other
grove practices are often responsible for the development of a
number of complex nutritional disorders of citrus trees, for
which it is difficult to diagnose the cause and to prescribe a
specific remedy.