Florida Agricultural Experiment Station


for their control. The more important diseases have been dis-
cussed and illustrated in greater detail than the minor ones,
although virtually all the diseases and injuries discussed have
been illustrated, that the grower may be able to identify them
readily. Technical expressions have been avoided as far as
possible.
 In the preparation of such a bulletin it is only possible to base
the discussion of the various diseases on the sum total of our
knowledge to date. It is expected that many of our present
views, especially those with respect to the physiological troubles
and our cultural and fertilizer practices, will be modified as ad-
ditional research work advances our knowledge. Unfortunately,
many diseases must be dismissed with but a brief general de-
scription and some must be omitted entirely for lack of definite
information covering them.
 Our knowledge of citrus diseases in general is decidedly less
well advanced than our knowledge of the diseases of deciduous
fruit trees. This is, in part at least, due to the fact that pro-
portionately less research work has been devoted to citrus dis-
eases since citrus-growing in the United States is confined to
but a very few favored sections and many of the problems are
peculiar to Florida. However, it is also largely due to the oc-
currence of a number of complex physiological or nutritional
troubles induced by certain soil conditions and cultural and fer-
tilizer practices and to our general lack of knowledge of the
physiology and nutrition of citrus trees, fertilizer requirements,
effect of different rootstocks, soil conditions under which the
different kinds of trees thrive best, and water requirements.
Many of these problems must be worked out individually for
Florida, and only when they have been solved are we likely to
arrive at a better understanding of the exact nature, cause and
control of a number of citrus diseases.
 ACKNOWLEDGMENTS
 In the preparation of this bulletin the writers have drawn
 upon all available sources of information and have made free
 use of the publications of this and other experiment stations, the
 U. S. Department of Agriculture, and Fawcett and Lee's book,
 "Citrus Diseases and Their Control". Much of the information on
 certain diseases treated in this bulletin, however, is the result
 of personal investigations and observations, some of which have