For two decades The Citrus Industry,
published in two volumes, has been the standard reference work on the
biology and culture of citrus throughout the world. It was
one of the first works to deal comprehensively with a single crop, and
it has had an enormous impact on the technology of citrus production.
The first volume, History, Botany, and Breeding,
edited by H. J. Webber and L. D. Batchelor, was published by the
University of California Press in 1943. The supply was soon
exhausted and a second printing of that initial volume was published in
1946, followed by a third printing in 1948. A larger
printing of the second volume, Production of the Crop, edited by
L. D. Batchelor and H. J. Webber, was published in 1948 by the
University of California Press. Thus, as this is written,
the information in the original volumes is somewhere between twenty and
twenty-five years old, if one allows about two years for review,
revision, editing, and printing.
During the past twenty-five years, the
production of citrus in the United States has almost doubled (there are
now more citrus trees in this country than all other fruit trees
combined). Similar expansions in citrus production have
taken place in many of the other principal citrus-growing countries of
the world. During this period, a parallel increase has
occurred in the tempo of citrus research. In the United
States and some other countries, the two decades following World War II
were years of unprecedented expansion of the support for scientific
research and development in general. The forces of
increased production and accelerated research have greatly stimulated
not only the development of new citrus technology, but also the harvest
of new, basic, scientific knowledge.
Many sections of the original volumes of The Citrus Industry
have been rendered obsolete. Some new areas of basic
knowledge and technology have arisen that were merely touched upon, or
not even considered in the original volumes. Thus, by the
time that supplies of the original volumes became exhausted (about
1961), it was clear that a substantial revision and expansion was
required, rather than further printings of unrevised
editions. Yielding to pressures from Dean A. M. Boyce and
other colleagues, I agreed to serve as editor for a new, revised
edition. Accordingly, Citrus Research Center and
Agricultural Experiment Station Project 2015 was initiated July 21, 1961
for "Revision of the publications, The Citrus Industry, Volumes I and II."
Material covered in the original Volume I
has been expanded to such an extent that it was necessary to divide it
into two volumes. Thus, distribution, botany, and
varieties. Revised Volume II will encompass morphology and
anatomy, physiology, climatic influences, mineral nutrition, genetics,
breeding, and seed reproduction. Volume III will deal with
the technology of citrus culture. It will include sections
on rootstocks, fertilization, leaf analysis, soil management, planning
and planting an orchard, propagation, pruning, thinning, girdling, plant
growth regulators, frost protection, irrigation, and chemical weed
control. Volume IV of this new edition of The Citrus Industry
will cover pests and diseases of citrus. This final volume
will include sections on the biology and control of seedbed, nursery,
and orchard diseases, virus diseases, post-harvest diseases, chewing
insects, mites, scales, thrips, aphids, snails, nematodes, and
rodents. Other chapters will deal with the replant problem,
biological control of insects, budwood certification, and quarantine
problems.
This is a University of California
publication, and most of the senior authors of chapters in this
four-volume series are members of the staff of the University of
California. The majority are closely affiliated with the
Citrus Research Center and Agricultural Experiment Station at
Riverside. The general outlook and treatment of subject
matter in some chapters for this reason tends inevitably at times to
reflect a somewhat regional outlook.
However, increased published information
from other areas of the world and improved transportation and
communications have provided the authors with a broader base of
information and experience than was available to the contributors to the
original volumes. A special effort was also made to expand
coverage of the technology of citrus production by stimulating authors
to visit other important producing areas and, in a few cases, to
collaborate with key colleagues affiliated with the U. S. Department of
Agriculture or the University of Florida. In the technology
sections, an effort was made to focus on basic principles underlying
practices and to devote less emphasis to details of current practices,
which rapidly become outdated anyway.
In preparing some of the topics included
in the original volumes, authors were requested either to revised
material or rewrite completely, depending on the extent of development
of knowledge and technology in the areas since the previous
publications. Most of the chapters in the four volumes of
this new edition have been completely rewritten. A few of
the chapters in Volumes I and II, however, have been revised, reflecting
areas in which advances have been less rapid in the past two decades.
On some subjects, where it was obvious
that considerable advances had taken place, topics previously covered in
one chapter were subdivided into two or more chapters to provide better
coverage and, in a few instances, to take advantage of the special
competence of certain authors. Relatively new areas of
technology, judged to be worthy of separate new chapters, were assigned
to the most competent authorities available. All authors
were requested to prepare a comprehensive review, evaluation, and
synthesis of knowledge on their assigned subject with the objective of
providing a reference work useful not only to their colleagues in the
research and teaching fields, but also to students, technical advisors,
intelligent growers, and others having an interest in the citrus
industry.
The four chapters in this first revised
volume are all concerned with topics covered in Volume I of the original
publication. It seems appropriate to mention briefly some
of the major changes or revisions in the material presented here.
In Chapter 1, which deals with the
history of citrus culture, minor inaccuracies have been corrected that
were brought to light by recent research. The scholarly
findings of Tolkowsky, Isaac, Andrews, and others, bearing on the dates
and routes of introduction of the various citrus species to the
Mediterranean and elsewhere, have been integrated into the
text. Brief sections on the early history of citrus
research and on recent developments in the citrus industry have been
added.
At the time H. J. Webber prepared his
original chapter, "The Commercial Citrus Regions of the World,"
statistical and other information on citrus culture was quite limited in
all but a few of the citrus-growing countries. The much
extended treatment in Chapter 2 by J. Henry Burke provides information
on many of the smaller but significant citrus-growing
countries. This improved coverage was made possible by
better statistical reporting, reinforced by Burke’s first-hand surveys
in most of the citrus areas of the free world during the period from
1948 to 1965.
The material presented in Chapter 3, "The
Botany of Citrus and Its Wild Relatives of the Orange Subfamily," has
been reprinted without major revisions. In reviewing it, P.
C. Reece added some material from pertinent recent references although
some recent progress or otherwise inconclusive reports were
omitted. The discussion on the Citrus species
concept was strengthened in the light of modern theories.
Reece also added a very useful detailed tabular comparison of the major
systems of classification within the genus Citrus.
However, W. T. Swingle's original taxonomic system remains intact,
reflecting in part the lack of support for this important area of
research in the past two decades. Editorial changes
included the correction of extensive bibliographical omissions, the
addition of improved or new illustrations, modernization of the
synonymy, and incorporation as far as possible of the recommendations of
the 1956 International Code of Botanical Nomenclature and the 1961 International Code of Nomenclature for Cultivated Plants.
The scope of treatment of the "Cultivated
Varieties of Citrus" considered in H. J. Webber's original chapter has
been greatly expanded by R. W. Hodgson in his completely new Chapter 4,
"Horticultural Varieties of Citrus." A far more
comprehensive coverage was attempted of both the commercial varieties
grown in the United States and of those grown in the major citrus
producing countries around the world. Thus, descriptions of
about 350 citrus varieties are included in Hodgson's treatment, while
Webber described only about 200 varieties. In addition,
Hodgson has given more emphasis to the horticultural characteristics of
varieties.
The system of taxonomic classification
followed by R. W. Hodgson is that of T. Tanaka rather than that
presented by W. T. Swingle in Chapter 3. The Tanaka system
is based largely on a pragmatic, utilitarian viewpoint, while Swingle
attempts to base his system primarily on genetic
relationships. Both viewpoints have validity, considering
the present status of knowledge on this problem. Thus, no
attempt is made to reconcile these divergent viewpoints in this
volume. Indeed, they reflect the current situation in
citrus literature. Hopefully, future research will provide
greater insight into the species problem in citrus and ultimately a
generally accepted system of classification will evolve.
I am greatly indebted to the revising
authors of the chapters in this volume for their wholehearted
cooperation and forbearance throughout the always time-consuming and
often tedious or even downright exasperating process of progressing from
the first submitted draft through numerous reviews, revisions, "final"
editings, and proofings. All who were consulted in the
review and editing of the manuscripts or who contributed in other ways
cannot be mentioned here: the list would be long and
incomplete. However, I would be remiss if I did not list
those who graciously submitted to unreasonable demands on their time and
patience in assisting with the preparation of this first volume for
publication.
Those who were most generous and helpful
in reviewing parts of the text dealing with their particular specialties
and fields of research include: Willard P. Bitters, James W. Cameron,
John B. Carpenter, William C. Cooper, Joseph R. Furr, Robert G. Platt,
Herman J. Reitz, and Robert K. Soost. A number of persons
assisted greatly in solving technical problems, often providing specific
data and information that was extremely useful. These
consultants include: Mildred E. Mathias, Edmond C. Calavan, Glenn E.
Carman, Homer D. Chapman, Harold J. Compere, Robert H. Hilgeman, Leo J.
Klotz, L. Carl Knorr, Edward O. Olson, Rainer W. Scora, O. T. Van
Niekerk, Frank C. Vasek, Harold F. Yates, and Ralph T. Brown.
I wish to express my thanks for the
efficient and tireless assistance given by Kathryn Forrest and the staff
of the Agricultural Library, Citrus Research Center and Agricultural
Experiment Station, and to Roy L. Kidman and the staff of the Library of
the University of California at Riverside.
Photographs of H. J. Webber and W. T.
Swingle for the dedicatory pages were furnished by Fera Webber Shear and
Maude K. Swingle, who were also helpful in supplying biographical
material on these two pioneers of the citrus industry.
Finally, gratitude is expressed for the
editing advice and assistance on publication problems given by William
W. Paul, manager of Agricultural Publications, and Lucy G. Lawrence of
his editing staff. Assistance in the preparation of
illustrations and in literature searches was given by Earl S. Morton.