Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 345
Title: Seasonal occurrence of tomato diseases in Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00026425/00001
 Material Information
Title: Seasonal occurrence of tomato diseases in Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 36 p. : ill., map ; 23 cm.
Language: English
Creator: Weber, George F ( George Frederick ), b. 1894
Kelbert, D. G. A ( David G. A )
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1940
 Subjects
Subject: Tomatoes -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by George F. Weber and David G.A. Kelbert.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00026425
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000924576
oclc - 18229680
notis - AEN5203

Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida






Bulletin 345


/1/


June, 1940


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA


WILMON NEWELL, Director




SEASONAL OCCURRENCE OF

TOMATO DISEASES

IN FLORIDA

By GEORGE F. WEBER and DAVID G. A. KELBERT


Fig. 1.-Tomato seedbed showing preparation and planting, and the framework (right)
for supporting the protecting cloth. (See page 21.)

Single copies free to Florida residents upon application to
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA








n31. / EXECUTIVE STAFF
John J. Tigert, M.A., LL.D., President of
S, //1 the University3
S Wilmon Newell, D.Sc., Director3
Harold Mowry, M.S.A., Asst. Dir., Research
V. V. Bowman, M.S.A., Asst. to the Director
J. Francis Cooper, M.S.A., Editor2
Jefferson Thomas, Assistant Editors
Clyde Beale, A.B.J., Assistant Editors
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Manager8
K. H. Graham, Business Managers
Rachel McQuarrie, Accountants


MAIN STATION, GAINESVILLE

AGRONOMY
W. E. Stokes, M.S., Agronomist1
W. A. Leukel, Ph.D., Agronomist3
G. E. Ritchey, M.S., Associate2
Fred H. Hull, Ph.D., Associate
W. A. Carver, Ph.D., Associate
John P. Camp, M.S., Assistant
Roy E. Blaser, M.S., Assistant
ANIMAL INDUSTRY
A. L. Shealy, D.V.M., Animal Husbandman1 s
R. B. Becker, Ph.D., Dairy Husbandman3
W. M. Neal, Ph.D., Asso. in An. Nutrition
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarians
N. R. Mehrhof, M.Agr., Poultry Husbandman3
W. G. Kirk, Ph.D., Asso. An. Husbandmans
R. M. Crown, B.S.A., Asst. in An. Husb.S
P. T. Dix Arnold, M.S.A., Assistant Dairy
Husbandman3
L. L. Rusoff, M.S., Asst. in An. Nutritions
ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agricultural Economist' s
Bruce McKinley, A.B., B.S.A., Associate
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Assistant
ECONOMICS, HOME
Ouida Davis Abbott, Ph.D., Specialist'
Ruth Overstreet, R.N., Assistant
R. B. French, Ph.D., Associate Chemist

ENTOMOLOGY
J. R. Watson, A.M., Entomologist'
A. N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant

HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturist'
F. S. Lagasse, Ph.D., Horticulturist2
Harold M. Sell, Ph.D., Asso. Hort.2
A. L. Stahl, Ph.D., Associate
F. S. Jamison, Ph.D., Truck Horticulturists
R. J. Wilmot, M.S.A., Specialist, Fumigation
Research
R. D. Dickey, M.S.A., Assistant Horticulturist
J. Carlton Cain, B.S.A., Asst. Horticulturist
Victor F. Nettles, M.S.A., Asst. Hort.

PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist1
George F. Weber, Ph.D., Plant Pathologists
L. O. Gratz, Ph.D., Plant Pathologist
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Assistant Botanist

SOILS
R. V. Allison, Ph.D., Chemist' 3
Gaylord M. Volk, M.S., Chemist
F. B. Smith, Ph.D., Microbiologists
C. E. Bell, Ph.D., Associate Chemist
H. W. Winsor, B.S.A., Assistant Chemist
J. Russell Henderson, M.S.A., Associates
L. H. Rogers, M.S., Asso. Biochemist
Richard A. Carrigan, B.S., Asst. Chemist


\BOARD OF CONTROL
H. P. A'lair, Chairman, Jacksonville
W. M. P,almer, Ocala
Chas. P, Helenstein, Live Oak
R. H. Gore, Fort Lauderdale
N. B. Jordani, Quincy
J. T. Diamond, Secretary, Tallahassee

BRANCH STATIONS
NORTH FLORIDA STATION, QUINCY
J. D. Warner. M.S., Agronomist Acting in
Charge
R. R. Kincaid, Ph.D., Asso. Plant Pathologist
Elliott Whitehurst, B.S.A., Asst. An. Husb.
Jesse Reeves, Farm Superintendent
CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Horticulturist in Charge
John H. Jefferies, Superintendent
Michael Peech, Ph.D., Soils Chemist
L. H. Greathouse, Ph.D., Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Asso. Entomologist
F. F. Cowart, Ph.D., Asso. Horticulturist
W. W. Lawless, B.S., Asst. Horticulturist
R. K. Voorhees, M.S., Asst. Plant Path.
EVERGLADES STATION, BELLE GLADE
J. R. Neller, Ph.D., Biochemist in Charge
J. W. Wilson, Sc.D., Entomologist
F. D. Stevens, B.S., Sugarcane Agronomist
Thomas Bregger, Ph.D., Sugarcane
Physiologist
Frederick Boyd, Ph.D., Asst. Agronomist
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, B.S., Asst. An. Husbandman
W. T. Forsee, Ph.D., Asso. Chemist
B. S. Clayton, B.S.C.E., Drainage Engineers
F. S. Andrews, Ph.D., Asso. Truck Hort.
SUB-TROPICAL STATION, HOMESTEAD
W. M. Fifield, M.S., Horticulturist Acting in
Charge
S. J. Lynch, B.S.A., Asst. Horticulturist
Geo. D. Ruehle, Ph.D., Asso. Plant Pathologist
W. CENTRAL FLA. STA., BROOKSVILLE
W. F. Ward, M.S., Asst. An. Husbandman
in Charge2

FIELD STATIONS
Leesburg
M. N. Walker, Ph.D., Plant Pathologist in
Charge
K. W. Loucks, M.S., Asst. Plant Pathologist
Plant City
A. N. Brooks, Ph.D., Plant Pathologist
Cocoa
A. S. Rhoads, Ph.D., Plant Pathologist
Hastings
A. H. Eddins, Ph.D., Plant Pathologist
E. N. McCubbin, Ph.D., Asso. Truck Hort.
Monticello
Samuel O. Hill, B.S., Asst. Entomologist2
Bradenton
Jos. R. Beckenbach, Ph.D., Truck Horticul-
turist in Charge
David G. Kelbert, Asst. Plant Pathologist
Sanford
R. W. Ruprecht, Ph.D., Chemist in Charge,
Celery Investigations
W. B. Shippy, Ph.D., Asso. Plant Pathologist
Lakeland
E. S. Ellison, Meteorologist2
B. H. Moore, A.B., Asst. Meteorologist2
1Head of Department.
2In cooperation with U.S.D.A.
8Cooperative, other divisions, U. of F.








SEASONAL OCCURRENCE OF TOMATO DISEASES
IN FLORIDA

By GEORGE F. WEBER and DAVID G. A. KELBERT

CONTENTS
PAGE PAGE
LOSSES CAUSED BY DISEASES ..................... 4 Seed Disinfection ....................................... 20
EFFECT OF ENVIRONMENTAL FACTORS UPON Preparation of Seedbed .............................. 21
TOMATO DISEASES ........................... 5 Soil Disinfection ................................... 22
Growing Season ......................................... 5 Damping-Off -......................................... 23
Soi pes ... ..... Soil Preparation and Plant Setting ........ 23
oil T ........................................ 10 Fungicides and Their Application ......... 27
Section 1 ...................................... 10 Rotation ........... ........................... 29
Section 2 ... ........................................ 15 Fertilizers and Their Application .......... 31
Section 3 .................................................... 16 Cultivation .................................................... 82
SEASONAL DEVELOPMENT OF DISEASES ........ 19 Harvesting .................. ......................... 32
Selection of Seed .......................................... 19 Packing and Transportation .................... 34

INTRODUCTION
The Florida tomato-growing industry has been materially in-
fluenced by the following factors: (1) the major portion of the
crop is grown during the winter and early spring months; (2)
almost the entire crop is placed in interstate commerce; (3) the
larger part of it is consumed fresh; and, (4) certain diseases
which cause considerable losses do not occur or are of minor
importance in other states.
Such conditions as soil, temperature, humidity and length of
day are different from those under which a large part of the
crop is grown in other sections of the United States. Because
of this typically "out of season" period of development, the
plants may respond differently as to nature of growth as well
as flower production and fruit set. Under these conditions the
plants are attacked by numerous parasites and often suffer
considerably because the environment is as favorable for the
development of the parasite as for the host plant. Other factors
such as continuous cropping of fields to tomatoes, lack of low
temperatures which would kill many parasites and their host
plants, and the free interchange of plants among growers at
transplanting time have a pronounced effect upon the prevalence
and importance of certain diseases in the different localities.
Furthermore, the severity of some diseases has often been
materially increased by certain activities and operations asso-
ciated with the growing and handling of the crop.
It is the purpose of this bulletin to discuss the seasonal occur-
rence of diseases of tomatoes in relation to their culture and to
point out and recommend measures that may aid in reducing
the losses suffered by tomato growers in Florida.

/k7k/






Florida Agricultural Experiment Station


LOSSES CAUSED BY DISEASES
During the 10-year period 1929 to 1938 an average of between
30,000 and 31,000 acres was planted annually to tomatoes in
Florida, producing a yearly average of approximately 7,000 cars
of fresh fruit valued at approximately $7,100,000.1 During this
period diseases caused losses in the field and in transit amount-
ing to an average of 25 percent, or $1,775,000 per year. The
total loss is greater than these figures indicate because most of
the diseases occur in the field and cause the losses before the
fruit is harvested, or in addition to that portion of the crop
that is actually put in transit. During the decade 1917 to 1926
the loss to tomato growers of the state from a single disease,
nailhead spot (Fig. 2), averaged 30 percent of the crop each
year. During the period 1925 to 1930 another destructive disease
known as phoma rot, originating in the field but destroying fruit
in transit, caused a yearly loss of approximately 15 percent.




I^ ^ '. w .





A., 4






Fig. 2.-Nailbead-spot lesions of various ages found on tomato fruits in Florida.

When conditions are exceptionally favorable for the develop-
ment of the diseases in the field, or in transit, some growers may
lose thousands of dollars and their labor for the season.
During the early days of tomato growing in Florida very little
trouble was experienced from diseases other than those caused
directly by environmental factors, principally frosts and floods.
Importations of fertilizers, stable manure, compost and seeds

'Agricultural Economics Department, Agricultural Experiment Station,
Gainesville, Fla.






Seasonal Occurrence of Tomato Diseases in Florida


for planting increased as the acreage of tomatoes expanded in
each section, and new diseases began to make their appearance
from time to time.
A study of Experiment Station bulletins' will give an idea of
the difficulties which tomato growers experienced in combating
new diseases as they were introduced and became of economic
importance. Some of the diseases discussed in early publica-
tions have become negligible while others have become of eco-
nomic importance only within the past few years and are causing
growers heavy financial losses.

EFFECT OF ENVIRONMENTAL FACTORS UPON
TOMATO DISEASES
Growing Season.-Tomatoes are planted in Florida from July
to the middle of the following March, resulting in a harvest
season extending from November until May. During this period
Florida is the chief source of fresh tomatoes in the United States.
Thus, the growing season in this state shows almost the reverse
in temperature and length of day relations to those in other
states. This change may be responsible for low production or
other discrepancies often encountered but seldom understood.
The earliest plantings are made in the summer in the ocean-
tempered, tillable lands of the keys and coastal sections on the
mainland in the extreme southern part of the peninsula. The
earliest portion of this crop often encounters some competition
in the markets from the end of the Northern commercial crop
that may have escaped frost or that was in temporary storage.
These early plantings on the keys are exposed to intense sun-
shine, varied moisture conditions and numerous pests, all of
which contribute to low yields and poor quality.
As the season progresses plantings are made farther north
along the East Coast, in the Lake Okeechobee section and on
the West Coast during late winter. Finally the central ridge
areas from Arcadia to Lake City come to the front in develop-
ment in early spring. By this time early plantings in the extreme
South have long since ceased to produce and fields in the coastal
regions have been abandoned.
The comparative importance of diseases in the different sec-
tions appears to be influenced by the environmental conditions
prevailing while the crop is growing and by the cultural practices

'Florida Agricultural Experiment Station Bulletins 18, 21, 47, 91, 117,
139, 146, 185, 249, 308 and 332.







Florida Agricultural Experiment Station


employed. Some of the diseases occur wherever tomatoes are
grown in the state, although their economic importance varies
widely among the different sections. Others appear to be more
or less restricted to certain sections. Temperature and moisture
as seasonal variables rather than daily or weekly factors are
probably of first importance in disease occurrence. The tasks
of tomato growers, marketers and plant pathologists are materi-
ally increased because of the various diseases developing during
the different seasons in the different parts of the state.
Tomatoes are least commonly grown in Florida during the
summer when conditions are most unfavorable for their growth
and when they are most plentiful in other states.


Fig. 3.-Phoma rot of tomato, which developed in transit on fruits that were apparently
sound at packing time.
The conditions and care under which the crop is grown deter-
mine to some extent the kind of diseases which develop and the
amount of damage caused by them. Septoria blight (Septoria
lycopersici Speg.), one of the most destructive diseases of the
tomato in the United States, has occurred in only a few scattered
sections of the state during the past 15 years. On the other hand,
during the decade 1917 to 1926, nailhead spot (Alternaria to-
mato (Cke.) Weber), caused as much as $3,000,000 annual loss






Seasonal Occurrence of Tomato Diseases in Florida


in Florida, but has scarcely been reported north of the Potomac
and Ohio rivers. Phoma rot (Phoma destructive Plowr.) (Fig.
3) has caused thousands of dollars of damage annually to toma-
toes in the field and in transit, yet few of the other South Atlantic
and Gulf states have reported damage caused by it and it seldom
occurs in other tomato-growing sections.
Seed for fall plantings usually are sown in the seedbed in July
to September and the seedlings are transplanted to the field a
month or six weeks later, depending upon growing conditions.
At the time the early fall plantings are made there are numerous
surviving or volunteer tomato plants of all ages growing in
abandoned fields, about old cull piles and along roadsides, ditch
banks and packinghouses. These plants, growing out of cultiva-
tion as weeds, harbor almost without exception one or more of
the destructive diseases of tomatoes and serve as sources of infec-
tion for the plants under cultivation. Consequently, unless the
seedlings are sprayed properly, they will show more or less
disease at the time they are ready for transplanting. The im-
portant diseases on the seedling at that time are early blight
(Alternaria solani (E. & M.) J. & G.) (Fig. 12), phoma spot,
and gray spot (Stemphylium solani Weber) (Fig. 4). They are
most destructive, however, during December and January.
Early blight usually occurs whenever and wherever tomatoes are

Fig. 4.-Tomato plants severely infected with gray spot in seedbed. Since such plants
cannot be used, the bed should be destroyed.







Florida Agricultural Experiment Station


Fig. 5.-Buckeye rot of tomato fruits. This disease is usually found in wet portions of
fields or where the fruits contact the soil.


I"'


Fig. 6.-Soil rot of tomato fruits, originating in the field.

grown in the state, but its importance depends upon moisture and
temperature conditions.
In the southern area many destructive diseases appear in the
felds from January to March. Their advent and rapid spread
are favored by the presence of volunteer plants, large fields that
are adjacent to each other, vigorous vegetative growth of the
plants, high humidity near the soil surface and the frequent
passing of workers, animals and machinery in the cultural opera-
tions. These factors are especially important in the distribution
and destructiveness of certain diseases, such as buckeye rot
(Phytophthora terrestrial Sherb.) (Fig. 5), soil rot (Corticium
vagum B. & C.) (Fig. 6), late blight (Phytophthora infestans


*- <,I






Seasonal Occurrence of Tomato Diseases in Florida


(Mont.) DeBy.) (Fig. 8), and phoma rot. These parasites grow
well at relatively cool temperatures and become especially de-
structive with abundant moisture. The height of the harvest
season continues through March, April, and possibly early May,
depending primarily on the prevalence of diseases, market con-
ditions and rainfall. Fields of tomatoes maturing during these
months usually are planted during January and February.
When the early crop is being harvested it is probable that certain
diseases are transmitted from the older to younger plantings.
In any event the disease problem of the Florida tomato grower
usually becomes more and more acute as the season advances.
At the close of the season in southern Florida tomatoes in
other sections of the state are in various stages of development.
The central East Coast and Gulf Coast sections are at the peak of
production or slightly past, while the more northern sections are
about to begin their picking season. The diseases encountered
in these various sections are somewhat similar, although in each
section certain troubles are more common and destructive than
in any of the others. For instance, Dade County plantings are
more subject to losses caused by phoma rot, late blight, buckeye
rot and soil rot, although early blight has been common. The
east central section suffers primarily from early blight, while the
Gulf Coast areas most often suffer more severely from mosaic,
gray spot, leaf mold (Cladosporium fulvum Cke.) (Fig. 9),
Bacterial spot (Bacterium vesicatorium Doidge) (Fig. 10), and
blossom-end rot. These diseases are aided materially by high
humidity and temperature of that section and by certain cultural
practices. The more northern sections suffer losses to a certain
extent from some of the diseases already mentioned but not so
much as from brown rot (Bacterium solanacearum E. F. S.)
which is seldom found doing damage in the other tomato-produc-
ing areas. Wilt (Fusarium lycopersici Sacc.) is widely dis-
tributed in the state but causes damage only occasionally in the
South Dade County areas. It becomes increasingly important
in sections farther north, culminating in the greatest losses in
northern areas during early summer. This is probably because
of the prevailing higher temperatures during the growing season
that are more favorable for the fungus. Southern blight
(Sclerotium rolfsii Sacc.) (Fig. 11) also is more common in
this area. It is well distributed in the interior and northern
areas and is particularly destructive with the advent of summer
temperatures ranging between 700 and 95 F. It is frequently






Florida Agricultural Experiment Station


found in the central coastal regions, but seldom in the extreme
southern portion. Blossom-end rot, a non-parasitic disease, is
found most commonly in this part of the tomato belt, especially
on sandy lands. Temperature and moisture are again probably
the governing factors. Thirsty soils require abundant moisture
to meet the requirements of the plants and when this is not con-
tinuously available blossom-end rot appears. This disease oc-
casionally becomes destructive in the Gulf Coast regions, where
the water content of the soil is variable, but seldom if ever causes
any losses in the more southerly counties where the crops are
grown during earlier, cooler months of the year and where
fluctuations in soil moisture are not so great.
Soil Types.-Tomatoes are grown on a great variety of soils in
Florida. No type exists in any large part of the state to the
exclusion of any other kind of soil. Consequently, there are
several different kinds of soil in almost any sizeable area adapted
to tomato production.
Instead of considering the soil types as such in each locality,
the state has been divided into three sections based upon the
more important factors within each section such as soil, climate,
natural vegetation, tomato culture and diseases. These divisions
are shown graphically in Figure 7. Characteristic details con-
cerning each of these sections are as follows:
Section 1.-A small part of the earliest crop found in Section 1
in southern Florida is planted on soil consisting of meager
amounts of sand and humus scattered among outcroppings of
rock locally known as the pinelands. The pinelands are not
normally flooded in the rainy seasons as are most other soils in
that area. The fields are prepared by clearing away the native
vegetation and scarifying the rocky surface with special imple-
ments. Tomato plants are set in the scantily accumulated loose
soil and rock particles. The annual acreage of pineland tomatoes
is comparatively small and is mentioned here only because of the
particular importance of such plantings in relation to the early
crop. The plants show principally such diseases as phoma spot,
early blight and other foliage and fruit diseases that are common
on tomatoes everywhere in Florida. Most of the tomatoes in this
section are planted on the bog soils, muck, peat, marl and their
combinations. The most extensive muck areas include a large
portion of the Everglades, especially from the north end of Lake
Okeechobee to the south end of the mainland, which area includes
all or parts of Dade, Collier, Broward, Palm Beach and Martin







Seasonal Occurrence of Tomato Diseases in Florida 11

counties. A large percentage of the marl lands of Dade and
Collier counties is adapted to tomato growing. These lands are
usually wet and often flooded a portion of the year. These soils
are gray to brown in color and high in organic matter and usually
cover a subsoil of variously colored sands, calcareous and clay


Fig. 7.-The tomato growing regions of Florida can be divided into three more or less
arbitrary sections, based partially on soil type, planting season and predominating diseases
found in each.







Florida Agricultural Experiment Station


mixtures or rock. The principal types of soil included are of the
Dade, Perrine and Rockdale series and tidal marshlands3. With
few exceptions most of the tomatoes planted on these lands are
grown during the mid-winter period when temperatures are rela-
tively low, rainfall is scanty and the water table is usually high
because of the preceding rainy season. The marl soils are sticky
and gumbo-like when they are wet and, consequently, offer the
most resistance possible to any kind of cultivation although they
work up well when of the proper moisture content. The muck-
peat soils which burn freely are highly organic, of peat-like con-
sistencies, often flooded and are increasingly productive under
cultivation, responding rapidly to corrective measures such as the
application of certain deficient salts and fertilizers and to aera-
tion. They predominate in the Everglades and are divided into
three kinds: The first is usually grown over predominantly with
custard-apple (Annona glabra L.) and is known as custard-apple
land; the second is known as the elderberry land because the
growth upon it is preponderantly elderberry (Sambucus simp-
sonii Reh.); and the third, comprising the larger portion of the




A,







-.3-


p..- rak


Fig. 8.-Mahogany rot of tomato caused by Phytophthora infestans.
stems this disease is usually called late blight.


On the foliage and


"Henderson, J. R. The Soils of Florida. Exp. Sta. Bul. 334. 1939.








Seasonal Occurrence of Tomato Diseases in Florida


'4


Fig. 9.-Leaf mold of tomato leaves occurs most often on the north side of rows running
east and west in the field.


_7: ~1
~
;~
-~Ba IBi
t ;---. ~-~


Fig. 10.-Tomato fruits affected with bacterial spot. This disease usually originates in
injuries caused by blowing sand.






Florida Agricultural Experiment Station


Fij. 11.-Southern blight of tomatoes showing decay and sclerotia of the fungus.
Everglades millet, barnyard and other grasses, smartweed, care-
(Mariscus jamaicensis (Crantz) Britton) predominates.
The virgin vegetation, exclusive of the pinelands of Section
1, in the Everglades area on muck and marl consists almost en-
tirely of saw-grass. In those regions that border on tidewater,
mangrove thickets appear. Other scattered groups, made up
principally of scrub and cabbage palmettos, oaks, willows,
sedges, grasses and vines of various sorts, appear as islands in
the saw-grass expanse.
After cultivation these soils become profusely and densely
populated with an entirely different vegetation consisting of
everglades millet, barnyard and other grasses, smartweed, care-
less weed, ragweed, nightshade, evening primrose, goldenrod,
moon and morning glory vines, beggarticks and fennel, willow,
elderberry, myrtle and saltbush.
These soils frequently contain certain amounts of sand,
although they are always gray-brown or black in color, light
in weight when dry and spongy when wet. Soils of this group,
while showing no particular influence on the parasitic diseases of
tomatoes that manifest themselves on aerial parts of the plant,
unquestionably favor those diseases caused by soil-inhabiting
parasites which attack the plants during cool growing periods.
This is particularly true with the soil rot fungus, which appears
in all soils of this class. This parasite kills the small roots of
the young plants, girdles the main stem of older plants, causes
lesions on the stems and branches and spots on the foliage and






Seasonal Occurrence of Tomato Diseases in Florida


fruit whenever they come in contact with the soil. Fruits bear-
ing unobserved, incipient infections may be packed for shipment
and there they infect the sound fruit with which they are in
contact. Buckeye rot is another disease appearing on this class
of soils that affects the host plant in very much the same way as
soil rot. It affects the fruit more often than does soil rot but
generally is not so common nor so severe on the vines. Several
other destructive diseases such as phoma rot, late blight and early
blight are common in plantings on this class of soils, primarily
because of greater humidity.
Section 2.- This sec-
tion consists of most of
the East Coast and about
a third of the West Coast
vegetable growing areas.
The interior portion is
not so extensive but is
sufficient to connect the
coastal regions, forming
an irregular band across
the state. Tomato grow-
ing in this section is sec-
ond early, since produc-
tion peaks are reached a
month or six weeks later
than the height of pro-
duction in Section 1.
Daily temperatures are
higher and increasing in
contrast to the more or
less constant tempera-
tures found during the
growing season in south-
ern Florida.
Natural vegetation on
the lands in this section
is almost entirely pine,
scrub oak and cabbage
palmetto interspersed
with cypress swamps, Fig. 12.-Early blight lesions on tomato leaf.
patches of gallberries, wild legumes, vines and grasses of
various kinds. Following clearing and cultivating, weeds and






Florida Agricultural Experiment Station


vegetation appearing in the fields are quite similar to those of
Section 1, although usually not so rank. All of Section 2, except
the protected coastal areas, is in the frost belt where light to
occasional killing frosts can be expected each year during
December and early January. Soils in this section are predomi-
nantly flatwoods with variations overlapping somewhat the
groups on either side, but generally showing a subsoil of calcare-
ous clays and hardpan. They vary considerably between sand and
marl and the color ranges from grayish-white to brown and black.
They include such series as Parkwood, Portsmouth, Bladen, Leon
and Plummer. These soils include almost all of the central
coastal regions of Section 2, typified by St. Lucie County on the
East Coast and Manatee County, with certain mucky hammocks
excepted, on the West Coast and the interior areas between them.
Several common and destructive diseases of tomatoes are found
in Section 2. Southern blight is often found here, while its oc-
currence on the marl soils is rare. Mosaic also appears to be more
widespread and causes greater losses in this section. Bacterial
spot is definitely associated with the sandy soils of this section.
Early planted staked fields suffer from this disease following days
of wind-blown sand. This trouble is not encountered on the marl
and appears only occasionally on young plants on dry sandy
muck. Gray spot was originally discovered in this section and
still remains more common and destructive along the coastal
regions than elsewhere.
Section 3.-The remainder of the state is in Section 3, which
is third earliest in production. The beginning of the picking
season overlaps the end of the season in Section 2, so that there
is rather a gradual shifting northward of the harvest rather
than an abrupt change. Cultural practices are different from
those in other sections, primarily because environmental condi-
tions are different. The native vegetation in this section is some-
what similar to that of Section 2. The undergrowth is not dense
except in isolated places and frequently consists of barren soil
or a scanty covering of vines, sedges and grasses and various
plants well adapted to growing in deep sand. Most of the tillable
land has been cultivated at one time or another. The soils are
different generally from those found in either Section 1 or 2,
although not readily differentiated from certain groups of soils
in Section 2. There may be overlapping of different soil types in






Seasonal Occurrence of Tomato Diseases in Florida 17

any one field. The soils are typically sandy, rolling, drought
and light colored, and include such representative series as the
Norfolk, Hoffman, and Orlando. These lands are characterized
by the extensive farming regions of Sumter, Lake, and Marion
counties.


-7i-


Fig. 13.-Tomato plants affected with brown rot, showing typical wilting symptoms.

Tomatoes are planted in Section 3 from the middle of Febru-
ary to the middle of March, depending upon the latitude and
when the last killing frost may be expected. Thus, the crop
develops and matures through April and May and up to the
middle of June. This period is one of scanty rainfall in Florida
and also one of almost summer temperatures. This peculiar
situation is definitely reflected in the occurrence of certain de-
structive diseases of tomatoes that are found only under these
conditions and most often on this group of soils. Brown rot
(Bacterium solanacearum E. F. S.) (Fig. 13), is found on this
class of soils almost without exception and while Fusarium wilt
(Fusarium bulbigenum (C. & M.) v. lycopersici (B.) W. & R.)






Florida Agricultural Experiment Station


(Fig. 14) causes the largest part of its damage in these areas, it
is encountered frequently in fields included in Section 2. Most
of these diseases are vascular in nature, systemic and produce
wilting symptoms in tomato plants. The extent of wilting varies
somewhat with rainfall and humidity, becoming more destructive
with a combination of thirsty soil, scanty rainfall and high
temperatures. Parasites causing these diseases are more or less
generally distributed throughout the area and survive for a
iiumber of years in the soil, affecting tomato plantings year after
year. Blossom-end rot (Fig. 15), a non-parasitic disease pro-
duced by alternating wet and dry periods during the growth
of the plants, is characteristic of this class of soils. Usually
during hot, dry periods it shows on the fruits as the collapse of
the tissue at the blossom-end of the fruit. This disease usually is
found in fields that show each or both of the wilt diseases
characteristic of Section 3. Blossom-end rot has occasionally
been found on soils in Section 2, but is extremely rare on the so-
called heavier soils of Section 1.
Summarizing, the tomato producing areas of the state can be
more or less definitely divided into three sections, each section

Fig. 14.-Poor stand of tomatoes resulting from planting on Fusarium-sick soil.






Seasonal Occurrence of Tomato Diseases in Florida


being characterized by
differences in natural
vegetation, seasonal de-
velopment of the crop,
soil types, cultural meth-
ods and prevalent dis-
eases. Parasites favored
by the soils and ac-
companying conditions in
Section 1 are different
from those found in Sec-
tion 3. These diseases
are considered "natural",
since they occur year
after year on these re-
spective soils. They will
increase in range from
year to year if tomatoes
are grown where they oc- Fig. 15.-Blossom-end rot of tomatoes resulting from
cur or e ll reman unbalanced water supply and nutrition.
cur or they will remain
more or less dormant during rotation or absence of the host
plant.

SEASONAL DEVELOPMENT OF DISEASES
Selection of Seed.-Cultural practices followed in producing
a tomato crop in Florida have been quite variable since the be-
ginning of the industry. In some places the methods are still
almost primitive, while in other areas modern methods are
practiced.
The selection of disease-resistant varieties as well as those
adapted to Florida conditions are important items to consider in
relation to successful production. Certain varieties grow and
produce well in Florida while certain others that are favored in
other parts of the United States usually are light yielders, pro-
duce fruits unsuited for the markets or are susceptible to disease.
Low grade seed or seed impure for strain very often are re-
sponsible for poor plants, low yields and a poor grade of irregular
and mal-formed fruits. It is safer to select varieties that have
been tried and proved desirable rather than plunge deeply with
some new introduction that has not been tested thoroughly. If
one wishes to try new varieties, trials should be made at first
on a small acreage where careful and frequent observation can






Florida Agricultural Experiment Station


be made and if the planting should be a failure the loss cannot be
great.
Vigor and percentage of germination vary with different lots
of seed, with different storage conditions and extent of mold
present and, consequently, cannot be guaranteed, although
specific percent germination and date is available. Seed ob-
tained from a single fruit are usually genetically alike, whereas
seed from different fruits from a single plant may not be genetic-
ally alike, although the possibilities for their being so are very
great. The seed contained in the fruit of the first hand or cluster
are no more apt to be pure for strain than seed contained in fruit
of the fourth or fifth cluster. There may be more vigor in the
seed produced early than late because of better growing condi-
tions for the plant. Large fruits might produce stronger (not
necessarily larger) seed in contrast to possibly fewer and more
shriveled seed produced in stunted, small, weak fruits. Under
average conditions the seed from a single plant will breed true
to the parental type since tomato flowers are about 98% self-
pollinated. Tomato seed should be stored in a cool, dry place
in containers to prevent mixing of different varieties or strains
and to prevent destruction by rodents, insects or fungi.
Seed Disinfection.-Tomato seed should always be disinfected
before they are planted. This is an inexpensive precautionary
measure which may prevent considerable loss of seed and seed-
lings from certain parasites carried on the seed. The disinfec-
tion will kill parasitic organisms and spores that may adhere
to the outside of the seed coat. Phoma rot, anthracnose
(Colletotrichum phomoides (Sacc.) Chest.) (Fig. 16), and bac-
terial spot are the most common diseases that may be prevented
by this treatment. Nailhead spot and late blight also may be
partially controlled by seed treatment. Fusarium wilt may be
seed-transmitted but seed purchased from reliable dealers should
insure its absence. The seed to be treated should be soaked for
six to eight minutes in a 1:1,000 solution of corrosive sublimate;
or soaked one hour in a copper sulfate solution prepared by dis-
solving one pound of bluestone in eight gallons of water; or
soaked in a normal organic mercury solution. Following soaking,
wash the seed in several changes of fresh water and spread on
cheesecloth or newspapers in the shade to dry. The seed may be
treated also with dust disinfectants such as zinc oxide, mercury
compounds and red oxide of copper at the rate of 1 to 2 ounces
of the dust to 10 pounds of seed. Forms of organic mercury are





Seasonal Occurrence of Tomato Diseases in Florida


Cr ~


Fig. 16.-Tomato fruit showing anthraenose lesions which originated in
the field but continued to develop in transit.
sold under commercial names and full directions are supplied.
Use wood or crock containers for solutions and when using dusts
place the seed to be treated with the dust in a container, such as
a glass fruit jar for small amounts or a revolving barrel such as
a barrel-churn for large quantities, and revolve the container
slowly until the contents are thoroughly mixed. Detailed in-
formation may be obtained from Press Bulletin 494 or from the
Agricultural Experiment Station.
Preparation of Seedbed.-Careful consideration should be
given to the selection of the site for the seedbed. The danger
from soil-inhabiting parasites is at a minimum on virgin land.
Some growers plant the seed in soils under cultivation, but never
previously planted to tomatoes, while others plant the seed in
the same seedbeds year after year, after taking precautions, in-
cluding soil disinfection, necessary to prevent the appearance of
any of the destructive tomato diseases.
The first consideration for the selection of a site for a seed-
bed is the size of the area, Fig. 1. Enough land should be avail-


Vo
tm% -






Florida Agricultural Experiment Station


able to accommodate properly the required number of seedlings to
plant the desired acreage. There are approximately 160,000 to
170,000 tomato seeds per pound and with 50 percent germination
this will usually insure a sufficient number of large normal plants
to plant 10 acres, since about 7,300 plants are required per acre
when the plants are set one and one-half feet apart in four-foot
rows. It is always advisable to have an excess of disease-free
plants on hand at setting time. The seed should be scattered
in the rows in the seedbed, so that the seedlings will not be
crowded and thus will be less liable to be killed by damping-off.
The soil surface should be so elevated as never to be flooded by
contaminated soil water or surface waters. The drainage should
be as near perfect as possible and water for irrigation should be
readily available. The seedbed should be well protected from
bright sunshine, strong winds, cold and possible frost damage,
since these factors are detrimental to seedlings and favor disease
development. Soil selected for the seedbeds should be fertile
so that vigorous plants will develop.
Soil Disinfection.-To be certain that the seedbeds are free
from plant pests, such as bacterial and fungous organisms, root-
knot, etc., it is best to disinfect the soil before planting. This
can be done most thoroughly by using steam, which can be
generated in any type of portable boiler and forced into the soil
under an inverted pan, for the required length of time at a specific
pressure. The soil can also be drenched with a formaldehyde
solution made by diluting 1 gallon of commercial formalin in 100
gallons of water and applying to the surface of the soil slowly
enough to prevent surface flow at the rate of 1 gallon per square
foot. This concentration is most desirable to use on sandy soils.
A double strength solution applied at the rate of one-half gallon
per square foot is better for heavy soils such as clay or marl.
The formaldehyde treated soil should be covered with canvas
or burlap for 24 hours and should not be planted for two weeks.
There are other methods of soil disinfection for the prevention of
damping-off in which other disinfectants are used, such as red
oxide of copper and formaldehyde dusts. Enriched seedbed soil
should be disinfected after manure or compost has been applied in
order to kill parasites that may be introduced, such as those
causing root-knot, soil rot, buckeye rot, brown rot and Southern
blight. (Soil Disinfection. Fla. Exp. Station Press Bulletin
491.)






Seasonal Occurrence of Tomato Diseases in Florida


After the seeds are planted the soil surface should be covered
with disinfected canvas or burlap to retain moisture until the
seedlings begin to emerge. Seedbeds planted in July, August and
September should be supplied with shade and those planted in
November, December, and January should be supplied with suit-
able covering to prevent cold and frost injury. To reduce time
required for seed to germinate in the soil in cool weather, they
can be sprouted indoors until the sprouts are visible before they
are planted. This procedure may reduce the time from planting
to emergence of the seedlings by a week.
Damping-Off.-Poor germination will reduce the stand in the
seedbeds. The stand may also be reduced by parasitic, soil-in-
habiting fungi commonly spoken of and known as Rhizoctonia,
Pythium, Sclerotinia, etc., that attack and kill young roots and
cotyledons before the seedlings emerge and the stems of the seed-
lings at the soil line after the cotyledons have expanded. The
injury to the seedlings in these stages of their development is
spoken of as damping-off. The last stage, where the stems are
attacked, is the one usually observed and then often not until
large numbers of seedlings have been killed. As soon as this
trouble is observed affected plants and soil and healthy plants
in the immediate vicinity should be wet with a normal solution
of organic mercury in such quantities as to wet the top one-half
inch of soil thoroughly. This should stop the disease within 36 to
48 hours. Conditions of seedlings similar to damping-off occur
when water or commercial fertilizer is applied to seedbeds in ex-
cessive amounts or at the wrong time, and extreme care should be
taken to prevent this scalding or burning. Water should be
applied during cooler parts of the day, morning preferred in hot
weather, and should be kept from the foliage. Fertilizer should
be applied and worked into the soil and prevented from coming in
contact with the plants. Plants and plant parts weakened or in-
jured by fertilizers are more susceptible than healthy plants to
certain diseases such as early blight, gray spot and phoma rot.
These diseases may appear in the seedbeds at any time, regard-
less of vigor of the seedlings, and for this reason the plants should
be sprayed with a 1-2-50 bordeaux mixture or cuprous oxide or
dusted with a 20-80 copper-lime dust often enough to keep all
parts covered and thus protected.
Soil Preparation and Plant Setting.-In the southern part of
the state preparation of the field soil previous to transplanting
varies from a single shallow furrow, plowed through burned-over





Florida Agricultural Experiment Station


lands, into which the plants are set, to thorough disking, plowing,
bedding, harrowing and rolling or planking. These extremes in
cultural practices may be observed in fields only a few miles
apart and both are more or less successful. With the former
method, which is followed by many farmers in Section 1 because
it is inexpensive, the rows are opened at desired intervals, the
tomato plants are dropped flat in the row at proper distances, a
handful of compost is placed over the roots of the plant and a like
amount of commercial fertilizer is placed close to the compost.
When the tops of the plants have grown up several inches the
remaining parts are covered by plowing soil onto them from a
furrow on either side. A second application of commercial
fertilizer is applied beside the plants in the new furrows and
this is covered by the soil from additional furrows. This con-
tinues at intervals as the plants grow until the middles between
the rows are plowed out, concluding the cultivation. No other
activities are practiced until picking time. In the more intensely
cultivated fields the soil is thoroughly prepared and in most cases
this results in a desirable plant medium. These fields are well
drained by main and lateral ditches. The lands are laid out
with roads approximately every 200 feet or on the acre lines.
The tilling of the soil and hauling of fertilizer and fruit is done
almost wholly by tractors and trucks. Rows are measured and
marked and the plants are set, occasionally with mechanical
setters, but more often by hand labor.
The disease-free plants that are set in these fields are grown
in seedbeds and are considered ready for transplanting in the
fields when the stems are one-eighth to one-fourth inch in
diameter and up to eight inches tall. The stockier the plant,
the more desirable it is to most growers. These seedlings are
removed from the seedbeds, packed in crates and taken to the
field where they are dropped in the furrows and the roots are
covered with compost, which is required for successful tomato
growing on the marl and certain muck soils. They usually re-
ceive harsh treatment. Plants should be spaded up from the
seedbeds rather than pulled, to conserve as much of the root
system as possible and to eliminate the breaking and crushing of
leaves and stems in the pulling process. For this last reason
they should not be packed tightly in the crates for transportation
to the field. They should be kept covered or in the shade until
they are dropped and then should be set in the ground as soon
after being dropped as possible. Injured leaves and stems are






Seasonal Occurrence of Tomato Diseases in Florida


always more susceptible to fungous and bacterial infection than
uninjured plant parts. When the seedbeds have been aban-
doned they should be plowed and planted to some other crop as
a sanitary measure because they are in most instances the pri-
mary source of infection for the numerous diseases affecting
tomatoes in that vicinity.
On the pinelands, which are composed of rocks with a scanty
amount of soil, cultural methods employed are different from
those used in other localities. On this type of land tomatoes
should be irrigated. They do not grow so luxuriantly as those
planted on deeper, richer soils. They are frequently infested
by insects and infected by diseases, probably because they are
planted early in the fall when the temperature is high. Usually
no cultivation is attempted except an occasional cutting of weeds.
This is also true of plantings on the Keys, except that these fields
are rarely even scarified. The abundant growth of shrubs and
vines on the keys is cut with machetes and partially removed
and the plants are set in the depressions and crevices in the rocky
terrain where small caches of soil occur. These plants receive
applications of fertilizer, but little or no other attention until
harvest.
More thorough and complete preparation of the soil in the
fields, as practiced in southern Florida, might be applied to the
ether tomato-growing sections of the state with but slight varia-
tion. Raised beds containing from 8 to 20 rows of tomatoes are
often found in fields in Section 2, where hardpan retains the
moisture effectively, offering little or no drainage. In such fields
water usually stands in the ditches between the beds. Sometimes
on these wet lands beds are not prepared, but instead the soil
is made into ridges and the tomatoes are planted on the tops of
them. In Section 3 the plants are usually set in furrows or de-
pressions where more moisture exists and to protect them from
cold winds.
In addition to all of the desirable operations performed in the
other areas, growers in Manatee County prune and stake the
plants to encourage better shaped fruit and to prevent losses
from disease. This operation calls for additional labor and
expense, but evidently it is a good investment. The plants are
set in the accurately spaced rows at various distances and each
plant is tied with raffia or cord to a 1/2 x 1" 5-foot cypress stake,
which is driven into the ground in the row about three inches
from the plant. If each plant is staked separately it is often








































































A- ?;1P






loi






Seasonal Occurrence of Tomato Diseases in Florida


pruned to a single stem or the first auxiliary branch may be
permitted to develop, resulting in two stems. When two plants
are tied to one stake they are pruned to a single stem. They
are planted closer together with every other space twice as
great. When the plant is 8 to 10 inches tall it is pruned and
loosely tied to the stake so that it cannot fall or be blown over.
As the plants increase in height they are tied and pruned until
they reach the tops of the stakes, when they are sometimes
topped. By this time four or five hands of fruit have already
set and little or no fruit develops above the tops of the stakes.
The practice of staking commercial tomatoes is found only in
Manatee and adjacent parts of Hillsboro and Sarasota counties
(Fig. 17). The staking of tomatoes is a very important factor in
regard to disease control. Leaf and fruit diseases are reduced
because the plants dry more rapidly after rains and heavy dews,
thus reducing the length of time when conditions are favorable
for diseases to spread. All aerial parts of the plants, particularly
the fruits, are kept from contact with the soil, thus reducing to
a minimum fruit and stem diseases, such as soil rot, buckeye rot,
Southern blight and most of the leaf diseases, especially mold.
The coverage with fungicides is also more complete on staked
plants and consequently results in a better control of diseases.
On the other hand, certain diseases are more prevalent on staked
plants. Mosaic appears annually but is most severe on staked
plants, because it is spread from diseases to healthy plants
through the handling operations' of staking and pruning. Blos-
som-end rot is also more frequently found among staked plants
because of wide variation in water supply and humidity, reduced
root area and greater and more rapid transpiration.
Fungicides and Their Application.-The extent and thorough-
ness of the use of fungicides usually varies directly with the
intensity of the general cultural operations. The application of
a fungicide is similar to insurance, it is a preventive rather than
a cure. Consequently, to be most effective it must be applied
before any disease appears. The plants in the seedbed should
be covered thoroughly with a good fungicidal spray or dust such
as 1-2-50 bordeaux mixture or 20-80 copper-lime dust from the
time the first true leaves appear. Many growers dip the seed-
lings in some disinfectant after removal from the seedbed and
before planting, but this practice has not proved satisfactory.

Fig. 17.-Unstaked and staked tomato plants of same age (page 26).






Florida Agricultural Experiment Station


After transplanting, the plants should be allowed several days
for recovery; in fact they should show some new growth before
any fungicide is applied to them. Plants in the field should be
sprayed or dusted with fungicides such as 2-4-50 bordeaux mix-
ture or 20-80 copper-lime dust. Subsequent field applications
should be made often enough to keep all parts of the plant
covered and thus protected from infection. If the first applica-
tion is thorough and is followed by cool, poor growing weather, a
two- or three-week interval may be entirely satisfactory, but if
the first application is made during, and followed by, warm,
humid, excellent growing weather, a weekly interval may be too
long. Consequently, the grower should make applications often
enough to protect the plants from common diseases, such as
early blight, gray spot (Fig. 18), leaf mold, phoma spot, and
others that may occur on the stems and leaves of tomato plants
from the time they emerge from the soil in the seedling stage.
Experiments have shown that liquid bordeaux is about one-
fourth more effective in controlling the various diseases listed
above than copper-lime dust. The machinery used in applica-
tion of fungicides should be efficient if good results are to be

Fig. 18.-Gray spot of tomato caused the loss of the crop in this field before the first picking.






Seasonal Occurrence of Tomato Diseases in Florida


expected. Hand sprayers and dusters, if well made, are effective
and are necessarily used where the fields are small or of such
nature that they are not accessible to other machinery. Where
possible, however, power machinery should be used for the
application of both liquid and dust fungicides, the spray should
be applied under pressure to dry plants in quantities ranging
from 40 to 100 gallons per acre per application, depending upon
the size of the plants. Dust should be applied for best results
to wet plants when there is little or no wind at the rate of 15
to 40 pounds per application per acre, depending upon the size
of the plants. Tractor-drawn power machinery may be so ar-
ranged as to cover several rows at a time. Certain growers have
successfully devised and operated machinery with 40 nozzle
outlets which cover 20 rows of tomatoes at each trip across the
field. On the other hand, the method of culture in Manatee
County, where the plants are staked, requires another type of
machine (Fig. 19). It is drawn between the rows of staked
plants and one side of each of two rows is sprayed simultaneously
on the side toward the machine. Thus, the machinery used must
be the kind best adapted for the type of culture, but under all
circumstances it must be efficient and effective. Fungicides con-
taining copper in some form have proved to be the most effective
in controlling diseases of tomatoes anywhere in the state. Sulfur
in any form should not be applied to tomatoes as a fungicide,
because it has proved detrimental in experiments conducted in
recent years.
Sprays and dusts used as fungicides are specific for a number
of the common and destructive diseases of tomatoes in Florida,
but there are several upon which they have no effect. The princi-
pal diseases of this group are brown rot, fusarium wilt and
mosaic. Those that may be partially affected under favorable
conditions are soil rot, Southern blight and timber rot (Sclero-
tinia sclerotiorum (Lib.) Mass.). These diseases are not affected
by the fungicides because all except mosaic usually infect the
plants through the root system where the fungicide does not
penetrate.
Rotation.-Plants affected with bacterial or fusarium wilt
show no other external symptoms of the disease than wilt in
the early stages. When the stems are cut, however, darkened
streaks are apparent in the vascular tissue, indicating the
diseased parts. Soil rot, Southern blight and timber rot
usually cause the affected plants to wilt as a result of a definite






Florida Agricultural Experiment Station


Fig. 19.-Type of spray machine used in staked tomato fields.
lesion girdling the stem at or near the soil line. Plants show-
ing these wilt symptoms should be removed from the fields and
buried or burned. If they are left to die in the field they will
become thoroughly overgrown by the parasite, thereby produc-
ing spores and increasing the. infestation as the plants rot.
Parasites causing bacterial and fusarium wilt survive in the
soil from season to season and as a rule infested areas in a
field enlarge from season to season, provided tomatoes or
other solanaceous plants are grown there successively. Conse-
quently, crop rotation with other plants should be practiced in
fields that show these diseases in tomatoes.
Mosaic, a contagious disease caused by a filterable virus, is
found principally on the lands of Section 2 where staking is done
extensively. The infective principle occurs in the sap of diseased
plants and is spread from plant to plant by sap-sucking insects
such as aphids and on the hands of laborers who prune and tie
plants. The principal control for this disease is the control of
insects in the field and the removal of plants that show the dis-






Seasonal Occurrence of Tomato Diseases in Florida


ease, so that it will not spread to adjacent healthy plants. Fungi-
cides will not control this disease.
Fertilizers and Their Application.-Fertilizer injuries to to-
mato plants are numerous. A common trouble is the use of too
little or too much. In case of the former the plants do not grow
well. They appear to be stunted and usually become more or less
yellow and often show dead areas in the leaves. In case of too
much fertilizer the plants may be severely "burned" or "scalded"
because of too concentrated solutions, resulting in wilting, drop-
ping of foliage and death. This type of injury does not occur
often. Another result of too much plant food is rank, succulent
growth of the plant and a consequent failure to set fruit, pri-
marily because of the "dropping" of flowers. Unbalanced nutri-
tion, irregular moisture, temperature and humidity and poor
pollination and sterility may result in the formation of pockets
between the placenta and seed and the outer wall. This disease
(Fig. 20), has recently been called "puffy tomato" and is import-
ant enough to be recognized in the United States' grades of fruit.
The most common injury from fertilizer is "burning" resulting
from the physical contact of it with any parts of the plant.
It will kill the roots of plants in the immediate vicinity. It will
cause lesions on stems and branches of plants and will cause areas


Fig. 20.-Puffy tomato, a condition thought by many to result from unbalanced nutrition.






Florida Agricultural Experiment Station


of the leaf blade to droop and die where contact is made. The
tissues thus killed offer excellent places for entrance into the
plant for a number of weak parasites that otherwise do not
attack the tomato. The first application should be made so as to
be available soon after transplanting time. Subsequent applica-
tions and side-dressings should be so made that there is no possi-
bility of the fertilizer coming in contact with the stem or main
roots of the plant.
Cultivation.-During the growing season cultivation may be
a means of transmitting mosaic from affected plants to healthy
ones. The plants may be bruised by the passing machinery and
the sap of diseased plants may come in contact with an injured
healthy plant and inoculate it. Certain of the wilt diseases may
also be spread in fields through the infested soil adhering to plows,
cultivators and feet of laborers and parts of dead wilted plants
may be carried by the machinery a few feet or for miles.
Natural dissemination of the diseases caused by movements of
plant parts and infested soil by wind and water also occurs. The
only way to prevent spread of mosaic or the wilt diseases is to
remove the diseased plants as soon as they show typical symp-
toms. The longer they are left in the field, the greater menace
they become. These plants very seldom produce any marketable
fruit, if allowed to remain in the field.
Harvesting.-Tomatoes are harvested when they are "mature
green", still green in appearance, firm and hard. In this state of
development the fruit can be removed from the plant and hauled
and packed with little or no injury, if due precautions are taken.
The exact time to pick the green fruit from the plant has long
been a question for argument and is still an unsettled point.
When tomato fruits are small they are covered with fine glan-
dular hairs that persist during enlargement. When the fruits
have reached their maximum size these hairs have almost en-
tirely disappeared, leaving the skin smooth and shiny, whereas
previously it was more or less adhesive to the touch and possessed
a dull surface. Many growers consider this smooth, shiny ap-
pearance of the skin as an indication of proper maturity for
pickling. Others associate a slight yellowish-green color and
size as signs of maturity. Experience and close observation show
that all of these factors are required and even then tomatoes are
often picked when yet too green. The result of picking fruit too
green is the lengthening of the ripening period and during this
time they lose weight and shrivel, usually resulting in a third






Seasonal Occurrence of Tomato Diseases in Florida


class product or a worthless cull. On the other hand, fruit picked
too late colors up, ripens and becomes soft in transit, resulting
in an unsalable product at destination. Properly picked fruits
will begin to color up in a few days so that upon arrival at
destination after a period in transit they are about 60 percent
colored and ready for the consumer.
Picking in a field usually is done at weekly intervals over a
period of from three to six weeks, depending upon the season.
Large picking crews are well organized and supervised. Each
picker carries a container, pail or basket, into which the fruit is
placed. When the container is filled it is carried either by the
picker or by an especially designated carrier to field crates of
one to two bushels capacity distributed along temporary roads
throughout the field. These filled crates are collected and taken
to local packinghouses where the fruit is packed for shipment.
There are certain precautions that might be taken by growers
and picking crew foremen that would result in a better grade of
fruit entering the packinghouse. Handle the tomatoes carefully.
Pickers should be fully instructed along these lines before they
enter the field. They should be shown fruits that are too green
and those that are too ripe for picking, so as to have the proper
knowledge of what they should collect. They should have their
fingernails closely trimmed to prevent fruit cuts by that means.
Actual count in one packinghouse showed 4.4 percent of the
fruit with a type of skin abrasion comparable to fingernail injury.
Picked fruit should be placed in the picker's baskets rather than
being dropped, tossed or thrown. Containers should be cloth
lined. Burlap or fertilizer bags offer an easily available material
that is adequate. The carriers should place the tomatoes into
the field crates gently from a low elevation and not pour them
out from a hip-high elevation, which results in bruising and
other injuries. This rough handling may cause skin cuts or
punctures in most of the tomatoes by rough and sharp-edged
containers and sand adhering to the containers and fruit. Such
injuries occurring in the field and packinghouse immediately
predispose the fruits to phoma rot. The fungus which causes
this disease also attacks the leaves and stems of tomato plants
in the field, where numerous spores are produced and distributed
over the fruits in the picking and packing process. Uninjured
fruits are not attacked but any kind of injury permits the fungus
to enter the fruit and cause decay. Fruit picked from a specific






Florida Agricultural Experiment Station


field, packed and put in transit showed 60 percent phoma rot at
destination, while fruit the same age left on vines did not show
any phoma rot. Pickers should avoid handling diseased fruits
in the field whenever recognized. The vines should be molested
as little as possible, both for the future production of the plant
and also because of the danger of spreading diseases. Picked
tomatoes should not be left long in direct sunlight because of
danger of sunscald and a resulting breakdown of the injured
tissues and probable rot.
Packing and Transportation.-The packing operation consists
of grading, wrapping and boxing fruit. In some instances this is
done by a single individual or his family, while in most instances
it is done in well equipped packinghouses, where several carloads
may be packed daily. In packinghouses the fruit is dumped out
of the field crates into water baths, from which they are removed
by an endless belt of rollers after an average immersion of about
one minute. This belt conveys the fruits under suspended mop-
cloths and often through an air tunnel to remove the water.
Thence, they go to a wide moving belt, where the defective ones
are sorted out and the remaining ones pass through mechanical
sizers into packing bins. The packers wrap and place the fruit
in shipping containers which are then covered, labeled and placed
in refrigerator cars for transit.
Unless certain precautions are exercised in the packing opera-
tions there is danger of inoculating a large percentage of the
fruits with decay-producing organisms. Growers of the winter
crop in the southern part of the state have experienced heavy
losses from phoma rot in transit, Fig. 3. If the disease appears
on the plants in the fields the fruit may be heavily laden with
spores of the fungus although they show no signs of diseases at
packing time. The pickers moving the vines about scatter the
spores on themselves and the fruit. If the fruits are handled
roughly they will be exposed to sand cuts and other mechanical
injuries. These spore-covered fruits are dumped onto the water
bath, where the spore loads are partially washed off the fruit
and they may be distributed and adhere to all the fruit put
through the water bath. These spores germinate and enter the
fruit through broken places in the skin. Thus, the necessity for
great care in handling fruit by the pickers. In addition to careful
handling, a disinfectant should be added to the wash water. Such
disinfectants as sodium pentasulfide and borax have been used






Seasonal Occurrence of Tomato Diseases in Florida 35

successfully and further experiments with other materials are
being conducted. The conveyors, racks, rollers, containers and
other machinery in the packinghouse should be carefully in-
spected to see that there are no nails protruding or other rough
or pointed obstacles that may cause injury to the tomatoes.




(4PW











Fig. 21.-Soil rot of tomatoes develops in transit, spoiling healthy fruits adjacent
to diseased ones. Right above, condition of fruit and wrapper upon arrival at shipping
destination.


Fig. 22.-Buckeye rot of tomatoes also spreads through wrapper to healthy fruit in transit.

The sorters and graders should have special instructions as
to what constitutes a cull. All blemished fruit, whether of
mechanical or parasitic origin, should be discarded. Soil rot and
buckeye rot fungi, Figs. 21 and 22, grow at low temperatures and
are often destructive in transit because they will grow through






Florida Agricultural Experiment Station


the paper wrappers and infect all fruit in contact with the
decayed ones. The pack should be solid but not too crowded and
should not bulge, as bulged packs usually result in losses from
mechanical injury.
Diseases which originate in the field and develop in transit can
be prevented to a large degree by careful inspection, grading and
general operation in the packinghouse. Certain types of
mechanical injury resulting from freezing or scalding, undue
delays and shifting of load may be attributed directly to causes
originating after the product has left the packinghouse.
During the past 60 years the general tomato disease situation
in Florida has been one of ever-increasing importance. It is
quite probable that the early growers experienced no trouble with
the diseases that are of the greatest importance today, because
they did not exist. However, as the industry developed and
expanded, resulting in more intensive cultural methods, the dis-
eases began to appear. There is reason to believe that they or
new ones will continue to cause trouble as long as tomatoes are
grown in the state.




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