Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 185
Title: Tomato diseases in Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00026410/00001
 Material Information
Title: Tomato diseases in Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 55-138 : ill. ; 23 cm.
Language: English
Creator: Weber, George F ( George Frederick ), b. 1894
Ramsey, Glen B ( Glen Blaine ), b. 1889
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1926
 Subjects
Subject: Tomatoes -- Diseases and pests -- Florida   ( lcsh )
Tomatoes -- Diseases and pests -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by G.F. Weber and G.B. Ramsey.
General Note: Cover title.
General Note: "In cooperation with Office of Vegetable and Forage Diseases, Bureau of Plant Industry, U.S. Department of Agriculture"--T.p.
 Record Information
Bibliographic ID: UF00026410
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000923491
oclc - 18172766
notis - AEN4042

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





December, 1926


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION


In Cooperation with Office of Vegetable and Forage Diseases,
Bureau of Plant Industry, U. S. Department of Agriculture






TOMATO DISEASES IN FLORIDA


By

G. F. WEBER AND G. B. RAMSEY


Fig. 58.-Typical Nailhead rust lesions on a mature tomato fruit



Bulletins will be sent free upon application to the
Agricultural Experiment Station
GAINESVILLE, FLORIDA


Bulletin 185





BOARD OF CONTROL
P. K. YONGE, Chairman, Pensacola
E. L. WARTMANN, Citra
E. W. LANE, Jacksonville
A. H. BLENDING, Leesburg
W. B. DAVIS, Perry
J. T. DIAMOND, Secretary, Tallahassee
J. G. KELLUM, Auditor, Tallahassee
STATION STAFF
WILMON NEWELL, D. Sc., Director
JOHN M. SCOTT. B. S., Vice Director and Animal Industrialist
SAM T. FLEMING, A. B., Assistant to Director
J. R. WATSON, A. M. Entomologist
ARCHIE N. TISSOT, M. S., Assistant Entomologist
H. E. BRATLEY, M. S. A., Asst. in Entomology
R. W. RUPRECHT, Ph. D., Chemist
R. M. BARNETTE, Ph. D., Assistant Chemist
C. E. BELL, M. S. Assistant Chemist
JACKSON D. HESTER, B. S., Assistant Chemist
J. M. COLEMAN, B. S., Assistant Chemist
0. F. BURGER, D Sc., Plant Pathologist
G. F. WEBER, Ph. D., Associate Plant Pathologist
J. L. SEAL, M. S., Assistant Plant Pathologist
ROBERT E. NOLEN, M. S. A., Lab. Asst. in Plant Pathology
K. W. LOUCKS, A. B., Lab. Asst. in Plant Pathology
ERDMAN WEST, B. S., Lab. Asst. in Plant Pathology
D. G. A. KELBERT, Field Asst. in Plant Pathology
W. E. STOKES, M. S., Agronomist
W. A. LEUKEL, Ph. D., Assistant Agronomist
A. F. CAMP, Ph. D., Associate Horticulturist
HAROLD MOWRY, Assistant Horticulturist
G. H. BLACKMON, B. S. A., Pecan Culturist
M. N. WALKER, Ph. D., Assistant Cotton Specialist
W. A. CARVER, Ph. D., Assistant Cotton Specialist
EDGAR F. GROSSMAN, M. A., Assistant Entomologist, Cotton Investigations
RAYMOND CROWN, B. S. A., Field Asst., Cotton Investigations
A. L. SHEALY, D. V. M.. Veterinarian
D. A. SANDERS, D. V. M., Assistant Veterinarian
C. V. NOBLE, Ph. D., Agricultural Economist
BRUCE MCKINLEY, B. S. A., Assistant in Agricultural Economics
H. G. HAMILTON, M. S., Assistant Agricultural Economist
OUIDA DAVIS ABBOTT, Ph. D., Head, Home Economics Research
LEONARD W. GADDUM, Ph. D., Assistant in Home Economics
IDA KEELING CRESAP, Librarian
J. FRANCIS COOPER, B. S. A., Editor
RUBY NEWHALL, Secretary
HENRY ZEIGLER, Farm Foreman
W. B. TISDALE, Ph. D., Plant Pathologist, in charge Tobacco Experiment
Station (Quincy).
Ross F. WADKINS, M. S., Lab. Asst. in Plant Pathology (Quincy)
JESSE REEVES, Foreman Tobacco Experiment Station (Quincy)
L. 0. GRATZ, Ph. D., Assistant Plant Pathologist (Hastings)
A. S. RHOADS, Ph. D., Assistant Plant Pathologist (Cocoa)
A. N. BROOKS, Ph. D., Assistant Plant Pathologist (Plant City)
STACY O. HAWKINS, Field Asst. in Plant Pathology (Miami)
J. H. JEFFERIES, Superintendent Citrus Experiment Station (Lake Alfred)
W. A. KUNTZ, A. M., Assistant Plant Pathologist (Lake Alfred)
GEO. E. TEDDER, Foreman, Everglades Experiment Station (Belle Glade)
R. V. ALLISON, Ph. D., Soils Specialist, Everglades Expt. Station, (Belle
Glade)
J. H. HUNTER, M. S., Assistant Agronomist, Everglades Expt. Station,
(Belle Glade)
J. G. KELLEY, B. S. A., Field Assistant, Everglades Expt. Station, (Belle
Glade)
K. H. GRAHAM, Auditor
RACHEL MCQUARRIE, Assistant Auditor


















CONTENTS


IN TRODUCTION ........... .. ......... .... .... ... ... .. ... --- --------
RELATION OF DISEASES TO PRODUCTION AND MARKETING


NAILHEAD RUST .........................
FUSARIUM W ILT ................................
M OSAIC ......... ---... .... .. ..
SOIL R OT ........ -... .--. ..........
BACTERIAL SPOT ............... ...-.
BUCKEYE ROT .......... ..-..- .....
PHOMA ROT ........... ... ........
SOUTHERN BLIGHT ......-..........
ROOT-KNOT .............-............-
BROW N ROT .........................
ANTHRACNOSE ............. ..
LEAF M OLD .................... .......
SEPTORIA (LATE) BLIGHT .............
STEM ROT .........--. ...... .........
BLOSSOM-END ROT ....................
BACTERIAL SPOT ...................-
DOWNY MILDEW .................-
FUSARIUM ROT .....................-
BOTRYTIS STEM AND FRUIT ROT ....
OOSPORA ROT .........................
DAMPING-OFF ................
RHIZOPUS ROT ........... ....---..-
PUFFY TOMATO ... ..........................
SUNSCALD .............. .... --. ....-
GROWTH CRACKS ..............-..
SKIN CRACKS ....... .. ..... ..
CAT FACE .............- ...... ......
CLOUDY SPOT ............ .. .......
LEAF ROLL ............ --. ....-...
BLOSSOM DROP ............. -....-...
SANITATION AND ROTATION ............
SEEDBED STERILIZATION ...............


Page
...........- 61
...-..- ..- ..-.- .-- 63
............. ..... 65
65
.- ..-..-.-.- 73
-. -...--.- .....- 76
..-.-. ..- ... 81
..-.-..-.- 85
-.-..-.-.. .. 87
-... --.....-- ..- 89
........ ...... 92
.........-.- 95
.... 99
...-.-.- 101
.....- ...- .....-. 102
......-.......... 104
................ 106
.- ...- ... 108
.........-....... 110
........-..-........ 111
-... .... ......... ..-. 113


.........................- ..- ..- ....-...-...... 114
........ .....-.-.- .- 115
......-.. -.. -.. -.. -.. ...-- -..- ..- .....- 116
........-......-.--.. -.-.... 118
... .... ..-.-. -.. 119
-...-.-..- ....-- ...- .... 121
.-.-.-.-.-.-.- ...- .... .. 122
---..-. -....-.- ...-... 1.. 24
.. .................-...--.. ....- .. ..... .. -. 125
... ....-..-.-.- .......... 126
-.. -...... -...- ..--...-.. ..... ...- 127
................. -- 128
...... ...-.. ... -. 129
-... ... ...-.-.- ..- ..-- 130


SEED DISINFECTION ..... ........ ......... ...
FUNGICIDES AND THEIR APPLICATION ...... .......-
SOME PERTINENT POINTERS ..............--. .... ....


... 131
..-.-.-.-.- 133
............ 137












TOMATO DISEASES IN FLORIDA
By G. F. WEBER AND G. B. RAMSEY*

INTRODUCTION
Tomatoes have been grown in Florida for a considerable num-
ber of years and in each successive season the acreage and pro-
ductioa have been advanced until at present the production of
tomatoes exceeds that of any other truck crop in the state.
Tomatoes are grown in all sections, the earliest plantings be-
ing made on the southernmost areas and even on the Keys, and
the latest plantings are made in the north central part of the
state. The tomato growing area might be divided into three
distinct sections, namely, (1) the East Coast section and the
Keys which is the earliest producing section, (2) the West
Coast area centered in Manatee County, and (3) the central
and northern section of the state which is at its height of pro-
duction in the late spring.
In certain parts of these areas the growing of tomatoes is
considerably concentrated and it is in this concentrated area
that plant diseases appear most frequently in destructive form.
Since tomato seed are obtained from a number of sections of
the United States, growers can expect this crop to be troubled
more or less with the diseases that are destructive to tomatoes
in this country. Old growers recall the time when mosaic,
nailhead rust and other destructive diseases were unknown.
The purpose of this bulletin is to bring together for the bene-
fit of tomato growers the best information concerning the to-
mato diseases that appear in the state at the present time. The
information contained herein has been collected during the past
four or five seasons. The Experiment Station has issued sev-
eral bulletins in the past dealing with diseases of tomatoes;
namely, Experiment Station Bulletins Nos. 18, 21, 47, 91, 117,
139 and 146. This bulletin, however, contains all of the in-
formation found in these previous publications and consider-
able additional data.
It is interesting to note the total value of agricultural prod-
ucts in Florida for a single year. Data obtained from the year-
*G. F. Weber, Associate Plant Pathologist, Florida Agricultural Ex-
periment Station. G. B. Ramsey, Associate Pathologist, Office of Vege-
table and Forage Diseases, Bureau of Plant Industry, U. S. Department of
Agriculture.






Florida Agricultural Experiment Station


book of the United States Department of Agriculture show the
total value of the truck crops, citrus and field crops for 1924
and 1925 to be as follows:
Year Truck Citrus Field Crops
1924 $35,102,000 $29,270,000 $27,807,000
1925 $30,083,000 $34,375,000 $18,437,372
In comparing these figures it will be noted that the average
farm value of truck crops for the last two years exceeds the
average farm value of either citrus or field crops.
As to the shipment in carload lots of tomatoes which are
consumed as a fresh vegetable, Florida retains its leadership
in the United States. The shipping season from Florida is
spread over the first half of the year from January to July,
the height of the season being March, April and May.
The following shows the carload shipments of tomatoes origi-
nating in the five leading tomato growing states during the
years 1917-1925 inclusive.
TABLE I.-CARLOAD SHIPMENTS OF TOMATOES, 1917-1925
I 1917 I 1918 I 1919 | 1920 1921 1922 1923 1924 t 1925
Florida .... 4695 3700 4501 3749 5774 10288 9791 9153 17134
Miss. ....... 1063 1379 1388 1363 1961 3441 2144 3775 3149
N. J. ........ 2239 2006 1012 2306 2130 1930 1648 2010 1903
Calif ..... 519 1514 2186 1958 1714 2305 3296 2363 2871
Texas ...-... 1278 1123 1205 1286 1954 1844 1091 1687 2386
Examination of this table reveals the fact that the carload
shipments of tomatoes from Florida almost equal the carload
shipments of the other four states combined.
A further examination of statistics for the years 1922-1925,
inclusive, shows the relative value of the six leading truck
crops in Florida to be indicated in the following table. It will
be noted that tomatoes return a higher total value than any
of the other truck crops listed, altho celery and potatoes begin
to approach the total value of tomatoes.
TABLE II.-TOTAL VALUE IN DOLLARS OF Six LEADING TRUCK CROPS
OF FLORIDA*
I 1922 1923 1924 1925
Tomatoes ........... 9,914,000 $13,558,000 $9,294,000 $9,276,000
Celery ................ 3,767,000 6,335,000 8,282,000 5,200,000
Potatoes ............. 6,085,000 4,976,000 6,868,000 6,757,000
Cucumbers ........ 5,929,000 4,535,000 3,875,000 3,366,000
Beans .............. 2,839,000 3,581,000 3,205,000 4,922,000
Watermelons ...... 2,113,000 1,762,000 2,263,000 2,964,000
*Yearbooks of the U. S. Dept. of Agriculture, 1924-'25.





Bulletin 185, Tomato Diseases in Florida


RELATION OF DISEASES TO THE GROWING AND
MARKETING OF TOMATOES

The importance of plant diseases in relation to the growing
and marketing of tomatoes cannot be too greatly emphasized.
Of the numerous crops of perishable produce shipped to the
markets in the large cities of the United States, there are few
that are subject to as great loss as the tomato. In addition to
the many parasitic diseases that may attack the tomato plant
thruout various stages in its development, there are numerous
diseases that follow as secondary agents after the way has been
opened by wounds or other diseases. The juice and pulp of the
tomato fruit are unusually good for a large number of fungi
and bacteria. While the invasion of the fruit is somewhat
controlled by the normal healthy skin and cuticle, the rupture
of this covering by either growth cracks, insects or mechanical
means provides ready entrance for these destructive organ-
isms. Many of them are not normally parasitic upon the to-
mato fruit, but they are able to grow rapidly and cause decay,
once they have gained entrance thru wounds. This is one rea-
son that tomatoes which appear free from disease at time of
packing often show an appreciable amount of decay on the re-
ceiving market. The wounds incident to harvesting and pack-
ing are often not noticeable or do not show infection at time of
packing and the rot develops during the transit and market-
ing period.
Very little can be done to control the development of disease
during transit and marketing. It therefore behooves us to de-
vise methods of procedure that will control the disease at the
source of infection, rather than try to cure or inhibit the de-
velopment of decay after it has started. It is, of course, real-
ized that this is easier said than done, but in this bulletin an
attempt has been made to bring together the best available in-
formation which has a direct bearing upon this important prob-
lem.
With tomatoes, as with other truck crops, the problem of
disease control becomes more and more complicated as the same
crop is planted year after year in the same locality. In addi-
tion to the diseases present in a given locality, new ones are
continually being brought in with the seed imported from other
tomato-growing regions. Consequently, after a few years,





Florida Agricultural Experiment Station


most of the diseases that are able to thrive under the soil and
climatic conditions in a given locality are present to a greater
or less degree. It is well to understand this phase of the prob-
lem of disease control in order that we may understand why
some diseases are present in one region and not another, and
why a given disease will cause serious loss during one season
and be absolutely negligible the next.
We may as well admit that a great number of our worst
plant diseases are well distributed thruout our best trucking
and farming regions and that the absence of a disease is more
likely to be due to unfavorable weather or soil conditions than
the result of our efforts to control it. This is a rather dis-
couraging outlook from many respects. If, however, we prop-
erly understand the importance of these environmental factors
in relation to plant diseases we at least are able to predict the
appearance of a disease and being forewarned we are able to
direct our efforts toward control measures to a much better ad-
vantage. For example, some diseases are so constantly associ-
ated with rains that growers are accustomed to saying such
and such a disease is caused by rain. While this is not true,
strictly speaking, it cannot be denied that rain is often the one
factor which makes possible the attack of the fungus or bac-
terium which does cause the disease. This is true in such dis-
eases of the tomato as soil rot, buckeye rot and downy mildew.
While our control measures in the field are rather limited,
we can to a marked extent reduce the amount of damage from
these diseases by anticipating their appearance and exercising
great care in harvesting, grading and packing tomatoes during
wet weather. In severe epidemics of the above diseases it
may even be advisable to stop picking or hold the tomatoes in
the field boxes for a few days until the infected fruits develop
lesions large enough to be seen and sorted out before packing.
This seems to be extremely hard on the growers, and it is, but
it is also extremely doubtful if any grower or packer ever
gained anything by shipping tomatoes seriously affected by
either of these diseases. Diseases of this type cause such rapid
decay that it is utterly impossible to pack visibly infected fruit
and have it arrive on the market in a usable condition. Not
only are the originally infected tomatoes lost, but very often
the disease spreads to other fruits during transit, or while held
in the ripening rooms. In addition to the loss of the tomatoes
and the money paid out for packing and transportation charges,





Bulletin 185, Tomato Diseases in Florida


the market is adversely influenced and the reputation of the
grower or packer suffers.
A great part of the decay which takes place during transit
is the result of field infection just previous to harvesting or in-
fection of the fruit during the packing process. The lesions
are not visible to the naked eye at shipping time and the grow-
ers and packers are entirely unaware of any appreciable de-
cay being present until they get a report back from the receiv-
ing market. Under some conditions it is entirely possible to
pack a car of tomatoes that show no apparent infection, and
yet have this car show 10 percent or more of the tomatoes in-
fected and decaying when it arrives on the market after a tran-
sit period of four or five days.
The report of the percentage of decay on arrival does not
take into account the decay which occurs in the green toma-
toes that must be held in the ripening rooms for three or four
days before they can be placed upon the market. There is a
great deal of variation in the percentage of ripe fruit in cars
on arrival, but on an average there is approximately 45 per-
cent mature green, 27 percent turning, 25 percent ripe and
3 percent of soft ripe tomatoes in the cars when they reach the
northern markets. Under the present system of packing to-
matoes in Florida, approximately half of the tomatoes are
ready to market soon after arrival and the other half must be
held in the ripening rooms for a few days until they are ripe.
The well matured fruits ripen quickly and without much
loss, but the tomatoes that were picked too green ripen so
slowly that a high percentage of them decay before they become
marketable. For the benefit of the grower as well as the con-
sumer, every effort should be made to see that only mature
green tomatoes are harvested, and that the pack is as nearly
uniform as possible.
We will now consider some of the diseases in detail.

NAILHEAD RUST
Nailhead rust is caused by the fungus Alternaria solani (E.
& M.) J. & G. This disease has been found in most of the to-
mato growing regions of the United States. In the northern
sections, however, it is of little importance. In the lower
Atlantic and Gulf States the disease is of considerable import-
ance and in some seasons it is very destructive. In Florida the





Florida Agricultural Experiment Station


whole tomato area is infected with this disease and it causes
serious damage in all parts of the state.
The disease attacks the foliage, stems and fruits of the to-
mato plant and is severe at all stages in the development of
the plant. The average loss is conservatively estimated at
from 10 to 15 percent. Some seasons show considerably great-
er losses in certain areas. The fungus lives from one season
to the next saprophytically on old tomato vines and prob-
ably as a parasite on wild solanaceous hosts, volunteer tomato
plants and other cultivated solanaceous plants such as potato
and eggplants. The spores are able to survive long periods of
weather conditions that do not favor their development. They
are disseminated by wind, rain, running water, cultivators, and
pickers, mentioned in the order of their importance as dissemi-
nating agents. Of this list the wind and air currents are prob-
ably responsible for 95 percent or more of the dissemination of
the spores.
The spores may settle on the foliage of the tomato plant and
with the aid of the daily dews germinate and infect the plant
in a very short time. They germinate in about four hours and
are capable of penetrating the tomato leaf in an equal length
of time, thus between sundown and sunrise when the dew is
on the plant the spores have plenty of time to germinate and
infect the host. A few days after a plant is infected evidence
of the disease can be observed on the foliage.. After 7 to 10
days the fungus is again producing spores which completes the
cycle in the life history of the fungus.
Recent experiments show that under favorable conditions
new spots may develop in mature green tomatoes that are
shipped to the northern markets.
The disease is first observed in the seedbed, where it is found
causing lesions on both stems and foliage of the seedlings.
From the seedbed it is carried to the field in the transplanting
of infected seedlings. In many instances there is only a smail
spot on the foliage of seedlings but this is enough to act as a
center of infection. As the season advances a general infec-
tion of the field takes place. The early developing fruits are
usually freer from the disease than the fruits developing later.
This is because the fungus is not so well disseminated early in
the season.





Bulletin 185, Tomato Diseases in Florida


SYMPTOMS
The disease is first observed in the field in the form of small
brownish black spots on the young foliage. The spots enlarge
rapidly and at the time they are one-quarter inch or more in
diameter concentric rings can be definitely distinguished cover-
ing the dark brownish portion of this spot. The tissue sur-
rounding this spot may become yellow in color, and in some in-
stances where the spot is located on one of the principal leaf
veins, the area beyond the spot to the margin of the leaf takes
on a yellowish cast and soon dies and becomes brown. (Fig.
59.) The spots on the leaves in many instances are as much
as an inch in di-
ameter but will
average somewhat
smaller. As the
season develops
and points of in-
fection become
more numerous,
the spots enlarge
considerably and
coalesce (run to-
gether). In the
latter part of the
season they are
exceedingly n u-
merou s, very
small and irregu-
lar and quite dif-
ferent in appear-
ance from the ear-
1 y manifestation Fig. 59.-Nailhead rust lesions on tomato leaves.
of the disease.
On the stems (Fig. 60) the spots are small when found in
the seedbed and the invasion of the cortex is barely accom-
plished. These spots become hardened and shiny on their sur-
faces and produce a sort of glazed appearance. Often they are
so numerous that the whole stem is more or less girdled with
this shiny brownish spotting. At this stage the seedlings are
decidedly stunted, in fact, their development is practically at
a standstill. This condition appears in the seedbeds usually





68 Florida Agricultural Experiment Station

after transplanting time, nevertheless, it acts as a source of
infection to the plants that have been transplanted to the field.
As the disease develops in the field this spotting on the stem
becomes of considerable importance in the development of the
plants. Almost without exception where infection is severe the


r



I

LII


Fig. 60.-Nailhead rust lesions on
the stems of tomato seedlings.

with the fruiting structures


plants in the field show the re-
sult of this stem infection. The
spots coalesce and the whole
stem becomes brownish and
hardened and ceases to enlarge
in diameter. This infection
tends to become less severe
toward the top of the plant.
These spots (Fig. 61) are usu-
ally more or less circular in
outline, becoming whitish in
the center surrounded by a
dark brownish band. The mar-
gin of the spot is distinct, the
surface is more or less rough-
ened and the tissue that has
been invaded and killed shrinks,
causing the spot to appear
slightly sunken.
On the fruits the infection is
first observed as a minute,
light brownish discoloration on
the epidermis. As the spot en-
larges the outline becomes
more definite and turns dark
brown. The epidermal cells
are killed and the inner area
of the spot fades until it is a
dull grayish white in color sur-
rounded by a narrow brownish
band. (Fig. 58, Frontispiece.)
This whitish inner area of the
spot is gradually overgrown
of the fungus and, as they are


black in color, the interior of the spots become at first smoky
in appearance and gradually turn velvety black. The spot (Fig.


4
./ .






Bulletin 185, Tomato Diseases in Florida


62) is slightly sunken, continues to enlarge and deepen. At
this stage of development the dry epidermal layer of cells rup-
tures, producing a roughened center. The spots enlarge consid-
erably and in many cases coalesce, causing the fruit to develop
irregularly. Single spots on green fruits have been observed
one-half inch in diameter. In ripening the area immediately
surrounding the infection spots retains its green color. The
spores of the fungus are developed in great numbers on these
lesions on the leaves, stem and
fruit. Their production is more
abundant on the fruit than on the
stems and foliage. After the pick-
ing season is over the whole plant
becomes involved by the fungus
and spores are produced on the en-
tire surface in great numbers, giv-
ing the plant a blackish appear-
ance.
CONTROL
At the present time no absolute
control for this disease is known
and even a commercial control that
is entirely satisfactory has .not

on the application of fungicides i
such as sprays and dusts has been
conducted during the past three or
four seasons in which all of the
commercial products have been
given a thoro trial, and at the Fig. 61.-Nailhead rust le-
present time nothing has been sions on the stem of a bear-
more satisfactory in the control of ing plant.
this disease than 4-4-50 Bordeaux mixture applied once a week.
The wet sprays have proved superior to dust applications, and
fungicides with metallic copper content are far superior to
fungicides that do not contain this ingredient. Several com-
mercial fungicides (Pyrox, Adhesio, and P. B. K.) applied as li-
quid sprays made up principally of copper, lime, and an insecti-
cide have proved almost as effective as colloidal copper, copper
hydroxide and home-made Bordeaux mixture. Copper-lime dust





Florida Agricultural Experiment Station


of different strengths and copper stearate as a dust are not as
satisfactory in controlling the disease as the sprays. Compar-
ing the above mentioned copper fungicides with non-copper fun-
gicides such as sulphur, ammonia, lime, nitrate of soda, used
either by themselves or in combination with each other, it has
been clearly demonstrated that the copper-containing mixtures
are far superior. A slight fertilizer value is gained by the ap-
plication of ammonia and nitrate of soda. Tomato leaves do
not take up ammonia or nitrate of soda in the liquid form when
applied to them. Sulphur is not effective when applied to con-
trol nailhead rust.



-.;











Fig. 62.-Nailhead rust lesions on tomato fruits of different sizes.

The data in Table III were obtained from one of the 20 or
more experiments conducted for the control of nailhead rust by
the application of fungicides. The experiment is made up of 24
individual plots treated with different fungicides as shown in
the third column. Duplicate plots are averaged. The percentage
of marketable fruit is shown in the next to the last column.
The last column, designated "rank," shows comparison of the
plots in the field following the last picking. The plot contain-
ing the most healthy looking plants is designated by 100. This
comparison was made before the percentage of marketable fruit
was calculated.






Bulletin 185, Tomato Diseases in Florida


TABLE III.-RESULTS OF DIFFERENT FUNGICIDES IN EXPERIMENT No. 1
FOR CONTROL OF NAILHEAD RUST (Calculated on one acre basis.)
Cost in Yield in Pounds
Dollars






1920 Pyrox 960 g. 7 $57.60 $26.56 9432 416 1016 89.23 80
1765 Bordeaux 953 g. 8 7.74 28.54 8712 7731 1301 85.07 100
1620 Adhesio 984 g. 8 34.52 27.26 6360 5132 1288 82.05 80
1832 P. B. K. 920 g. 7 20.24 25.36 8032 6504 11528 80.89 80
Cop.-Lime
1680 Dust 147 lbs. 8 18.27 2.96 6920 5305 1614 76.03 35
2008 Ammonia 936 g. 7 4.64 26.00 6240 4480 1760 71.8 20
Nitrate
1768 Soda 960 g. 7 2.40 26.56l 8224 5864 2360 71.31 20
1760 Check .. ........ -..-- .. 7684 5010 2474 68.05 20
1768 Kilrust 994 g. 8 39.78 27.57 7106 4338 2768 61.52 25
1752 Sulphur 174 lbs.1 8 6.08 | 3.44 8120 4832 3288 58.53 20
In dividing the plots into two groups, the first including
those yielding more than 75 percent healthy fruit and the sec-
ond those yielding less than 75 percent healthy fruit, it will be
noticed that the fungicides applied to the first group each con-
tained metallic copper while none of the fungicides of the sec-
ond group contained metallic copper. Another classification of
the plots shows those yielding more than 81 percent of market-
able fruit had the copper-containing fungicides applied to the
plants in the liquid form. The copper-containing dusts aver-
aged close to 10 percent better than the non-copper dusts. Sul-
phur compounds did not give any control of the disease, com-
pared with the check plots to which no fungicide was applied.
SANITATION AND FERTILIZATION
It is strongly recommended that fields to be planted to toma-
toes be well plowed, cultivated and drained.
In respect to fertilizer, the experimental work of the past
two seasons does not give any evidence that varying formulae






Florida Agricultural Experiment Station


effect the amount of disease present. A fertilizer high in am-
monia or nitrogen is no different in respect to the disease than
one that is low in nitrogen and high in potash. Tomato plants
in a soft. succulent, growing condition have not been fouod to
be more susceptible than plants in a good growing condition
but considerably harder in texture.

VARIETAL RELATIONS

During the season of 1923-24 a plot consisting of 56 varie-
ties of commercial tomatoes was grown at Vero. The Varie-
ties were obtained from different parts of the United States
















r.

Fig. 63.-Portion of a staked tomato field which was a complete loss
because of nailhead rust.

and from the U. S. Department of Agriculture. Observations
and notes were made as to the development of these plants and
the amount of infection present. A certain number of varie-
ties were freer from the disease than the others. These varie-
ties are, in the order of their resistance to this disease: Marvel,
Norduke, Norton, Globe, Cooper's Special, and Gulf State Mar-
ket. The Marvel, which had been developed by investigators
in the United States Department of Agriculture as being the
most resistant to fusarium wilt, was also resistant to nailhead
rust. The variety plots have been repeated each year and the
resistance of these plants has continued to show up. Numerous






Bulletin 185, Tomato Diseases in Florida


crosses have been made and grown in Florida. One made by
the United States Department of Agriculture that appears to
be especially adapted to Florida conditions is a cross made be-
tween Marvel and Globe, resulting in the type of tomato that
has been named Marglobe. This new tomato, altho still in the
experimental stage, has proved satisfactory to the grower, both
in respect to resistance to nailhead rust in the field and as a
desirable market type of fruit. It is grown extensively in the
tomato producing areas in the southern part of Florida. The
Marglobe is not, however, completely resistant to this disease
but it shows much greater resistance than Globe and for that
reason will probably become more important as a commercial
tomato than any other tomato grown in the state.

FUSARIUM WILT

The common wilt disease is caused by the fungus, Fusarium
lycopersici Sacc. This disease is widely distributed and severe
in many areas in the United States. It appears wherever toma-
toes have been grown. It is worst in the Mississippi River Val-
ley and in the southeastern portions of the United States. The
section east of the Mississippi River and south of the Ohio
River suffers the greatest losses. The percentage of loss in
some of these states has averaged close to 15 percent over a
number of years. In Florida the disease has been found in all
tomato growing sections. The annual loss is almost constant
and will average from 5 to 8 percent. The disease is more se-
vere in the central and north portion of the state than the south-
ern part, altho it has been severe in the southern part during
favorable periods for its development.
The fungus is a soil-inhabiting organism, living in the soil
from one season to the next, and has been known to survive in
soil which has not been planted to tomatoes for a number of
years. It lives and develops best in soil that contains consid-
erable moisture but is inhibited in its development in exceed-
ingly wet soils. This fungus will tolerate considerable acid in
the soil in which it lives and its development has been found
to be inhibited in soils that show an alkaline reaction. The
temperature best suited for its development is around 80 de-
grees F., which very well coincides with the temperature in
which the tomato crop in central and northern Florida devel-






Florida Agricultural Experiment Station


ops. The soil moisture of this section is very well adapted to
this fungus, since rains appear frequently but the soil drains
well.
The fungus is distributed over the tomato-growing area by
the spores adhering to the seed, by the transplanting of in-
fected seedlings from the seedbed to the field and by infected
soil adhering to the roots of seedlings at transplanting time.
It is distributed locally by tools used in the cultivation of the
seedbed and field.
The seedlings may be infected at any time after germination.
When they are in-
fected at an early
Stage of development
S. they gro w abnor-
Fig. mally and at trans-
W planting time are
somewhat stunted. If
the early infection is
severe the seedlings
may be killed in the
S seedbed before they
are transplanted.
Plants also may be-
come infected after
they are removed
from the seedbed
and transplanted to
the field.
The disease pro-
gresses rapidly and
manifests itself on
: the young plants at
about blossoming
time or soon there-
after, resulting at
first in a yellowing
Fig. 64.-A healthy and wilted tomato plant.
Wilt caused by Fusarium lycopersici. of the older (lower)
leaves. This yellow-
ing process gradually includes more and more of the foliage and
is accompanied by a wilting condition of the tenderest foliage at
the top of the plant during the hottest part of the day. This top






Bulletin 185, Tomato Diseases in Florida


wilting becomes more marked and extensive from day to day
and finally the wilted plant collapses (Fig. 64), withers and dries
up. There are no definite markings on the plant to identify
the disease.
SYMPTOMS

The first appearance of the
invasion of the seedlings by
this fungus can be detected by
an early stunting, otherwise
the disease cannot be distin-
guished until the leaves show
a slight rolling from the edges.
Soon after the development of
the rolled leaves they begin to
turn yellow and after they are
killed become brown and hang
vertically from the main stem.
This condition is followed by
the periodic wilting of the tops,
after which the plant is rapid-
ly killed. In an examination of
such a plant the disease can be
distinguished by cutting across
or slightly lengthwise of some
of the main stems. The vas-
cular tissue (food supplying
vessels) immediately under the
cortex (bark) is often dark
brown in color. This decided
browning of the vascular tis-
sue (Fig. 65) is characteristic
of this disease in Florida and
can be used as a definite cri-
terion for its identification. No
portions of the stem other than
the vascular tissue becomes dis-
colored, at least until after the
plant is dead and secondary or- Fig. 65.-Portions of a tomato
ganisms invade it. Often one- stem affected with fusarium
wilt, showing the darkened vas-
half of the tomato plant will cular tissues.





Florida Agricultural Experiment Station


wilt while the other will remain apparently healthy. This is
due to the fact that the vascular system on one side of the plant
has become invaded by the fungus while the vascular system
on the other side is functioning normally. There is no evidence
of the disease on the outside of the stems, foliage or fruits by
which it can be characterized.

CONTROL

The control of this disease is accomplished by planting re-
sistant varieties. Considerable investigational work has been
carried on in respect to the development of marketable varie-
ties that are resistant to this disease. The varieties of toma-
toes found to be the most resistant to this disease are Marvel,
Norton, Norduke, Marglobe, Globe, Cooper's Special, Louisiana
Red, Louisiana Pink, Greater Baltimore, etc.
Other methods that can be practiced in the control of this
disease are sanitation and rotation. Growers should take pains
to go thru the field and remove all plants that show wilting
produced by this disease before the plants are completely killed.
Rotation of tomatoes with other crops is recommended. The
exact number of years the fungus may live in different types
of soil has not been determined. Rotation with other crops
over a number of years is beneficial in ridding the soil of this
fungus. It is not practical or economical to sterilize the soil.
Neither will the application of fungicides such as Bordeaux
mixture, copper-lime dust, etc., be of any benefit whatever.

MOSAIC
The mosaic disease of tomatoes belongs to the group known
as "virus" diseases. The exact nature of the cause is not
known. It has been found in the United States wherever toma-
toes have been grown and for a number of years has proved
to be one of the serious diseases of tomatoes. In Florida the
disease has been found only in the West Coast trucking section
where it has been most destructive and is the worst disease in
that part of the state. It has not been observed in the central
part of Florida nor in the tomato section on the East Coast. The
severity of this disease has been increasing from year to year
in the infested area and during the past season caused from 10
to 25 percent damage to different plots.







Bulletin 185, Tomato Diseases in Florida


Over this area there appears to be a series of periods of in-
fection. Often the disease is not observed to any marked ex-
tent in the field until the plants have set considerable fruit,
then suddenly 60 to 90 percent of the plants show this disease.
In other plots the disease becomes serious soon after the plants
are transplanted or at least before blossoming time, when
three-fourths of them show the disease.
The sources of infection have not been definitely located.
Thirty-five different host plants have been found in the state
showing this disease. Among these are a large number of wild
plants that grow along ditch banks and in the woods. It is pos-
sible that these plants are hosts for the disease and transmission
is accomplished by certain sucking insects, such as aphids or
plant lice.
At the present time no organism has been designated as caus-
ing this disease. Extensive work has been conducted in an en-
deavor to find the cause for the trouble but so far it has been
unsuccessful. The disease can be produced artificially by rub-
bing the leaves of a diseased plant against those of a healthy
plant. When the sap of the diseased plant is introduced into
a healthy plant it causes the disease.
After the disease has once appeared in the field the laborers
who do the cultivating, staking, tying and pruning, as well as
thepickers, act as disseminators. Pruning is not usually done
until the first hand or two of fruit has set and often at this
time fields are 100 percent infected so it is evident that other
sources are important in the spread of this disease. It is pos-
sible that the disease is taken to the field on the young plants
as they are taken from the seedbed for transplanting. Con-
siderable evidence appears to substantiate this possibility in
that very often the first appearance of the disease in the field
will be on two or three plants together, in between a number of
healthy plants. This condition has been found to prevail over
large areas, which would lead one to believe that the infection
did not start from a single source in the field or from the edges
of the field but rather was spread from the seedbed. The earli-
est infections noted have been on plants which were about eight
inches high. In such instances the plants did not develop nor-
mally and the fruits that were set never grew large enough for
the market. Clusters of fruit set before the disease is visible
usually develop in a normal manner, but fruit that is set after







Florida Agricultural Experiment Station


the disease is visible develops into light colored, malformed,
stunted fruits that are unmarketable. The time of infection


Fig. 66.-The linear type of tomato mosaic.


varies in adjoining fields. The time of infection is the most
important factor in determining the amount of marketable
fruit that may be harvested. Often the disease does not develop
on plants until they have set five or six clusters of fruit. In
such a field practically no damage is done by this disease.






Bulletin 185, Tomato Diseases in Florida


SYMPTOMS
The first knowledge of the presence of the disease is derived
from the condition of the foliage of the plant. There are sev-
eral manifestations of the disease showing on the leaf as fol-
lows: linear development (Fig. 66) of the leaf, a distinct
dwarfing or crinkling of the leaf and rosetting of the tip and
a typical mosaic mottling of the leaves which are almost normal
in size.
The filiform type of mosaic has been observed only in scat-
tered instances in Florida. The leaves in this case are quite
long and slender, irregularly notched and in some instances
they almost fail to develop blades at all, but appear to be peti-
oles which are slightly greenish. The blossoms of a diseased





-.











Fig. 67.-The crinkled type of tomato mosaic.

plant of this sort in more than 60 percent of the cases observed
do not develop normal floral parts but instead the sepals, petals
and stamens were replaced by malformed leaflets, giving the
flower cluster a distinctly witches broom effect. Little or no
marketable fruit has ever been found on plants affected with
this type of mosaic.
The second type (Fig. 67) characterized by the small, crin-
kled, delicately fringed leaves and stunted tops, is decidedly the
most common, in fact more than 95 percent of the affected
plants show these symptoms of mosaic. It has never been ob-
served in the seedbed but has been found in the fields where






Florida Agricultural Experiment Station


100 percent of the plants have been infected before the first
flowers developed. In such cases the tomato crop was a total
loss. This is the type of mosaic that develops on the older
plants following top pruning after the fruit has set. These
plants are easily detected as far as one can distinguish char-
acters in the tomato field and are readily pointed out because
they are decidedly stunted and of a lighter green color than
normal plants.




















Fig. 68.-Mal-formed fruits grown on mosaic tomato plants.
The third type of mosaic is distinguished by a mottling of
the leaves. It may be a mild type of the second form just de-
scribed. Many stages ranging between the second and third
types have been found in a single field.
The mottle type of mosaic conforms more nearly to the dis-
ease as it is found on tobacco and poke weed, in which the light
and dark green areas on the leaf blades are distinctly contrast-
ing. This condition is spoken of as calico leaf. This type of
mottling is more common than the linear type but in no way
approaches the amount of mosaic of the dwarf, fringy type.
The fruits also are distinctly shaped and marked by the disease.
They develop in shapes varying from almost egg-shaped (Fig.
68) to the shape of a flat scalloped squash. The partitions of
the fruits are usually raised on the outer surface while the






Bulletin 185, Tomato Diseases in Florida


intervening space is sunken, giving them a rough appearance
on the outside. Such fruits are very often puffy and in no
case are they suitable for market. Such fruits are found on all
plants that show the symptoms of mosaic at the time the flow-
ers develop.
CONTROL
Extensive experimental work is being conducted at the pres-
ent time in an endeavor to determine if possible the source of
this disease so that some control measures can be recommended.
Control of insects in the seedbed and around the tomato field
is strongly recommended. It is important that all wild plants
showing this disease be eradicated from the vicinity of the
seedbed and that the plants showing the primary infection of
this disease in the field be removed and replaced by healthy
plants. There is no use attempting to control it by the appli-
cation of fungicides, nor are fertilizers responsible for its pres-
ence. There are no commercial varieties of tomatoes suitable
for growing in Florida that are not subject to this disease.

SOIL ROT
Soil rot is caused by the fungus Corticium vagum Berk. &
Curt. (Rhizoctonia solani Kuhn) and has been found doing
damage to tomatoes in most sections of the United States. In
Florida, soil rot is distributed over the tomato growing area
but is more important in the southern half of the state than
in the central and northern portions.
The damage done by this fungus has been somewhat con-
fused with other diseases. During the past few seasons the
trouble caused by this fungus has been exceedingly important
to the grower because of the extensive damage it does to imma-
ture fruit previous to picking. This disease is confused in
most instances with buckeye rot which is caused by an entirely
different fungus. During the past two or three seasons it has
been found that the soil rot is as destructive as buckeye rot. It
does the most damage to plants that are growing in the marl
and muck soils of the lower East Coast of Florida and in the
muck soils of the lower West Coast. The fungus is most de-
structive in February and March during the periods of wet
weather and low temperatures. Where plants are not staked
the foliage almost covers the ground and it is in this condition
of development that soil rot assumes its most destructive form.





Florida Agricultural Experiment Station


Instances during the past year or two have been noted in which
large portions of fields have been total losses because of the
inroads of this fungus. Such instances are exceptional, but the
disease may be considered present and under favorable condi-
tions destructive.
The fungus attacks tomato plants at all stages of develop-
ment and is severe on seedlings both in the seedbed and where
the seed has been planted in the fields, causing "damping off,"
which will be discussed later. It has been found attacking the
stems of plants soon after they have been transplanted into
the field. At the soil line and an inch or two above, it causes
the epidermis and cortex to become hard and brittle. Further
expansion of these parts becomes impossible and finally the
plants become top heavy and break over. This condition has
been prevalent in tomato fields where seasonal conditions were
favorable for the development of the fungus and the plants in
the field were yet small. The larger branches of the tomato
plants are attacked where they come in contact with the soil.
Here the fungus invades the cortical tissue and causes large
cankers to appear, often completely girdling and killing the
stem.
The fungus attacks the fruits wherever they come in contact
with the soil and in some instances has been found causing a
rot of fruits that are 14 to 18 inches above the soil. The fruit
seems to be more susceptible to invasion by this fungus than the
plant stems, with the exception of the seedlings.
The fungus lives in the soil from one season to the next. It
is spread in the field by wind, rain, flowing water, and by the
distribution of plants from infected seedbeds at transplanting
time.
Most of the spots are large enough at packing time that in-
fected tomatoes can be easily graded out, but if any are over-
looked and get into the pack they are sure to be decayed by the
time they reach the market. Wounds are not necessary for in-
fection and for this reason the fungus often infects neighboring
tomatoes in the basket by passing thru the moist wraps. When
the wraps are moist by leakage of the tomato juice they be-
come matted down to the tomatoes by the brownish mycelium
and sclerotia of the fungus. When such fruits are unwrapped
at the receiving market patches of the paper adhere to the
surface.






Bulletin 185, Tomato Diseases in Florida


SYMPTOMS
The disease on the seedlings is a typical "damping off." In
this case the fungus is exceedingly important, causing first a
slight wilting and shortly killing the plant. In the older plants
the fungus invades the cortical tissue of the stems, causing
them to become brown and roughened. The tissue is killed
down thru the cambium and becomes soft and sloughs off, leav-
ing large cank-
ers which in a
goodly number
of instances com-
pletely gird 1 e
(Fig. 69) the
stem, killing the
plant. In the
development o f
these cankers the
plants appear to
be dwarfed and
in an unhealthy
condition, finally
a slight wilting
is observed and
eventually the
plant withers
and dies. E x-
amination
in most instances
will reveal a few
brownish, shiny,
hair-like threads
of the mycelium ,
of the fungus
over the invaded ; .
tissue and reach- .,
ing on the outer
surface into the
healthy tissue. *
The fungus Fig. 69.-Stem cankers of tomato caused by
causes the fruit soil rot.
to decay (Fig. 70) in all stages of development, penetrates the
epidermis and invades the tissue, causing numerous small





Florida Agricultural Experiment Station


brown sunken spots on the side of the fruit that may be in
contact with the soil. Usually, there is a single point of in-
vasion by the fungus and as this spot enlarges it assumes a
concentric brown zoning which is somewhat typical of buck-
eye rot. This marking may be distinguished from buckeye
rot in most instances by the narrowness of the concentric


.-. .. .i .













Fig. 70.-Soil rot of tomato fruits in the field.

zones. With this disease the zoning is extremely definite and
more pronounced than buckeye rot. In transit these markings
gradually disappear as the spots enlarge, so that by the time
an affected fruit reaches the market this zonation is entirely
obliterated. It might be added also that in most cases the epi-
dermis is ru p-
tured at the cen-
ter of the spot
in soil rot while
in buckeye rot
the epidermis is
very seldom
broken. It d e-
velops much
more slowly
than buckeye rot
and does not
produce a wa-
tery soft decay.
In very few in- Fig. 71.-Soil rot of tomato as developed in tran-
In very few in- sit. (Courtesy U. S. D. A.)





Bulletin 185, Tomato Diseases in Florida


stances can the fungus mycelium be detected on the- outside
(Fig. 71) of invaded fruits in the early stages of the disease,
but in the more advanced stages it may be seen if the toma-
toes are moist or if they have been kept in the wraps.
CONTROL
The most important methods of control for this disease
are the sterilization of the seedbed to prevent damping off
and careful regulation of moisture. The disease has been
found to be of no importance in fields where the plants have
been staked and pruned.
Losses in transit may be controlled by exercising great
care in sorting the tomatoes picked following rains.
BACTERIAL SPOT
This disease is caused by the organism Bacterium vesicato-
rium Doidge. It has been only in the last few years that spe-
cial recognition has been given to this trouble, principally be-
cause of its scarcity. Recently, however, it has become a fac-
tor in tomato growing in the Eastern and Southern states. It
has been found in Michigan, Illinois, Indiana, Iowa, Kansas,
Tennessee, Texas, Georgia, and Florida. It was first collected
in Florida several years ago and since that time has been in-
creasing in severity with each successive season. During the
past season it has been more destructive than ever before in
Florida.
The occurrence of this disease has been limited almost wholly
to the trucking section on the West Coast of Florida. It is of
considerable economic importance at the present time in that
section, having caused 2 percent loss last season because of
spotted fruits.
The disease has been found on fruits of all sizes. Its severity
and the amount of infection increase as the season develops.
The foliage of the plant is lightly attacked, the disease has been
found on few leaf blades and fruit spurs. It has not been found
on seedlings or in seedbeds, altho there is evidence of it origi-
nating there. The only other host of economic importance that
has been found attacked by this disease is pepper. In this sec-
tion of Florida this plant is more severely attacked than the
tomato and the general distribution of the disease on the pep-
per exceeds that on the tomato. The organism is carried on
the surface of the seed and lives on old leaves and plants in the





Florida Agricultural Experiment Station


field. The disease is spread from primary infection in the
seedbed and in the field by wind, rain, pickers and to a certain
extent by insects. Progress of the disease is favored by
abundant rainfall, dew and moderate temperature (about 750
to 850 F.).
The small green fruits of the tomato become infected without
any apparent wound or injury, while on the other hand, infec-
















Fig. 72.-Tomato fruits showing bacterial spot.

tion of older fruits takes place thru wounds or following insect
punctures such as those made by the stink bug and the tar-
nished plant bug. Infection of the leaves takes place thru the
stomata.
SYMPTOMS

Bacterial spot on the leaves and fruit spurs is recognized
in the form of small brown sunken, water-soaked, circular
spots. They rarely assume large proportions, usually being
about one-eighth inch in diameter. They are distinguished
from the early blight disease by the difference in the markings
of the spot. The bacterial spots lack the concentric zoning
which characterizes the nailhead spots. On the fruit the early
symptom is a very minute black speck surrounded by a slightly
lighter area. As the spot (Fig. 72) enlarges it becomes brown-
ish in color, scab-like, slightly raised on the edges and sunken
in the center. The epidermis of the fruit finally ruptures and
curls back from the center of the spot. This is the most char-






Bulletin 185, Tomato Diseases in Florida


acteristic symptom of this disease on the fruit. Often these
spots have faintly distinguishable light color surrounding the
spots which are dark brown to black in color. The bacterial
spots are very seldom deeper than half way thru the outer fleshy
layer of the tomato fruit. Severely infected fruits often become
malformed because of the retarding of the growth in these
areas.
CONTROL
Treat the seed in a solution of mercuric chloride (1-1,000)
for 5 to 8 minutes and rinse thoroly before planting. No direct
control measures have been worked out on this disease but it
has been observed in plots where attempts have been made to
control nailhead rust that the application of copper sprays and
copper-lime dust have kept bacterial spot under control. Prac-
tice sanitation in fields that show the presence of this disease
by removing diseased fruits from the field and disposing of
culled fruits other than returning them to the field.

BUCKEYE ROT
Buckeye rot is a disease caused by the fungus Phytophthora
terrestrial Sherb. The range of this fungus over the United
States is limited and it is rarely found of serious economic im-
portance outside of the Southeastern and Gulf states. In Flor-
ida the disease is common over the tomato area, altho not ex-
ceedingly destructive except in the southern portion of the state.
The fungus develops better on soil types such as marl and muck
than on sand and sandy loam. It is more destructive in periods
of wet weather and is worse where drainage is poorest. The
fungus has not been observed on other parts of the plant than
the fruit. It has been found causing a rot on the fruit in all
stages of its development and is usually found invading those
that are in contact with the soil. This is not always the case,
however, since it has been observed on half mature fruits that
were a foot or more above the soil, probably infected by the
spattering by rain of infected soil particles. In instances
where the fungus is attacking fruits that are not touching the
soil the weather conditions have been exceptionally favorable
for its development. During periods of extended rainfall the
disease has manifested itself in epidemic form causing com-
plete losses. The loss from this disease is 1 to 3 percent.
Wounds are not necessary for infection. The fungus is able






Florida Agricultural Experiment Station


to penetrate moist wrappers and in this manner spreads from
one fruit to another in the basket during transit.

SYMPTOMS
On the fruits that are touching soil the fungus enters at the
point of contact, causing a slight brownish spot. As the fun-
gus develops it produces a series of irregular brownish and
light colored concentric bands which as the invaded area en-
larges produce a typical buckeye effect, hence the very appro-
priate name for it. (Fig. 73.) Fruits are very rapidly de-
cayed and break down in a semi-rot. All stages in the growth
of tomato fruits are attacked by the fungus. In some instances















Fig. 73.-Buck eye rot of tomato fruits

where the fruits remain damp and moist for a day or two at a
time the concentric zoning effect may be quite feeble and the
invasion of the fruit by the fungus exceedingly rapid. Under
these conditions the invaded area becomes brown and the fruit
collapses without the production of the marked concentric
zones. It has been observed that fruits may become completely
rotted with no definite markings upon them except a solid, dull
brown color. In some cases where the epidermis is ruptured
the mycelium of the fungus can be distinguished.
CONTROL
Drainage is the most important factor in the control of this
disease. Where the excessive moisture can be withdrawn from
the field the disease seldom appears to be of serious economic






Bulletin 185, Tomato Diseases in Florida


importance. Staking plants is of considerable benefit, making
possible adequate ventilation. To prevent loss from this dis-
ease in transit it is important to grade and pack the tomatoes
carefully. Infected fruit will decay in transit and spread the
disease to other tomatoes in the baskets.

PHOMA ROT

This disease is caused by the organism Phoma destructive
Plowr. It is not common in the United States except, in the
southern tomato growing areas where it is often destructive.
It has been observed on the markets in Northern states in many
instances, but always the fruits have originated from Southern
and sub-tropical shipping points. In Florida this disease is
distributed over the whole tomato growing area and appears
more or less sporadically from season to season. In the north-
ern and central portions of the state it causes considerable dam-
age to the foliage
of the tomatoes in
the late fall, altho
at this time of the
year it has not
been observed on
the fruit. In the
extreme southern
portion o f Flor-
ida this disease
begins to show up
in the fields prin-
cipally on the
fruits and incon-
spicuously s p o t-
ting the leaves.
The decay is
more prevalent in
transit than in Fig. 74.-Phoma spotting of tomato leaves.
the field. The
fungus is apparently able to live from one season to the next in
decaying plant material. It is spread in the field by infected
seed, by sporulating lesions (spots) on the seedlings either on
the stem or foliage, that are transplanted from the seedbeds to






Florida Agricultural Experiment Station


the field and by lesions on the fruit that may be transported
to the packing house and there thru the packing process the
spores are distributed over the large numbers of. fruits that
may become infected thru injuries received in packing.
Experimental test shipments have shown that mature green
tomatoes showing no evidence of phoma rot at time of packing


may develop visible
reach the Northern




II 1


decayed spots by the time the tomatoes


markets.

*^t


Fig. 75.-Phoma lesions on the stem!
of tomato seedlings.


The amount of infection, how-
ever, depends directly upon
the number of growth cracks
or other wounds present, and
upon surface moisture. The
spores cannot germinate and
penetrate the tomato unless
they are moistened by rain
or dew, or by the tomato
juice coming from wounds.
The fungus, Phoma, can
grow at temperatures as low
as 420F. and as high as
920F., but it is most favored
by a temperature of about
800F.
SYMPTOMS
On the foliage there first
appear small black spots on
either surface of t h e leaf
which may be round or ir-
regular in shape, slightly
sunken either along the mar-
gin or the blade of the leaf.
(Fig. 74.) These spots en-
large rapidly and are typi-
cally zonate as in nailhead
rust. In fact, it is necessary
to examine these spots very


critically with a hand lens to ascertain whether they are p'homa
rot or nailhead spots. They enlarge and often coalesce, caus-
ing the leaves to become yellow and curl up, adhering to the
main stem of the plant in much the same manner that nailhead






Bulletin 185, Tomato Diseases in Florida


manifests itself. The pycnidia or fruiting bodies are produced
in these spots on the foliage, immerged or sunken in the leaf
tissue with only a small opening to the outside. Thus they are
very difficult to observe and without a hand lens it is almost
impossible to make a definite determination. On the stems the
lesions (Fig. 75) are black, elongate and faintly zoned. Plants
are attacked from the seedling stage to maturity.
On the fruit the spotting takes place only where the fruits
have been injured and in most cases the fungus enters thru
growth cracks around the stem end. It enters in some in-
stances thru punctures made by insects.















Fig. 76.-Phoma rot of tomato fruits.

When it enters the growth cracks it produces a distinctly
sunken spot almost black in color which enlarges rapidly and
involves large portions of the fruit. (Fig. 76.) The disease
is readily distinguishable from other rots by the black color
of this spot which is speckled with small black pimple-like
eruptions. These specks are the pcynidia or fruiting bodies of
the fungus.
The spotting of packed fruit in transit is more important
from the standpoint of direct losses than the occurrence of the
disease in the field, altho indirectly occurrence of the disease
in the field is responsible for all loss that takes place in transit.
The typical injury inflicted on fruit in the packing and transit
period is a scarring that takes place around the stem end. In
packing the fruit into baskets and the baskets into crates the





Florida Agricultural Experiment Station


general practice is to make a bulging package. The top layer
of fruits of this bulging pack are not completely protected and
becoming injured are subject to the attack of this fungus.

CONTROL

Disinfect the seed (see page 131) before planting. Spray the
seedbed with a 2-4-50 Bordeaux mixture or dust with copper-
lime dust. In the field follow the spray schedule as suggested
for nailhead rust control. Copper sprays and dusts are the
most beneficial. Pack only smooth fruits, discarding any that
show any spotting or lesions. The general type of pack should
be regulated or changed so as to prevent the bruising and in-
jury of the top layer in bulging packs.

SOUTHERN BLIGHT

Southern blight is caused by the fungus Sclerotium rolfsii
Sacc. This disease is typically Southern in its range, altho it
has been found in scattered places in some of the North Cen-
tral states. The disease is common and widespread in Florida,
being serious in all sections of the state. It has been collected
in Florida on 30 or more different host plants, both cultivated
and wild, including woody perennials. It has no particular
preference for soil types, being almost as common on muck
or heavy hammock land as on light sandy soil. It is most fav-
ored in its development by an adequate supply of moisture.
This disease has assumed very destructive form during the dry
parts of the year when the temperature has been low. Its de-
velopment on heavy hammock soil is aided materially by irri-
gation of this land. Surface irrigation is most favorable to it.
Sub-irrigation is a better way of getting the water on the land
without aiding the fungus. It develops on the light sandy soils
during the rainy season and at this time of the year grows luxu-
riantly and extensively in the soil, attacking almost any plant
that may be in its immediate vicinity.
Because of the growing of tomatoes during the winter and
early spring the disease has very seldom been found attacking
seedlings or small plants. It is most common on plants that
have just reached the peak of productiveness. It attacks such
plants at the soil line, completely girdling them and causing






Bulletin 185, Tomato Diseases in Florida


the top of the plant to wilt and die (Fig. 77) in a manner very
similar to fusarium and bacterial wilt. At this time it is ex-
ceedingly destructive on plants that have not been staked and
has been observed attacking such plants and fruit at almost
every place they come in
contact with the soil.
The fungus develops .
small sclerotia which act
in the same way as seeds
of plants in carrying the
fungus from one season
to the next. These
scerotial bodies ar e
brown to dark brown in o
color and vary in size, d
averaging about the size
of mustard or cabbage
seed. They are exceed-
ingly. resistant to ad-
verse weather condi-
tions and develop rap-
idly when conditions are
right for their growth.
These sclerotia distin-
guish the disease wher-
ever it is found. They
are produced usually
above the surface of the
soil on the stem and
fruits of the plant. (Fig.
78.) They remain in
the soil thru the cultiva-
tion period and thru un-
favorable seasons of the Fig. 77.-Healthy (right) and wilted (left)
tomato plants. Disease is southern wilt.
year. They are scat-
tered back and forth by the tilling of the soil and in extreme
cases actually seed down large portions of fields.
This disease first becomes serious on tomatoes in Florida in
the most southern portions of the tomato section. It develops
as the season advances, being destructive in the north and cen-
tral portions of the state in May and June.






Florida Agricultural Experiment Station


SYMPTOMS
The first indication that a plant is attacked by this disease
is a wilting of the leaves. The plant in general assumes a
drooped condition. This general wilting develops until the
plant is unable to
revive at any time
S during the night
Sand from this
.. time on rapidly
declines until it
dies. At the time
the plant is un-
able to revive one
can almost with-
out exception find
the brown selero-
tia and the white
mycelium around
the base of the
stem at the soil
line.
On the fruits
the fungus is cap-
able of penetrat-
ing the epidermis
and entering at
the point where
the fruits come in
contact with the
soil. The early
infection is quite
distinct in that
the area becomes
sunken, is slight-
ly yellowish in
color and by the
time the invaded
Fig. 78.-Sclerotium rolfsii on tomato stems.
area is one-half
to three-quarters of an inch in diameter the epidermis is vis-
ibly ruptured. From this stage until the total destruction of
the fruit the fungus makes rapid headway and within a very
few days the whole fruit has collapsed and shriveled, leaving





Bulletin 185, Tomato Diseases in Florida


only the exterior portions to be overrun by the white mycelium
and covered by the brown sclerotia in abundant numbers. It
is this condition of the disease that is most common in the
fields. (Fig. 79.)
No commercial variety of tomatoes is resistant to this dis-
ease. The best protection against it is sanitation. Whenever
diseased fruits or plants are found in the field they should be
collected and disposed of, preferably by burying two or three
feet deep in the soil. In this way the general seeding of large





"









Fig. 79.-Sclerotium rolfsii on tomato fruits, showing type of rotting and
the numerous sclerotia.
fields will be prevented and to a large extent the disease will
be controlled, since these sclerotia are so large that they can-
not be carried by the wind and there are so few of them in com-
parison to the number of spores usually produced by other fun-
gi that the amount of disease will be exceedingly limited if
strict sanitation is practiced. Another important item is the
careful regulation of irrigation waters and the adequate facili-
ties for draining a field during rainy periods. It is well to
stake tomatoes in fields that are overrun with this disease.
This will keep the fruits from touching the ground and thus
prevent infection. The application of fungicides or the use of
various fertilizer formulae are of little or no use in the control
of this disease.
ROOT-KNOT
The small worms commonly known as nematodes (Hetero-
dera radicicola), readily attack tomato plants and cause serious
trouble. They invade the roots, causing swelling galls, or knots,





Florida Agricultural Experiment Station


hence the common name, root-knot. The adults are barely vis-
ible to the naked eye and will be overlooked unless one is famil-
iar with them. The disease itself, however, cannot be mistaken
because it is the only disease of tomatoes in which these knots
appear on the roots.
The young nematodes work their way thru the soil until they
come in contact with the root of a plant they prefer. They
then bore into
S: the roots and
feed upon the
'" juices. At the
same time they
irritate the plant
causing it to
form knot like
galls. (Fig. 80.)
In this way the
e feeding roots of
er the plant are
: rendered worth-
Sless or practi-
cally so as a
,. means of sup-
e port and growth
for the host
plant.
The worms are
widely distrib-
uted thru most
Fig. 80.-Root-knot of a mature tomato plant. sections of Flor-
ida, especially in well drained sandy fields that have been
cleared for several years. They are much worse on sandy soils
than on clay, and also on well drained soils than on wet lands.
These worms are dormant during a certain period in the win-
ter. At Gainesville they remain more or less dormant from
November to the last of March. Farther south the dormant
period is much shorter and in the extreme south they may be
found active all the year.
The eggs are laid in the knots on the roots, the young hatch
in three or four days if conditions are favorable, otherwise the
eggs may lay down a thick wall around themselves and remain






Bulletin 185, Tormato Diseases in Florida


3 "4











Fig. 81.-Life history of the nematode, Heterodera radicicola (Greef)
Mull, (sizes not comparable). Top, four stages of development of the
egg. Nos. 1, 1, 2, stages of growth of young worms. Nos. 3, 4, 6, de-
velopment of the female. Others, four stages in development of male.
(After Stone, G. E., and Smith, R. E., Mass. Agric. Exp. Bul. 55, 1898.)





Florida Agricultural Experiment Station


dormant in this encysted stage for indefinite periods, even years,
until conditions are favorable for them to hatch. Moisture,
temperature, and air in certain combinations are necessary for
their development.
DESCRIPTION

Since the roots of the plants are the only parts attacked it is
impossible to tell when infection takes place on the plants.
After the worms have entered the roots and their presence has
cut down the food supply to the plant it will be noted that the
plants fail to grow as rapidly as the healthy ones. They are
stunted and finally actually stop growing. Often they remain
in this condition for weeks, not putting on new growth nor com-
pletely dying. Generally however, if the attack is severe dur-
ing the seedling stage the plants will be killed before they have
developed many leaves.
If the plants become infested late they grow during the whole
season and produce fruit. These plants can be readily distin-
guished from the healthy plants in the field by the yellower
leaves and slower growth. In pulling an infested plant and ex-
amining the roots one will find the various sizes and shapes of
knots. The worms (Fig. 81) will be found by opening these
knots and examining with a lens. On older roots the knots
often become brown and in various stages of disintegration. By
this process the worms and eggs are distributed in the soil.
CONTROL

Fumigation by cyanide and other chemicals may be used to
free a field of nematodes but it is too expensive an operation for
the tomato field. It can be used on the seedbed very success-
fully. A' better method for the field is to starve the nematodes
out by growing crops for two or three years on which the nema-
todes will not feed, such as corn, oats, velvet beans, etc. See
Bulletin 159 of this Station.
The summer fallow method is probably the most efficient
method to rid the soil of nematodes in a single season. The
land is plowed immediately after the crop is off and kept bare
of vegetation all summer; it must be harrowed at least once a
week and after heavy rains. It is essential that a crust does
not form over the soil because it excludes air and prevents the
eggs of the nematodes from hatching. By continued cultiva-





Bulletin 185, Tomato Diseases in Florida


tion the eggs are hatched and the young worms, finding no
food plants, starve to death. This method of control is very
severe on the soil, materially reducing the fertility.
A slight modification of this method is the planting of bush
velvet beans instead of leaving the soil bare, thus retaining
present fertility and also gaining the benefit of a cover crop.
The beans must be well and frequently cultivated. In fact all
weeds must be removed from the field to insure starving the
nematodes.
BROWN ROT

This is a bacterial disease caused by Bacterium solanacearum
E. F. S., and is found attacking numerous plants such as toma-
toes, potatoes, and eggplants. On tomatoes it is not as severe
as on other solanaceous plants. In the United States it has been
found distributed thru the Eastern and Southern states. In
Florida the distribution of this disease almost coincides with
the tomato growing area. Even tho it is generally distributed
it is of very little economic importance and very seldom has it
appeared to cause losses that are noticeable, except in places
where tomatoes are rotated with potatoes or eggplants. It has
been found to be more severe on the light sandy soils of central
and northern Florida than on other types of soil and more seri-
ous in late spring when the temperatures are high than during
the early part of the growing season. The disease has seldom
been found in the southern half of Florida.
It produces a complete wilting of the plant. There are no
lesions, spots or blemishes and usually not even discoloration
of the parts above ground to distinguish this disease. There is
practically no yellowing of the lower leaves as is the case in
fusarium wilt. In examining a diseased plant the inner por-
tions of the stem when cut across show a darkened vascular
system almost always involving the central part or pith of the
stem. With fusarium wilt the darkening is confined to the vas-
cular system and is found in the pith only in extreme cases or
when secondary organisms have invaded the diseased areas.
The brown rot disease may be distinguished also by cutting a
stem across, then touching the cut surfaces together and slowly
separating them. Between them will be noted fine glue-like
threads that will stretch short distances before breaking. This
typifies the presence of bacteria.





Florida Agricultural Experiment Station


This disease is spread in the fields by planting infected seed
and by transplanting infected seedlings from the seedbed. It
is transmitted also in the field from one plant to another by in-
sects. The plants also may become infected thru the roots.

SYMPTOMS

A diseased plant is noticeable by its wilted condition. This
wilting (Fig. 82) is rapid and complete and is not accompanied
by a distinct yellowing of the lower leaves. Plants that are at-


Fig. 82.-Bacterial wilt of tomato affecting plant on right.
Plant on left healthy.


tacked by this disease frequently appear stunted before the wilt-
ing takes place. Plants that have completely wilted rapidly die
and dry up. This disease is most prominent in the field on
plants about blossoming time and thereafter.
CONTROL

Control is obtained by sanitation, sterilization, and crop rota-
tion. Avoid rotation with solanaceous crops. Remove wilted






Bulletin 185, Tomato Diseases in Florida


plants from the field before they have been completely killed.
The application of fungicides is of no consequence and can be
considered as waste of time and material.

ANTHRACNOSE

Anthracnose is a common disease caused by the fungus Colle-
totrichum phomoides (Sacc.) Chester. This trouble has been
found widespread on tomatoes in the United States but has
caused little or no damage except to ripe fruit. In Florida this
disease is widespread but it has never been found serious in the
field and it is seldom of any consequence during transit or on
the market until the shipping season is practically over. Great-
est losses occur in fruits that have been matured on the vine















Fig. 83.-Anthracnose of tomato fruits.

for local markets. This disease has not been observed on green
fruits and the fungus cannot enter healthy mature fruits.
It is purely a wound parasite and enters ripening fruits thru
openings caused by mechanical injury or by insects and thru
skin and growth cracks that may develop on the fruit in the
field. The disease develops rapidly and causes a characteristic
soft rot. It is spread in the field by spores which are easily de-
tached and scattered by the wind and rain. In transit the ripen-
ing fruits that have been infected rapidly become involved in a
soft rot. The presence of leaky packages materially lowers
the price of fruit on the market. The fungus lives from year
to year in the diseased tomato tissue that remains in the soil.






Florida Agricultural Experiment Station


SYMPTOMS
The first sign of infection is a sunken, water-soaked spot on
the fruit (Fig. 83). It enlarges, forming a circular spot which
is distinctly sunken and soon involves large portions of the
fruit. If the fungus enters thru a growth crack the tissue on
each side of the crack collapses and in a very short time in-
volves the whole fruit. The epidermis rarely becomes ruptured
in case of infection at a single point. The fruiting- bodies of
the fungus develop on the epidermis. They are irregular in
shape and vary in color from pink to brownish black. These
fruiting bodies or acervuli are often arranged in concentric
circles but this is not always the case. The disease has not been
observed on the stems, petioles, or foliage of the tomato plants.

CONTROL
It is suggested that fruit for the local market be removed
from the plants when they show the first pink color and be
ripened off the vines to prevent this disease. General spray
practices as made for nailhead rust will assist materially in
controlling this disease. The loss in transit can be lessened
by the careful handling and packing.

LEAF MOLD

Leaf mold is caused by the fungus Cladosporium fulvum Cke.
This disease is more or less common on tomatoes in the United
States. In the northern section of the country it is considered
more serious as a greenhouse trouble than in the field. It is
important in the fields of the eastern tomato sections and in
the South. The disease is common and widespread in Flor-
ida, its geographical distribution coinciding with the tomato
area.
Its importance and destructiveness depend on seasonal con-
ditions. It is most serious in the state along the West Coast,
especially in Manatee County areas. Actual loss is difficult to
calculate because the disease is found only on the leaves of the
plants and there is no direct way to measure it. There is a
higher percent of infection and more destruction in the low
places in the tomato fields on both staked and unstaked plants.
The spores of the fungus mature rapidly and, being exceed-
ingly small and light, are carried extensively by wind and rain.






Bulletin 185, Tomato Diseases in Florida


The disease is worse in the cooler periods of the tomato season
than in the warmer periods.

SYMPTOMS
The disease is usually first observed on the oldest leaves.
Naturally these are the ones closest to the ground where the
ventilation is poorest and the period of excessive moisture is
most uniform. It is detected by the appearance of small light
colored spots on the leaf which turn to a distinct light yellow
color, followed by the death, browning and drying of the cells
in this area. Often when infection is severe these spots coal-
esce and in this way rapidly kill the foliage. The fungus sporu-























Fig. 84.-Leaf mold of tomato leaves.

lates on the lower surface of the leaf but very rarely is found
producing spores on the upper surfaces. In picking a yellow
spotted leaf one will observe a sort of olivaceous mold on the
lower surface almost exactly coinciding with the yellow area,
the only discrepancy being that the yellow area may be a trifle
larger than the patch of mold. This patch of mold (Fig. 84) is
more dense in the center than at the edges and of a slightly






Florida Agricultural Experiment Station


deeper color. This dense mass is composed of spores of the fun-
gus. They are readily disseminated by air currents. When
the spores settle on another tomato plant they are capable of
causing a similar spot.
This disease has been found on the leaves only and not on the
fruits, petioles or stems of tomato plants in Florida.

CONTROL
Leaf mold is controlled by the application of copper sprays
and dusts. Staking, pruning and ventilation are also import-
ant factors. Staked tomato fields in which the rows run north
and south have been found to be freer from the disease than
unstaked fields or staked fields where the rows run east and
west.

SEPTORIA (LATE) BLIGHT

This leaf spot disease of tomatoes is caused by Septoria lyco-
persici Speg. It is common and destructive in the Central
and Northern states east of the Mississippi River and has been
found as a more moderate trouble in the states bordering on
the Mississippi River on the west. In the central portion of
the United States, east of the Mississippi River, it is considered
the worst disease on tomatoes. It probably causes as much
damage in this section as all other diseases combined. In Flor-
ida the occurrence of this disease is exceptionally rare, in fact,
during the past five years the disease has been found only
three different times and in none of these instances were the
plants killed. One diseased area on the West Coast during the
past season included several acres of staked tomatoes and as
the season advanced the disease probably did some damage.
The older leaves (Fig. 85) closer to the ground are the first
ones attacked and they are often badly spotted by the fungus.
When the spots are exceptionally numerous on a leaf they coal-
esce, causing the leaf to turn yellow and die.
The disease spreads rapidly from the primary infection by
means of spores which are scattered by wind, rain, running
water, and cultivators. The disease flourishes and causes more
damage during the warm parts of the growing season than
otherwise. It spreads rapidly in dry weather. Abundant dews
are all that is necessary for germination of the spores, and in-
fection of the plants. The fungus lives over unfavorable peri-






Bulletin 185, Tomato Diseases in Florida


ods during the year on dead plant material such as stems and
leaves and is scattered in this way over considerable areas in
the fields. When conditions are favorable for development the
spores germinate and penetrate the plants.

SYMPTOMS

Infection of a plant by the septoria fungus is first made notice-
able by the appearance of small water-soaked spots on either


Fig. 85.-Tomato leaves killed by late blight.


surface of the leaf. The spots rapidly enlarge until about a
quarter of an inch in diameter. Very few become larger than
this unless a number of them coalesce. The spots are brownish
black to a dull slate white and usually when light colored are
surrounded by a dark margin. In examining leaves that are
spotted in this way usually the fruiting bodies or pycnidia can
be observed as little black specks in the spot. These pycnidia






106 Florida Agricultural Experiment Station

vary in number from about 3 to 15 per spot. When the disease
is severe the leaves are rapidly killed, turn brown and hang
vertically on the plant.
The spots may be confused with nailhead spots by one who is
not accustomed to their appearance, but in general they are
quite different in that there is no zonation in the spot as is
characteristic of the nailhead spot. In this disease the fruit-
ing bodies manifest themselves as small black specks that are
buried in the tissue and can be observed without the aid of a
lens, whereas nailhead spots never have these black specks.

CONTROL

Seed treatment and seedbed sterilization are to be recom-
mended. The application of fungicides such as copper sprays
and dusts should be done at regular intervals similar to the ap-
plication of the same for the control of nailhead rust. Sanita-
tion is as important as any other item in the control of this dis-
ease and in sections of the fields where this disease has ap-
peared it is recommended that the old plants be removed, piled
and burned and that as soon as possible after the crop is re-
moved this land be plowed deeply.

STEM ROT

The disease caused by the fungus Sclerotinia sclerotiorum
(Lib) Mass., and Sclerotinia minor Jagg., is not a common
disease of tomatoes in Florida. It has been reported occasion-
ally doing some damage but in general comparison with other
diseases it is of minor importance. It has been found only in
the south central and western portions of the state, in which
instances the area almost coincides with the celery and lettuce
sections of Florida. The fungus develops in cool moist weather
on muck soils and causes in most instances the damping-off dis-
ease as described elsewhere and the typical wilt disease.
The fungus attacks bearing plants at the soil line, invading the
cortical tissues and vascular system, eventually girdling them,
causing the tops to wilt and die (Fig. 86). It has been found
attacking the branches where they touch the ground and also
invading the fruit under similar conditions.
This disease is found in tomato fields during the whole sea-
son. It has never been found in epidemic form. The fun-





Bulletin 185, Tomato Diseases in Florida


gus has been found attacking lettuce, celery, cabbage, potatoes,
eggplants, peppers, beets and numerous other cultivated crops.
It survives from one season to the next thru the resistant scle-
rotia which are black, hard growths of the fungus capable of
surviving considerable periods of un-
favorable weather conditions. When .
conditions are favorable for growth
they develop delicate apothecia which
produce spores of the fungus in large
numbers. These spores are scattered
by the wind and rain and are capable
of causing the disease wherever they
find favorable environment.

SYMPTOMS

The seedling disease caused by this
fungus is a typical damping-off, result-
ing in the quick wilting, and finally,
death of the seedlings. In the invasion
of the older plants the fungus usually
attacks them at, or slightly above the
soil line. The mycelium invades the
epidermal and cortical layers of the..
main stem, penetrating the vascular
system and cutting off the food sup-
ply. The plant shows a marked wilt-
ing condition and eventually withers
and dies. An examination at this time
will show a large canker at the base
of the plant girdling the stem causing
the softer tissue to disintegrate and at
the same time revealing the black,
hard sclerotia which have been devel-
oped by the fungus. The fungus in-
vades the prostrate branches and the
fruit of the plant that may be touch-
ing the soil. On these parts the my-
celium grows luxuriantly, forming large Fig. 86.-Tomato plant
killed by stem-end rot.
wefts of white thread-like growth in-
clined to advance up the outside of the stem and fruit. The
fruits disintegrate rapidly into a watery soft rot.





Florida Agricultural Experiment Station


CONTROL
The most important things in the control of this disease are
rotation, adequate drainage, and the practice of sanitation in
the field. If the moisture supply can be controlled there is usu-
ally little trouble to be feared. Do not rotate with celery or
lettuce. Staking is of considerable advantage in preventing
this disease.

BLOSSOM-END ROT
There has been no definite organism associated with this
disease. In fact the present consensus of opinion is that this
trouble is of a purely physiological nature, the exact cause of
which is not known. The disease is exceedingly common in the
United States and has been found wherever tomatoes are grown.
It is worst in the Mississippi Valley and in the Southern states.
In Florida it is present every year and takes annual toll of the
tomato crop varying somewhat with the seasons. It is worst
in the central and northern portions of the state in which re-
lationship it corresponds with the sandier types of soil upon
which tomatoes are grown. It is not found to be important on
marl and muck types of soils. Often as high as 50 percent of
the fruit in single fields have been found to be attacked by this
disease.
Test plots grown during the last two or three years contain-
ing more than 100 different varieties have shown the presence
of this disease on all varieties.
It has been found that this condition appears during the
warmer parts of the tomato growing season and is seldom
found during the early, cooler periods. It is probable that in
Florida temperature and soil type are related in this influence
on the disease. During the cooler part of the season tomatoes
are grown on marl and muck soils in the southern part of the
state. As the season develops tomatoes are grown in the cen-
tral and northern part. During the hotter periods of the sea-
son the temperature is around 700F. One theory is that it is
purely a moisture relationship associated with change in tem-
perature. In cool weather the plants have established them-
selves and are growing in a satisfactory manner and during
this period evaporation from the leaves takes place slowly. As
the temperature rises the amount of moisture given off thru
the leaves increases and the roots of the plants, being unable






Bulletin 185, Tomato Diseases in Florida


to keep up with this evaporation, the moisture from the fruits
is withdrawn from the cells farthest from the stem end, thus
resulting in the appearance of small brown spots at the blossom
end of the fruit. This continued evaporation causes the spot to
enlarge and involve most of the fruit. The disease has been found
on tomato fruits in all stages of their development from mere
buttons as large as the end of one's finger to fruit that is ma-
ture. The disease involves most fruits when they are about one
and one-half to two inches in diameter.

SYMPTOMS

First symptoms of this disease on tomato fruits are always
at the blossom end where small brown patches begin to appear.
These patches (Fig. 87) enlarge into definite spots which be-

in circular outlines. The
part of the fruit that
is involved shrinks and .,
becomes dry as a dis-
tinctive dry rot unless
it becomes overrun with
secondary organisms
(Fig. 88) which may
cause a soft rot. The
fruit becomes flat on
the blossom end. In ob-
serving a cluster of
fruit that has blossom-
end rot it will be noted
that the color of these
fruits on the upper sur- __ _
face is a lighter green tu
than that of healthy
than that of healthy Fig. 87.-Blossom-end rot of tomatoes.
fruit. As the rot ad-
vances the whole fruit becomes involved and in many instances
is mummified and persists on the vine.

CONTROL

Control measures suggested are that the water supply of
plants be regulated and that as the temperature increases, the






Florida Agricultural Experiment Station


water also be increased. This will insure a constant growth of
the plants and will probably prevent the occurrence of this dis-
ease. It is also well to keep the young plants in a healthy grow-
















Fig. 88.-Blossom-end rot of tomatoes, showing infection by
secondary organisms.

ing condition while in the seedbed and see that they are well
developed before transplanting to the field.

BACTERIAL ROT
This disease has been very common during the past season
in tomato fields in Florida. It is caused by bacterial organisms
such as Bacillus carotovorus Jones, and Bacillus aroideae
Towns. The organisms causing the disease in Florida have not
been definitely determined. The two listed have been found as-
sociated with this disease in other places in the United States.
The losses in the United States are principally in the extreme
eastern sections and in the South. In Florida this disease has
been more common during the past season than ever before and
has been found covering a larger range in this state than many
of the other diseases. It was found quite uniformly invading
the fruit in variety plots where more than 100 different varie-
ties of tomatoes were grown. The loss in some plots was as much
as 25 percent. This disease increases in severity as the season
develops. Early in the season when tomatoes were being har-
vested in the lower East Coast area very little of the disease





Bulletin 185, Tomato Diseases in Florida


was found. It developed with the season until in June consid-
erable loss was suffered in the central and northern parts of the
state. This disease was destructive in tomatoes that were grown
for local market where the fruit was left to mature on the vines.
In this case the disease increased in severity as the fruit ripened.
It has been found affecting the fruits from the time they were
as large as walnuts to maturity.
The organisms gain entrance to the fruit thru wounds. Num-
erous wounds are produced on the fruits by cultivation, prun-
ing, and insect attacks as well as thru openings made by cracks
in the epidermis and growth cracks around the stem end. The
disease manifests itself in the form of a watery soft rot. This
soft decay develops very rapidly and in a day or two will in-
volve the whole of a single tomato fruit. The contents of the
fruit become soft and watery and remind one very much of a
thin rubber bag (Fig. 89) half to three quarters full of water.
Fruit in this condition per-
sists on the vine for several
days, or if ruptured, the '
ill-smelling contents leak
out. Often the contents
evaporate and the epidermis
dries up and persists on the
vine long after the field has
been abandoned.

CONTROL

Disinfect seed before
planting (see page 131).
Control the insects, es-
Control the insects, es- Fig. 89.-Bacterial rot of tomato
specially the stink bug and fruits.
tarnished bug. They are
undoubtedly the most important factors in the spreading of the
disease. The practice of sanitation in the field would eliminate
the disease to a considerable extent and the application of cop-
per sprays and copper-lime dust would prevent the spread of
the disease.
DOWNY MILDEW

The disease known as downy mildew of tomato is caused by
Phyto.phthora infestans (Mont.) DeBary, the same fungus that





Florida Agricultural Experiment Station


causes late blight of potatoes. Because this disease is practi-
cally limited to regions where the temperature is moderately
cool during rainy seasons, it is seldom of economic importance
to the tomato crop in Florida.
The fungus causing buckeye rot of tomatoes is a near rela-
tive of this fungus and it causes serious decay of tomato fruits
during wet weather, but does not attack the vine. Downy mil-
dew causes considerable damage to the plant, and also produces
a very destructive rot of the fruits. Affected tomatoes decay
very rapidly during transit and are a serious menace to the
load because the fungus is able to penetrate the moist wrap-
pers and pass from one fruit to another in the baskets.
No varieties of tomatoes are known to be immune to this
disease. The importance of downy mildew is almost entirely
determined by weather conditions. Hot, dry seasons are so
unfavorable for the growth and distribution of the fungus that
it is unable to cause an appreciable amount of disease, while on
the other hand, wet, moderately cool seasons favor its develop-
ment so much that it may cause serious damage to the tomato
crop.
DESCRIPTION

The lesions produced on the leaves are usually rather large,
irregular, greenish, water-soaked areas. In wet weather a
fine white mildew may be seen on the diseased tissues on the
under side of the leaf. The spores are borne in great numbers
in this white mildew and are spread rapidly by wind, rain and
insects. In severe epidemics this leaf blight may destroy the
majority of the plants in a field.
The spots on the fruits appear as large, greenish water-
soaked, irregular blotches. These lesions do not have the
brown markings so characteristic of buckeye rot. In very wet
weather a fine white mold may be seen on the surface of the
badly decayed fruits.

CONTROL

This disease may be controlled by spraying the plants thoroly
with 4-4-50 Bordeaux mixture, or other good copper sprays and
dusts. Tomato fruits that show water-soaked blotches should
never be packed for shipment.





Bulletin 185, Tomato Diseases in Florida


FUSARIUM ROT

The common rot found in tomatoes that are grown for local
markets and for home use is caused by Fusarium spp., and is
considered in the group of secondary organisms. This rot is
distributed over the tomato area of Florida, being more com-
mon in the central and northern portions of the state. The
fungus has not been observed on green fruits at any time and
artificial inoculations have demonstrated that the fungus will
not invade the mature fruit if the epidermis is intact. In other
words, this fungus is a typical wound parasite attacking the
fruits thru natural openings at the blossom end, punctures


















Fig. 90.-Fusarium rot of tomato fruits.

caused by insects, worms, and growth cracks. This rot is most
common on the mature fruit that is ripening on the vines. It
is common and most destructive following periods of wet weath-
er and in fields where blossom-end rot is prevalent.
This rot is considered a dry rot in that the fungus develops
rapidly in the fruit, causing it to shrivel and dry. Except in
rainy weather the invaded fruit mummify, these mummies per-
sist on the vines. In wet weather the rot is of a soft, watery
nature. The fruits usually break open at the point of injury
and the contents leak out, leaving the epidermis adhering to the
vine.





Florida Agricultural Experiment Station


The rot is characterized by the pinkish color of the surface of
the invaded area. This pink mass consists of multitudes of
fungous spores. The disease causes damage in transit when the
fungus invades fruit that has been injured during grading and
packing.
SYMPTOMS
The rot is first characterized by the sunken area around the
ruptured epidermis. This sunken area enlarges in extent rap-
idly and after 24 to 48 hours a pinkish growth develops over
the surface. The rot produced, except under rainy conditions,
is a semi-dry rot (Fig. 90). The fruit gradually shrivels up,
becoming ridged and furrowed, covered with a pink growth,
and often hangs on the vine for a considerable time after it is
completely dry.
CONTROL
The general spray schedule as practiced and applied for nail-
head rust is of considerable assistance in controlling this dis-
ease. Fruits that have been attacked by insects and those that
have growth cracks should be removed from the field and fruit
that is to be used locally should be picked in the pink stage
rather than left on the vines to fully mature. Care should be
exercised in sorting and packing to prevent the inclusion of
infected fruit.

BOTRYTIS STEM AND FRUIT ROT
The fungus, Botrytis sp., is so widely disseminated and such
a common parasite on truck crops that it is not surprising to
find it attacking tomatoes occasionally. When it attacks the
tomato plant, it usually is under very humid conditions such as
are found in greenhouses or during wet weather in the field.
The fungus gains entrance thru leaf-scars or other dead or
dying tissue and from there it works its way into the living
parts of the plant. Under favorable conditions Botrytis may
develop lesions severe enough to cause wilt, or even death of
the plant. Occasionally tomato fruits become infected thru
wounds, growth cracks and possibly following insect injuries.

DESCRIPTION
On the stems the disease is characterized by large, water-
soaked areas which, during wet weather, soon become covered





Bulletin 185, Tomato Diseases in Florida


with the grayish-brown mycelia and spores of the fungus. The
lesions produced on the fruit are watery, blister-like areas with
a light brown or tan colored central region. The decay devel-
ops rapidly and the fruit is converted into a soft watery mass
within a few days. If the skin is broken the grayish mycelium
and clusters of spores develop within a few hours.

CONTROL

This disease is not important enough in the field to warrant
special control measures. The spray schedule for the control
of nailhead rust is sufficient. In the greenhouse good ventila-
tion and cutting down the water supply will do much toward
stopping its development and spread.

OOSPORA ROT

This decay is caused by the fungus Oospora lactis parasitica
P. & P. It is one of the secondary organisms. It has not been
found widely distributed in the United States nor has it been
known except locally to cause considerable damage. The dis-
ease in Florida is very common and destructive during rainy
periods. These periods are not only favorable for its develop-
ment but are also conducive to the development of growth cracks
wherein it gains entrance to the fruit. It is strictly secondary in
that the injury it causes in Florida is found in bruises and insect
punctures where the epidermis is ruptured, and following in
growth cracks where the flesh beneath the epidermis is exposed.
The disease is the most common under the last condition and is
more serious in the central and northern parts of Florida because
tomatoes in these sections are maturing during the early part of
the rainy season. The disease has not been found on green
fruit unless they have been wounded or crushed. It is very
active on the mature fruit and may sometime cause consider-
able loss in transit.

SYMPTOMS

During rainy periods when the temperature is high this fun-
gus can be found in practically all tomato fields where the fruit
shows growth cracks. The moisture held in these crevices is
ideal for the development of the fungus which grows rapidly
and in 12 to 24 hours shows a distinct whitish scum-like






Florida Agricultural Experiment Station


growth (Fig. 91). The organism invades the tissue on either
side of the point of entrance and rapidly breaks down the cells,
causing the watery, soft decay. The disease develops rapidly
and under favorable conditions involves the whole fruit within
48 hours.
CONTROL

Fruit that is being developed for the local market and home
use is best removed from the vines when it begins to show pink,
thus overcoming the possibility of its becoming cracked and















Fig. 91.-Oospora rot of tomato fruits.

affording an entrance for the fungus. In fruit that is picked
green the disease can be almost wholly controlled by careful
grading and packing.

DAMPING-OFF

The wilting and falling over of young seedlings in the seed-
bed is spoken of as damping-off. It is encountered every year,
affecting seedlings in seedbeds and in the field. This trouble
is not confined to tomatoes but is found on seedlings of numer-
ous truck crops. It is often difficult to name the organism
causing the trouble. In fact it has been found in a large num-
ber of cases that there are several organisms concerned. Those
listed are in order of their prevalence and destructiveness in
the seedbeds in Florida: Rhizoctonia solani Kuhn; Pythium de-
baryanum Hesse; Sclerotinia sclerotiorum; and Fusarium spp.






Bulletin 185, Tomato Diseases in Florida


There are others that have been found associated with diseased
seedlings but usually they have been found secondary to those
already mentioned.
Rhizoctonia solani Kuhn is without doubt the most cosmo-
politan of the group. It is more widespread in the trucking
areas of Florida than any of the others listed and probably
causes as much loss from damping-off as all the other damping-
off fungi combined.
The actual destructiveness of Pythium debaryanum is small.
It has been found in isolated cases doing damage but in very
few cases has it been found in epidemic form causing damping-
off of tomato seedlings.
Sclerotinia sclerotiorum (Lib) Mass., is more localized in its
distribution and in the severity of the disease it causes.
Fusarium spp. are in a large number of cases associated with
the damping-off of tomato seedlings. It is doubted whether
these fungi are capable of causing the disease without the as-
sociation of one or more of the above organisms.

SYMPTOMS
The symptoms of the disease resulting from invasion of the
plant tissue by any of the above organisms are in most cases
quite similar. The first indication of the trouble is a slight
drooping of the cotyledons at the tips and a general lack of
turgidness of the seedlings. This drooping of the tips of the
cotyledons rapidly develops into a marked wilting and very
shortly, often within 12 to 24 hours, the stem appears water-
soaked at the soil line and soon the plant falls over, unable to
revive, the stem bending at the surface of the soil. During the
next 24 hours the mycelium of the fungus overgrows the pros-
trate seedling. It can be readily detected in the early morning
over the surface of the soil and the prostrate seedlings by the
spidery web-like threads covered with moisture. This disease
may be found in spots in the seedbed where it is developing
from a primary infection, killing the seedlings in more or less
circular patches, or it may be found generally infecting seed-
beds, completely killing large numbers of seedlings. The de-
velopment of this disease is to a large extent controlled by the
amount of moisture present in the soil and the amount of venti-
lation that is possible among the young seedlings.






Florida Agricultural Experiment Station


CONTROL
Soil sterilization is the only sure way of controlling damping-
off in the seedbeds. This can be accomplished either by the
application of a solution of formalin and water applied to the
soil, by treating the soil with live steam, or by using mercuri-
chlorophenol compounds commercially known as Uspulun and
Semesan. Some control is to be gained by the practice of seed
treatment. The seed should be treated, however, under any
circumstances, whether the seedbed has been sterilized or not.
If the seedbed has not been treated it is necessary to treat the
seed to kill seed-borne organisms.
Another important thing to be considered is the selection of
the seedbed in reference to the type of soil, moisture relation-
ships and ventilation. A general practice that has been found
of considerable importance is the stirring of the soil between
the rows of seedlings by the use of small hand tools as soon as
the rows can be distinguished.

RHIZOPUS ROT

This soft rot is produced by Rhizopus nigricans Ehr., and is
not exceedingly important in Florida except as a ripe rot. It
has not been found on green fruits except where they have been
previously injured or crushed and in such instances its appear-
ance is exceedingly rare. Neither does it appear on ripe fruit
that is sound. Thus this fungus may be considered a secondary
organism decaying mature fruit. In the field this rot usually
follows up injury produced by insects, altho it invades natural
cracks in the epidermis. The amount of fruit that is matured
on the vines in Florida is small in proportion to that which is
picked green, and for this reason this disease is not important.
It is important in transit upon the fruits previously injured
that have ripened in shipment. This fungus enters thru the
injured places, causing soft, watery rot of the fruit. The fun-
gus is favored in its development by humid conditions and high
temperatures.
SYMPTOMS

The infection of growth cracks shows considerable growth
of the fungus mycelium in the first 12 to 18 hours. After this
time there appear in the mycelium small white specks which







Bulletin 185, Tomato Diseases in Florida


after six to eight hours turn black, appearing as small round
black knobs on the end of the fungus threads. These small
heads are clusters (Fig. 92) of spores of the fungus and are
dislodged by the faintest touch or disturbance. The tissue
around the infection collapses rapidly as the fungus invades it,
producing a soft, watery rot. In 36 to 48 hours the whole















Fig. 92.-Rhizopus rot of tomato fruits.

fruit may be broken down and mushy. Tomato crates which
have diseases fruit in them may be detected by the leaking
of the contents.
CONTROL

To reduce the loss of fruit for the local market and home
consumption it is suggested that the fruits be picked as soon
as they show the first indication of ripening. This is applicable
especially in rainy weather. To avoid loss from this disease in
transit the fruit should be carefully graded before packing and
all fruits showing growth cracks or mechanical injury should
be discarded.

PUFFY TOMATO

Puffy tomato is a non-parasitic disease which is widely dis-
tributed in the South. In Florida it is most important, and
the losses from it are greater than from any other non-parasitic
disease. This condition is common over the whole tomato area
of Florida and in all sections the disease is destructive year






Florida Agricultural Experiment Station


after year. It appears at the beginning of the season and in
many instances affects the fruits thruout the season. The con-
sensus of opinion is that this disease is caused by an unbalanced
fertilizer and moisture relationship in which excessive nitro-
genous material is made available in too large quantities for the
best assimulation by the plant.

SYMPTOMS
The fruits are the only part of the plant affected, altho
plants that show puffy fruit are usually of an exceedingly suc-
culent growth. The fruit may vary in shape from perfectly
normal to a scalloped shape, the partitions protruding and the
fleshy portions between them being sunken. Puffy fruits are


Fig. 93.-Sections of puffy tomato,


showing interior cavities.


usually detected because of their light weight. They can be de-
tected by one familiar with the condition by their slightly light-
er color. They are also hollow to pressure applied by the hand.
In cutting such fruit in two it will be observed that there are
large unfilled spaces in the interior of the fruit between the
solid seed mass and the fleshy part of the skin. The outer lay-
er of flesh next to the epidermis in most cases is of normal
thickness and of good texture, whereas the central portion of







Bulletin 185, Tomato Diseases in Florida


the fruit appears to be hard, compact and undeveloped. The
different stages of puffiness are shown in Figure 93. This con-
dition prevails from the time the young fruits are two-thirds
developed in size until they are completely ripened on the vines.

CONTROL

No methods of control have been worked out. It is thought,
however, that fertilizer applications associated with excessive
moisture may be the most important factors to keep under ob-
servation.

SUNSCALD
Sunscald of tomato fruits may be attributed to the com-
bined action of light and heat resulting from direct exposure
to the sun. This type of injury is very common over the
United States in general and in Florida appears in individual
fields usually after the middle of the picking season. This in-
jury is serious on both staked and unstaked tomatoes. It as-
sumes its most dangerous proportions after the first and sec-
ond pickings. The reason for this is that the pickers go thru
the fields and turn the vines over in search of the marketable
fruit and instead of turning the vines back to their original
place they leave them with the bottoms turned up, exposing the
undeveloped and unpicked fruit to the direct sunlight. On the
staked plants this injury is usually found immediately follow-
ing a severe pruning of the plants in which the protecting foli-
age is cut away, exposing the fruits. This injury is conducive
to the invasion of secondary organisms which invade the dead
areas. Once they have entered the fruit they involve the heal-
thy portions. They produce spores which are scattered far and
wide and from these sources infect many other fruits that may
have escaped infection, even tho injured.

SYMPTOMS
The injury is usually located on the sides or top half of the
tomato fruit and appears in the form of a whitish shiny, blis-
tered area. It is apparent that the chlorophyl which gives the
plant the green color is completely killed, leaving the tissue
white. In some cases cells break down, leaving the surface
shiny, soft, and often wrinkled. The injury is always on the






Florida Agricultural Experiment Station


outside of a cluster of fruit. In case where no secondary (Fig.
94) infection takes place the spot often remains light colored
when the remaining part of the fruit ripens.

CONTROL

This condition can be completely controlled if in picking the
fruit the pickers are careful to leave the vines in the same po-
sition they found them, thus preventing the exposure of the













Fig. 94.-Sunscald. Second and third (from left) fruits infected by
secondary organisms.

unpicked fruit to the direct rays of the sun. As for the staked
tomatoes, it may be well to plant them thicker in the rows so
that when pruning takes place the fruit will not be unduly ex-
posed.

GROWTH CRACKS
This condition of tomato fruits is found more or less wher-
ever tomatoes are grown. In Florida it is found over the en-
tire state and is attributed directly to the moisture and fertil-
izer relationships which tend to produce quick growth. Even
tho it is widespread the losses from this trouble are not large,
except when secondary rot-producing organisms invade these
wounds. However, this is a very common occurrence during
transit and marketing. Its appearance is not common on small
green fruit but is found before maturity. Most of the fruit
is picked while still green and the trouble is less important
than it might be if the fruit were ripened on the plant. As
the ripening process takes place these cracks begin to show up
around the stem end. The percentage of fruit showing these






Bulletin 185, Tomato Diseases in Florida


cracks increases proportionately with the stage of ripeness.
Often where fruit is completely ripened on the vines the loss
from growth cracks increases to 50 percent.

SYMPTOMS

The first sign of growth cracks appears around the stem end
where the fruit is attached to the vine. The cracks at this time
are exceedingly small and radiate from the stem. As the fruit
develops these cracks become deeper and develop (Fig. 95) thru
the fleshy part of the tomato, exposing the seed. In some cases
a circular, concentric cracking manifests itself around the stem
















Fig. 95.-Growth cracks of tomato fruits.

end, often three or four distinct circular cracks appearing in
the upper half of the tomato. These cracks cross at right
angles to the cracks radiating from the stem end. Another
type of cracking is the splitting of the epidermis of fruits that
have begun to show the pink ripening condition. This is par-
tcularly common and destructive during rainy weather and is
also important because of the invasion of secondary organisms.

CONTROL

Fruit that is to be used for local markets and home consump-
tion should be picked from the vines in the early pink stage and
ripened off the vine to prevent the invasion of secondary organ-
isms. Fruit that is picked in the green stage for shipment






Florida Agricultural Experiment Station


should be very carefully graded because of the possibility of
loss in transit.

SKIN CRACKS
This condition of the fruits is distinct from the type of in-
jury commonly known as growth cracks. In the case of skin
cracks the ruptures are only in the epidermis. They are not
noticeable in the early development of the fruit. Secondary
organisms enter these openings and decay follows. This trouble
is attributed to physiological conditions not well understood at
the present time. It is more or less associated with individual
plants rather than a general condition in the field. The af-















Fig. 96.-Skin cracks of tomato fruits.

fected fruits are exceptionally thin skinned. All fruits that
show this condition are unfit for marketing and should be culled
out in packing. Altho this is not a general trouble, it is quite
common on fruits that are beginning to ripen.

SYMPTOMS
These cracks are usually very small and linear, only one-
sixteenth to one-eighth inch in length. As they develop the epi-
dermis peels back from the original crack. The ruptures are
barely thru the epidermal layer of cells (Fig. 96) and are of
consequence only as openings for the invasion of the fruit by
secondary organisms that are not able to penetrate the epi-
dermal layer.






Bulletin 185, Tomato Diseases in Florida


CONTROL
No control methods can be recommended at this time. It is
suggested, however, that plants showing fruit affected in this
way be removed from the field, since the fruit will not be
marketable.

CAT FACE
This name has been applied to fruits that show a distinct
marking and distorted shape at the blossom end. The condi-
tion is common in tomatoes over the United States wherever
they are grown and has been observed in all the tomato sec-
tions of Florida. Inquiries have been made as to the general
cause of the same and what should be done to prevent it. It















Fig. 97.-Cat face of tomato fruits.

is not caused by organisms of any sort but rather is considered
to be a variation in varieties, the exact cause being unknown
at the present time.
The trouble has been found in Florida on more than 100 dif-
ferent varieties of tomatoes, so it can be safely stated that it is
not peculiar to any particular variety. The fruits on a single
plant have a tendency to show some variation of this distinct
marking, whereas the fruits on the adjoining plant may be all
of first class marketable type.
As to loss that may result from this condition it is quite im-
possible to make a calculation that will be definite and valuable.
None of the fruits, however, marked this way are fit for ship-






Florida Agricultural Experiment Station


ping. Most of them so affected are total loss and are left in
the fields unpicked to be overcome by the attacks of secondary
organisms that cause numerous rots and decays.

SYMPTOMS
Fruits that are typified by the name cat face are those that
are mal-formed, showing ridges, furrows, protuberances, ribs,
creases, (Fig. 97) indentations and blotches at the blossom end
of the fruit. They are usually unbalanced in contour and un-
evenly developed.
CONTROL

No definite recommendations for control can be given, since
the cause of this trouble is not known, but as it is considered a
varietal variation, it is suggested that the best seed should be
secured so that the plants will develop true to the desired type.
Care should be exercised in packing and all fruits that show
any of these markings should be discarded, since they bring a
very low price on the market and are much more apt to be
bruised and injured in the packing process because of their un-
evenness of contour. Secondary organisms will cause loss to
these fruits in transit and those adjoining them.

CLOUDY SPOT
This physiological trouble has been recently found scattered
more or less uniformly over the whole tomato growing area of
Florida. No causal organisms have been associated with its
occurrence. It is not common and is in no way associated with
puffy tomato which is a different and distinct condition. This
condition is not associated with definite areas of the field, but
rather seems to be confined to individual plants. A certain
plant may have from 50 to 90 percent of the individual fruits
showing this disease, whereas the plant next to it will be nor-
mal. Less than 1 percent of the plants show this condition, con-
sequently the resulting loss is negligible. All fruits that show
this cloudiness should be culled out in the packing house.
The cause of cloudy spot is unknown at the present time, and
it will be necessary to do further work in order to give any defi-
nite information as to its cause.





Bulletin 185, Tomato Diseases in Florida


SYMPTOMS
The trouble is noticeable on the fruits in the form of light
colored, almost whitish blotches (Fig. 98) which are irregular
in shape, appearing in the tissue under the epidermis on the
surface of the fruit. Half-matured tomatoes have been found
almost completely covered with this cloudy blotching. Fruits
have been collected which show this blotching quite distinctly
following the vascular system and appearing as a network of















Fig. 98.-Cloudy spot of tomato fruits.

veins in the epidermis. Cutting thru the epidermal layer into
this light colored area, one finds groups of silvery white cells
signifying the lack of moisture. The tissue affected is in all
cases the parenchyma cells immediately under the epidermis
commonly spoken of as the fleshy part of the skin. These
blotches may be barely visible or they may involve the complete
surface of the fruit. No control methods are known.

LEAF ROLL
Leaf roll is a condition of the tomato plant that is very simi-
lar to a disease of the same name on potatoes. On the potato
the disease is transmitted in the tubers. With tomatoes very
little is known as to its transmissibility. The disease is com-
mon in Florida. Plants having leaf roll can usually be found
in almost any field during the latter half of the tomato season.
The trouble appears to be more common on staked tomatoes
that have been severely pruned than on those that are not






Florida Agricultural Experiment Station


staked. Leaf roll does not manifest itself markedly on an indi-
vidual plant until about the time of setting of the fruit in the
first and second clusters. At this time the leaves begin to roll
and the disease manifests itself rather suddenly. It involves
practically all the leaves on the lower half of the plants. When
the plants show leaf-roll in this way they appear to be stunted,
and their growth is very slow. No investigation has been made
to show the relation of this condition to yield.

SYMPTOMS
When the trouble is first observed the margins and tip of the
older leaves begin to roll upward, thus tending to form curved
leaves, shaped quite like the hollow of a spoon. As it progresses
these leaves often become more cylindrical, the margins touch-
ing or overlapping the midrib, the ends of the cylinder remain-
ing open. In severe cases three-fourths of the leaves on a sin-
gle tomato plant have been involved in this rolled condition.
The leaves affected are harsh to the touch. (They are brittle
and at times almost leathery.) They are much thicker than nor-
mal leaves and become stiffened and are shiny on both the up-
per and lower surfaces. The leaves that have been long af-
fected are so brittle that they will break rather than bend to
the touch. Except for stunting, other parts of the plant do not
appear to be materially affected.

CONTROL
No method of control can be recommended at this time since
no investigational work has been conducted to determine the
prevalence and dissemination of this trouble. Always procure
good seed from reliable seedhouses.

BLOSSOM DROP
Blossom drop is a physiological disease characterized by
shedding of the blossom at the beginning of the blooming period
and continuing for sometime thereafter. The exact cause is
not known. This trouble is general and has been experienced
by tomato growers over the United States, but no epidemic has
been reported. In Florida the condition is not so prevalent as
in other sections of the United States, altho at times it causes






Bulletin 185, Tomato Diseases in Florida


considerable unrest among growers when they find this trouble
in the field.
Some growers are of the opinion that temperature is the de-
ciding factor and that considerable fluctuations will cause the
shedding of numerous blossoms. Others lay the shedding of
the blossoms wholly to the moisture. If there is abundant mois-
ture the plant tends to excessive vegetative growth and sets
few fruits.
Another opinion is that an unbalanced fertilizer relationship
is more important than either temperature or moisture. When
too much moisture is present an over-supply of nitrogen is
made available in too short a period and the plant takes up
this food in excess. This causes a very succulent vegetative
growth of the plant. In this type of plant less fruit is set. It
seems probable that each of the above factors, acting individu-
ally or collectively, may be responsible for blossom drop. A
plant that is growing succulently has very little tendency to
change from the vegetative state to the reproductive state and
the factors that are responsible for the shedding of blossoms ap-
parently have a direct relationship to the vegetative growth of
the plant. These conclusions have been drawn merely from ob-
servations in the field where this disease has been prevalent
and are not based on definite data developed by experimental
work.

SYMPTOMS
The blossoms separate from the plant at the first joint in the
blossom petiole. The shedding flowers include buds that are
not yet opened as well as blossoms that are declining. The plant
is not injured by this shedding process.
Nothing definite in the line of control measures can be rec-
ommended.

SANITATION AND ROTATION

It is absolutely necessary to practice sanitary methods in
both seedbed and the field to insure a good crop of tomatoes
with the least amount of disease. Under Florida conditions
many of the diseases of tomatoes live from one season to the
next in old refuse and wild plants. In harvesting tomatoes all
fruits not suitable for shipping are left in the field. It is usu-






Florida Agricultural Experiment Station


ally these fruits that are infected with numerous diseases;
such as nailhead rust, buckeye and phoma rot. This culled fruit
should be disposed of, preferably by burying 2 or 3 feet deep.
After the plants are removed from the seedbed, utilize that
soil by planting it to some other crops instead of leaving it to
become overgrown with obnoxious weeds and straggling toma-
to plants left there at transplanting time. Plant it to beans,
corn, peppers, etc., thereby not only producing a useful crop
but also insuring crop rotation instead of a growth of diseased
tomato plants and weeds.
Diseases (non-parasitical and parasitical), tend to become
more numerous and severe on tomatoes as the industry becomes
concentrated. In this concentration and centering of tomato
growing, one crop tends to follow the preceding crop more
closely. This practice is not favorable for the best development
of the industry. Consequently a definite rotation program is
strongly recommended. Such a program necessitates the grow-
ing of other crops on the land planted to tomatoes during the
period of the year when tomatoes are not growing. It also
calls for a rotation from year to year. Grow a legume, cucurbit,
hay, corn or root crop on the land following tomatoes. Should
the diseases of tomatoes cause considerable damage, rotate for
two years instead of one. Care should be exercised in planning
the rotation schedule so that tomatoes do not follow potatoes,
eggplant, tomatoes, celery or lettuce. The reason for this pre-
caution is that some of the destructive diseases on these plants
are also important on tomatoes.

SEEDBED STERILIZATION

It is necessary to combat certain diseases of tomatoes in the
seedbed, because there is where they first appear and cause con-
siderable loss. Even when the conditions are such that little
loss occurs in the seedbeds, there is still the danger of carrying
the disease to the field where it might cause damage when con-
ditions are favorable for its development. Then it would be
in a position to spread rapidly over the field. In sterilizing the
seedbed a thoro job should be done. Two efficient methods of
sterilizing soil to be used as a seedbed are given below.






Bulletin 185, Tomato Diseases in Florida


SOIL STERILIZATION WITH FORMALDEHYDE

After the soil selected for the seedbed has been well stirred
and loosened, apply a formaldehyde solution made of 4 pints of
formaldehyde and 50 gallons of water at the rate of 1 gallon to
1 square foot of soil surface. The solution is best applied with
a common garden sprinkler. In that way there is little danger
of its running into low places before soaking into the soil.
After the solution has been applied the surface of the soil
should be thoroly covered with a tarpaulin, canvas, or bur-
lap bag. This covering prevents too rapid evaporation of the
disinfectant. The covering should be left on the soil for at
least two days, after that it can be removed and the soil stirred
to hasten evaporation of the formaldehyde. Seven days after
applying the solution and five days after uncovering and stir-
ring it, the soil can be prepared and the seed planted.

SOIL STERILIZATION WITH STEAM
This process necessitates the use of a steam boiler of consid-
erable capacity and a rectangular galvanized iron pan large
enough to cover a considerable area but small enough to be
moved by four men. The pan should have sides six to ten
inches high with sharp edges, so that it can be inverted and
pushed down into the soil. In this position it is connected to
the boiler by rubber hose so that steam from the boiler is dis-
charged into the inverted pan. Steam should be discharged
into this pan until a potato of medium size buried 6 inches in
the soil under the pan is cooked. Then remove the pan to an-
other portion of the bed and repeat the process. This method
is more satisfactory than the formaldehyde method, but it is
considerably more expensive.

SEED DISINFECTION
Seed disinfection is recommended to all tomato growers, in
fact, it should be practiced with every planting. The process
is easy and takes only a short time and the results are profit-
able. In treating the seed all pathogenic organisms adhering
to the seed, such as bacteria and fungi, are killed. The seed
themselves are not harmed and will germinate almost as quick-
ly and produce as strong plants as ones which have not been
treated.






Florida Agricultural Experiment Station


The disinfection process is as follows: Place the seed in a cloth
bag, tie the top securely, leaving plenty of space in the bag for
the seed, for instance twice as much room as the seed occupy.
Submerge the bag of seed in a solution of corrosive sublimate,
strength 1:1,000, for 7 to 8 minutes. During this time it is
well to move the bag around in the solution, using a short
stick. This will insure the removal of air bubbles so that all
seed will come in contact with the disinfectant. After the 7 or
8 minute period is up, remove the bag of seed from the disin-
fectant and rinse in several changes of clear water. After the
seed are thoroly rinsed, spread them out in the shade to dry.
When dry the seed are ready to plant.
The container should not be of metal because some of the
mercury in the corrosive sublimate unites with the metal, thus
weakening the solution. Instead use wooden containers such
as pails, half barrels or earthenware crocks.
The disinfectant can be purchased from your local druggist
and can be obtained in the form of dry crystals or made up in
the form of tablets. An ounce of the crystals dissolved in 71/2
gallons of water makes a solution the designated strength,
1:1,000. When smaller quantities of the disinfectant are de-
sired it is advisabe to use tablets. One tablet dissolved in one
pint of water gives a solution of the strength of 1:1,000. If a
gallon of the disinfectant is desired, dissolve eight tablets in a
gallon of water.
Corrosive sublimate is a deadly poison when taken internally.
Consequently it should be kept away from children. When the
solution is made up it looks like water, being tasteless and odor-
less, yet deadly poisonous. Necessary precautions should be
taken in disposing of the liquid after it has been used so that
nothing will drink it.
Seed may be treated without soaking by the use of different
mercurichlorophenol* compounds prepared in the form of dusts.
The seed are disinfected by thoroly mixing certain amounts of
them with a specific amount of the dust. The above dusts can
be purchased from most seed and spray machine dealers.
*There are a number of mercurichlorophenol compounds used for the
treatment of seed of various kinds. The most commonly used compounds
are sold under the trade names of Uspulun and Semesan.







Bulletin 185, Tomato Diseases in Florida


FUNGICIDES AND THEIR APPLICATION
It has been an established fact among successful tomato
growers that plant diseases are their worst enemies. If they
could control the diseases that attack the host plant they could
produce a good crop of tomatoes almost every season. The use
of fungicides for the control of diseases has not been generally
practiced thruout the tomato growing sections of the state,
altho more growers are using some sort of fungicide for the
control of diseases than ever before.

BORDEAUX MIXTURE
Home-made Bordeaux mixture, 4-4-50, is the most valuable
spray for the control of tomato diseases. Altho not used ex-
clusively by the growers, it is probably used more than all
other fungicides combined. When weather conditions are nor-
mal it gives good control if properly made and applied.
If a large amount of spraying is to be done it is most con-
venient to make up stock solutions of bluestone and lime in such
proportions that one pound of either bluestone or lime is con-
tained in each gallon of water. These stock solutions will keep
indefinitely providing they are not allowed to dry out. When
a stock solution is once made the surface level should be marked
on the inside of the container so that water lost by evapora-
tion can be replaced and the whole thoroly stirred before any
of the materials are used. Keep stock solutions covered.
Stock Solution A, Bluestone: Dissolve at the rate of 1 pound
of bluestone to 1 gallon of water; put 50 pounds of bluestone
into a clean bag and suspend it in the top of a 50-gallon barrel
of water. It will dissolve over night. Never use a metal con-
tainer for this purpose. Always stir the stock solution before
using.
Stock Solution B, Lime: Slake 50 pounds of rock lime and
dilute it in 50 gallons of water. Be careful not to drown or
burn the lime while slaking. Do not stir the two stock solu-
tions with the same stick.
Hydrated lime may be used in place of rock lime. If hydrated
lime is used it is necessary to use 1/2 again as much as rock
lime. Thus 75 pounds rather than 50 pounds should be used in
50 gallons of water.






Florida Agricultural Experiment Station


In making Bordeaux mixture observe the following direc-
tions: Dilute the required amount of bluestone solution to half
the amount of spray to be made. Dilute the required amount
of lime in a separate container to half the amount of spray to
be made. Then at the same time pour the contents of the two
containers into a third container or spray tank, stirring the
combined mixture as the two are poured together. Be sure to
place a fine strainer either over the faucets on the barrels or on
top of the spray tank so that all of the liquid will be well
strained; this will prevent nozzle trouble in the field.
Mixing Platform: If many acres are to be sprayed during
the season, it will be necessary to construct a mixing platform
(Fig. 99) where the Bor-
deaux spray can be conven-
iently mad e. The first
thing to consider is the wa-
ter supply. Build the plat-
form in a place convenient
to both the water supply
and the field to be sprayed.
The platform should be well
built and high enough to
permit the solutions to flow
by gravity into the spray
tank. Upon this platform
Should be built a smaller
platform upon which t h e
stock solutions are made.
The smaller platform
should be elevated enough
Fig. 99.-Bordeaux mixing plant. so that the stock solutions
(Courtesy U. S. D. A.)
can flow into the barrels
on the main platform. By following these principles in a gen-
eral way the laborious job of making Bordeaux mixtures is ex-
tremely simple.
It is essential that this mixture be applied soon after it is
made. It is of little value after standing 24 hours.
Different Amounts of 4-4-50 Bordeaux Mixture: In making
50 gallons of the mixture, use 4 gallons of stock A, diluted to
25 gallons, and 4 gallons of stock B, diluted to 25 gallons. Run






Bulletin 185, Tomato Diseases in Florida


both of these into the sprayer at the same time with the agi-
tator going.
To make 100 gallons of spray, use 8 gallons of stock A, di-
luted to 50 gallons, and 8 gallons of stock B, diluted to 50 gal-
lons. Mix as above.
To make 200 gallons of spray, use 16 gallons of stock A, di-
luted to 100 gallons, and 16 gallons of stock B, diluted to 100
gallons. Mix as above.
If it is impractical to use the above method of mixing the
Bordeaux, the following method may be used: Pour the diluted
lime solution into the spray tank, set the agitator going and
add slowly the diluted bluestone solution.
Other sprays that have been used and found efficient are:
Colloidal copper, copper hydroxide, Pyrox, Adhesio and P.B.K.*

THOROUGHNESS IN SPRAYING NECESSARY
Spraying must be done thoroly to be a paying proposition.
The tank pressure should not be below 100 pounds. The plants
must be covered completely so that the spores of the fungi will,
be killed. The spray should be applied often enough to keep
the growing plants well protected. This usually calls for an
application every week or 10 days.
Spraying should begin as soon as the plants are well up and
it should be continued methodically until the crop is gathered.
Some variation in exact time of application usually occurs, de-
pending upon the development of the plants and also upon the
general absence or occurrence of specific diseases.
Power spraying machinery: In order to thoroly spray toma-
toes often enough, where large acreages are grown it is neces-
sary to select a power sprayer that is fitted to your needs. It
is important to select a machine that maintains a pressure of
200 pounds when several nozzles are running. A machine with
plenty of pressure produces a mist and covers the plants with
a fine film.
A spray machine equipped with a four or five horse-power
gasoline engine as motive power for operating the pump will
give good service, altho there are certain objections to the use
of an engine, since it is often difficult to keep it in operating

*Pyrox, Adhesio and P. B. K. are the trade names of copper com-
pounds used as insecticides and fungicides.






Florida Agricultural Experiment Station


condition. More surface of the plant will be covered when high
pressure is maintained.
Spray machines should be thoroly cleaned immediately after
use. Do this by running several buckets of water thru the noz-
zles by operating the pump. If this precaution is taken regu-
larly, considerable time will be saved, as it will not be neces-
sary to spend time cleaning out the nozzles when the machine
is used again. If the spray material is allowed to remain in the
machine, it will dry and form flakes or cakes that will not pass
thru the nozzles.
A good traction-driven spray machine will often give good serv-
ice, if it is given the proper attention and kept in good condi-
tion, oiled frequently and cleaned thoroly.
Hand spraying: A large number of growers plant only small
acreages of tomatoes and for other reasons the use of power
sprayers is out of the question. In such cases it is necessary to
do the spraying with smaller sprayers the power of which is fur-
nished by hand labor. An efficient sprayer for small acreages is
a knapsack sprayer. The rod is easily handled and the plants
can be thoroly sprayed.

Copper-Lime Dust

The use of copper-lime dust is looked upon with much favor by
a large number of growers, principally because of the ease of
handling and the larger acreages that can be taken care of by a
single machine. The cost of material is considerably higher,
however, when enough is used to give the same control that is
obtained with home-made Bordeaux mixture.
In selecting a power duster give it the same consideration you
would a power sprayer, both in operation and after the opera-
tions are finished. There should be plenty of power, preferably
furnished by an engine rather than by traction. The dusting
should always be done when the plants are wet with dew or rain
and when there is little or no wind in order to obtain the best
results. Dust that contains 6 to 7 per cent metallic copper should
average 30 to 40 pounds per acre when the vines are covering
two-thirds of the ground. Younger plants require less dust per
acre and older plants more. The 80-20 (80 percent lime and 20






Bulletin 185, Tomato Diseases in Florida


percent hydrated copper sulphate) dust has proven most sat-
isfactory. When using power dusters, two nozzles per row are
very satisfactory. They should be arranged so as to direct the
dust on each side of each row. Thus on average dusters carrying
eight nozzles four rows can be dusted, providing they are not
planted too far apart.
Hand dusting: In smaller fields where the maintaining and
operating of power dusters is not practicable it is necessary to
use smaller dusters worked by hand. These dusters are very
efficient and several acres can be cared for by a single duster.
Hand dusters are easy to operate, throw a continuous, powerful
stream of dust which penetrates the densest foliage. The
amount of dust applied can be definitely regulated.

SOME PERTINENT POINTERS

Nailhead rust of tomatoes is more detrimental to the growing
of this crop in Florida than all the rest of the diseases of toma-
toes combined. When planting tomatoes take this into consid-
eration. This disease is caused by a fungus which spreads rap-
idly and causes losses in field, transit and on the market. Plant
varieties resistant to this disease. Practice sanitation in the
field and spray from the time plants are up until thru the pick-
ing season.
Mosaic is a very important disease of tomatoes in Florida.
Practice sanitation for the control of this disease. It is useless
to plan to control it by the use of fungicides.
Fusarium wilt is probably second in importance as a destruc-
tive disease of tomatoes in Florida. The disease is caused by a
soil inhabiting fungus. Rotation is first to be recommended.
Second, plant strains of seed resistant to this disease. The ap-
plication of fungicides in the form of spray or dust in an effort
to control this disease is useless.
Staked tomatoes are freer from disease than are unstaked.
If convenient, stake them. It is a profitable undertaking.
Black rot is a serious disease in transit and probably causes
growers as much loss after their product has left the packing-
house as any other disease. Prevent this disease in handling
the fruits after they are picked by eliminating bruises and cuts.
The black rot fungus cannot enter unless the fruit is injured.
In the packing process eliminate all fruits that show growth






Florida Agricultural Experiment Station


cracks, skin cracks, cat face or any other blemishes. You are
only paying freight in shipping them.
Tomato seed should always be disinfected before planting
in the seedbed. Soak them for 7 minutes in a 1:1,000 solution
of corrosive sublimate, rinse them thoroly and dry. They are
then ready to plant.
Southern wilt and southern blight are two diseases which if
found in the field cannot be controlled by spraying or dusting.
It is better to remove them from the field.
Sanitation is one of the important items in the culture of to-
matoes. The losses due to disease can be cut in half if strict
sanitation methods are followed.
In applying fungicides to tomato plants make it a point to do
a thoro job. First, use a good machine, second, plenty of pres-
sure, third, the right fungicide, and fourth, completely cover
the plants. Apply the fungicide once a week.
A liquid copper spray is better than a copper dust. Fungi-
cides containing copper are to be recommended over fungicides
not containing copper.




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