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Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: Tomato diseases
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
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Permanent Link: http://ufdc.ufl.edu/UF00026409/00001
 Material Information
Title: Tomato diseases
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 117-132 : ill. ; 23 cm.
Language: English
Creator: Sherbakoff, C. D ( Constantine Demetry ), b. 1878
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1918
Copyright Date: 1918
 Subjects
Subject: Tomatoes -- Diseases and pests   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by C.D. Sherbakoff.
General Note: Cover title.
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Bibliographic ID: UF00026409
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - AEN3274
oclc - 18162231
alephbibnum - 000922765

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Full Text


Bulletin 146 March, 1918


UNIVERSITY OF FLORIDA


Agricultural Experiment Station



TOMATO DISEASES

By C. D. SHERBAKOFF























FIG. 32.-A, upper side, B, lower side, of tomato
leaf affected with leaf mold



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























BOARD OF CONTROL

JOE L. EARMAN, Chairman, Jacksonville.
E. L. WARTMANN, Citra, Fla.
T. B. KING, Arcadia, Fla.
J. B. HODGES, Lake City, Fla.
J. T. DIAMOND, Milton, Fla.
BRYAN MACK, Secretary, Tallahassee, Fla.

CONTENTS
PAGE
General Recommendations ................................... .. 119
Bacterial Blight ..................... .......... ... ........... 120
Septorial Blight ................................. ... ......... 121
Sclerotial Blight ................................... ............ 122
Phytopthora Blight ................ ........................... 123
Fusarial Wilt ................................... .............. 123
Early Blight .................................... .. ........... 125
Black Spot ............................................ 126
Leaf Mould .............. .................................. 126
Buckeye Rot ........................................... 127
Brown Rot ................................................ 129
Soft Rot ........................................ ............. 129
Root-Knot ............................................ 130











TOMATO DISEASES
By C. D. SHERBAKOFF
Tomatoes are subject to many diseases any of which may
cause great damage to the crop. The amount of damage re-
sulting will usually vary directly with the season. Some of
these diseases occur only in certain localities or on certain soils;
others are general thruout the State. A season rarely passes
without an outbreak of some disease sufficiently serious to show
the grower the necessity of observing all general precautionary
measures. These measures may be stated briefly as follows:
GENERAL RECOMMENDATIONS
1. Use the best seed obtainable; free from disease, if possible.
2. Choose a seed-bed soil not previously used for growing
tomatoes or related crops; or, better still, a soil sterilized with
steam or formalin.
3. Spray plants in the seed bed and in the field with a good
fungicide, such as bordeaux mixture. Apply thoroly about
every ten days. For spraying in the seed bed use the 3-4-50
bordeaux formula, increasing the strength to 4-4-50 or 5-5-50
for field spraying. The stronger field concentration is preferable
only in controlling early blight or rust. Field spraying is not
necessary in periods of drouth in the absence of both rain and
dew.
4. Keep in check the various insects working on the plants.
This may be done by adding to every 50 gallons of bordeaux
mixture 1/2 pint of Black Leaf "40" and 1 pound of zinc arsenite
or lead arsenate. If spraying is not practiced, dust the plants
with a mixture of tobacco dust, zinc arsenite or lead arsenate
and flowers of sulphur.
5. Where plants are likely to suffer from drouth, some means
for irrigating should be provided. If this is impracticable, pre-
pare the soil and cultivate the crop in such a way as to conserve
moisture in the soil as much as possible. The plants should
be well spaced.
6.. On low lands the plants should be staked.
7. Nitrate of soda is preferable to other forms of nitrogen
(ammonia) for fertilizing tomatoes. Avoid a heavy applica-
119







120 Florida Agricultural Experiment Station

tion of stable manure; also, do not use potassium chloride.
Neither should manure or compost containing old tomato vines
be used.
8. Keep the field in a sanitary condition. Examine it regu-
larly and remove all rotted fruit and sickly plants. Destroy
this material either by burning or by dumping into a hole in
the ground and covering with some disinfectant, such as bleach-
ing powder, lime, or powdered bluestone.
9. Practice crop rotation. If the preceding tomato crop was
infected with wilt or bacterial blight do not replant the field
to tomatoes for several years.
BACTERIAL BLIGHT
"The appearance of bacterial blight is pronounced at blossoming
time or somewhat later. Usually only a single branch or leaf
of the plant begins to show the disease
at first, but the entire plant is soon
involved and killed. Diseased plants
or plant parts commonly remain green
for awhile, even after they are thoroly
infected, and then more or less sudden-
ly wilt and droop (fig. 33). Blighted
Systems, in cross-section, show dark-
brown discolorations of the woody ele-
ments and often of the adjacent tissues.
The browning, frequently accompanied
by shrinking of the diseased stems and
S 'l branches, is often outwardly visible. A
development of numerous knob-like in-
FIG. 33. Tomato plant
showing an early stage cipient roots is usually evident on the
of bacterial blight. Note affected stems.
drooping of the tops
and large leaves ops Under conditions very favorable to
the disease an entire crop may be lost.
Where tomatoes are seriously affected with the trouble, the soil
becomes contaminated with the causal bacteria and the field
for several years is unfit for the production of another tomato
crop. Neither should eggplant, Irish potatoes, tobacco, nor,
probably, peppers and peanuts, follow the diseased tomato crop
for they are also susceptible to the blight.
The bacteria causing this blight can enter the plant only thru
a wound, and are usually introduced by insects at work on the
plant or by the root-knot nematodes. Injuring the roots in







Bulletin 146, Tomato Diseases 121

transplanting also exposes the plant to attack by the bacteria.
Altho the disease becomes evident only when the plants are full-
grown, nevertheless they are most dangerously subject to it
while yet in the seed bed.
CONTROL.-1. Make the seed bed on a soil not previously
used for growing tomatoes or other crops susceptible to the
disease, or sterilize the seed-bed soil with steam or formalin.
2. Rotate crops in the field so that tomatoes or crops related
to them will not be planted on the same soil more often than once
in several years. While this rule is generally a good one to
follow, experienced tomato growers say its observance is im-
perative following a crop once affected with the blight.
3. The tomato field should be frequently inspected for blight
and every diseased plant removed and destroyed.
4. Keep in check the various insects that may be at work on
the plants. (See General Recommendations, No. 4.)
5. Do not plant tomatoes in a soil infested with root-knot
nematodes.
6. Do not injure the plant roots unnecessarily in trans-
planting.
SEPTORIAL BLIGHT
Septorial blight is important mainly by reason of its destruc-
tiveness to tomato foliage on which it appears in spots. These
numerous spots (fig. 34) have light gray centers and dark
margins by which they can usually be readily recognized and
distinguished from other tomato leaf spots. The diseased
leaves soon turn yellow and die. Lower leaves are affected first,
and the disease gradually spreads upward. In cases of severe
attack, the entire crop may be lost. No other crop is subject
to this disease.
In the northeastern states Septorial blight is usually con-
sidered the most important disease of tomatoes but at present
is unimportant in most of the other states, including the south-
eastern states. Indications are, however, that it may become of
importance in Florida and some of the other states.
CONTROL.-1. Make the seed bed on a soil not previously
used for growing tomatoes, or sterilize the seed-bed soil with
steam or formalin.
2. Spray tomato plants in the seed bed with 3-4-50 bordeaux
mixture or with some other good fungicide of corresponding
strength. Spray about once every ten days. Spraying plants








122 Florida Agricultural Experiment Station



























FIG. 34.-Tomato leaves affected with Septorial spots. (Fromme &
Thomas, Va. Agr. Exp. Sta., Bul. 213)

in the field is also advisable; use either 5-5-50 bordeaux mixture
or an equally good fungicide.
3. Tomatoes should not be planted to follow tomatoes but
should be rotated, with other crops, planting tomatoes not more
often than once in three years.
4. Do not use stable manure or a compost containing diseased
tomato plants in the tomato field.
SCLEROTIAL BLIGHT
Sclerotial blight occasionally causes considerable damage to
the tomato crop in a large area of the United States; roughly
stated, from Texas to Maryland, east and south. It attacks the
plant stem at, just below or just above the level of the ground,
where it causes a colorless rot. The affected plants usually wilt
at the top first, aind die. The disease also affects Irish potatoes,
peppers, peanuts and some other crops.
CONTROL.-Moisten the soil around the plant stems with am-







Bulletin 146, Tomato Diseases 123

monical solution of copper carbonate. Decaying masses of
weeds, or other vegetation are likely breeding places for the
fungus Sclerotium which causes the disease. They should not
be allowed to remain in or near the field.
PHYTOPTHORA BLIGHT (LATE BLIGHT)
Phytopthora blight has been found destructive to tomatoes in
Pennsylvania, Virginia and some other states, It produces
water-soaked, rapidly spreading spots on the leaves, and a rot
of the fruit; the rot usually starting at the stem end. (Fig. 35.)
















FIG. 35.-Phytophthora rot of tomato fruit. (Fromme & Thomas, Va.
Agr. Exp. Sta., Bul. 213) .

In moist weather the affected foliage is quickly killed while the
affected fruit decays in a short time. The disease also attacks
Irish potatoes, with about the same destructive 'results. On
potatoes the disease is of even much greater importance and of
more general occurrence and is_ popuarly known thruout the
country as late blight.
CONTROL.-Spray with a 4-4-50 bordeaux mixture, or some
other good fungicide, about once every ten days.
FUSARIAL WILT
Plants affected with Fusarial wilt show a gradual wilting
which usually progresses from the lower branches upward and
is accompanied by a noticeable yellowing of the diseased parts.
Stems of affected plants, in cross-section, show dark discolora-
tions of the woody elements but no browning of the adjacent
tissues as observed in the case of bacterial blight.







124 Florida Agricultural Experiment Station

This wilt is caused by a soil-living fungus which does not
attack other crops related to tomatoes. The fungus is spread
by contaminated soil and probably also by contaminated seed.
Once introduced into a soil it remains there in an active state
for several years. Altho the disease is in evidence as a rule only
when the plants are full-grown, nevertheless, infection may
occur in the seed bed and precautionary measures there are of
the greatest importance.


























FIG. 36.-Tomato leaves spotted with early blight
CONTROL.-1. Make the seed bed on a soil not previously used
for growing tomatoes, or sterilize the seed-bed soil with steam
or formalin.
2. Manure or compost containing dead tomato vines should
not be used in the tomato field.
3. Plant tomatoes in rotation with other crops. If the last
crop was affected with the wilt, do. not replant the field to to-
matoes for several years.







Bulletin 146, Tomato Diseases 125,

4. Use homegrown seed from the best fruit picked from the
best perfectly healthy plants. The fruit should be thoroly dis-
infected and rinsed before the seed is removed. Properly dry
the seed and store it carefully u itil needed. All this should be
done in a clean room free from dust, and not in the tomato field.

EARLY BLIGHT (MACROSPORIAL SPOT, BROWN RUST,
NAILHEAD RUST)
The early blight, sometimes called-Macrosporal spot, brown
rust, or nailhead rust, spots the leaf, veins and fruit of the
tomato plant. The
leaves are eventual-
ly more or less seri-
ously injured, some-
Stimes killed, and the
fruit are decayed.
The spots vary in
color from reddish
brown on the fruit
to brown on the
leaves and some-
times have a dis-
t i n c t target-like
marking. (Figs. 36,
37 and 38.)
The disease is.
commonly present
in most tomato
fields and some-
times greatly dam-
ages the crop espec-
"ially by injuring
the fruit. On low
lands where the
FIG. 37.-Tomato stems spotted with early
blight plants make a dense
growth and heavy
dews occur, the disease may spot nearly every fruit in the field.
CONTRoL.-Spray the plants with bordeaux mixture or some
other good fungicide; in the seed bed use a 3-4-50 mixture,
and in the field use a 5-5-50 mixture. Spray at least twice in
the seed bed, and at intervals of ten days in the field.








126 Florida Agricultural Experiment Station

























FIG. 38.-Tomato fruit spotted with early blight
BLACK SPOT (PHOMA SPOT, BLACK RUST AND ROT,
STEM-END ROT)
Spots produced on the leaves and fruit of the tomato plant
by black spot, also known as Phoma spot, black rust and rot,
and stem-end rot, vary from dark browri to black and are usually
covered with numerous pimple-like fruiting bodies of the causal
fungus. This is particularly true of spots on the fruit. The
effect of the disease on the fruit (fig. 39) and on the leaves is
much like that of the early blight, but the disease is of great
importance only during a season of continuously rainy weather.
These conditions are likely to prevail at times in south Florida.
Frequently the rot starts at the stem end of the fruit, which
gives rise to the name, stem-end rot.
CONTROL.-Spray as recommended for the early blight.
Spraying plants in the seed bed is of special importance. Us.
a seed-bed soil in which tomatoes have not been grown, or
sterilize the soil. Practice crop rotation if possible.
LEAF MOLD
Leaf mold attacks only the foliage of tomato plants where it







Bulletin 146, Tomato Diseases 127

appears in the form of diffuse, pale spots. These spots are
somewhat more distinct on the lower-side of the leaves than
on the upper side (fig. 32). With age, the spots on the lower
side become covered with a velvety, cinnamon-brown layer of
spores of the causal fungus.
The disease is of very common occurrence from Maryland
southward. Under favorable conditions it spreads rapidly and
decreases the yield of the plants considerably by greatly re-
ducing the healthy leaf surface.
CONTROL.-Begin spraying early with 4-4-50 or 5-5-50 bor-
deaux mixture. Apply thoroly about once every ten days, and
especially to the underside of the leaves. ..

i71
















L -

FIG. 39.-Tomato fruit affected with Phoma spot and rot
BUCKEYE ROT WATER-LOGGED FRUIT, BROWN ROT)
Buckeye rot is a disease common on low lands in southern'
Florida. It may also be known as water-logged fruit, or brown
rot. The disease affects a large percentage of the fruit in the
field and damages still more of it in- transit. As a rule, an
experienced buyer is unwilling to accept tomatoes from a field
affected with this rot. The disease is caused by a soil-living







128 Florida Agricultural Experiment Station

fungus (Phytophthora terrestria), and only fruit that touches
the ground or hangs very close to it is affected. Figure 40 shows
tomato fruit affected by this disease.
Buckeye rot varies from gray to dark grayish brown in color.
It is similar in appearance to another disease known as brown
rot, but can be distinguished at a glance by a difference in color
and a wider zonation of the markings. (See Brown Rot.)
CONTROL.-Stake the plants so as to prevent the fruit touch-


































FIG. 40.-Various stages and forms of buckeye rot on tomato fruit. Upper
right, advanced stage of the rot developed at high temperature in
transit; lower right, characteristic development of rot in field at low
temperature; fruits at left, three stages of the rot, the infection just
beginning to show on the upper fruit while the entire lower fruit is
affected.







Bulletin 146, Tomato Diseases 129

ing the ground. If the plants are not staked and there is the
slightest indication of the presence of the disease, the picked
fruit should be spread in a shallow layer in the packing house
or in a shed for a few days before being packed for shipment.
If the disease is present it will develop sufficiently during this
short period to be plainly visible, and all affected fruit can be
culled out.
BROWN ROT
This rot is in many respects similar to buckeye rot. While
this brown rot is also caused by a soil-living fungus (Rhizoc-
tonia solani) the disease
Scan be readily distin-
guished from the buck-
eye rot by a much closer
donation of the affected
part of the fruit, by the
distinctly brown color of
the rot, and by its sunken
appearance. A typical
case of brown rot is il-
lustrated in fig. 41. The
disease has not been ob-
served to cause as great
damage as has been ob-
served in some instances
FIG. 41.-Brown rot of tomato fruit. of the buckeye rot. It is
Often the affected part is cracked, of less importance as a
covered with a brown felt of the fun-
gus, and with some soil adhering, cause of fruit rot in
transit and storage altho
it is of more common occurrence than buckeye rot and generally
affects a sufficient percentage of the fruit to warrant taking
necessary measures for its control.
CONTROL.-Stake the plants in the field as recommended for
controlling buckeye rot.
SOFT ROT
In some cases soft rot is of considerable importance. This rot
is cauEed by the same bacteria that produce soft rot of many
other vegetables, such as carrots, potatoes and peppers. The
affected tomato fruit will be entirely converted within a few
days into a soft, watery, colorless, decayed mass. An early
stage of this rot is shown in fig. 42.






130 Florida Agricultural Experiment Station

The bacteria causing soft rot can invade the fruit only thru
injured skin and for this reason the rot is usually started by
insects which injure the fruit.
CONTROL.-Destroy insects that work on the plants. (See
General Recommendations, No. 4.)
Pick and destroy all affected fruit as soon as the rot is evident.
BLOSSOM-END ROT
Blossom-end rot is of importance during a drouthy season,
and especially on light soils. Cases where most of the fruit is
affected with the trouble are fre-
quently reported. It appears at
first as a bruised, water-soaked,
.. darkish spot near or at the blos-
som end of the fruit. Soon the
spot increases in size, turns brown
or black, and becomes hard and
leathery. (Fig. 43.)
The disease is due to certain
conditions adverse to a normal
growth of the plant. Irregular
water supply, or rather a sudden
check in it, is chief of these condi-
FIG. 42.-Soft rot of tomato tions. In some cases it appears
fruit; appearance at end of
two days that fertilizers are of importance
in the development of the disease,
for under certain conditions an application of nitrate of soda
checks the trouble. Liming the soil is also sometimes bene-
ficial.
CONTROL.-If practicable, irrigate the plants regularly. If
not, prepare the soil and cultivate the plants in the best way to
conserve soil moisture.
Nitrate of soda should be applied to the plants in preference
to other forms of amonia (nitrogen). Avoid heavy applications
of stable manure. An application of lime is sometimes beneficial,
while one of potassium chloride may be harmful.
ROOT-KNOT
Root-knot produces numerous knots, galls and swellings on
the roots of plants. (Fig. 44.) These affected roots soon decay
and the whole root system is more or less severely reduced, or
is entirely destroyed. The affected plants are first retarded in
growth and later turn yellow and die. The disease is especially






Bulletin 146, Tomato Diseases 131

bad on light soils and during warm weather. It is unknown in
open fields subject to severe cold in winter and on land that is
continuously under water for a month or more. New land is
also free from root-knot. However, this reference is to virgin
soil and not to land that has produced a-growth of weeds for
a number of years. Certain weeds are also susceptible to root-
knot and a soil occupied by them may become as severely infested
with the disease as if it were cultivated to a crop susceptible to
root-knot. R oo t-
knot affects all vege-

tent, and many
other cultivated and
wild plants. Some
plants are only
slightly affected
while others are en-
tirely free from it.
Root-knot is,
caused by minute
eel worms or nema-
todes which feed on
the roots of suscep-
tible plants. The
nematodes may re-
"remain alive in the
FIG. 43.-Blossom-end rot of tomato fruit soil for a year or
more even if no
susceptible plants are grown, yet the number is greatly reduced.
If no crop of vegetables or weeds susceptible to root-knot is
permitted to grow on the land for two or three years, the soil
becomes practically free from the nematodes.
CONTROL.-1. Tomato seedlings must be free from root-
knot. To produce such plants the seed bed must be free from
the disease; that is, the soil must be either new or, better, steam
sterilized. A soil infested with root-knot may be disinfected
to advantage with chemicals, one of which is cyanamid. Cyana-
mid is commonly used as a source of ammonia (nitrogen) in
commercial fertilizers and can usually be obtained. Apply it
several weeks before seed planting time. Make the application
at the rate of one or two tons per acre and mix the chemical
thoroly with the soil to the depth reached by plant roots, and







132 Florida Agricultural Experiment Station

then thoroly saturate the soil with water. For details of this
treatment see Fla. Exp. Sta. Bul. 136.
2. When a field is infested with the root-knot nematodes
they may be starved out if the field is cultivated for at least two




























FIG. 44.-Roots of tomato plant affected with root-knot

years to a crop resistant to root-knot, such as barley, Florida
beggarweed, corn, millet, rye, sorghum, velvet beans, nearly
any of the grasses, winter oats, and Iron and Brabham cowpeas.
The crops should be kept entirely free from weeds. Or the
nematodes can be killed either by treating the soil with a
chemical poisonous to them, as suggested for control in the
seed bed, or by flooding the soil with water for twenty-five days
or longer.





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