Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 91
Title: Tomato diseases
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Permanent Link: http://ufdc.ufl.edu/UF00026407/00001
 Material Information
Title: Tomato diseases
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 13-34, 3 leaves of plates : ill. ; 23 cm.
Language: English
Creator: Rolfs, P. H ( Peter Henry ), 1865-1944
Publisher: Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1907
 Subjects
Subject: Tomatoes -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by P.H. Rolfs.
General Note: Cover title.
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Bibliographic ID: UF00026407
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000921792
oclc - 18159640
notis - AEN2260

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HISTORIC NOTE


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

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida







BULLETIN NO. 91.


Florida


Agricultural Ex








TOMATO


periment Station.








DISEASES



BY


P. H. ROLFS.








The bulletins of this Station will be sent free to any address in
Florida upon application to the Director of the Experiment Station
Gainesville. Fla.


E. O. Painter Printing Co., DeLand, Fla.


DECEMBER, 1907-










SUMMARY AND CONTENTS.


(I) RUST (See page 15) may be prevented by using Bordeaux
mixture. Dry Bordeaux is less effective.
(2) FUNGUS BLIGHT (See page 17) may be avoided only by
rotation of crops, or the field may be abandoned.
(3) SCLEROTIUM BLIGHT (See page 19) may be controlled
by avoiding the use of manure or similar organic ma-
terials, by spraying about the roots and cultivating close
to the plants.
(4) BACTERIAL BLIGHT (See page 22) is difficult to control
when once started in a field. Some good may be done
by destroying infected plants.
(5) DROPPING OF BLOOM BUDS (See page 24), (a) cannot
be remedied when due to continued cold weather. (b)
When due to too vigorous growth it may be controlled
by checking the growth. (c) When due to the minute
green fly it is difficult to secure an effective remedy.
(6) When LEAF CURL (See page 26) is caused by too much
moisture, the remedy is to relieve the soil of the super-
abundant moisture; if a result of too drastic pruning,
this should be discontinued.
(7) DAMPING OFF (See page 27) is remedied by letting in
sunlight, drying off the seedbed, and applying a soluble
fungicide.
(8) HOLLOW STEM (See page 27) may be prevented by hard
ening plants off before setting out.
(9) ROOT KNOT (See page 28) may be controlled by rotation
and destroying diseased plants.
(Io) The FRUIT WORM(SCe page 30) is best controlled by
using arsenical poison to kill the young larvae, and the
more mature ones should be destroyed with the wormy
tomato fruits.
ii) CUTWORMS (See page 33) are most easily killed by
using poisoned bait.
(12) MOLD (See page 34) is easily controlled by using a sul-
phur compound, or even by the use of dry sulphur.














PLATE I.


RusT.-Leaflet in an


advanced stage of the disease. The tips
are attacked first.















TOMATO DISEASES.



BY P. H. ROLFS.



RUST.

NAME.-This fungus has been known to inflict serious
damage on the tomato fields in the state of Florida ever
since the cultivation of this crop has been taken up. From
time to time different common names have been given to
it. Among these is the name rust, which is now almost
the only one used by the tomato planters; spot, black spot,
blight, leaf blight, and other terms have also been used.
GENERAL APPEARANCE.-The general appearance of
this disease in the advanced stage is well illustrated by Plate
I. The leaflet there shows its end infected and dried up,
while the central portion and the part near the stem are
still green, but spotted with brown areas of various sizes.
The first visible appearance of the disease on the leaf is
as a minute brown speck, which is frequently so minute
that it can scarcely be made out with the unaided eye.
These minute specks may occur on seedlings in the seed-
bed, but more frequently the plants are well advanced in
the field before they are plainly noticeable.
CAUSE.-The cause of this disease has been known for
many years, and the fungus has been carefully studied by
scientists. Scientifically it is known as Macrosporium
(Alternaria) solani. The disease has its beginning from a
minute spore which may have been borne to the plant by
the wind. Frequently the diseased plants are so evenly
and so widely distributed in a field that it is really difficult
to see how any other agency could have disseminated the









16 Florida Agricultural Experiment Station.

spores so promiscuously. Usually the rust originates in
certain portions of the field and is distributed from these
to other parts.
The fungus spore falling upon the leaf germinates,
and the germ tube penetrates the tissues. The fungus
grows within the leaf-blade, and after a shorter or longer
period begins to mature spores of the same kind that
originally infected the leaf. Whilst producing spores the
fungus continues to spread in the leaf tissue, and thus the
diseased area becomes daily larger. A number of these
diseased areas may grow together, producing larger areas.
(See Plate I.) Finally the entire tissue of the leaf is
destroyed. (In some cases the fungus produces more or
less concentric rows of dots; these, however, are not al-
ways present.)
REMEDY.--In the case of rust, as in the case of almost
every other disease, prevention is much cheaper than cure.
This disease can be most effectively prevented in the be-
ginning by spraying the plants with Bordeaux mixture
while they are still in the seedbed. Though it is not practic-
able to cover all the leaves, yet the spraying should be
done as thoroughly as possible in order to fortify the plants
against infection at the time they are set out in the field.
As the disease does not have a regular time for occur-
ring and is not always disastrously severe, most tomato
growers prefer to wait and see whether the plants are go-
ing to be affected. Every tomato grower should, however,
keep a very careful lookout to detect the first signs of the
presence of this fungus. Spraying should then be begun
at once and carried out vigorously and thoroughly. While
in some years the climatic conditions are such as to enable
the tomato plants to produce a fair crop without spraying,
the probability is that the presence of this disease in a
field will practically.ruin the crop if not controlled during
its earlier stages.
From what has been said it will readily be understood
why any portion of the tomato leaf that is not protected by
a thin film of Bordeaux mixture is liable to be attacked;
consequently the work of spraying should be done as thor-












Bulletin No. 91.


oughly as is possible with the time and appliances at hand.
Where dry Bordeaux is used, it should be applied at least
as frequently as once every week. The dry Bordeaux is
about a half or a third as effective as ordinary Bordeaux
mixture.*

FUNGUS BLIGHT.


(Fusariumn.)

The term blight has been applied to so many different
diseases that it has no distinctive significance. In fact, it is
not infrequently applied to insect pests. The disease which
is known as fungus blight has probably caused a greater
loss to the tomato growers in the state of Florida than any

How to make Bordeaux mixture.-Solution No. I: copper sul-
phate (bluestone), 6 pounds; water, 5o gallons. Solution No. 2:
caustic lime (quicklime), 4 pounds; water, 5o gallons.
It is advisable to have three kerosene barrels of about fifty gallons
capacity in the field. Dissolve 6 pounds of copper sulphate in a barrel
of water (5o gallons). The copper sulphate will be dissolved slowly
in cool water if it is suspended near the top of the barrel in a feed
sack or other coarse cloth. If it is desirable to dissolve it quickly,
this may be done by placing it in a barrel and pouring on hot water.
After the 6 pounds of copper sulphate have been dissolved, the barrel
may be filled to the 5o-gallon mark. Tin or iron vessels should not
be used in connection with Bordeaux mixture or the copper sulphate
solution; always use copper or wooden vessels.
Slack the 4 pounds of lime in just enough water to cover it. Be
careful to stir it well and see that it does not burn dry. This is best
done in a wooden vessel, as there is considerable heat generated by
the lime in slacking. If the stone from which the lime is made coi-
tains much sand, it will be necessary to increase the number of pounds
of lime used. If there is a quantity of air-slacked lime also present,
it will be better to reject this and simply use the part that has not
been air-slacked. After the lime has been slacked add water to make
50 gallons.
Stir the copper sulphate solution (No. I) thoroughly, and take
out about one-half as much as the spraying apparatus will hold. Pour
this in the third barrel; then stir the lime water thoroughly and take
out just as much lime water (No. 2) as already taken of copper sul-
phate solution; pour this into the third barrel and stir the two to-
gether immediately and briskly for a minute or two. You will then
have formed a greenish-colored substance, which is Bordeaux mixture.
Put it into the spraying pump and apply it at once. Bordeaux mixture
is not so good after it has settled, and after it is twenty-four hours
old it had better be poured away and fresh Bordeaux made. The
lime water and copper sulphate solution may be kept separately for
an indefinite time without deterioration.








18 Florida Agricultural Experiment Station.

other disease. For a considerable number of years its true
nature was not understood, and the difficulties in the field
were ascribed to improper fertilization, drought, moisture,
too much fertilizer, too little fertilizer, too much cultiva-
tion, want of cultivation, or almost any other adverse con-
dition. Later scientific investigations, however, have
shown that the disease is due to a specific fungus which
occurs in the soil, and from this attacks the plant.
DESCRIPTION OF THE DISEASE.-The fungus blight
may attack the most vigorous growing plants in any por-
tion of the field or it may attack those of low vitality.
Since the fungus is found in the soil, it is impossible to tell
beforehand whether there is any of the disease present or
not. The first symptom that is noticed is that the lower
leaves (usually the largest ones) turn rather pale, and
finally quite yellow. The leaves usually dry up from the
tip, and where the disease is not accompanied by rust no
spots are seen. By cutting the leaf stalk with a sharp
knife darkened veins can frequently be seen. If the tomato
plant is pulled up and the stem cut across the darkened
veins are usually found in this portion, especially on the
side to which the diseased leaf is attached. The rapidity
with which the disease develops in a plant depends on cli-
matic conditions and on the condition of the plant. If the
plant has been growing rapidly and is rather soft the fun-
gus is apt to make considerable headway, especially if some
dry weather follows the infection. Not infrequently the
first leaf dries up completely, only the leaf stalk being left
green, and this may fall off or not as the conditions deter-
mine. After the first leaf has shown considerable distress,
the second and third leaves, and finally the entire plant
may show the presence of the disease.
EXPERIMENTS WITH THIS DISEASE.-A great many
experiments have been inaugurated and carried out with a
view of finding a method of avoiding this difficulty. One
of the first that suggested itself was that of trying various
varieties to see if any of them were immune. In following
out this work, seeds of over sixty varieties of tomatoes
were secured from American seedhouses; also seeds from








Bulletin No. 91.


tomatoes grown in Mexico, and some varieties from
Europe. One set of these plants was placed in a field at
Boynton and another set was planted out near Miami. In
both cases care was taken to see that the field was thor-
oughly infected with fungus before the plants were set out.
This was an easy matter, since every year this fungus kills
out quite a number of fields. Of all the varieties of toma-
toes tested not one proved capable of resisting this form
of blight; consequently, that line of investigation had to
be discontinued.
TREATMENT.-About the only practical method of
treating this disease at the present time is that of rotation
of crops. Usually there is a sufficient amount of land
present in the tomato growing sections to allow a crop of
tomatoes to be grown and the land to be abandoned for
two or three years. After the lapse of this space of time.
the field may again be planted out to tomatoes with a fair
degree of certainty that the fungus will not make cropping
unprofitable.


SCLEROTIUM BLIGHT.

This disease of the tomato was discovered by the
writer during the spring of 1892. At that time it was
found to be very widely distributed, and in many tomato
fields almost completely destroyed the crop. Immediate
steps were. taken towards discovering a remedy for this
trouble and means of preventing it. With our present
knowledge of this disease it is by no means so difficult to
handle as some of the others. For the most part this dis-
ease is prevented by methods of clean culture, and by not
using stable manure or other decaying vegetable matter
for fertilizer where this may be avoided.
DESCRIPTION OF THE DISEASED PLANT.-In the case of
sclerotium blight the first symptom is the wilting of the
terminal portion of the plant. This characteristic distin-
guishes the sclerotium blight rather sharply from the fun-
gus blight: since with the former the top of the plant is










20 Florida Agricultural Experiment Station.

the portion that shows the disorder, while the presence of
the fungus blight is shown by the yellowing and dying off
of the lower leaves.
CAUSE.-The cause of the disease is a fungus, which
up to the present time has remained unidentified because
it has not been possible to demonstrate what the spore-
bearing form is. The disease is carried over from year to
year by means of small bodies, which in their mature state
resemble mustard seeds. Sometimes these sclerotia are
more minute than the finest mustard seed. Sometimes a
number of them grow together into a larger body and
make up a somewhat irregular mass. The color of the
mature sclerotia varies from very dark-almost black-to
mahogany red. The young sclerotia are milk white. This
fungus, like the preceding one, lives in the soil; but it
differs from the fusarium fungus in requiring a consider-
able amount of vegetable matter to enable it to continue
to exist from year to year.
REMEDY.-Plants attacked by this fungus rarely show
the presence of the sclerotia, excepting when the disease
has developed to an advanced stage, and then the sclerotia
are found only under certain conditions. They, however,
form on the stems of dead tomato plants, and during the
cultivation of the soil are distributed rather widely in an
infected field.
As the fungus attacks the plant from the soil, either
at the base of the stem or in some of the larger roots, it is
manifestly impracticable to prevent it by spraying the
top of the plant. The writer has, however, shown that it
is readily treated by using some soluble form of fungicide:
such as Eau celeste or ammoniacal solution of copper
carbonate.*

Ammoniacal Copper Carbonate.-
Copper carbonate ............................. 5 oz.
Ammonia water 26 degrees Beaume ........... 3 pts.
For use dilute to fifty gallons.
Pour one gallon of water in a wooden or earthen vessel. Pour
in the 3 pints of ammonia and stir so as to mix evenly. Take the
. ounces of copper carbonate and shake it in the ammonia water,
stirring the liquid all the while. If the copper carbonate all dissolves,







Bulletin No. 91.


One of these fungicides, preferably the ammoniacal
solution of copper carbonate, should be sprayed on the soil
about the stem of the plant. By spraying on a half tea-
cupful at this point the plant is usually perfectly protected
against infection. In using this remedy it should be re-
membered that where the fungus has gained entrance in-
to the tissues of a plant before the fungicide has been ap-
plied, the remedy will be of no avail. So many tomato
growers, however, have used this remedy effectively
against the fungus, that we must conclude that it is a first-
class remedy for this form of blight.
In addition to the use of the fungicide, the ravages of
this disease are very greatly reduced by pruning and stak-
ing the plants. This should be done in such a way as to
allow the air to circulate freely around the base of the
plant, and the "vines" should be kept off the ground.
Cultivating the soil so as to keep it loose and dry around
the plants kills much of this fungus and further protects
the tomatoes.
PLANTS AFFECTED.-The sclerotium blight of the to-
mato is. unfortunately, a very wide-spread disease, attack-
ing many other plants. In addition to tomatoes, we find
egg-plants. Irish potatoes, beans, cowpeas, summer squash-
es. cabbages, beets and melons among the garden plants
that are often severely attacked. Even fig trees from one
to one and a half inches in diameter have been attacked
and killed by it. Hydrangeas and Daphnes are among the
ornamental plants that succumb to the disease. In addi-
tion to these, there are many weeds and some of our for-
age crops that may be affected. The sclerotium blight
grows in almost any kind of decaying vegetable matter.
The writer has found it especially abundant in compost
heaps, and in heaps of decaying comptie pulp.

put in an additional amount of it until a small quantity remains un-
dissolved. When the undissolved copper carbonate has settled to the
bottom, pnur the clear, blue liquid off into some vessels that can be
tightly corked, such as jugs, or bottles. The writer's experience has
been that this stock solution does not keep well for more than from
a few days to a week or two, even in tightly corked vessels; con-
sequently, the material should be made up just at the time when it is
to be used.








22 Florida Agricultural Experiment Station.

BACTERIAL BLIGHT, WILTS.
(Bacillus solanacearum.)

The bacterial blight of the tomato is rather widely dis-
tributed in the United States, and during some years it
has been extremely severe in Florida. During other years
it has been almost absent from the State. It usually be-
comes very severe in fields where it makes its appearance;
especially if this is during the early part of the growing
season.
CAusE.-Dr. E. F. Smith proved conclusively that the
disease is due to a bacterium which gains an entrance into
the tissues of its host plant, where it develops, and that it
may be transferred from one plant to another, especially by
biting and sucking insects. Although it is of course im-
possible in practice to eliminate the insects from a vege-
table field, yet it can be readily understood that the se-
verity of an attack of this disease in a very large measure
depends upon the numbers and kinds of insects present.
TREATMENT.-As the biting and sucking insects are
the main carriers of this disease, so far as we know, it is
manifestly impossible to prevent the disease by using fun-
gicides; such as Bordeaux mixture and ammoniacal cop-
per carbonate. We can, however, do a great deal towards
reducing the disease after it has made its appearance by
reducing the number of insects as much as possible. It is
possible for insects to transmit the disease from one dis-
eased plant to a great number, and as it takes some (lays
for the development of the disease, a very large percentage
of our plants may become inoculated before we discover
its presence. It has been the writer's experience with this
disease that it almost invariably spreads over the field
from certain centers. Sometimes the disease has been so
general that it was difficult to find exactly the first point
of infection; but this can usually be located by the dead
plants being more numerous in some points than in others.
As soon as a plant in the field is discovered to be dis-
eased by a bacterial blight, it should be pulled out at once,
and destroyed either by burying, or by carrying from the









Bulletin No. 91.


field and putting it in such a place that insects will be un-
able to migrate from the diseased plants to the healthy
ones.
OTHER PLANTS AFFECTED.-While it has not been
definitely proved that this bacterium may live in the soil
from one tomato season to another in Florida, it is pos-
sible, in any case, for this disease to be carried over from
one year to another on some of our wild plants which are
subject to it. Consequently, a field that has been severely
affected by the bacterial blight one year, should not be
planted either to tomatoes, Irish potatoes, or eggplants
during the succeeding year. In addition to these vege-
tables, the Jamestown weed, black nightshade, and several
weeds of this family (Solavaceae), are affected by this bac-
terium.
DESCRIPTION OF A DISEASED PLANT.-I1I some cases it
is rather difficult to distinguish between plants that are
affected with the bacterial blight and those that are dis-
eased with the sclerotium blight. Typical cases of each
form have many points of similarity. As a general rule, a
plant that is suffering from the bacterial blight becomes in-
fected through a leaf. This leaf shows that it is infected
by wilting. Next, that portion of the plant to which the
leaf is attached begins to wilt; and finally the entire plant
will become involved. In the case of the sclerotium blight
the whole plant usually shows the distress at once, and
does not, as a rule, die off as quickly as a plant attacked
by bacterial blight. In the case of bacterial blight a dark
gummy substance is apt to be deposited in the woody
portion of the stems. Sometimes these dark streaks also
grow in the leaf stalks. In this respect the bacterial blight
may be confused with the fungus blight (see page 20).
It is not usual for this dark, gummy substance to be de-
posited in the stems of the plant or in the leaf stalk when
the plant is attacked by the sclerotium blight.
These three forms of blight may be easily diagnosed
by the plant pathologist with his microscope in the labora-
tory, but they have so many points of similarity that it is
very difficult to describe them in such a way as to enable









24 Florida Agricultural Experiment Station.

the tomato grower to distinguish them beyond a question
of doubt. The plant pathologist, however, who comes in
contact with the three forms of blight regularly has no
difficulty in diagnosing them in the field.

DROPPING OF BLOOM BUDS.

During some years this trouble occasions a greater
loss to the tomato growers than any of the diseases that
are caused by micro-organisms. The plant puts out the
bloom hands or clusters, but after the blooms have opened
they drop off, leaving no fruit set. The plant continues to
grow and produce new blooms, but these in turn may be
shed.
CAUSES.-There are a number of causes which bring
about this condition.
First,- and among the most general and widespread
causes for the dropping of bloom buds is the sudden occur-
rence of cold or cool weather, coming at a time when the
plants in the tomato field are in active blooming condition.
The temperature is too low to permit the pollen to fertilize
the ovaries, and consequently, the blooms drop off. In
cases of this kind we have no effective remedy, but have
to wait for favorable weather. This condition does not
usually continue for more than a few days at a time. It,
however, does occasionally happen that we have a period
of ten days or two weeks during which we have continu-
ous cold, raw winds. In addition to this cold weather
causing the bloom to drop off for want of fertilization, the
after effect of the cold is shown by the plants being de-
bilitated to such an extent that a considerable period fol-
lows during which the tomato blooms do not set.
Secon~d.-Just the opposite condition may sometimes
occur. Plants may grow too rapidly, especially if the
formula of the fertilizer used is high in ammonia and the
weather is favorable to the most rapid growth. In this
case the tomato plant grows very rapidly and grows to
weed instead of producing fruit. When this is the case
the vegetative function of the plant is carried on too






Bulletin No. 91.


rapidly to allow fruiting. Fortunately, this condition
is under our control. In the first place, we should use a
fertilizer that is not too one-sided in ammonia content;
but we must reckon with the fact that a fertilizer which
would prove to be the very best during a dry year would
prove to be too high in ammonia during a year when the
amount of moisture was normal or above the normal.
Where the bloom buds are shed on account of too rapid
growth of the vine, this condition may be checked almost
immediately by cutting out the growth buds at the termi-
nals of the plants. Care should be taken to leave at least
two "hands" of bloom buds. This makes the process of
disbudding a little more tedious, but if all the bloom buds
are removed the plants will not be able to set any fruit. In
disbudding rapidly-growing plants to make them set fruit,
care must be taken not to carry this operation to an ex-
treme: otherwise, we introduce a disease which is known
as leaf curl, or roll leaf, and is described in subsequent
pages.
Third.-A third cause for the dropping of many
blooms is due to the presence of a minute greenish insect
very similar to the suck-fly of the tobacco, which has a per-
nicious habit of spending most of its time on the bloom
buds of the tomato plant. By means of its slender beak it
pierces the stems of the fruiting hands, and in this way
injures them to such an extent as to cause the shedding
of buds, and even, in severe cases, to cause the dropping of
newly set fruit. The insect is rather shy, and not readily
discovered, especially if the tomato plant is brushed
against or moved. If. however, the observations are made
very quietly, there is no difficulty in finding one or more
of these small flies engaged in its disastrous work.
REMEDY.-The life history of this insect has not been
carefully studied out so far as the writer knows, but the
mature insect may be killed by spraying with a nicotine
solution, and by some of the other contact insecticides. It
is, however, a rather difficult matter to get the insecticide
on the pest, because at the least disturbance of the vines
it flies away and gets out of danger by hiding under a leaf.







26 Florida Agricultural Experiment Station.


LEAF CURL, OR ROLL LEAF.

The causes of this disease were thoroughly investi-
gated by Prof. G. F. Atkinson, Professor of Agriculture
in Cornell University, and published in a bulletin (No. 53,
May, 1893) from the Cornell Experiment Station. The
appearance of the plant when affected by this disease is
so striking that all tomato growers are familiar with it.
Plate II shows a figure of this disease in its characteristic
form, so that it will need no further description.
CAusEs.-There are a number of causes which lead up
to this difficulty. The most important one in Florida is the
presence of too much moisture in the soil. Another very
prolific cause of this disease is the too severe pruning of
the tomato plants. Where this is carried on rather drastic-
ally, it is almost certain to produce the disease. As disbud-
ding is practiced by many of our growers, and staking of
tomatoes is also customary over a large area, we find this
disease not at all uncommon. The bad effects of it, how-
ever, are as a rule not recognized, since the leaves usually
remain green and the plant continues to grow. A plant,
however, that has been pruned or disbudded to the extent
of producing leaf curl is less productive than one that has
not been pruned to such a degree.
REMEDY.-Where leaf curl is due to too much mois-
ture in the soil, care should be taken to plow the field in
such a way as to relieve it of the superabundance of mois-
ture. Where leaf curl is due to pruning, the pruning should
be discontinued, or deep plowing, and plowing rather close
to the plant, followed. This plowing will in a measure re-
lieve the soil of the surface moisture, and at the same time
do a considerable amount of root pruning. In this way we
cut off a portion of the moisture that would otherwise be
taken up from the soil.





PLATE II.


2/


LEAF CURL, OR ROLLED LEAF.


41T),/-











Bulletin No. 91.


DAMPING OFF.

This disease rarely occurs, excepting in the seedbed.
It manifests itself by the plants falling over, and looking
very much as if they had been gnawed off by some insect.
These apparently gnawed-off areas occur at different
points in the seedbeds, and the fungus which causes the
trouble spreads out from these points in all directions.
The disease occurs usually when the plants are covered,
as in a cold frame, or when the seedbed is located in a
moist hammock. Damping off is specifically caused, for
the most part, by one or more fungi which inhabit the soil.
REMEDY.-In case the seedbed is located in a moist
hammock it should be ditched around so as to draw the
water oft and dry the bed thoroughly. If the plants are
very thick set in the bed it would be best to remove a por-
tion of them so as to let in the sunlight on the ground. In
addition to this, a great deal of good can be done by spray-
ing the soil thoroughly with an ammoniacal solution of
copper carbonate. (See page 18). Stirring the soil be-
tween the seedlings is a further aid towards reducing the
loss from these fungi. Seedlings in rows can be easily
handled in this way.

HOLLOW STEM.

This diseased condition of the plants manifests itself
in the field shortly after they have been set out. The
plants at the time of setting out may look perfectly healthy
and normal, but after some days or a week, they begin to
fall over, remaining green after they have fallen over, but
making no growth. Even the plants that do not fall make
only an indifferent growth and many of them do not re-
cover. Those that are so weakened as to fall over almost
never recover. On examining such plants the stems will
be found to be hollow. Many of the plants that are still
standing will also be found to have hollow stems.
CAUSE.--The cause of this trouble is that the plants






28 Florida Agricultural Experiment Station,

have been grown in a seedbed that has been overfed with
nitrogenous material, and which has been given more
moisture than is necessary to produce vigorous plants. In
short, they are extra forced plants. These conditions fre-
quently arise in years when the seedbeds have been frozen
out and the tomato grower wishes to force his plants with
all possible speed to get them large enough to set in the
field.
TREATMENT.-The tomato growers suffer less loss
than they did a few years ago from this trouble, inasmuch
as the majority of them know how to handle the plants
in the seedbeds so as to prevent this difficulty. If the
plants are growing too luxuriantly to be in the best condi-
tion for setting out; that is, if the plants are too tender to
stand adverse field conditions, the tomato growers now
harden off their plants by withholding a portion of the
water from the beds. This must not be clone too abruptly,
otherwise a large proportion of the plants may be afflicted
with hollow stem in the seedbed. If the plants have been
thus hardened off for some days or a week, they will be in
a condition to plant in the field.


ROOT KNOT.

This serious disease of the tomato plant causes far less
loss to the tomato growers of Florida now than it did
several years ago, as a result of the fact that many growers
who have sustained heavy losses have gained knowledge
through sad experience with the disease. The malady is
so well described by the name and is so generally known,
that it needs no further description.
CAUSE.-The cause of the disease is a microscopic
worm which occurs in the soil, from which it attacks the
plant. In the tissues of the plant the mother worms pro-
duce myriads of eggs, the young from which in turn swarm
in the soil and infest the neighboring plants; or they may
be carried by water or other means to distant portions of
the field or adjoining farms. The young worms attack the









Bulletin No. 91.


tender and growing portion of the roots, where they cause
an abnormal enlargement of the tissues. These tissues be-
ing excessively enlarged and very soft are especially apt
to be attacked by fungi, which then cause decay to start.
As soon as decay sets in, the roots are unable to perform
their functions, and deterioration of the plants rapidly
proceeds.
METHODS OF DISTRIBUTION.-In selecting the site for
a seedbed it is extremely important to see that it is not in-
fested with root knot, otherwise the young nematode
worms will attack the seedling plants, and when they are
set out in the field the disease will be distributed through
all parts of the area. At the time of setting out the tomato
plants, it is difficult, and in some cases impossible, to tell
whether they are affected with root knot. Diseased
plants, however, are worse than no plants at all, and should
be discarded immediately. In addition to this method of
distributing root knot over the field, the disease is spread
over cultivated areas by means of the farming implements.
As these nematodes attack a great many plants other than
the tomato plant, almost all of our cultivated fields have
become at least slightly infested. The diseased plant,
when being dragged through the field by means of farming
implements, scatters eggs and worms all along its track.
The worms and eggs are so minute that hundreds and
thousands of them may be carried from one place to an-
other in the soil that clings to our boots as we are walk-
ing through the fields.
PREVENTIVE.-Tomatoes, egg-plants, okras, and
cantaloupes are among the plants that are severely at-
tacked by root knot. The banana and pineapple have also
been found to be subject to attacks of root knot. Velvet
beans, beggar-weed, crabgrass, corn, rice, and the grasses
generally, are almost quite immune to its attack. It is evi-
dent that plants which are badly attacked by the nema-
todes should not be planted on fields where we know that
root knot was severe the previous year. It is best to plant
the field in the second year to one of the crops that is not
likely to be attacked at all, and to keep the field free from








30 Florida Agricultural Experiment Station.

all broad-leaved plants. By following this line of rotation,
the amount of root knot in a tomato field may be kept
sufficiently low to enable us to plant it in tomatoes, at
regular intervals of time. If a field of tomatoes be found
to be severely attacked by root knot, the tomato planter
should make a point of destroying the tomato plants as
soon as the crop has been gathered. He should then plant
the field to some such crop as velvet beans, corn, or beg-
garweed, or let it grow up to crabgrass. One variety of
cowpea, the Iron, is fairly immune to the attack of root
knot. However, under certain conditions, even this va-
riety has'become severely affected.
A great many different kinds of chemicals have been
used with a view of destroying the root knot worm in in-
fested fields. A great many different kinds of fertilizers
have also been tried. Up to the present time nothing has
been discovered that can be profitably applied to a tomato
field with a view of killing out the root knot worm.


FRUIT WORM.

(Heliothis armigera.)
This is one of the most omnivorous of our insect foes.
It is a severe pest on nearly all of our most important
crops, and on each crop it receives a different common
name. Thus, it has the name bollworm, when it attacks
cotton; corn worm, when it attacks corn; tobacco bud
worm, when it attacks tobacco, etc. By referring to Fig.
I, the different stages of the insect will be seen. A and B
represent different views of the egg; C, the mature worm;
D, the chrysalis; and E and F, the moth, all about natural
size, excepting A and B, which are greatly enlarged.








Bulletin No. 91.


FIG. I. Heliothis armigera: a and b, egg enlarged; c, larva; d, earthen
pupa case; e and f, moth; all natural size.
(By courtesy of L. O. Howard, chief of Bur. of Ent., U. S. Dep. of Agr.)

In the early stages of its life history the larva feeds
for the most part, upon the leaves, or bores into the tender
portions of the stem of the plant. Even when it is well
advanced in size, it will bore into the stem of the tomato
plant if no fruits are present. About the time that the
larva becomes one-half or two-thirds grown it prefers the
tomato fruit for its diet. Professor Quaintance, in study-
ing this insect, found that it was not satisfied with boring
a hole into one tomato, and feeding on that; but frequently
emerged from one tomato and bored into another one, so
that one worm might destroy a number of tomatoes. Dur-
ing warm weather, it takes about thirty days from the time
the egg is laid until the mature moth emerges. The moth
then lays about 500 eggs, which hatch in a few days and
begin their destructive work. As it would be possible for
a new brood to come out every thirty days, and for each fe-
male to lay 500 eggs, we can readily see that our crops










32 Florida Agricultural Experiment Station.

would soon be entirely eaten up if all the eggs that were
laid should result in mature moths.
REMEDY.-When the tomato worm occurs in great
abundance, much good may be done by spraying with
Paris green, or arsenate of lead, since the young larvae
feed for some time on the tender foliage of the tomato
plant. As a rule, however, the tomato worm is not present
in sufficient abundance to pay for the cost of poisonous
sprays. The life history of this insect is such that the
first set of larvae reach about full growth at the time that
the first picking occurs. It is therefore of the greatest im-
portance that all wormy tomatoes should be destroyed
from the beginning of the picking season. It may seem a
small matter to throw down one wormy tomato in the
field, but 'the throwing down of this one wormy tomato
would mean the destruction of 500 to Iooo tomatoes in the
course of about thirty days, should this worm live through
its life cycle and deposit its eggs in a favorable position.
From this we can readily see that the destruction of a
single larva, when the first picking of tomatoes is being
made, is easily equal to the saving of a crate of marketable
tomatoes thirty days later. As many of our tomato fields
produce a shipping crop for as much as sixty days, we
can see how highly important it is that the first lot of the
tomato worms should be destroyed, and none allowed to
escape. To demonstrate the efficacy of this method of
destroying the tomato worms, two fields were chosen near
Terra Ceia, in 1894. From one of the fields the wormy
tomatoes were carefully gathered up and all the larvae
destroyed. In the other field which was about forty rods
away, the usual non-attention that is given to these wormy
tomatoes prevailed. In the field in which the worms had
been carefully killed off there was scarcely any perceptible
increase in the number of wormy tomatoes, while in the
field but a short distance away in which the wormy toma-
toes were dropped in the middle of the rows, fully 80 per
cent. of the tomatoes had become worm-eaten before the
close of the shipping season.







Bulletin No. 91.


CUTWORMS.

The term cutworm covers a multitude of species of
moth larvae. In general, their life history is the same as
that of the fruit worm. That is, they go through four
stages-the egg, the larva, the chrysalis, and the adult.
The length of time that is required for them to go through
these four stages varies with the species. A considerable
number of different species yield to the same remedial
treatment, though they do not all belong to the true cut-
worm family.

REMEDY.-Some forms of cutworms burrow into the
ground, and during the night come out, cut off the young
tomato plants, and after having eaten their fill, burrow
into the ground again and hide for the day. Other forms,
such as those that live under the large tomato plants,
crawl up the vines, eat a number of holes into the tomato
fruits, and drop on the ground again. For these various
forms there is one general treatment; that is, the use of
poisoned bait. There are a number of different substances
which may be used for this purpose, all of which are more
or less effective according to the thoroughness of, the
treatment. In general, we may say that a heaped tea-
spoonful of Paris green added to a quart of bran or cot-
tonseed meal, and mixed up with an amount of
water sufficient to make a rather stiff pasty mass, is about
right. Some people have better success by adding a small
amount of sweetening matter, say, a tablespoonful or two
of syrup. This keeps the mash from drying up, besides
being possibly a little more palatable to the worms. The
ingredients are thoroughly mixed, and a small quantity
of the mixture is dropped under each plant that is infested.
If the plant is a large one, three or four pellets are used.
If the cutworms are working on newly-set out plants, a
pinch of this mixture may be dropped at the foot of each
plant in that section of the field where the cutworms are
causing damage. Care should be taken not to allow
poultry or any domestic animals that might eat this mash.
to run in the field where it is being used.








34 Florida Agricultural Experiment Station.

MOLD, WHITE MOLD, PHYTOPTOSIS.
(Phytoptus calacladophora.)

Florida appears to be the only state in the Union in
which this particular disease does any great amount of
damage to the tomatoes. This little four-footed mite,
however, occurs at very rare intervals on tomatoes as far
north as South Carolina.
Tomato plants are not usually attacked by this mite
until they have about reached the blooming size. If one
is standing in a tomato field shortly after sunrise, or near
sunset, and looking across the field in the direction of the
sun, the plants which are attacked will be easily distin-
guished from the others in the field by the peculiar white,
fuzzy appearance of the upper portion of the stem. In
later stages of the development of the tomato plants, the
terminal portion will appear as shown by Plate III.
In spite of the fact that this disease is not a mold, but
due to this little mite, the tomato growers of the state
continue to call it mold or white mold.
TREATMENT.-The cause of this disease was discover-
ed by the writer in 1892. Experiments with a view of find-
ing a remedy were immediately taken up, with the most
gratifying results. Sulphur spray (Sec Fla. Agri. Exp.
Sta. Bul. No. 76, Page 227) was found to be a thoroughly effi-
cient and almost immediately effective remedy. Other in-
secticides, such as the lime-sulphur spray, dry sulphur, dry
sulphur and lime, are also excellent remedies. One appli-
cation is usually all that is necessary.












PLATE III.


- t4


.NOLD.--f This disease gives the stem, growing parts and young
leaves the appearance of having been covered with starch.




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