• TABLE OF CONTENTS
HIDE
 Front Cover
 Board of control and station...
 Table of Contents
 Some pertinent pointers
 Pink rot of celery
 Early blight
 Late blight
 Blackheart
 Root-knot
 Transportation diseases
 Damping-off in seedbeds
 Mosaic of celery
 Root rot
 Slime mold
 Non-parasitic diseases
 Bacterial leaf spot
 Soft rot
 Phoma root rot
 Celery yellows
 Selection of celery seed and celery...
 Celery seedbed sterilization
 Seedbed and field sanitation
 Bordeaux mixture, how to make and...
 Spray machines






Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 173
Title: Celery diseases in Florida
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Permanent Link: http://ufdc.ufl.edu/UF00028044/00001
 Material Information
Title: Celery diseases in Florida
Series Title: Bulletin - University of Florida. Agricultural Experiment Station ; 173
Physical Description: Book
Creator: Foster, A. C.
Weber, G. F.
Publisher: University of Florida Agricultural Experiment Station
Publication Date: 1927
 Record Information
Bibliographic ID: UF00028044
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Front Cover
        Page 21
    Board of control and station staff
        Page 22
    Table of Contents
        Page 23
    Some pertinent pointers
        Page 24
        Page 25
    Pink rot of celery
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
    Early blight
        Page 31
        Page 32
        Page 33
    Late blight
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
    Blackheart
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
    Root-knot
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
    Transportation diseases
        Page 50
        Page 51
        Page 52
        Page 53
    Damping-off in seedbeds
        Page 54
        Page 55
    Mosaic of celery
        Page 56
        Page 57
    Root rot
        Page 58
    Slime mold
        Page 59
        Page 60
    Non-parasitic diseases
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
    Bacterial leaf spot
        Page 66
    Soft rot
        Page 67
    Phoma root rot
        Page 68
        Page 69
    Celery yellows
        Page 70
        Page 71
    Selection of celery seed and celery seed disinfection
        Page 72
    Celery seedbed sterilization
        Page 73
        Page 74
    Seedbed and field sanitation
        Page 75
    Bordeaux mixture, how to make and how and when to apply
        Page 76
        Page 77
        Page 78
    Spray machines
        Page 79
Full Text



Bulletin 173 (Reprinted June, 1927) December 15, 1924

UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
In Cooperation with Office of Vegetable and Forage Diseases
Bureau of Plant Industry, U. S. Department of Agriculture


CELERY DISEASES IN FLORIDA
By
A. C. FOSTER
Pathologist, Ofice of Vegetable and Forage Diseases,
Bureau of Plant Industry, U. S. D. A.
and
G. F. WEBER
Associate Plant Pathologist, Florida Agricultural Experiment Station

.9.
*ci-^ ^c


Fig. 14.-Late blight of celery showing small lesions on leaf blades.







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
HOUSDEN L. MARSHALL, M. S., Assistant Chemist
JACKSON D. HESTER, M. S., Assistant Chemist
J. M. COLEMAN, B. S., Assistant Chemist
O. 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. R. ENSIGN, M. S., Truck Horticulturist
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 Agricultural Economist
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. O. GRATE, 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 (Belle Glade)
J. H. HUNTER, M. S., Assistant Agronomist (Belle Glade)
FRED W. WALKER, Assistant Entomologist (Monticello)

K. H. GRAHAM, Auditor.
RACHEL MCQUARRIE, Assistant Auditor












CONTENTS


SOME PERTINENT POINTERS ........................... .......................... ---... .. 24
PINK ROT OF CELERY ..........---- ....--- ..........- ..------- -------------. 26
E ARLY BLIGHT ...................................... ............... ............. 31
LATE BLIGHT ..........--- ........---- ......-......--..-------- -..... .----- 34
BLACKHEART ........................ ..--------- -------- -- ---------------- 39
ROOT-KNOT .................................... -----------------.... ........ 45
TRANSPORTATION DISEASES ....... -----................ ..--------------. 50
DAMPING-OFF IN SEEDBEDS .................................... .................. ...... 54
M OSAIC ...........---------........ ....... .......- ...--.............. 56
ROOT ROT ...-...........--------------- ----... ..-......... -----......--....... .... 58
SLIME MOLD ..........-..... .. ------------------------------ ---.--. ------------ 59
NON PARASITIC DISEASES ................-.....--...........------------------..- 61
Cracked Stem s ................................... .... ..... .... -------.....--- 61
Stunting ...........----------------------.--- --- -----... ..-- -- ........ 61
Growth Cracks ................... ........................--- ---...----- 62
Hollow Stem or Pithiness ....................--..--- --..... .---- .--.-- 63
Brown Stem .....---....~.... ..-.....-...... ------------ ------ --------.... 64
Red Root ........----------------------------..........--------.. 65
BACTERIAL LEAF SPOT ................................... ...---........ 66
SOFT R OT ...................... ......... ........ ........ -- .. .. ..........-... ...-........... 67
PHOMA ROOT ROT ...... --..................... ------------..... .------ 68
CELERY YELLOWS ..................------ -................. ...... ----------- 70
SELECTION OF CELERY SEED ........................ ......... ....................... 72
CELERY SEED DISINFECTION ....... --............. -- .. .... --------------- 72
CELERY SEEDBED STERILIZATION ........... ...... ..... .... ......................... 73
SEEDBED AND FIELD SANITATION ...........---- ...-- --.----------.-- --------.-- 75
BORDEAUX MIXTURE, How to Make and How and When to Apply-..........--. 76
SPRAY M ACHINES -........... .....-................ ... ............. ----- 79










SOME PERTINENT POINTERS


Pink Rot of celery is one of the worst field diseases of celery
in Florida. It is caused by the fungus Sclerotinia sclerotiorum
(Lib.) Massee. This fungus develops rapidly in transit, reduc-
ing crates of apparently healthy plants to soft, watery, decayed
masses. When this condition is found in transit the disease is
known as watery soft rot. Strict sanitation in the field, careful
handling and packing and pre-cooling for shipment are essential
for commercial control of these diseases.
Early Blight can be controlled by careful spraying at frequent
intervals with 4-4-50 Bordeaux mixture. Begin spraying in the
seedbed.
Late Blight is usually introduced with the seed. The selec-
tion of disease-free seed is the most important phase of control
measures. If it is found in the field, spray with 4-4-50 Bordeaux
mixture.
Plan for a convenient platform for the making of Bordeaux
mixture. This spray is necessary in Florida for the production
of celery; it will control most of the important diseases of cel-
ery in this state.
Blackheart is caused by unbalanced water relations. Do not
take chances on this part of the business of growing celery.
Practice the best cultural methods known and there will be no
occasion to fear losses from this disease.
Field Sanitation is very essential in celery growing. Clean up
the debris in the field as soon as possible after the crop is cut.
This waste material is saturated with the spores of fungi which
cause disease. Burn or bury it instead of dumping indiscrimi-
nately.
Use a good spraying machine. Make your own Bordeaux
mixture. Keep the pressure of the sprayer up at all times and
be sure to cover all parts of the plants.








CELERY DISEASES IN FLORIDA


By A. C. FOSTER AND G. F. WEBER1
Celery growing in Florida has developed from relative unim-
portance to an industry furnishing the chief source of income
to hundreds of people. During the last few years the farms
devoted to the production of this crop have increased steadily
in number and the land under cultivation has been improved
materially. The industry is highly developed and specialized.
The production of celery in Florida has increased rapidly in
the last few years. At present over 7,100 carloads are shipped
annually from the State, mainly from Sanford and Bradenton
vicinities. Sanford is the most important celery-growing com-
munity in the State. The other important areas in which this
plant is profitably grown are Manatee and Orange Counties.
Manatee County shipped about 1,500 cars and Orange County
about 100 cars during the 1923-24 season.
The accompanying table gives comparative data2 of the four
leading celery-producing states in the United States during the
season of 1923-24.

TABLE 1.-COMPARATIVE DATA OF ACREAGE, ACRE YIELD IN CRATES,
TOTAL CRATES, VALUE OF THE CRATE, AND TOTAL FARM VALUE OF CELERY
IN THE FOUR LEADING CELERY-PRODUCING STATES DURING 1923.


State Total
o 2 03 2 Value


California .................... 5,250 155 814,000 $2.93 $2,385,000
Florida ....................... 3,200 350 1,120,000 3.18 3,561,000
Michigan ..................... 4,210 221 930,000 1.44 1,339,000
New York ................ 3,190 250 950,000 1.72 1,634,000


Compared with the three leading states, Florida has fewer
acres devoted to the production of celery, but at the same time
it produces more crates (different sized crates duly considered)

'Foster, A. C., Pathologist, Vegetable and Forage Crop Diseases, Bu-
reau of Plant Industry, United States Department of Agriculture; Weber,
G. F., Associate Pathologist, Florida Agricultural Experiment Station.
Photographs by D. G. A. Kelbert.
""Commercial acreage, yield per acre, production, price and farm value
of celery 1919-23," Division of Crop and Livestock Estimates, Bureau of
Agricultural Economics, U.S.D.A., Dec. 7, 1923.

(
rP






Florida Agricultural Experiment Station


of celery to the acre than any other state. In actual money re-
ceived for the crop, Florida topped the list with the highest
crate price and the highest total receipts. The money received
for the Florida crop exceeded the money received for the Cali-
fornia crop by more than $1,175,000. In figuring acre returns,
the Florida grower received $1,112, the California grower $435,
the New York grower $417, and the Michigan grower $318.
Thus the Florida celery grower received for his 1923 crop $677
more to the acre than did the California grower, $794 more than
the Michigan grower and $695 more than the New York grow-
er. The production of celery and value received for it in Flor-
ida during the 1924 season was considerably more than in 1923,
but comparative results can not be made because of the lack of
figures from other states.
With the advent of the culture of celery so extensively and
intensively, certain conditions have arisen tending to promote
the introduction, spread and growth of many destructive para-
sites, which cause heavy losses annually to growers, buyers,
shippers and consumers.
The continuous-culture system of growing celery on the same
land year after year without any attempt to rotate except
within the year, or to rest the land, tends to make the soil
"celery-sick," or to infest it thoroly with organisms that pro-
duce disease. This is especially true in the case of root-knot
and pink rot. The culture of an early and late crop of celery
in the same community also makes it possible for certain dis-
ease-producing parasites to pass from the early crop to the
late crop. This is true because the organism does not have to
undergo a starvation period.
The purpose of this bulletin is to place in the hands of the
celery growers of Florida information concerning seasonal oc-
currence, description and control of celery diseases. The rec-
ommendations contained herein are endorsed by the United
States Department of Agriculture and the Florida Agricultural
Experiment Station.

PINK ROT OF CELERY
Pink rot of celery is caused by a fungus (Sclerotinia sclero-
tiorum (Lib) Massee). It is one of the most destructive dis-
eases of this crop, especially during years when climatic condi-
tions are favorable for the development of the fungus. It






Bulletin 173, Celery Diseases in Florida


causes a damping-off of young plants in seedbeds, a light pinkish
rot of the stalks in the field during any stage of the growth of
the plant and a watery soft rot in transit. Decay is most com-
mon on plants that have been papered for blanching, but often
the greatest damage is done in transit after the celery has been
placed in the car. The disease is prevalent in Florida and is
also found in many northern celery-growing areas, both in
greenhouses and in fields.

DESCRIPTION OF PINK ROT
The disease in the seedbed is characterized by a typical damp-
ing-off of young plants that cannot always be distinguished
from similar diseases caused
by other organisms (see fig.
32). The seedling falls over
on the ground because the
fungus which has entered
the small stem has killed
the cells and weakened the
plant so that it cannot
stand up. A typical watery .
soft rot soon begins near
the crown. In advanced
stages of the disease, under
favorable temperature and
moisture conditions, the fun-
gus develops a fine, white,
cottony growth. This growth
appears over the surface of
the affected parts of the
plants and eventually the
black irregular resting bod-
ies or sclerotia are formed. .
The disease on older
plants is usually found near Fig. 15.-Pink rot of celery; plant
the surface of the ground, first attacked in growth crack.
the fungus probably entering the plant thru injuries or growth
cracks and gradually growing up the stalks (fig. 15). Surfaces
of diseased stalks become water-soaked and appear pinkish. This
is followed by a fine cottony growth, watery soft rot, and a






Florida Agricultural Experiment Station


Fig. 16.-Pink rot of celery, prir" y infection on stalks and leaves.






Bulletin 173, Celery Diseases in Florida


later development of irregular black sclerotia, or resting bodies.
Often the plant is attacked first higher up on the stems, which
soon decay (fig. 16). The disease spreads rapidly over the en-.
tire plant and soon kills it. After the celery is papered for
blanching the disease often spread _*iAgrge number of succes-
sive plants in the row, entirely dest ng long stretches of them.
Climatic conditions in Floriida are favorable for the deeop-
ment of the parasite which causes this troull e, sin t thrives
best at a moderately low temperature, such as is f(uin'here
during winter months. The life history of the pink'ot or-
ganism is rather simple, but because of the peculiar and long-
lived resting bodies formed, it is practically impossible to pre-


.vent tne disease or control it
after it becomes established
ri a field. The white, cot-
tony growth of mycelium'
that is formed over the sur-
face of affected plants pro-
duces sclerotia o r resting
bodies (fig. 17). The scle-
rotia are produced in large
numbers over the surface
of the diseased plant. When
the dead plant dries up or
decays to the ground, the
sclerotia drop to the ground,
and remain there for indef-
inite periods or until mois-
ture and temperature condi-
tiu~o ar e right for their
growtl.vr i i,: Y iX : r: -
In Florida the sclerotia or
resting bodies remain dor-
mant during sumnepr ,and,


%&


Fig. 17.-Sclerotia or resting bodies
of the fungus causing pink rot dis-
ease. (Natural size.)
early fall. 'After the first cool


weather, usually in December, they come out of their dormancy,
begin to grow, and send up fruiting bodies (known as apothe-
cia) which look much like small mushrooms. In the apothecia
millions of spores are formed by which means the fungus is
disseminated or spread in much the same manner as weeds are
scattered by seed. distribution. The spores are forcibly dis-
charged .from the, apothecia and the wind scatters them from


'-------- j


fr_7


~II.






Florida Agricultural Experiment Station


one part of the field to another and from one field to another.
If temperature and moisture conditions are right, the spores
grow on the plants on which they fall.
The sclerotia live in the soil
under Florida conditions for
several years, and a field, once
infested, probably remains in-
fested as long as it is cultivated
to crops attacked by the fungus.
The fungus is capable of attack-
ing a large number of vegeta-
bles, especially celery, lettuce,
eggplants, potatoes, carrots,
cabbage, pepper, spinach, beans
and cucumbers.

CONTROL OF PINK ROT
.k Pink rot cannot be controlled
effectively by the use of Bor-
I deaux mixture,. altho spraying
the lower portions of the plant
with this material is recom-
mended as a precaution. If
spraying is done thoroly and
carefully, a certain amount of
success may be expected. It is
advisable to lower the spray
nozzles to the surface of the
ground and apply the spray
under high pressure. This gives
uniform distribution over the
whole area.
The safest precaution is to
remove all affected plants from
the field and bury deeply or
Fig. 18.-Late stage of pink rot (better) burn. Rotation of let-
in the field. Note sclerotia in
decayed area. tuce and celery will not help to
control the disease, because
both crops are susceptible. It is advisable also to maintain a
dry mulch over the surface of the soil by frequent cultivation,
since the organism thrives best under moist conditions.






Bulletin 173, Celery Diseases in Florida 31

EARLY BLIGHT

The first appearance of early blight (Cercospora apii Fr.) in
Florida dates back to the earliest culture of celery in the State.
This disease appears in other states where celery is grown,


CII
Bra


-`K'I


Fig. 19.-Early blight on celery leaf showing
stages.


typical spotting in first


but it is not as destructive as in Florida, because climatic con-
ditions elsewhere are not so favorable for its development. In
northern states it apparently causes greater losses in New York
and New Jersey thad in Michigan and California.






Ftorida Agricultural Experiment Station


In Florida the disease can be found to a greater or less extent
almost any time of the year when celery is growing. It often
appears in seedbeds early in October when the plants are small,
and is carried from there to the fields, where it continues to
thrive and do damage. Variation in climatic conditions in
Florida affects the development of the disease, since usually it
is prevalent during fall on what is known as the early crop.
When cool weather arrives the spread of the disease is checked
considerably. But from March to the last of May the disease
again becomes prevalent, and it is at this time that it evidently
does the greatest damage.
Plants affected within early blight require considerable strip-
ping. This reduces the size of the bunches and decreases the
yield materially. Furthermore, if affected plants are loaded
into the car for shipment, decay is likely to set in on affected
areas, thereby giving the crop a poor appearance and making
it unfit for storage.

DESCRIPTION OF EARLY BLIGHT
The disease attacks leaves in all stages of their development,
but it is most prevalent on old leaves (fig. 19). It is often
found also on stems and petioles. It appears first on leaves as
small, circular, yellowish brown spots. These spots enlarge rapid-
ly, becoming darker in color and eventually assuming a grayish
appearance. The grayish appearance is due to growth of the
fungus, which produces a heavy growth of small needle-like
spores over the surface of the spot on the leaf. The disease is
spread to other celery plants by these spores which are scat-
tered by wind and other agencies. On the stems the disease
appears as light brownish gray streaks, gradually turning black,
often extending for several inches along the stem. The spores
are developed on the surface of these spots also (fig. 20).

CONTROL OF EARLY BLIGHT
Early blight of celery can be controlled successfully by thoro
and systematic spraying with liquid Bordeaux mixture. Care-
ful spraying and dusting experiments have been conducted at
Sanford to determine the most effective means to follow to con-
trol this disease. The 4-4-50 Bordeaux mixture consistently
gave best results. To effectively control the disease, the
spray should be applied first in the seedbed as soon as the young







Bulletin 173, Celery Di~t es, in Florida


leaves begin to develop. The spray should: be applied once a
week or every ten days, depending somewhat on the amount of
blight present and climatic conditions. In cool weather it is not
necessary to spray so often, unless late blight appears in the
vicinity, since cool weather
is unfavorable for the de- 1 "
velopment of early blight.
In the field the spray should ::
be applied once a week or i f
every ten days, and some-
times as often as twice a !
week. The spray should be
made and applied according
to directions in this bulletin.
The dusting experiments
mentioned above were car-
ried on in the spring of the
year on a late crop of cel-
ery, when conditions were
most favorable for develop- .
ment of blight. The dusted
plots consisted of four rows
approximately 600 feet long,
or approximately one sev-
enth of an acre. The dust
was applied on the different
plots in early morning, at
midday and late in the after- Fig. 20.-Early blight on celery stems
noon. It was applied also showing destructiveness of the dis-
ease.
in different amounts and
with different types of dusting machines. A hand duster, trac-
tion duster and power-driven duster were used. On some plots
the spray was applied once a week and on others twice a week.
Check plots were left in several parts of the field for compari-
son with sprayed and dusted plots. Spots of the disease were
counted on several hundred plants from each plot to determine
the control of the disease from each treatment.' Data secured
are not tabulated because they are inconclusive, having been ob-
tained during the latter part of a single season, but are sum-
marized here for the benefit of the reader.
Liquid 4-4-50 Bordeaux mixture applied at the rate of 100
gallons to the acre gave best results.






34 Florida Agricultural Experiment Station

Dust applied twice a week at the rate of 40 pounds to each
application, or a total of 80 pounds, gave about as good con-
trol as 100 gallons of liquid Bordeaux mixture applied once a
week. Comparing the cost of liquid Bordeaux and copper-lime
dust, it cost approximately 85 cents to prepare 100 gallons of
Bordeaux mixture including cost of material and labor. Costs
of applying dust and liquid Bordeaux were considered equal.
At the time the experiments were conducted dust cost 12 cents
a pound, or $9.60 for 80 pounds, the amount required to secure
the same results obtained by using 100 gallons of liquid spray
which cost 85 cents. At present dust can be bought for 8 or
10 cents a pound, depending on the amount bought. This con-
trol was obtained only when the dust was applied with the
power-driven duster early in the morning when the plants were
wet with dew.
Dust applied with the traction duster (at the same rate of
material, 40 pounds twice a week) did not give nearly as good
control as the power-driven duster.
Dust applied at midday, when the plants were dry, with the
traction-driven duster at the rate of 15 pounds to the acre, did
not give any better control than the untreated plot.
In order to secure good control, dust must be applied when
plants are wet, when little wind is blowing, and when a good
power-driven duster is used. It should be applied more fre-
quently than liquid spray.
It is thought advisable to recommend the use of Bordeaux
spray until dust has proved equally as effective and as cheap.
At present it' is apparent that the use of dust will cost any-
where from three to four times as much as the liquid, depend-
ing on cost of labor and materials.

LATE BLIGHT
The disease known at late blight (Septoria petroselini apii Br.
& Cav.) has been more or less destructive to celery during the
last 30 years. It is generally considered a cool weather disease.
Its name describes the time of its appearance in the northern
celery-growing areas of the United States. Celery matures in
late summer and early fall, when the temperature is cooling. It
is at this time that the organism which causes this trouble at-
tacks plants. Hence it is called late blight to distinguish it from
early blight (Cercospora apii Fr.) previously described.






Bulletin 173, Celery Diseases in Florida


In Florida the relation of temperature to the development of
plants is almost the reverse of that farther north, except for
the extremely early fall plantings. Celery is planted during
fall and winter and its early development takes place during
the cooler season. It is also
noted that late blight attacks
plants at this time. This rever-
sal of seasonal conditions in rela-
tion to the development of plants
and the prevalence of the disease
may be of vital importance as re-
gards the amount of damage
done to the crop.


It was found that the warm
weather of the latter part of
April, 1924, was important in the
control of the disease. The dis-
ease was of a more serious na-
ture and more widespread in the
State last season than ever be-
fore, probably due to the plant-
ing of large quantities of infect-
ed seed and also because of the
exceptionally late spring. Cool
weather lasted a month longer
than it usually does.
The disease attacks all parts
of the plant above ground, being
conspicuous and disastrous on the
foliage and on the older leaf peti-
oles (fig. 21). The lesions on the
petioles differ from those of early
blight in that they are much
smaller. They are more oval than
linear and are speckled with black
dots. Lesions on leaves in many
cases can be distinguished from
early blight only by the presence
of these small black specks (pyc-
nidia). There were apparent-
ly two strains of the fungus


Fig. 21.-Late blight of celery on
stalks showing four-fifths of
petioles affected and unsalable.







Florida Agricultural Experiment Station


found in the Sanford district last season. One strain produced
a small lesion which is easily detected and identified. The other
strain produced lesions that were distinguished with difficulty
from early blight lesions. The production of pycnidia was
often delayed in the larger lesions, in which instances it was
almost impossible to distinguish these lesions from those caused
by early blight fungus (fig. 22).




















Fig. 22.-Late blight of celery showing typical lesions of both large and
small types. (Slightly enlarged.)
DESCRIPTION OF LATE BLIGHT
The disease is found principally on the leaf blades where it
produces small circular spots about one-sixteenth (1-16) of an
inch in diameter. (See fig. 14; on cover.) Spots are at first
slightly darker than surrounding healthy tissue. Gradually
they become almost black. The edge of the spot is not sharply
defined, blending off gradually into the natural green color of
the leaf. The spores of the fungus develop in the small, al-
most invisible, black specks produced in the leaf tissue of the
lesions. These spore-producing bodies (or pycnidia) are often
produced in apparently healthy leaf tissue beyond the edge of
the lesion. Often lesions are so numerous on a leaf that they
coalesce (run together), resulting in a rapid killing of the leaf.






Bulletin 173, Celery Diseases in Florida


The second type of lesion is much larger than the one just
described, being from a fourth to half an inch in diameter.
These lesions are more distinctly marked around the edges and
are often slightly lighter colored in the center. The pycnidia


Fig. 23.-Late blight of celery showing typical large sized lesions.

are produced somewhat later than those previously described
Sand are not formed beyond the edge of the lesion in healthy
tissue.







Florida Agricultural Experiment Station


Both types of lesions were found last season on the same plant
(see fig. 22). On stems there is no distiguishable difference be-
tween lesions. They are decidedly oblong up and down the
stems. The tissue is slightly brownish at first and later turns
light brown but not black. The whole area is thickly speckled
with pycnidia, often the lesion is so deep that the petiole breaks


Fig. 24.-Late blight of celery on stalks enlarged twice to show lesions
and clustered pycnidia.

over. Lesions are most conspicuous on older stalks. They are
always more numerous on the outer surface of the stalk than
on the inner surface (fig. 24).

CONTROL OF LATE BLIGHT
The first precaution to take in the control of late blight is to
secure disease-free seed. If infected seed must be planted, it
is advisable to plant those two or three years old. If old seed
are ndt obtainable, it is necessary to treat the seed either in hot
water or corrosive sublimate. If the disease is found in the
field, the only control method recommended at present is careful
and thoro spraying with 4-4-50 Bordeaux mixture at least once







Bulletin 173, Celery Diseases in Florida


a week. It should be emphasized that this spraying must be
thoro This disease is more difficult to hold in check by spray-
ing than early blight.
When the field is harvested instructions should be given and
care taken to strip the stalks from plants that show lesions
caused by the fungus. This is advisable because the fungus
-which grows well in cool temperatures-continues to develop
in transit, producing spores and reinfecting other plants. In a
field which was badly diseased the waste from stripped stalks
and discarded plants should be raked up; removed from the
field and either burned or buried, after the crop is harvested.
This is an important factor in the control of the disease, be-
cause it is known that spores in the pycnidia remain viable from
one season to the next.

BLACKHEART
Blackheart often causes greater losses to Florida celery
growers than any other disease. Occasionally it is reported as
being severe in California
and appearing in almost all .
other celery-growing areas.
In Florida during certain
years this disease has de-
stroyed completely many
celery fields and on frequent
occasions it has caused seri-
ous damage. It is one of
the non-parasitic diseases,
since no organism is asso-
ciated with it or related in
any way with its appear-
ance. Saprophytic organ-
isms usually enter the dis-
eased parts after blackheart
has appeared and further
promote decay. Fig. 25.-Characteristic chlorotic mot-
Blackheart, as found in things of leaf of celery plant af-
Blackheart, as found in fected with blackheart.
the South, is distinctly dif-
ferent from "heart rot" or "crown rot" which have been re-
ported from northern states and Europe. The latter is a
typical soft rot, evidently caused by bacteria of the Bacillus






Florida Agricultural Experiment Station


carotovorus group, and the
former, or Florida blackheart,
is not a soft rot but a typical
dry rot followed by the prema-
ture death of the growing
crown.

DESCRIPTION OF BLACKHEART
Blackheart of celery appears
on the younger leaves and in
the growing heart, causing a
blackened portion. Hence the
name blackheart. Often t h e
older leaves assume a yellow, or
chlorotic, appearance before the
blackened portions of the plant
appear (fig. 25). On the older
leaves the tips often die, turn
brownish black and shrivel up.
In the heart of the plant, where
the disease most visibly mani-
fests itself, it appears first in
the young leaflets folded up in
the crown and is conspicuous
only when the plants are sliced
open. The disease spreads in the
crown, eventually involving this
entire part which turns black
(fig. 26). This condition may be
followed finally by soft decay.
Frequently blackheart involves
all of the growing crown, leaving
only a stump at the base of the
inner stalks. This stump is
surrounded by a few of the
older stalks fringed around the
outside edge of the crown en-
closing a barren center.
During the spring of 1924
fertilizer experiments were con-
Fig. 26.-Blackheart of celery. ducted to determine the relation
Note the black leaves in the of nitrate of soda to the produc-
heart of an otherwise healthy
celery plant. tion of blackheart.







Bulletin 173, Celery Diseases in Florida


TABLE 2.-CELERY EXPERIMENT CONDUCTED AT SANFORD IN 1923-24,
SHOWING VARYING AMOUNTS OF NITRATE OF SODA APPLIED AND PERCENT-
AGE OF BLACKHEART PRODUCED.

Treatment Result
No. of plot 2 tons to the acre of 6-6-6 fertilizer % of blackheart
applied to each plot.

53 500 pounds of nitrate of soda................. 0
54 1000 pounds of nitrate of soda.................. 0
55 1500 pounds of nitrate of soda.................. 0
56 2000 pounds of nitrate of soda.................. 0


Nitrate of soda was applied at the rate of from 500 pounds
to 2,000 pounds to the acre, and blackheart failed to appear
in any plot. Similar experiments were conducted in 1925 and
1926 and the results secured confirm those reported in the above
table.
CAUSE OF BLACKHEART

The cause of blackheart was not definitely known until re-
cently. Many suggestions as to its possible cause have been
offered by both growers and plant pathologists, but evidently
many of them have not been supported by careful observation
or experimental data. It was once thought that various ferti-
lizers, such as nitrate of soda and kainit, applied heavily would
cause the disease. But this theory was disproved by experi-
ments conducted in the Sanford area during the last two years.
(See table 2.) Many growers have thought that the higher
temperatures of April and May are favorable for the develop-
ment of blackheart. But while this may be an important factor,
there are certainly other important ones, since the disease ap-
pears during cooler months.
Experiments conducted near Sanford over a period of two
years apparently indicate that the most important factor as-
sociated with the production of blackheart is unbalanced water
relations. There are other factors, however, that may have
some relation to the disease; such as, age of plants, tempera-
ture conditions, soil conditions and variety of celery grown.
Plants of all ages are susceptible when conditions are favorable
for the development of the disease. A plant that has grown to






Florida Agricultural Experiment Station


maturity and is then allowed to remain in the field is more sub-
ject to blackheart than a younger immature plant. The old
Golden Self-Blanching strains of celery are evidently more sus-
ceptible to blackheart than the Pearly White strains. Black-
heart appears in its destructive form on the late crop mainly
during April and May, because the celery has reached its grow-
ing period then and any unfavorable conditions-such as check-
ing the growth of the plant, high temperature, too dry or too
wet soil-may cause its appearance.
An experiment was conducted to determine, if possible, the
relation of the three different fertilizer elements-nitrogen,
phosphorus and potash-to the appearance of blackheart in
celery. Another purpose was to determine the relation of lime
and ashes to the same disease.
It was thought that the use of Schreiner's "Triangle system
for fertilizer experiments" would give best results and his sys-
tem was followed thruout these experiments.
New land was used. It was rather heavy sandy loam, more
or less typical of Florida celery lands unless perhaps a little
heavier than average land.
The strip of land was divided into two equal parts, on one
half lime was applied at the rate of 2,400 pounds to the acre,
and on the other half ashes were applied at the rate of 3,600
pounds to the acre. The fertilizer trials were run in duplicate
on these plots. The plants were set in the field January 9, 1923,
in rows 32 inches apart with the plants 3 inches apart in the
rows. Each plot consisted of four rows 25 feet long and con-
tained a total of 400 plants.
The first application of fertilizer was made on January 10,
and succeeding applications were made at one-month intervals
until five applications had been made. The fertilizer was ap-
plied at the rate of approximately 1,000 pounds to the acre for
each application, making a final total of 5,000 pounds to the
acre.
The plants were kept thoroly sprayed with 4-4-50 Bordeaux
mixture from the time they were set in the field until har-
vested, applications being made from two to eight times a
month, depending on climatic conditions and the development
of blight in the vicinity. Six check plots were used, three in
each duplicate plot. Two of these check plots were located on
the east and west ends, and two in the center of the field.







Bulletin 173, Celery Diseases in Florida


TABLE 3.-SHOWING PLOT NUMBER, PERCENTAGE OF FERTILIZER APPLIED
AND PERCENTAGE OF BLACKHEART FOUND ON THE VARIOUS PLOTS AFTER
FLOODING.


Percentage fertilizer applied


Ammonia Phosphorus


Potash


Percentage of blackheart in
plots after flooding.

2,400 lbs. hy- 3,600 lbs. wood
drated lime to' ashes to the
the acre acre


During the growing season-from January to the last of
April-frequent examinations were made of the different plots,
and notes were recorded as to the condition of the plants, such
notes as, growth, color, relative amount of disease present and,
especially, the development of blackheart.
From the beginning the plots given most nitrogenous fer-
tilizer made the best growth, had the brightest green color and
best all-round appearance. In no instance did there appear any
indication of the injurious effects of nitrate of soda. The pot-
ash plots and phosphate plots lacked the green color of the
nitrogen plots, and the plants in them were stunted thruout
the growing period.
Altho seasonal conditions at Sanford were ideal for the de-
velopment of blackheart in most fields, it rarely appeared in any
of the plots until after April 20. To this !ate no blackheart
was produced with any of the various fertilizer elements, either
singly or in combinations of twos or threes. As a last resort


Check
1
2
3
4
5
6
7
8
9
10
11
Check
12
13
14
15
16
17
18
19
20
21
Check






Florida Agricultural Experiment Station


it was decided to flood the plots. On April 20 the wells were
opened wide and the water allowed to flow thru the tiles until
it reached the surface. This required approximately 24 hours
for the lower half of the plot and 36 hours for the upper half.
After from 36 to 48 hours a large number of the plants devel-
oped blackheart. After three days the disease developed to such
a degree that it could be easily detected by a casual examina-
tion of any plant, except in check or unflooded plots which were
relatively free from the disease. On April 30 the celery plants
were harvested and an accurate count of the diseased and
healthy plants was made. (See table 3.)
The one factor that has most to do with the production of
blackheart is unbalanced water relations. This has been dem-
onstrated under experimental conditions and repeatedly veri-
fied from observations made in the field. Blackheart has been
produced repeatedly in the field by flooding. It required 36
hours to bring the water to the surface thru the subirrigation
system. About 48 hours later the disease appeared in the
plants in the field, usually in the growing hearts. Adjoining
celery in check plots-that were not flooded-did not 'develop
blackheart.
The data presented in table 3 show the percentage of black-
heart that developed in the plots treated with different ferti-
lizer mixtures. Apparently there isl no relation between any of
the fertilizer mixtures and the appearance of blackheart.
CONTROL OF BLACKHEART
Since the cause of blackheart is not definitely understood,
definite measures for its control cannot be given. But certain
precautionary measures can be offered. Generally speaking
blackheart can be prevented to a certain extent by carefully fol-
lowing cultural methods favorable for the growth of celery.
This plant requires lots of moisture for its best growth and this
should be supplied frequently. The soil should never be al-
lowed to become water-logged. Good drainage is necessary to
prevent blackheart. Furthermore, a celery field should not be
allowed to become very dry and then suddenly flooded. In case
the soil becomes water-logged and packed, it should be sub-
soiled. Celery should be cut as soon as mature, since overripe
celery is liable to blackheart and decay. Furthermore, celery
that has been stutted or set back in its growth is apt to develop
this disease.






Bulletin 173, Celery Diseases in Florida


A grower who has grown celery for a number of years and
has learned from experience the best cultural methods rarely
ever has blackheart appear in his field.

ROOT-KNOT'
One of the most serious troubles of celery is root-knot. This
name is given because of the swollen appearance of the roots of
attacked plants, which look
much like badly knot-
ted ropes. (See fig. 27.)
This disease is caused by a
minute worm (Heterodera
radicicola Atk.), which be-
longs to the general group
known as round worms or
nematodes, which include
the hookworm and vinegar
eel. The full grown female
is pear-shaped and is barely
visible to the naked eye.
The young and the males
are shaped like a corkscrew
and are practically invis-
ible. The, young work their
way slowly thru the soil
(from about 10 to 15 feet a
year) until they come in
contact with roots of a plant
they prefer. They then bore
into the roots and feed upon
their juices. At the same
time they give off a poison
which causes the plant to
form knot-like galls.
This poisoning of the
roots is a serious matter and Fig. 27.-Heavy infestation of nema-
greatly retards the plant's todes on the roots of celery plant.
The plant has reached its maxi-
growth. Some rapidly grow- mum growth.
Ing plants are able to en-
dure attacks without suffering greatly. Others, including cel-
"Root-Knot and Its Control was written by J. R. Watson, entomologist.






Florida Agricultural Experiment Station


a


Fig. 28.-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.)


- 04






Bulletin 173, Celery Diseases in Florida


ery, remain stunted and take on a sickly yellow color and ulti-
mately die.
The worms are widely distributed thru the warm areas of
the South, and are present in practically every well-drained
sandy field in Florida that has been cleared several years. They
are much worse in sandy soils than in stiff clay, and are much
more abundant in well-drained than wet soils. They are less
active in winter. At Gainesville they are practically dormant
and inactive from the first of November to the first of April,
but farther south they are more or less active all the year.
The eggs are laid in the knots on the roots, and from these
eggs the young hatch out in from three or four days, if condi-
tions are favorable. But, if conditions are not favorable, the
eggs have the ability to form around themselves a thick wall
and lie dormant in this "encysted" stage for months or even
years until conditions again become right for their development.
Conditions necessary in the soil for the hatching of the eggs are
a certain degree of heat, moisture and air. If any one of these
three conditions is absent, the eggs or at least some of them lie
in the encysted stage until all three conditions are present.
Like all animals, these worms have their enemies-largely
other species of nematodes-and it often happens that a field
badly infested will be found clean a few months or even a few
weeks later. However, it is never safe to depend on natural
enemies to clean up an infestation.

CONTROL MEASURES FOR ROOT-KNOT
Seedbed.-It is necessary that the seedbed be free of nema-
todes. This is because it is made up at a time of year when
nematodes are most active, and because young plants are easily
killed. Plants taken from an infested seedbed may spread the
infestation over an entire field. For these reasons it is essen-
tial that the grower be sure that there are no nematodes in
the seedbed.
The best way to ascertain whether or not the seedbed has
nematodes in it is to plant a few hills of summer squash a few
weeks before the time to sow celery seed. They come up quickly
and grow rapidly, and in two or three weeks can be pulled up
and examined for the characteristic knots. There is nothing
on squash roots that is likely to be confused with the knots
caused by nematodes. (On roots of legumes one might confuse






Florida Agricultural Experiment Station


the nodules of the nitrogen-fixing bacteria with the knots caused
by nematodes. And on some woody plants galls made by crown
gall somewhat resemble root-knot swellings.) If summer squash
is not available, one may plant okra or susceptible varieties of
cowpeas as test crops. If the seedbed is found infested with
nematodes, it either should be abandoned or disinfected.
One of the best methods of freeing seedbeds of root-knot is
by disinfecting with sodium cyanide and ammonium sulphate.
After the seedbed is plowed, distribute over the soil sodium
cyanide, dissolved in water at the rate of 800 pounds to the
acre. Then irrigate the soil so as to wash the chemical into the
soil. Just before the land is completely saturated with water,
ammonium sulphate is applied at the rate of 1,200 pounds to
the acre and this is also washed down until the soil is thoroly
saturated. The ammonium sulphate reacts on the sodium cyan-
ide to liberate hydrocyanic acid gas, which kills all nematodes
in the soil as well as all insect and other animal life. This
treatment not only kills the nematodes but leaves the soil rich
in nitrogen, so that plants will grow rapidly. Some truckers
estimate that the value of the treatment is returned to them
in fertilizer alone, to say nothing of eradicating nematodes.
This treatment should be given at least two or three weeks be-
fore the seedbed is planted. As soon as it is dried out it should
be plowed to let the air in and the poison escape.
Recent experiments at the Station indicate that calcium cy-
anide may be substituted for sodium cyanide and ammonium
sulphate at a considerable saving in cost. It seems that about
1,200 pounds to the acre of calcium cyanide will give best re-
sults. This material is applied as a dust in the bottom of the
furrows as the field is plowed. It is not necessary to apply
ammonium sulphate. Not only the cost of the material but
also the labor bill is much less than with sodium cyanide. It
does not, however, leave the land as rich in introgen.
If steam is available, one of the best methods of sterilizing
land is to, turn live steam thru it (see page 74 which begins
a discussion of steam sterilization), or it can be saturated with
hot water. Experience has indicated, however, that unless the
trucker has a supply of steam available the cost of this method
is greater than cyanide fumigation.
In the Field.-Fumigation by sodium cyanide may be used,
of course, to free a field of nematodes, but it is almost too ex-






Bulletin 173, Celery Diseases in Florida


pensive for so large an area. For that reason, other and cheaper
methods, even tho not as thoro, are recommended. The old
time-honored method of getting rid of nematodes is to starve
them out by growing on the land for two or three years crops
on which the nematodes will not feed. These plants include most
members of the grass family-corn, oats, etc.-and velvet beans.
Iron and Brabham cowpeas are highly resistant to nematodes.
For a full list of resistant and susceptible plants see Bulletin
159 of this station.
A serious objection to this method, from the standpoint of
the celery grower, is that he loses the use of his land, as far as
celery is concerned, for a year or two. To avoid this the Sta-
tion has developed a means by which the nematode will be
practically controlled in a single season. This is known as the
summer-fallow method and it has proved to be one of the most
efficient means of destroying nematodes.
According to this method the land is plowed immediately after
the spring crop is harvested and kept bare of vegetation all
summer. The land must be harrowed at least every week or
ten days and after every heavy rain which would pack the sur-
face of the soil. It is essential that a crust never be allowed
to remain on the land, because it excludes air from the soil and
thus removes one of the conditions necessary for nematode eggs
to hatch. Otherwise the eggs will lie in the encysted stage.
When the air is allowed to penetrate the soil, assuming that the
moisture and warmth conditions are present, the eggs are forced
to hatch. Once hatched, if there is no vegetation on the soil,
the young worms starve to death. This method of fighting
nematodes has been used successfully on some soils. But on
most soils it is injurious to soil fertility. Not only is humus
burned out of the soil but the bacterial content is also decreased.
The soil is "dead" or nearly so. This method is particularly
harmful to light sandy soils poor in humus. On heavy soils
well supplied with humus it does not seem to be so injurious.
Bush Bean Method.-To avoid the injurious effects of the
summer fallow on soil fertility the Station has worked out a
modification of the summer fallow, which consists in growing
bunch velvet beans on the land thru the summer. The beans
must be cultivated constantly, as in the case of the summer
fallow, and, in addition, they require one or two hoeings and
possibly a hand weeding. All weeds MUST be destroyed, as
many of them are hosts of the nematodes.






Florida Agricultural Experiment Station


Experiments extending over several years show that if this
method is applied carefully thruout the summer, the land will
be sufficiently free of nematodes to allow the growing of a
celery crop the following winter. Thus the grower does not
lose the use of his land for a single trucking season. Corn may
be planted in the rows with velvet beans but corn is not abso-
lutely immune to root-knot and may diminish the effectiveness
of the method. Bush velvet beans should be used, as running
varieties interfere with cultivation. They should be planted
thickly enough to shade the ground well and prevent deterior-
ation by the summer sun.
Unfortunately velvet beans will not grow well on many of
the low-lying celery lands of Florida, altho in many instances
they will grow if planted on a ridge. If velvet beans will not
grow, the trucker will be obliged to substitute Iron or Brabham
cowpeas. These are highly resistant and will greatly diminish
the number of nematodes in the soil, even tho the work is not
as thoro as if velvet beans were used.
Flooding.-Nematodes can be drowned out of the soil by
flooding, but it is usually necessary that the land be under water
for at least six weeks or two months. This usually leaves the
land in poor mechanical condition and is objected to by most
truckers. Recently good results were reported from alternately
flooding and draining the land. The land was kept flooded
with water for two or three weeks, allowed to dry out and then
cultivated for two or three weeks to force the eggs to hatch.
Then the land was flooded again. This is repeated two or three
times, and seems to be effective in ridding the land of nema-
todes. It avoids some of the undesirable effects of prolonged
flooding.
TRANSPORTATION DISEASES
The price the grower receives for his celery depends largely
on the pack he produces. Careful stripping, grading and pack-
ing are just as important to insure a profitable return as is the
growing of the crop in the field.
A celery plant affected with pink rot should never be placed
in a crate for shipment, as it is not suitable for culinary use
because of its bitter taste. The disease is likely to be carried
to the car, altho all apparently affected portions have been re-
moved. All dead and blighted leaves and hollow or pithy stems
should be stripped from the plants. Celery should be handled







Bulletin 173, Celery Diseases in Florida


carefully to avoid bruising, cutting and crushing its stems. A
pack of celery so handled will not bring a fancy price.
During recent years the practice of washing and bundling
celery has been adopted in the South. It is especially desirable
to pre-cool celery if it can be done properly, as this checks the
growth of fungous parasites that cause decay in transit.
Many of the common field diseases of celery that cause such
heavy losses to the grower in the field also cause heavy losses
after the product has been placed in storage or in the car for
shipment. This is especially true with pink rot, early and late
blights and blackheart, when followed by secondary organisms
that cause further decay.
The organism that causes pink rot thrives at a relatively
low temperature and will live at a temperature just above freez-
ing. It will grow at a temperature of 400 F., the temperature
ordinarily maintained in cars in transit. Cars that have been
inspected at consigning points often show pink rot thru as
much as 75 percent of the contents.
Early and late blights rarely ever spread to healthy plants
after they have been crated and placed in the car, but they
often are followed by a slimy soft rot. Plants affected with
either of the blights, when followed by a slimy soft rot, will
shed the affected leaves. As a result of this the celery will be
of a poor quality and, after stripping, the size of the bunch will
be reduced.
Only healthy celery plants should be crated and shipped, if
the grower expects to secure a fair profit from his crop. Strip-
ping should be thoro and carefully done. Diseased plants that
have been stripped should never be placed in storage, because
it is seldom that all infections will be removed and, unless
this is done, the disease will spread. This is particularly true
with celery infected with watery soft rot fungus (Sclerotinia
sclerotiorum (Lib) Massee). This fungus grows and spreads
at storage-house temperatures. In such instances the fungus
spreads from plant to plant and reduces the crate to a wilted,
collapsed mass of tissue from which the watery content has
leaked. Tufts of white mycelium are found in the early stages
of the rot, but in the later stages these are scant. Numerous,
irregularly shaped black sclerotia are found during the later
stages of decay.
A number of celery car-inspection certificates were selected
at random from the file case containing the 1923 and 1924 cer-






Florida Agricultural Experiment Station


tificates. The data on the 367 certificates selected were carefully
examined and tabulated. The tabulation contains the number
of cars in which the celery was attacked by primary and sec-
ondary diseases as follows: Blackheart, early blight, late blight,
slimy soft rot and watery soft rot. In cars showing more than
one disease the less important are classed as secondary. As an
example, watery rot was found to be the primary disease in
142 cars. Blackheart was found to be secondary in 6 of these
cars, early blight in 18 cars, late blight in 6 cars and slimy rot


in 10 cars. Also under secondary diseases it
watery rot was found in 12 cars.
TABLE 4.-THIS TABLE SHOWS THE OCCURRENCE
IN TRANSIT AND THEIR COMPARATIVE IMPORTANCE.


will be seen that


OF CELERY DISEASES


4-3

Primary diseases and
number of cars >
where found. S

No disease --............ 102 0 0 0 0 0
Blackheart ................ 22 9 0 5 4
Early blight ............ 34 0 2 9 1
Late blight .............. 11 3 0 2 0
Slimy rot ................. 56 11 13 4 7
Watery rot .-........... 142 6 18 6 10 -
TOTAL ...................... 367 20 40 12 26 12

Of the 367 cars tabulated in the table the contents of 102 cars
were found free of disease from a commercial standpoint.
Watery rot, caused by Sclerotinia sclerotiorum (Lib) Massee,
was the most common disease and the most destructive, appear-
ing as a primary trouble in 142 cars and as secondary in only 12.


Fig. 29.-This graph shows the presence at destination of primary and
secondary diseases, in percentage, that appeared in 367 carloads of cel-
ery shipped from Florida during 1923-24.







Bulletin 173, Celery Diseases in Florida 53

The average percentage of damage found in these cars was 14.5
percent, or, in other words, 141/2 cars of celery out of every 100
cars showing this disease were a total loss. The data shown in
table 4 are.shown graphically in figure 29.
The accompanying graph shows plainly the relative import-
ance of transportation diseases. Of the total number of cars
tabulated 72.3 percent of them showed diseased conditions. The
second outstanding fact is where watery rot is present it usu-
ally is of primary importance. It was of primary importance in
142 cars and of secondary importance in only 12 cars. In trans-
portation the disease is serious, because it continues to spread
rapidly from plant to plant and also because temperatures are
not low enough to check its growth until the car is near its
destination.


'I /H_





k!i _L1 i
4V o
jo -U l--1
j; N_41..


Fig. 30.-Diagram illustrating the average temperature ('F.) of carloads
of pre-cooled celery in transit from Florida to New York, season of
1915. (Ramsey & Markell, U.S.D.A. Bul. 601: 20, 1917.)

The following is quoted' as valuable information:

"Figure 30 shows the average temperature in each car from
the time it was loaded until it reached the market. The tem-
perature of the outside air during the entire trip is shown also.
The divisions at the left indicate degreesof temperature. The
bottom division indicates the time in days. The small circles
on each of the curves are placed at the intersection marking the
time that the reading was made and the temperature at that
time. The lower curve represents the temperature of the pre-
cooled car and the upper curve that of the non-pre-cooled car.
'Ramsey & Markell, U.S.D.A., Bulletin 601: 20, 1917.


I



t
":
~






Florida Agricultural Experiment Station


The irregular curve running through the chart marks the out-
side air temperature.
"The pre-cooled car was loaded about noon on March 3, but
was not cooled until the following morning at which time the
temperature of the car was only about 500 F. The first part
of the curve illustrates this pre-cooling period and shows the
length of time required to pre-cool the car and the tempera-
ture of the car at the time it was shipped. This point, 370 F.,
was known to be lower than the ice would hold it; but as this
was the first car shipped under initial icing, it seemed desirable
to be on the safe side by starting with a low temperature. The
diagram shows very clearly how the temperature crept slowly
up to 41 F., and also how it remained at that point for al-
most two days in spite of large fluctuations in the outside tem-
perature. It began to drop below 400 F. again, owing to the
cold outside temperature that the car encountered in the north."
In considering the prevalence of watery rot it is well to use
the information contained in figure 30. It will be seen that in
the regularly iced car (as are most of the cars sent from Flor-
ida) the temperature did not reach 400 F. until the fifth day
after loading, while the pre-cooled car was started out at a
temperature below 400 F. The watery rot fungus is given four
or five days to develop and destroy celery before its growth is
materially checked. For this reason it is strongly urged that
celery affected with pink rot in the field be placed on southern
markets and that all celery shipped to distant points be pre-
cooled before starting.

DAMPING-OFF IN SEEDBEDS

Damping-off of celery seedlings is attributed to numerous
fungi, including Pythium de baryanum, Sclerotinia sclerotiorum,
Fusarium sp., and Rhizocton.a sp. These organisms exist in the
soil, living upon dead plant material or lying dormant in a re-
sistant form. The conditions that favor their development are
similar to those that favor the germination of seed. Consequently
when seed are planted and begin to grow, these fungi also grow.
They grow better under moist, even wet, conditions than under
dry conditions. For this reason watering the seedbed is of
primary importance. One method of applying water after the
seed are sown is thru open ditches around the beds in which the
water is kept fresh and circulating (fig. 31). Sub-irrigation,
except as mentioned above, is practiced but little in Florida.
If possible the surface of the soil should not become wet. Over-
head sprinkling of the seedbed is most favorable for the devel-
opment of damping-off fungi, and for this reason this method
of watering should be done thoroly but not often.







Bulletin 173, Celery Diseases in Florida


Disinfected seedbeds are seldom troubled with this type of
disease, altho sterilization will not prevent reinfestation during
the planting of the seed and care of the young plants. Pre-


4-.


J-


Fig. 31.-Celery seedbed covering and irrigation method used most com-
monly at Sanford.


cautionary measures should be adopted and practiced in taking
care cf the seedbeds. Special care should be taken with tools
used in the weeding and mulching of the young plants. Should
a spot appear in the seedbed where the plants are being killed,
it would be well to remove this spot, the plants and several






Florida Agricultural Experiment Station


inches of soil from the seedbed (fig. 32) and then saturate sides
and bottom of the hole with a solution of formaldehyde (see page
74). If the attack is more general, covering a larger area (see
fig. 45), do not water for several days and in the meantime


Fig. 32.-Circular spot in a seedbed where young celery plants were killed
by damping-off (Sclerotinia sclerotiorum (Lib.) Massee).

spray thoroly with Bordeaux mixture. Seedbeds need careful
attention at all times, in order to prevent serious losses from
this disease.
MOSAIC OF CELERY
This disease is one of a group known as "virus" diseases. The
exact cause of mosaic is at present unknown. This disease was
common last season in the Sanford vicinity and has been re-
ported occasionally for years. It has not been serious with the
possible exception of certain late fields last season. The re-






Bulletin 173, Celery Diseases in Florida


lation of mosaic of celery to mosaic of numerous other plants
has not been determined. A
survey of wild host plants
conducted near Sanford last
season showed that a dozen
or more wild plants of dif-
ferent species possessed char-
acteristic symptoms of the
disease. A large number of
these diseased plants were
growing along ditches and
fences bordering on the cel-
ery fields. These plants, if a
source of "infection," were
certainly in excellent places
from which to spread the dis-
ease. Whether the disease is
spread by mechanical means
or by seed is not known.

DESCRIPTION OF MOSAIC
The disease is easily de-
tected by characteristic light
and d a r k green mottlings
over the blades of the leaves
(fig. 33). This mottling has
been found marked and dis-
tinct. It is difficult to find on
young leaves, because they
are usually of a light yellow-
ish color until quite large. As
soon, however, as they begin
to turn green the mottling
appears (fig. 34). The plant Fig. 33.-Celery plant showing typ-
appears (fig. 34). The plant ical mosaic mottling on leaf blades.
thus attacked is more or less
stunted, in height particularly, and one can almost invariably
locate it in the field before the mottling can be detected at a
considerable distance because of this dwarfed condition.






Florida Agricultural Experiment Station


Fig. 34.-Mosaic of celery leaf, typical mottling.


ROOT ROT

The disease known as root rot (Rhizoctonia sp.) is common
on celery wherever grown in Florida. It has been reported
from Seminole and Manatee Counties. The disease is found
most frequently on young plants still in the seedbeds and also
at the time of transplanting from the seedbed. The probable
reason for the occurrence of the disease at that time is because
moisture conditions are then most favorable for its growth.
Moisture conditions are adjusted to favor the most rapid growth
of the plants in the seedbed and also at the time they are set in
the field. Another reason why the disease is so prevalent at
transplanting time is that the roots are more or less injured dur-
ing this operation and are easily attacked by the fungus. Tem-
perature conditions also favor its growth at this time. As the
plants grow older those that are not killed gradually outgrow
the fungus, overcome the disease and develop into marketable
plants not easily distinguishable from healthy ones.







Bulletin 173, Celery Diseases in Florida


DESCRIPTION OF ROOT ROT

The first symptom on young plants is a characteristic damp-
ing-off. In this case the young seedlings are attacked and fall
over because of the fungus infecting them at the surface of the
soil. The stem of the plant appears decidedly shrunken and in
most cases is slightly brownish in color. Plants that survive
the extremely young seedling stage may be attacked later when
the presence of the disease is indicated by a stunting of the
plant. Stunting is followed often by wilting and finally the plant
is killed. When plants are attacked following transplanting they
appear to have difficulty in recovering and putting out new
growth. They seem to stand still, as far as development is con-
cerned, for a long time, while healthy plants show new growth
in a few days. The fungus kills numerous plants at this time
and as a general rule those that survive this period usually de-
velop into strong vigorous plants.

CONTROL OF ROOT ROT

Sterilize seedbeds before planting. Keep them free from dis-
ease while the plants are growing. Exercise care in moving
plants at transplanting time. Avoid excessive moisture. Prac-
tice field sanitation.

SLIME MOLD

Several species of slime mold have been collected at different
times on living plants, but the one found on celery is probably
Physarum cinereum (Batsch.) Pers. This organism is not found
often on celery and, since it is found as often on straw, grass,
weeds and sticks in the celery fields, it is of no economic import-
ance. Many inquiries have been made, however, concerning it
and for this reason it is included here.

DESCRIPTION OF THE ORGANISM AND ITS RELATION
TO THE HOST

The organisms when first noticeable appear light colored, of
a gelatinous consistency and usually are in well-shaded moist
places. Soon this plasmodium begins to change to a cream color
and then rapidly darken to a yellowish brown. During this
change the gelatinous consistency becomes thicker and gran-







Florida Agricultural Experiment Station


ular and begins to climb up anything with which it is in con-
tact, whether celery, grass, dead straw or sticks. From this time
the development of the slime mold is rapid. It was found by
actual observation that it climbed about an inch an hour.
The development described above took place during 12 hours
of daylight. At dusk the slime mold had just begun to climb.
Several observations up until midnight showed steady progress
up the stems of the plants. In the morning the organism was
on the top leaves of plants eight inches tall and had developed
spores. When disturbed a cloud of spores arose from the sporu-
lating surface, resembling a spore cloud produced by disturbing
a mature puff ball. This sporulating mass almost completely
covered the leaves but apparently was not injuring them (fig.















Fig. 35.-Slime mold on celery and adjacent weed.

35). New leaves on these plants developed later and no difference
could be detected between the attacked plants and those free
from the fungus. The only damage done was a possible limiting
of the development of the attacked leaves. The fungus did not
spread to other plants in the vicinity. It was not parasitic.

CONTROL OF SLIME MOLD

Carefully cut off and remove from the field any stems and
leaves of plants showing this fungus on them. This measure
may prevent a more general occurrence when conditions are
again favorable for its development.







Bulletin 173, Celery Diseases in Florida


NON-PARASITIC DISEASES
There are several celery diseases appearing in Florida every
year that have no fungi or other parasites associated with them.
For that reason they are called
non-parasitic diseases. T h e s e
diseases are of considerable
economic importance, s i n c e
they materially disfigure the
plant, check its growth, or make
conditions favorable for the en-
trance of fungi that cause fur-
ther damage.
CRACKED STEM
A prevalent non-parasitic dis-
ease of celery is cracking of the
stems. This is not the common
longitudinal cracking known to
many growers, but rather a
transverse cracking of the epi-
dermis abo ve the vascular
bundles. The disease manifests
itself by the appearance of
cracks or breaks in the epi-
dermis of the stalk, extending
often along the entire area.
These breaks or cracks appear
immediately over the ribs or
vascular bundles. The epidermis
curls back, appearing much like
the teeth of a saw (fig. 36).
The cause of this condition is
not fully understood, altho it
probably is associated with un-
balanced fertilizer, climatic and
moisture conditions. It probably
is caused by an excessive use of
lime. Control measures have not
been worked out.
Fig. 36.-Cracked stem of celery
STUNTING plant.
The experienced celery grow-
er often detects stunted plants in the field, and many of them






Florida Agricultural Experiment Station


recognize the cause of this trouble. Stunting is often caused
by improper setting, the tap root being either crooked upward
toward the plant or injured. Often when roots are buried shal-
lowly, stunting of the plant
F will follow. In many cases
stunted plants have a normal
green color but simply refuse
to grow, and often they ap-
pear yellow. Stunting due to
improper setting can be dis-
SI1 tinguished easily from stunt-
ing caused by root-knot, since
in the latter case the plants
are yellow and lack vitality
and vigor.
Growers should frequently
caution setters against hasty
setting of plants and point
out to them the importance of
placing the roots straight
down into the ground and
pressing the soil firmly
against the roots. Thoro wa-
tering will also insure good
healthy plants when properly
set. A vigorous growing plant
will not develop from a poor-
ly or improperly set plant. If
a dibble were substituted for
the trowel, much better re-
Fig. 37.-Cracked stems of celery sults would be obtained in
slightly enlarged. securing plants of uniform
size over the entire field. The
proper setting of celery plants is a most important step in
growing celery, and greater care should be exercised in this
operation.

GROWTH CRACKS
The appearance of large growth cracks at the base of the
celery stalks is common in Florida. These growth cracks appear
most frequently during seasons when there is excessive rain-







Bulletin 173, Celery Diseases in Florida


fall and unfavorable growing conditions. Growth cracks (fig.
38) not only reduce the value of celery but also leave openings
for fungi to enter, especially the pink rot organism, and cause
decay either in the field or in transit. (See fig. 15.)

HOLLOW STEM OR PITHINESS;
During the spring of 1924 celery growers in the Sanford and
Bradenton areas lost considerable celery because of the general
prevalence of hollow stem
or pithiness. This is a non-
parasitic disease and is of
considerable economic im-
portance, not only in Flor-
ida, but wherever celery is
grown. The outer stems of
the stalk become hollow,
pithy an d soft. In many
cases this trouble extends
thruout t h e entire plant,
rendering it worthless. As a
general rule the growers
make an effort to strip off
all pithy stalks when har-
vesting. Considerable loss is -
incurred in doing this, as
the sizes of the bunches are
reduced.
Hollow stem or pithiness
is said to be a seed-born -
characteristic that evidently
has been prevalent especi-
ally i n American grown
seed. French-grown seed ap-
parently are relatively free
from t h i s characteristic,
supposedly because greater
care is exercised in select- Fig. 38.-Growth crack of celery.
ing and breeding. This fact
may be true to a certain extent under many climatic conditions,
but observations made near Sanford do not substantiate it
entirely.






Florida Agricultural Experiment Station


Under Florida conditions hollow stem or pithiness is preva-
lent one year and almost entirely absent another. Furthermore,
the same lot of seed will act differently with respect to pithi-
ness when handled differently
and planted in different local-
ities and on different soils.
The appearance of the dis-
ease may be associated with
unfavorable growing condi-
tions, such as frequent ap-
pearance of low temperatures
which check growth and the
resumption of favorable grow-
ing weather. In fact, any con-
dition that checks the growth
of the plant-such as, mois-
ture, culture, setting, fertiliz-
ing, or adverse weather--may
cause pithiness. Often seed
from the same lot, if planted
both where they are and are
not protected from cold, act
differently with reference to
pithiness. In the Sanford
area plants in a field near the
lake shore were relatively
free from pithiness, while
those planted farther away
from the lake where no pro-
tection was given from cold
weather developed consider-
able hollow stem. Both of
these plantings were from the
same lot of seed.
BROWN STEM
Often a rather peculiar
browning appears on the out-
er stem of the plant (fig. 39).
This browning is apparently
Fig. 39.-Brown stem of celery, underneath t h e epidermis.
The disease is non-parasitic and of considerable economic







Bulletin 173, Celery Diseases in Florida


importance. Its appearance cannot be attributed to any definite
cause, but it is frequently noticed on plants that have grown
to maturity and allowed to remain in the field too long before
cutting. This disease not only disfigures the plant (fig. 39), but
is probably followed by decay in transit. The disease appears
frequently on plants affected with blackheart, and it may be
that the two are caused by the same agent.


Fig. 40.-Brown stem of celery, enlarged.

RED ROOT
Red root of celery is a condition that can be found in almost
any celery field or seedbed. Celery growers should examine
roots of plants often, their appearance being something of an
index to the vigor and prospects for good growth.
Red root cannot be attributed to any specific organism or con-
dition, but often it is thought to be caused by injuries from fer-
tilizer burning, thru which secondary fungi, such as Fusarium






Florida Agricultural Experiment Station


sp., afterward enter. Extremely acid soils may be responsible
for red root, but this has not been determined.

BACTERIAL LEAF SPOT
This disease of celery is caused by a bacterial organism (Bac-


diF


Fig. 41.-Bacterial leaf spot on leaflets of Golden Self-Blanching celery.
Approximately x%/ (I. C. Jaggar, Jour. of Agri. Res., Wash., D. C.,
21: 185. 1921).
terium, apii Jag.). Up to the present time it has not been found
in Florida. It has been reported from New York, Michigan and
Minnesota, and in these first two states it caused a loss in 1923
of from 2 to 5 percent."

'Plant Disease Bulletin Sup. 26, 1923. B.P.I., U.S.D.A.






Bulletin 173, Celery Diseases in Florida


DESCRIPTION OF BACTERIAL LEAF SPOT
The spots on the leaves are rusty brown in color, irregularly
circular in outline and rarely exceed a quarter of an inch in
diameter (fig. 41). These spots resemble spots on celery leaves
caused by late blight and can be distinguished with certainty
only by the absence of the small black specks or pycnidia found
on late blight spots (see fig. 22). The spots do not often kill the
whole leaf; they are found almost exclusively on the leaf blades."

CONTROL OF BACTERIAL LEAF SPOT

Spraying tests during several seasons have shown that liquid
Bordeaux mixture will control bacterial leaf spot satisfactorily.
Thus this disease can be controlled while spraying for early
blight.
SOFT ROT
There are several rots of celery (Bacillus carotovorus Jones
and closely related species) which cause some damage. This
damage, in relation to the growing of celery in Florida, may be
said to be wholly in transportation. The diseases produced by
these organisms have not been collected in celery fields in the
State, but have been reported occasionally from northern mar-
kets as occurring on Florida celery.

DESCRIPTION OF SOFT ROT
The decay is characterized by being located usually in the
crown, stalks and leaves of the plant and by being exceptionally
soft and mushy but not slimy. This rot develops rapidly, soon
involving the whole crown, the leaf petioles and the leaves.
Bunches of celery showing slight decay are tossed aside as a
total loss.
CONTROL OF SOFT ROT
Since the disease has not been found in the field, the control
measures resolve themselves into careful control of other dis-
eases in the field and careful handling of the plants from the
time they are cut until they are in the car ready for shipment.
'Ivan C. Jaggar, Jour. Agri. Res. 21:185, 1921.






Florida Agricultural Experimrent, Station


Any bruises or cuts make excellent openings :for. bacteria to
enter the plant and start decay.. The organisms that cause, soft
rot enter the plants not only thru bruises and cuts made by
rough handling but also thru tissue killed by other fungi in the
field.
Spots caused by early and late blight fungi on the leaf blades
and petioles are excellent places for bacteria to enter. The
disease is found at first on dead tissue in these spots and from
there spreads to healthy portions of the plant.
Blackheart and pink rot are two other important diseases in
relation to the occurrence of soft rot. To adequately control
soft rot in transit it is necessary to control the other fungous
diseases in the field. Celery being crated for shipment should
be thoroly stripped of stalks and leaves showing spots and blem-
ishes, as these openings are the places where soft rot organisms
enter plants to cause serious losses. Pre-cooling and sufficient
icing of cars are necessary to prevent decay in transit.

PHOMA ROOT ROT
Phoma root rot (Phoma apiicola Kleb.) of celery, commonly
found in northern and eastern sections of the country, has never
been found in Florida. Since the fungus grows best in cooler
weather, there is every reason to suspect that sooner or later
it will appear in this state in winter. The disease has proved
to be more destructive locally than as an epidemic. For the
foregoing reasons this mention and description is given here,
thus enabling Florida growers to become familiar with it and
enabling them to control it, should it appear in their fields. It
has been found' that the fungus causes similar diseases on other
closely related plants; such as, parsnips, water cress, carrots
and parsley.
DESCRIPTION OF PHOMA ROOT ROT
The first indication of the disease in the field is the dying of
the outer leaves. This condition gradually spreads to the inner
leaves and in severe cases kills the plant. When less severe
the plant appears unhealthy and stunted. Killed leaves remain
attached to the crown of the plant for sometime. The disease,
generally speaking, is limited to under-ground parts of the
'C. W. Bennett, Mich. Tech. Bul. 53. 1921.






'Billetin 173, Celery Diseases in Florida


plant and for this reason early infections are difficult to detect.
jIt is at this time that the disease is most destructive. There
it attacks the root and crown of plants, causing them at first to
become bluish green in color and later black (fig. 42). Rot sets in


Fig. 42.-Diseased plants as they appear before all the roots are rotted
away. (C. W. Bennett, Mich. Agri. Exp. Sta. Tech. Bul. 53: 34. 1921.)

and gradually the smaller roots are killed. Often the crown is
severely attacked. Plants seldom are killed outright, but rather
appear stunted and unhealthy. When plants are attacked severe-
ly the black discoloration appears up the stems of the leaves
and the plants finally fall over. The small black fruiting bodies
of the fungus often can be found on the diseased parts at this
time (fig. 43). Young plants are more susceptible than old
plants and infection on the leaf blades is scarce. The fungus
is known to live from one season to another in trash and debris
left in the field.

CONTROL OF PHOMA ROOT ROT
Plant disease-free seed in sterilized seedbeds. Destroy all
plants that show symptoms of the disease. Practice strict sani-
tation in the field after the crop is set and rotate crops.






Florida Agricultural Experiment Station


CELERY YELLOWS
The disease known as yellows (Fusarium sp.) has never been
found in Florida. This disease is found, however, in many north-
ern celery-growing states, especially Michigan and New York,


Fig. 43.-Diseased base of plant showing pycnidia (x8). (C. W. Bennett,
Mich. Agri. Exp. Sta. Tech. Bul. 53: 39. 1921.)

where it has caused considerable uneasiness among growers,
because of its destructive nature and the difficulty encountered
in controlling or eradicating it after it has once become estab-
lished in the field.






Bulletin 173, Celery Diseases in Florida


DESCRIPTION OF CELERY YELLOWS
The disease is detected in the field by the appearance of
stunted yellowish green plants. If an affected plant is sliced
open, a dry brownish discoloration of the stem will be noted. The
small roots are brown in color and more or less rotted off at their
ends (fig. 44). Experiments have been conducted by Coons" in
which resistant strains were selected and proved to be well-


-7

Fig. 44.-Typically diseased celery plants, showing dry rot of interior of
the crown. (R. C. Thomas, Monthly Bul. Ohio Agri. Exp. Sta., 9: 88. 1924.)
adapted to growing conditions and acceptable on the markets.
The resistant strains develop well on fusarium-sick soil.

CONTROL OF CELERY YELLOWS
Since the fungus that causes this trouble lives in the soil
for considerable lengths of time, its control resolves itself into
two modes of attack. First, soil sterilization, by which the
'Coons, G. H., Phytopath. 13: 56. 1923.






Florida Agricultural Experiment Station


fungus is killed; and, second, selection of resistant strains. The
sterilization method is so expensive for large fields that it is
out of the question. Resistant strains already have been found
and considerable progress has been made in their improvement.
Consequently, this is the most logical way to overcome the
disease.
SELECTION OF'CELERY SEED

There are about twenty commercial varieties of celery (Ap-
ium graveolens), and many of the varieties now cultivated were
developed within the last 45 years. Celery is usually a biennial,
requiring two years to produce seed, but often it is an annual
under Florida conditions.
Celery may be classified into two groups: green varieties
and self-blanching varieties. The green varieties were form-
erly grown exclusively because of their excellent quality. But
they do not blanch as easily as the self-blanching varieties. The
latter have replaced the green varieties mainly because of this
fact. As a rule many of these strains are identical, altho grown
by different seedsmen and given different names. The strain
known as Golden Heart, or Old Golden, or Golden Self-Blanch-
ing, was for many years the principal strain used in the San-
ford area. During recent years other strains have been intro-
duced, including Pearly White, and many so-called "special"
strains. The Golden Self-Blanching strain is rather. susceptible
to early blight, blackheart and many physiological diseases, and
often it has the undesirable feature of producing green hearts.
As a rule Golden Self-Blanching is favored for an early winter
crop under Florida conditions, while Pearly White and the special
strains are planted for the late spring crop. Good celery seed
are naturally hard to obtain and the grower should exercise
caution and judgment when purchasing them.

CELERY SEED DISINFECTION
Generally speaking, Florida celery growers do not practice
seed disinfection. The principal reason for this is that only one
of the important diseases carried on the seed-late blight-is
controlled by seed treatment, and to control this disease other
methods are recommended. It has been found, however, that
seed disinfection is valuable, in that it tends to eliminate weak
seed which produce poor plants. Methods of seed treatment,






Bulletin 178,. GaleAy Diaatwes, in Florida


as given below, have reduced gernmiatieonril.fexperimental plots,
But when plants were set in the field, it; was found that the
best plants were obtained from' treated plots, principally be-
cause the weaker seed were killed, which left only the more vig-
orous seed to produce plants. These plants were as numerous
as in untreated plots and weak, poorly developed, straggling
plants were entirely eliminated. There are two methods recom-
mended for treating celery seed. These methods were developed
to control late blight and are considered severe treatments;
but such treatment is necessary, since the fungus causing, the
disease is imbedded in the seed coat.

HOT WATER TREATMENT
Fill a cheese-cloth bag about half full of seed and submerge
in a water bath. The temperature should be kept stationary at
480 C. (1180 F.) for 30 minutes. The temperature should not
rise higher than 490 C. (1200 F.), for the seed are liable to be
injured, and not lower than 450 C. (1130 F.), or the fungus is
liable not to be killed. It is necessary to prepare a bath that
will cover the seed with water. It is also necessary to have a
standardized thermometer to read the temperatures correctly."

CORROSIVE SUBLIMATE1" TREATMENT
In using this method of seed treatment it is necessary to in-
close the seed in cheese-cloth bags and soak them in warm (not
hot) water for half an hour, then remove from the water bath,
drain a few minutes and submerge in a 1-to-1000 solution of cor-
rosive sublimate for another half hour. The seed should be
rinsed thoroly and dried after this treatment. The seed coats
are softened by the warm water and the spores which are im-
bedded in the seed coat are exuded from the pycnidia, thus
facilitating their destruction by the poison.

CELERY SEEDBED STERILIZATION
It is necessary to combat certain diseases of celery in the
seedbed, because there is whee;,they first appear and cause con-
siderable loss. Even tho conditions were such that little loss
occurred in the seedbeds, there would still be the danger, of
carrying the disease to the,field where it might cause a little
'By W. S. Kront, Jour.Agri. Res. 21: 369-72, 1921.
"Coons and Levin, Mich. Agri. Exp. Sta., Spec. Bul. 77, 1916.






Florida Agricultural Experiment Station


damage before conditions were 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, because
half a job is no better than no job. There are two efficient ways
to sterilize soil for use as a seedbed.

SOIL STERILIZATION WITH FORMALDEHYDE
After the soil selected for the seedbed has been well stirred
and loosened, apply a formaldehyde solution of 4 pints of formal-
dehyde and 50 gallons of water. Apply this solution at the rate
of 1 gallon to 1 square foot
of soil surface. The solution
is best applied with a com-
mon garden sprinkler. In
that way there is little dan-
ger 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
burlap bag. T h is covering
Fig. 45.-Damping-off in seedbed can prevents too rapid evapora-
be prevented by soil sterilization.
tion of the disinfectant. The
covering should be left on the soil for at least two days, after
which it can be removed and the soil stirred to hasten evapora-
tion of the formaldehyde. Seven days after applying the solu-
tion and five days after uncovering and stirring it, the soil can
be prepared and the seed planted.

SOIL STERILIZATION WITH STEAM

This process necessitates the use of a steam boiler of consider-
able capacity and a rectangular galvanized iron pan large enough
to cover considerable area but small enough to be moved by
four men. The pan should have sides six to ten inches high with
a sharp edge, 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 discharged into the in-
verted pan. Steam should be discharged into this pan until
an Irish potato of medium size buried 6 inches in the soil under







Bulletin 173, Celery Diseases in Florida


the pan is cooked. Then remove the pan to another portion of
the bed and repeat the process. This method is more satisfac-
tory than the formaldehyde method, but is considerably more
expensive. (See fig. 46.)


Fig. 46.-Steam sterilization of seedbed showing inverted pan with at-
tachments to steam boiler. (Courtesy Dr. James Johnson, Hort. Dept.
Univ. of Wis.)

SEEDBED AND FIELD SANITATION

It is absolutely necessary to practice sanitary methods in
both seedbed and in the field to insure a good crop of celery with
the least amount of disease. Under Florida conditions many of
the most important diseases of celery live from one season to
the next in old refuse. In harvesting celery all plants not suit-
able for shipping are left in the field. It is usually these plants
that are infected with numerous diseases; such as, pink rot,
early blight and late blight.
The black irregular sclerotia or resting bodies of pink rot
fungus are resistant to the elements and live a long time in the
soil. They develop under favorable conditions, produce spores
which are scattered by wind and irrigation water and readily
infect plants over large areas. The same may be said of late
blight fungus. By carefully collecting this refuse as soon after






Florida Agricultural Experiment Station


harvest as possible and removing it from the fields, the sources
of infection of these diseases are removed. This refuse should
be buried a foot or more under soil or thoroly burned. Do not
dump it along the roadside or in the edge of the woods, because
in these places the fungi are still in a position to produce spores
which are easily scattered.
After the plants are removed from the seedbed, utilize that
soil by planting it instead of leaving it to become overgrown
with obnoxious weeds and straggling celery 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 celery plants and weeds.

BORDEAUX MIXTURE, HOW TO MAKE AND HOW AND
WHEN TO APPLY
As a fungicide, homemade 4-4-50 Bordeaux mixture has
proved to be the most efficient spray for the control of celery
diseases under Florida conditions. It is used almost exclusively
on celery where fungicides are applied for the control of dis-
eases. The success of spraying with Bordeaux mixture de-
pends largely upon how it is made. For convenience where large
acreages are to be sprayed it is advisable to make up stock
solutions of bluestone and lime in such proportions that 1 pound
of either bluestone or lime is contained in each gallon of water.
These solutions will keep well for a long time, the only pre-
caution necessary is that water lost by evaporation be added
and the whole thoroly stirred before the materials are used.

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 container for this purpose. Always
stir the stock solution before taking any out.

STOCK SOLUTION B, LIME
Unslaked lime should be used in making Bordeaux. Slake 50
pounds of this lime and dilute it in 50 gallons of water. Be
careful not to drown or burn the lime while slaking. Always
stir the stock solution before taking any out. Do not stir the
stock solutions with the same stick.







Bulletin 173, Celery Diseases in Florida


These stock solutions will keep for indefinite periods. Some
marks should be made on the inside of the containers at the
surface of the solutions so that water lost by evaporation can
be restored before the solutions are used. Keep the stock solu-
tions covered.
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.
If many acres of celery are to be sprayed during the season,
it will be quite necessary to construct a mixing platform where
the Bordeaux spray can be
conveniently made. The first
thing to consider is the water
supply. Build the platform 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 solu-
tions to flow by gravity
into the spray tank. Upon
this platform should be built
a smaller platform upon
which the stock solutions are
made (see fig. 47). The small-
er platform should be ele-
vated enough above the main
platform so that the stock
solutions can flow into the Fig. 47.-Bordeaux mixing plant. (U.
barrels on the main platform. S. D. A Farmers' Bulletin 1220: 69.
1921.)
By following these principles
in a general way the laborious job of making Bordeaux mixture
is extremely simple. Figure 47 shows a handy mixing platform.
It is essential that this mixture be applied soon after it is made.
It is of little value after standing 12 hours.






Florida Agricultural Experiment Station


FOR 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 gal-
lons. Run both of these into the sprayer at the same time with
the agitator going.
To make 100 gallons of spray, use 8 gallons of stock A, diluted
to 50 gallons, and 8 gallons of stock B, diluted to 50 gallons.
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.
Spraying must be done thoroly to be a paying proposition.
The tank pressure should not be below 200 pounds. Three noz-
zles should be used to each row, one on each side turned slightly
upward and one from the
top turned downward. The
plants must be covered com-
pletely so that the spores of
the fungi will be killed, also
those spores that fall upon
the plant later. The spray
should be applied often
enough to keep the growing
plants well protected. This
usually calls for an applica-
tion every week or ten days.
Spraying should begin in
seedbeds as soon as the
plants are well up (fig. 48),
and it should be continued
methodically until the crop
Fig. 48.-Bordeaux mixture applied
with hand sprayer in the seedbed. is ready for cutting. Some
variation in exact times of
application usually occurs, depending upon the development of
the plants and also upon the general absence or occurrence of
specific diseases.






Bulletin 173, Celery Diseases in Florida


SPRAY MACHINES

Under Florida conditions it is absolutely impossible to grow
celery without spraying it often and thoroly. In order to accom-
plish this it is important to select a spray machine that main-
tains a pressure of 200 pounds and preferably of between 250
and 300 pounds. It is necessary to maintain this high pressure,
in order to form a fine mist of the spray material and to cover
the surface of the plant uniformly with a thin 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 often is difficult to keep it in operating
condition. More surface of the plant will be covered when high
pressure is maintained, and there will be greater penetration
into the dense foliage of the plant.
Spray machines should be thoroly cleaned immediately after
use. Do this by running several buckets of water thru the noz-
zles, operating the pump. If this precaution is taken regularly,
considerable time will be saved, as it will not be necessary to
spend a half day 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
service, if it is given the proper attention and kept in good con-
dition, being oiled frequently and cleaned thoroly.
A spray machine equipped with a four-row boom with three
nozzles to the row, making a total of twelve nozzles, delivers
approximately 100 gallons of spray mixture to the acre in one
hour. If the openings in the disks in the nozzles are enlarged
because of use from spraying or by the insertion of small nails
purposely to enlarge holes, the capacity of the spray delivered
will be increased, and it is likely that the liquid will be dis-
charged as a coarse rather than a fine mist, and the efficiency
will be decreased. It is desirable to replace worn disks with new
ones frequently.




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