• TABLE OF CONTENTS
HIDE
 Title Page
 Credits
 Introduction
 Historical
 Climatic conditions of Florida...
 Basic principles in the prevention...
 Diseases due to parasitic fungi...
 Injuries due to physiological...
 Injuries due to meteorological...
 Preparation of spray mixtures
 Stomach poisons
 Contact sprays
 Combinations of standard spray...
 Spray dilution table for ready...
 Powdered spray materials for...
 Spraying outfits
 Dusting outfits
 Spraying accessories
 Spray schedule














Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 178
Title: Diseases of grapes in Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027363/00001
 Material Information
Title: Diseases of grapes in Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 73-156 : ill. ; 23; cm.
Language: English
Creator: Rhoads, Arthur S ( Arthur Stevens ), b. 1893
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1926
 Subjects
Subject: Grapes -- Diseases and pests -- Florida   ( lcsh )
Grapes -- Diseases and pests -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Arthur S. Rhoads.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00027363
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000923477
oclc - 18171667
notis - AEN4028

Table of Contents
    Title Page
        Page 73
    Credits
        Page 74
    Introduction
        Page 75
    Historical
        Page 75
        Page 76
    Climatic conditions of Florida in relation to those of other grape growing sections
        Page 77
    Basic principles in the prevention of grape diseases
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
    Diseases due to parasitic fungi and bacteria
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
        Page 114
        Page 115
        Page 116
        Page 117
        Page 118
        Page 119
        Page 120
        Page 121
        Page 122
        Page 123
        Page 124
        Page 125
    Injuries due to physiological causes
        Page 126
        Page 127
        Page 128
        Page 129
        Page 130
        Page 131
        Page 132
    Injuries due to meteorological causes and animals
        Page 133
        Page 134
        Page 135
        Page 136
        Page 137
        Page 138
    Preparation of spray mixtures
        Page 139
        Page 140
        Page 141
        Page 142
        Page 143
        Page 144
    Stomach poisons
        Page 145
    Contact sprays
        Page 146
        Page 147
    Combinations of standard spray materials for summer spraying
        Page 148
    Spray dilution table for ready reference
        Page 149
    Powdered spray materials for dusting
        Page 149
    Spraying outfits
        Page 149
        Page 150
        Page 151
        Page 152
        Page 153
    Dusting outfits
        Page 154
    Spraying accessories
        Page 154
        Page 155
    Spray schedule
        Page 156
Full Text

January, 1926


UNIVERSITY OF FLORIDA
Agricultural Experiment Station



DISEASES OF GRAPES

IN FLORIDA

By

ARTHUR S. RHOADS


Fig. 40.-Growing grapes for the cull pile, the result when spraying is
neglected. These grapes were culled on account of black-rot, bitter-
rot and hail injury.


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


Bulletin 178







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
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
E. W. COWAN, A. M., Assistant Chemist
J. M. COLEMAN, B. S., Assistant Chemist
0. F. BURGER, D. Sc., Plant Pathologist
G. F. WEBER, Ph. D., Associate Plant Pathologist
A. N. BROOKS, Ph. D., Assistant Plant Pathologist (Plant City)
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
STACY O. HAWKINS, Field Asst. in Plant Pathology (Miami)
W. E. STOKES, M. S., Grass and Forage Crops Specialist
W. A. LEUKEL, Ph. D., Assistant Grass and Forage Crops Specialist
A. F. CAMP, Ph. D., Plant Physiologist, Cotton Investigations
W. A. CARVER, Ph. D., Assistant Cotton Specialist
EDGAR F. GROSSMAN, M. A., Assistant Entomologist, Cotton Investigations
RAYMOND CROWN, Field Asst., Cotton Investigations
A. L. SHEALY, D. V. M., Veterinarian
D. A. SANDERS, D. V. M., Assistant Veterinarian
BRUCE MCKINLEY, B. S. A., Assistant in Agricultural Economics
OUIDA DAVIS ABBOTT. Ph. D.. Head, Home Economics Research
HAROLD MOWRY, Assistant Horticulturist
G. H. BLACKMON, B. S. A., Pecan Culturist
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)
J. G. KELLEY, B. S. A., Lab. Asst. in Plant Pathology (Quincy)
JESSE REEVES, Foreman Tobacco Experiment Station (Quincy)
L. 0. GRATZ, Ph. D., Assistant Plant Pathologist (Hastings)
A. S. RHOADS, Ph. D., Assistant Plant Pathologist (Cocoa)
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)


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







DISEASES OF GRAPES IN FLORIDA
By ARTHUR S. RHOADS

INTRODUCTION
Hitherto there has never been any systematic work attempted
in regard to the study of grape diseases in Florida, their com-
parative frequency of occurrence and economic importance,
and the relative resistance and susceptibility of different varie-
ties to these diseases. The majority of the vineyards now in
the state are of comparatively recent origin and therefore com-
paratively free of diseases. With the increasing age and num-
ber of vineyards, diseases may be expected to increase in both
number and severity. Diseases that may not be known to oc-
cur at present may be found later and some that now appear
of little or no particular consequence may prove serious at some
future date. Only time will reveal the full extent to which
grape diseases and insects may prove a handicap to grape grow-
ing in Florida under modern viticultural methods.
In view of the rapid development of the grape industry in
the state during the past few years and the increasing de-
mands for information on grape diseases and methods for their
control, this bulletin has been prepared to convey to the grower,
in simple language, the available information on this subject.*
HISTORICAL
Grape culture in Florida is by no means a recent enterprise.
The early Spanish settlers brought with them the European
grapes (Vitis vinifera) and planted these along the eastern
coast and along the Keys in an attempt to establish a wine in-
dustry. In common with all the early attempts to grow the
European grape on the Atlantic Coast, however, the efforts of
the Spaniards met with decided failure.
Later, about 1880-1885, after the grape industry of the North-
eastern states was established on a firm basis by the breeding
of varieties containing the blood of the native fox grape
(Vitis labrusca) of that section, another and more concerted
attempt at grape culture in Florida was made, the emigrants
to Florida from the North and Central West introducing the
best varieties of those regions. The center of this early grape
*All illustrations, unless otherwise acknowledged, are reproduced from
photographs made by the writer, most of them having been made during
the course of his studies on grape diseases while pathologist of the Mis-
souri State Experiment Station.







DISEASES OF GRAPES IN FLORIDA
By ARTHUR S. RHOADS

INTRODUCTION
Hitherto there has never been any systematic work attempted
in regard to the study of grape diseases in Florida, their com-
parative frequency of occurrence and economic importance,
and the relative resistance and susceptibility of different varie-
ties to these diseases. The majority of the vineyards now in
the state are of comparatively recent origin and therefore com-
paratively free of diseases. With the increasing age and num-
ber of vineyards, diseases may be expected to increase in both
number and severity. Diseases that may not be known to oc-
cur at present may be found later and some that now appear
of little or no particular consequence may prove serious at some
future date. Only time will reveal the full extent to which
grape diseases and insects may prove a handicap to grape grow-
ing in Florida under modern viticultural methods.
In view of the rapid development of the grape industry in
the state during the past few years and the increasing de-
mands for information on grape diseases and methods for their
control, this bulletin has been prepared to convey to the grower,
in simple language, the available information on this subject.*
HISTORICAL
Grape culture in Florida is by no means a recent enterprise.
The early Spanish settlers brought with them the European
grapes (Vitis vinifera) and planted these along the eastern
coast and along the Keys in an attempt to establish a wine in-
dustry. In common with all the early attempts to grow the
European grape on the Atlantic Coast, however, the efforts of
the Spaniards met with decided failure.
Later, about 1880-1885, after the grape industry of the North-
eastern states was established on a firm basis by the breeding
of varieties containing the blood of the native fox grape
(Vitis labrusca) of that section, another and more concerted
attempt at grape culture in Florida was made, the emigrants
to Florida from the North and Central West introducing the
best varieties of those regions. The center of this early grape
*All illustrations, unless otherwise acknowledged, are reproduced from
photographs made by the writer, most of them having been made during
the course of his studies on grape diseases while pathologist of the Mis-
souri State Experiment Station.





Florida Agricultural Experiment Station


industry was at Orlando and it spread rapidly to adjoining parts
of the state, until, by 1895, there was an aggregate of several
thousand acres of American grapes growing in Florida.
It was soon found, however, that the varieties containing a
high percentage of the blood of the fox grape, when grown in
a warm, humid climate, were but little more resistant to dis-
eases than the European grapes. It was the failure of these
grape plantings that led to the first investigations of Florida
grape growing by the United States Department of Agricul-
ture. In order to test the different types of grape growing for
Florida the Department, in 1899, established an experimental
vineyard on the estate of Baron von Luttichau, a practical grape
grower of Earlton, near Gainesville. Here a large collection of
European, native bunch grapes and muscadine grapes were
tested, these experiments being designed largely to see if the
European, or vinifera grape, could not be grown in this :tate.
The results of these experiments did not warrant the recom-
mendation of either the European or American bunch grapes
as a reliable basis for an extensive commercial industry, the
vines in general proving too short-lived.
The Department then directed its attention to the develop-
ment of the muscadine grape as the basis of a profitable grape
industry not only for Florida, but for the entire Southeast.
This work of developing the native muscadine grape began in
a vineyard at the Ronnoc grove at New Smyrna and has been
continued steadily for about 20 years with very promising
results.
The history of early grape culture in Florida certainly is not
an encouraging one to look back upon, but reveals an expendi-
ture of money, devotion and energy, and an ultimate disap-
pointment that is pathetic to contemplate. Many of these
failures were the result of indiscriminate planting on unsuitable
land, especially inadequately drained land. Most unfortunate-
ly, these pioneers had neither resistant varieties adapted to
local conditions nor our present mastery over the diseases and
insect pests attacking the grape. This early grape growing in-
dustry, however, notwithstanding its handicap in starting, did
have a certain degree of success and it is probable that the
growers would have pulled thru by continued experimentation
and elimination to a resistant rootstock basis if they could have
but marketed their product satisfactorily. Grape growing in
Florida at this early date obviously was a precocious venture





Bulletin 178, Diseases of Grapes in Florida


for the status of the commercial development of that period.
The industry did not expire of its own volition, but was killed,
largely by the lack of suitable transportation facilities.
Within the past generation great advances have been made
which have revolutionized methods previously in vogue. The
failure of the fox grape generally thruout the Middle and Low-
er South directed the attention of the plant breeder to the na-
tive grapes of this section, which were promising as the founda-
tion of a future grape industry. Of fundamental significance
in this connection is the renowned work of T. V. Munson of
Denison, Texas, in developing the Munson hybrid varieties of
grapes as a result of cross-breeding the finer strains of Ameri-
can and European varieties with the native wild vines. These
hybrids are generally recognized as the foundation of Florida
grape culture.
It has been demonstrated beyond the shadow of a doubt that
American varieties of bunch grapes can be grown successfully
commercially in Florida. This can be done on many of the
better types of soils that have been passed up for citrus culture
because of insufficient protection from frost. Grape growing in
Florida, however, is still largely in the experimental stage inso-
far as our knowledge of the selection of varieties for planting
and of the adaptability of these varieties to the different types
of soil and soil moisture conditions is concerned. These points
can be worked out for the different types of planting sites only
by actual vineyard tests, made on a small scale, of the diverse
array of varieties offered, after which the most promising can be
developed on a larger scale.
It may be truthfully said that the ideal commercial variety
of grape for Florida conditions has not yet been found. Sev-
eral of the varieties grown more or less extensively at pres-
ent will unquestionably be supplanted gradually by other va-
rieties of superior quality. Many of the highest quality of
grapes adapted to Florida conditions, however, are more diffi-
cult to grow by virtue of their greater susceptibility to fungous
diseases.
CLIMATIC CONDITIONS OF FLORIDA IN RELATION TO
THOSE OF OTHER GRAPE GROWING SECTIONS
The climatic conditions of any section of the country offer
most important criteria for determining the severity with
which grapes will be attacked by various fungous diseases. It





Florida Agricultural Experiment Station


is largely due to the long, dry summers that such important
diseases of the vine as anthracnose, black-rot and downy mil-
dew have never become established in California, at least to
an appreciable extent. Florida, however, is in a somewhat
more precarious position in regard to grape diseases, since, in
contrast to many other sections of the country, the crop ma-
tures and ripens largely during what is usually the rainy sea-
son of the year, the period of ripening extending from May 15
to July 25. In some years, however, the rainy season does not
start until the latter part of this period, in which case early
ripening varieties can be harvested without this handicap. For-
tunately, however, the rainy season is not characterized by
prolonged periods of rain and cloudy weather. The periods of
rain generally are interspersed with hours of bright sunshine,
accompanied by breezes which prevail almost every day during
the summer season, so that after a comparatively brief dry
period following a shower the grapes are in condition to har-
vest. In any case, however, the high degree of humidity of
the air and the general prevalence of rains during the latter
part of the ripening period offer to the grape grower in Flor-
ida a problem that requires considerable ingenuity, skill and
science to overcome.
On the other hand, by virtue of the mild climate, Florida
vineyards are not troubled by winter injury to the vines nor
by damage from late frost, both of which are often factors of
considerable importance in more northern localities.
For the same reason, vines in Florida have a much longer
growing season and commonly produce commercial crops of
fruit but a year and a half from the time they are set out, in-
stead of requiring from three to four years as in the majority
of the Northern states.

BASIC PRINCIPLES IN THE PREVENTION
OF GRAPE DISEASES
THE SELECTION OF A SUITABLE VINEYARD SITE
In selecting a site for a vineyard, prospective grape growers
should fully realize that no variety of grape will tolerate "wet
feet." Land lacking adequate natural drainage should never be
planted to a vineyard under any condition unless good drainage
by artificial means can first be assured at a reasonable cost.






Bulletin 178, Diseases of Grapes in Florida


In this connection it may be stated that grapes in general do
best on soils otherwise suitable where the water table is fairly
constant thruout the year. Grapes grown in soils which, when
wet, are too wet, and, when dry, are too dry, are bound to suf-
fer more or less from root pruning occasioned by these extremes
in the relative position of the water table with respect to the
roots.
Moreover, in the selection of a vineyard site it should be
borne in mind that the fungous diseases make greater head-
way under conditions favorable to the retention of moist-;re on
and about the vines. For this reason avoid low spots, locations
along streams or drainage canals and along stretches of tim-
ber, where the vineyard will be partly shaded or sheltered
from the winds, especially from the south side. These situa-
tions not only lack good air circulation but they favor the re-
tention of moist conditions which are so favorable for the de-
velopment of fungous diseases. For the same reason the rows
of trellised vines should be laid out north and south in order
to facilitate the drying action of the morning sun, sites on
southern slopes being preferable to those on northern ones. For
the same reason also the rows should not be spaced too closely,
nor should the vines be planted too closely within the rows.

THE SELECTION OF VARIETIES ADAPTED TO THE
VINEYARD SITE
Although there are many varieties of grapes that are being
successful: grown in Florida, it must not be assumed that all
varieties will do equally well under all conditions that offhand
may appear to be favorable to successful grape culture. Grape
varieties often exhibit decided preferences for different types
of soil, soil moisture and climatic conditions and those varie-
ties that thrive in one particular locality or on one type of land
may not do so on another. For example, many varieties will
tolerate a highly calcareous soil while others grown on such
a soil soon develop chlorotic foliage and die.
Aside from the usual consideration of grape varieties with
regard to the purposes of the planting, therefore, one must also
be governed in his selection by the character of the soil, drainage,
uniformity of the water table thruout the year, climatic condi-
tions, and topography of the area to be planted, and select





Florida Agricultural Experimfent Station


those varieties that are best adapted to thrive under the ex-
isting local conditions.
Generally speaking, those varieties that contain a relatively
high percentage of vinifera blood do best on the higher and bet-
ter drained types of soil where air drainage assists nature in
warding off the inroads of fungous diseases, to which these
finer types of grapes are particularly subject.
The following grouping of the varieties most commonly cul-
tivated in Florida, based on observations made in the central
part of the peninsula, is given to show their relative resistance
and susceptibility to fungous diseases.*
Group I.-Varieties most resistant: Bailey, Beacon, Bell,
Carman, Dr. Collier, Extra, Herbemont, R. W. Munson and W.
B. Munson. These varieties can be grown on the lower sites
and require less spraying.
Group II. Varieties moderately susceptible: Brilliant,
Captivator, Goethe, Headlight, Manito, Rommell, and Wap-
anuka. The varieties in this group can be grown on mod-
erately high land or any good type of well-drained soil with
only a moderate amount of spraying. This group contains some
very choice table varieties, many of which are ideal for home
use.
Group III.-Varieties most susceptible: Armalaga, Edna,
Ellen Scott, Last Rose, Manson, Mathilda, Ronalda and Volney.
These varieties, which are among our finest table grapes, con-
tain a high percentage of vinifera blood. They should, there-
fore, be planted only on high elevated and well-drained land,
the higher the better as long as the soil is of good quality.
Even on the high lands of the interior of the peninsula these
varieties often require frequent and timely sprayings if the
best results are to be secured.

VINEYARD SANITATION
The inauguration of a general system of vineyard sanitation
will prove a most valuable means for controlling the more im-
portant fungous diseases of grapes and materially diminish, al-
tho by no means obviate, the need for their control by spraying.
Any measure that will help to eradicate the causal fungi in their
winter quarters will be of importance in the control of these

*For this grouping the writer is largely indebted to Mr. H. G. Gardner
of the Southern Nurseries Co. at Bartow.





Bulletin 178, Diseases of Grapes in Florida


diseases. Since the infection of vineyards by anthracnose,
black-rot and certain other fungous diseases in the spring is
initiated by the dissemination of the spores developed on the
infected canes, tendrils, clingers, and old mummied fruit, in-
cluding both that which adheres to the vines and that which
may have fallen to the ground, it is highly desirable to eliminate
these sources of infection of the new growth as far as practi-
cable. When infection of the new growth occurs in the spring
the opportunities for further infection have been increased a
thousandfold.
After the work in the packing shed is over the litter of rot-
ten berries that have been culled out, or that may have accu-
mulated on the ground about the packing shed, should be
cleaned up and burned or buried instead of allowed to lie about
and provide a source of infection to the vineyard the following
year. When the vineyard is pruned, those canes bearing num-
erous anthracnose or black-rot lesions should be cut out insofar
as this is practicable. At the same time any clusters of mum-
mied fruit remaining on the vines should be collected and later
destroyed by burning. All trimming from the vines should
likewise be removed and burned, except insofar as cuttings
from healthy canes are needed for propagation. It is also high-
ly desirable and often profitable to collect or burn off the old
clinging tendrils from the wires. The most vulnerable point of
attack is against the mummied fruit.
In the spring, before the new growth starts, the vineyard
should be plowed thoroly, care being taken not to injure the
roots of the vines. A grape-hoe may be used to work up close
to the vines to turn the remaining dirt back from the vines into
the furrow. This tillage of the vineyard, in addition to being
good viticultural practice, serves to bury the fallen rotted fruit
and diseased leaves so that the spores discharged later cannot
infect the vines.
It is highly desirable that good soil drainage be maintained
in order to reduce the amount of surface moisture and to facili-
tate a more rapid drying after rain. Air drainage is also of
much importance, since a good circulation of air facilitates the
rapid evaporation of surface moisture from the vines after rain,
dew or fog and thus retards the germination of spores and
subsequent infections. For this reason vineyards should not
be located in the lower parts of valleys, and rolling land is pref-





Florida Agricultural Experiment Station


erable to flat land. Allowing the vines to grow too dense, hav-
ing the trellis wires too low or allowing them to sag greatly
retards the circulation of air through the vineyard. For the
same reason the shoots should not be allowed to spread out
over the ground, for they constitute prime centers of infection
for such fungi as anthracnose, black-rot and downy mildew.
Weeds and grass are not only a detriment to good air drainage
but, in addition, help to increase the humidity of the air about
the vines and thus favor the development of the fungi, to say
nothing of their detriment as users of valuable soil moisture.
The vineyard should be kept in a good state of cultivation
thruout the growing season, after which a cover crop should
be planted.
The picking off and subsequent destruction of diseased ber-
ries during their development is often attempted as an addi-
tional means of vineyard sanitation. This practice is regarded
as of considerable value in a vineyard nearly free from rot but
would not be practicable in a badly infected vineyard. In the
former case it is highly desirable to promptly rid the vineyard
of scattered diseased berries, since each one may become a
source of infection to adjacent ones that may not have been
thoroly sprayed and to newly developing shoots and leaves of
the vine. Since each rotten berry must be removed in any case
before the bunches are packed, it is far better to remove them
while the bunch is still growing so that the space left may be
filled in by the other berries, thus making a more compact and
attractive looking bunch.
Covering the bunches with paper bags of a good quality,
which are securely fastened by twine to the supporting cane,
soon after the blossoms fall is usually an effective means of
preventing fungous and insect attacks. This also affords ex-
cellent protection against attack by birds and injury by hail.
This procedure is very laborious and expensive, however, ex-
cept where only a small number of vines are grown or where
special market prices make it advisable for high class table
grapes. Where but few grapes are grown it is more satisfac-
tory than spraying insofar as protecting the fruit from rot and
mechanical injury is concerned. Spraying, however, in addition
to protecting the fruit, is of considerable value in protecting the
foliage from attacks by fungi and insects and thus increases the
general health and vigor of the vines.





Bulletin 178, Diseases of Grapes in Florida


SVines should always be maintained in a thrifty and vigorous
state of growth by good cultural practices, fertilization and
spraying. It is universally conceded that unhealthy vines are
more subject to attacks by diseases and insects than are those
kept in the prime of condition. Vines that have acquired a
weakened or sickly condition should be examined without de-
lay to diagnose and correct the cause of the trouble. They
should then be stimulated by the application of some nitrogen-
ous fertilizer.

DISEASES DUE TO PARASITIC FUNGI AND BACTERIA
ANTHRACNOSE

Distribution' and' ecoAomic importance: Anthracnose, or
bird's-eye rot, of grapes is a disease virtually as old as civiliza-
tion, having been well known in ancient Greece and Rome. It
is now found practically thruout the world wherever the grape
is cultivated, altho it probably originated in Europe, where
it has occurred to a serious extent for many years. The fungus
causing anthracnose doubtlessly was imported from Europe at
some time prior to 1881, for in that year it was first discov-
ered in this country in central Illinois and later was found in
many other parts of that state. By 1885 the disease had been
noted generally over the Eastern and Middle-Western states.
Anthracnose is characterized by its sporadic nature, some-
times becoming very serious in one locality or on a particular
variety, but not of general occurrence over widespread areas
of the country. It is usually confined to localized sections,
where it spreads progressively, but slowly. Anthracnose is,
however, a disease that may cause great injury when it becomes
epidemic, particularly in view of the fact that it is very ob-
stinate in yielding to treatment. It ranks fourth in general
importance among the fungous diseases of the grape east of
the Rocky Mountains, black-rot, downy mildew and powdery
mildew being more destructive in the order listed. In Florida,
however, anthracnose appears to be of foremost importance.
Symptoms: All the green parts of the vine are subject to
attacks by anthracnose at any period thruout the growing
season, but especially while the growing parts are still tender.
Occasionally the flower clusters may be attacked before they
are fully formed. The disease is most common, however, on





Florida Agricultural Experiment Station


the leaves, shoots and berries. In serious outbreaks the fruit


Fig. 41.-Leaves of R. W. Munson grapevine attacked by anthracnose,
showing the characteristic lesions caused by this disease on the leaf-
stalk, larger veins and intervening soft tissue. Natural size.






Bulletin 178, Diseases of Grapes in Florida


may be almost wholly destroyed and the vines materially
damaged.
On the leaves the disease first appears as minute, irregular,
dark-brown, slightly sunken spots. The centers of these spots
usually become lighter colored when old and frequently crack
or fall out, leaving small, irregular, dark-edged holes. Anthrac-
nose spots may also occur on the petioles, or stalks, of the
leaves and on the larger veins on the under side (fig. 41), in
which case they are more prominent and appear like those on
the shoots and tendrils. The scars occurring on the stalks or
veins may cause
contractions and
distortions o f
ver y variable
nature.
On the shoots
a n d tendrils,
which may be
attacked almost
immediately af-
ter the break-
ing of the buds
in the spring, the
earliest m an i-
festations con-
sist of small,
isolated, light-
brown spots,
somewhat small-
er than a pin-
head at first
and reminding
one of a minia-
ture bruise.
These spots
Fig. 42.-Anthracnose lesions on shoots of R. W. Mun- soon become a
son grapevine. 2/3 natural size. Photo by D. G. A. little depressed
Kelbert. in the center
and develop a slightly raised, darker-colored rim or border. In
the later stages the center of the spot becomes more depressed





Florida Agricultural Experiment Station


and, with the destruction of the bark over these spots, the color
becomes grayish. In early summer the center of the scar is
usually of an ashy-pink color, surrounded by a blackish rim.
The pinkish appearance of the center is caused by the devel-
opment of the summer spores, or conidia, which are produced
in enormous numbers at this season. The spots continue to in-
crease in size, mainly in the direction of the main axis of the
shoot, assuming irregular shapes and ultimately forming the
scars characteristic of the disease (fig. 42). These scars be-
come sunken as they spread, giving the shoot much the appear-
ance of having been corroded or burned. Should several scars
form close to one another, or even a single scar extend into
the pith, the shoot may be so weakened as to be easily broken
off by the wind. When the vines are severely attacked during
the growing season the growth of the primary shoots is checked,
causing the development of a great number of lateral or secon-
dary shoots, and there is generally a weakening of the foliage
indicated by its paler and often yellowish hue. In rare cases
the disease upon the shoots may be so severe as to cause the
destruction of the young leaves even when the latter are not
directly attacked.
On the fruit the disease produces the well-known bird's eye
spots. These spots first develop as dark reddish-brown or near-
ly black specks on any part of the berry. These specks gradu-
ally increase in size to 1/8 to 1/4 of an inch in diameter, usually
preserving a somewhat rounded outline. Their centers become
gray or grayish-pink but the border remains dark. Later the
grayish centers of the spots may become somewhat sunken,
but not so deeply as in the case of the scars on the shoots. As
the spots enlarge they retain a more or less regular outline and
sometimes there appears between the light-colored portion and
the dark-colored border a well-defined band of bright red. The
appearance thus resulting has given rise to the name "bird's-
eye" rot (fig. 43).
Frequently two or more spots may unite and involve a
considerable part of the berry. Berries attacked on only one
side when not more than half grown often become mis-shapen
due to the tissues of the diseased spot making no further devel-
opment. As a result of the unequal tensions induced by the
continued growth of the rest of the berry the diseased side
often cracks open, exposing the seeds, which are sometimes





Bulletin 178, Diseases of Grapes in Florida


forced out by the unequal growth. The bursting of the ber-
ries and the exposure of the seeds, however, may ensue also
from other causes, such as powdery mildew, hail and certain
insect injuries. On the other hand, when berries are only
slightly affected and the progress of
the disease is checked by spraying,
they may outgrow the effects of the
disease, in which case the only evi-
dence of the spots left is a gray or
dark-brown scurf covering a portion
of the surface.
During the progress of the disease
there is no general softening or
browning of the berries as in the case
of black-rot, but the tissues beneath
the spots gradually lose their turgor
and the cells of the spots eventually
collapse and become dry and hard.
Neither does the skin shrivel to the
extent of leaving prominent or very
irregular ridges as in the case of
black-rot, altho badly affected berries
finally wither and dry up, often appar-
ently nothing but the skin and seeds
being left. In advanced stages of de-
cay the berries, which may be reduced
to one-fourth of their original size,
usually retain the distinct outline and Fig. 43.-nthracnose or
bird's-eye rot on El-
more or less of the color of the origi- vira grapes. Reduced.
(After F. Lamson
nal spots. Scribner, in Report of
The stem of the cluster or its the Commissioner of
Agriculture, 1886.)
branches may also be attacked, Agriculture, 1886.)
in which case the berries depending upon the functioning of
the diseased parts for nutrition and water conduction remain
small, with little sugar in them, or wither.
Cause of anthracnose: Anthracnose is caused by the fungus
Sphaceloma ampelinum De By. The pustules or fruiting bodies
of the fungus appear most commonly on the diseased berries and
canker-like spots on the canes. These structures burst thru
the epidermis of the berries and shoots and produce spores in
great abundance. These spores ooze out in a gelatinous mass.





Florida Agricultural Experiment Station


The sticky matrix binding the spores together dissolves in water
and the spores are disseminated by dew or rain. The growth
produced by the germinating spores readily penetrates the un-
broken epidermis of any succulent green part of the vine and in
about eight days the characteristic anthracnose spots begin to
appear on the new infections. With the advent of the dormant
season the fungus suspends activity until spring. The micro-
scopic, thread-like filaments which constitute the vegetative
portion of the fungus live during the winter in the tissues of
the canes and mummied fruits and in the spring the spores de-
veloped in these centers of disease bring about the first new in-
fections of the vines.
Control measures: Until recently but little has been done in
American vineyards to prevent anthracnose, altho its con-
trol is well understood in Europe. Recommendations based on
the results of careful experimentation follow:
1.-In connection with the regular pruning, cut out and burn
all diseased canes showing anthracnose lesions; also collect and
burn all diseased mummied fruit clusters.
2.-While dormant, spray the vines thoroly with copper
sulphate (4 pounds to 50 gallons), preferably just before the
buds begin to swell in the spring.
3.-Plow the vineyard in the spring. This is commendable
both as good viticultural practice and in order to bury all fallen
mummied fruit.
4.-During the growing season spray the vines thoroly with
Bordeaux mixture (4-3-50) as follows: first, when the shoots
are from 8 to 12 inches long; second, just after the blossoms
are swelling and before they begin to open; third, after the
blossoms have fallen and the fruit has reached the size of buck-
shot. Subsequent applications should be made at intervals of
10 days to two weeks, depending upon the weather and the se-
verity of the disease. If the weather be dry, without rain or
heavy fog, applications need not be so frequent, but if the
weather be wet and humid, especially after the fruit has set,
the application should be made at least every 10 days. Spraying
should be continued at these intervals until about May 15 to
June 15, or within a month of harvest time. After this date it
is preferable to use some one of the sprays leaving a practically
colorless residue, such as the copper acetates (see page 143).





Bulletin 178, Diseases of Grapes in Florida


5.-Do not allow shoots of the vines to trail out over the
ground.
BLACK-ROT
Distribution and economic importance: In regions east of
the Rocky Mountains black-rot is the most generally distributed
and destructive disease of the grape, occurring on practically
all wild and cultivated vines. What apparently was black-rot
was known in this country as early as 1804 but the first impor-
tant records of this disease come from Missouri in 1861. At
that time there was a rise in the grape industry near St. Louis,
which, especially from 1860 to 1864, was accompanied by epi-
demics of black-rot. Since then heavy losses due to black-rot
have been experienced in a number of states, and in many sec-
tions this disease proved so destructive that grape growing has







-UC










Fig. 44.-Blight of blossom clusters of Carman grapes caused by the black-
rot fungus, showing a normal cluster at left, which has set fruit. %
natural size.
been abandoned. The existence of black-rot in the interior
of virgin forests upon most of the wild species of grapevines of
the United States, from the Rocky Mountains to the Atlantic
Ocean and from Canada to the Gulf of Mexico, proves beyond
question that this disease is of American origin.
The loss from black-rot varies greatly from year to year, ac-
cording to the character of the weather, being much worse in




Florida Agricultural Experiment Station


rainy or warm, humid weather than in dry weather. During
wet seasons, where the disease is severe and spraying is not
practiced, losses as high as 75 to 80 percent have been reported


Fig 45.-Black-rot spots on leaf and leaf-stalk of cultivated grape. 3/5
natural size.
in some localities, and in some vineyards there has been a total
loss due to the destructive action of black-rot.
It seems to be the general experience that practically all the
more commonly cultivated varieties of bunch grapes are more


j






Bulletin 178, Diseases of Grapes in Florida


or less susceptible, especially the fruit of varieties of the Her-
bemont group. The muscadine group, on the other hand, is
much more resistant to attack, at least insofar as the fruit is
concerned, altho even here the blossom clusters of the Scupper-
nong grapes are often subject to attack. For commercial pur-
poses, the growing of bunch grapes would be impossible in most
localities if the disease were not controllable by spraying and
cultural practices.
Symptoms: All the green parts of the vine are subject to
attack by black-rot but the damage to the fruit is by far the
most important. Where rainy weather prevails during the
blooming period and the disease is prevalent it may even attack
the blossom clusters, causing them to rot, blacken, and to dry
up and fall off (fig. 44).
On the leaves black-rot appears in late spring in the form of
sharply defined,
reddish brown,
more or less cir-
cular spots (figs.
45 and 46).
These may b e
few or many, ac-
cording to the se-
verity of the in-
fection. As the
spots increase in
size the central
areas become
ashen-gray b u t
the margins re-
main bro w n.
During the
course of the
summer, whe n
the spot has at-
Fig. 46.-Black-rot spots on leaf of Thomas grape- trained full size,
vine, a cultivated variety of Vitis rotundifolia. a series of min-
Natural size. ute black pus-
tules, or fruiting bodies, most abundant on the marginal por-
tion of the spot, break thru the cuticle on the upper surface
of the leaf. Black-rot lesions also occur on the petiole, or stalk,





Florida Agricultural Experiment Station


of the leaves and on the larger veins on the underside, in which
case they resemble those on the shoots
and tendrils.
On the shoots, tendrils and flower
stalks the character of the black-rot
lesions is somewhat different from that
on the leaves. They first appear as
small, dark depressions, which soon be-
come black. The lesions vary in form,
appearing as small circular to ellipti-
cal or much elongated spots, which may
be as much as half an inch long, altho
they are much smaller as a rule. Num-
erous minute black pustules, or fruit-
ing bodies, eventually appear on these
lesions. On the canes the lesions fre-
quently cause lentil-shaped cracks in
Sthe bark but rarely extend more than
a quarter of the distance around and
never become so deep as to cut off the
sap supply. This happens occasionally,
however, on the leaf-stalks, quite com-
monly on the tendrils and stalks of the


Fig. 47. One year old
canes o f grapevine,
showing small black-
rot lesions as they ap-
pear at the end of the
growing season. Nat-
ural size.

berries, but rarely on
the stems of the clusters.
On the berries, which
usually are not attacked
until after they are half-
grown, black rot ap-
pears as small circular,
purplish or livid brown,
soft spots which quick-


Fig. 48.-Early stage of development of
black-rot on berry of wild grapevine
(Vitis aestivalis), showing the sharply
sunken lesion and the pustules develop-
ing in the center. Enlarged 7 times.





Bulletin 178, Diseases of Grapes in Florida


ly become flattened or sunken due to the collapse of the tissues
at the point of infection (fig. 48). When the rotten spot is


















Fig. 49.-Hernito grapes attacked by black-rot, showing the successive
stages in the progress of the disease. The berry at the left in the top
row is a normal green one, the one at the right of it is half rotted,
and the rest completely rotted and in the process of drying down to
mummies. 8/9 natural size.


Fig. 50.-A Hernito grape reduced to a mummy by black-rot,
showing the characteristic folds in the blackened skin
and the numerous spore-bearing pustules dotting the
surface. Enlarged 7 times.


about
three-
eighths of
an inch
or more
in diam-
eter, num-
erous min-
ute, brown
pustu 1 e s
appear at
the cen-
ter. These
are the
fruit i n g
bodies of
the black-
rot or-
gan ism,
which, in
a few
hours, be-





Florida Agricultural Experiment Station


come so numerous as to give the spot a blackish aspect. As
a rule the rot quickly involves the whole berry. At about the
same time that the blackening appears the berry begins to lose
its spherical contour and to shrivel perceptibly (fig. 49).
These rotten berries ultimately become dry, hard, wrinkled,
blackish mummies with pustules, or fruiting bodies, dotting the
entire surface (fig. 50). Occasional berries on a cluster, parts
of a cluster, or even the whole cluster may be attacked by black-
rot and the fruit reduced to mummies (fig. 51). At this stage
the disease is unmistakable. When the berries have become
















Fig. 51.-Black rot on Hicks grapes, showing a perfect cluster at the left
and two badly diseased ones on which all of the affected berries have
been reduced to the characteristic hard, wrinkled, blackish mummies.
natural size.,

mummified they cling to the bunches with great tenacity and
clusters thus affected commonly remain hanging on the vines
thruout the winter.
Berries of the muscadine group of grapes show a high de-
gree of resistance to black-rot, altho the leaves are very sus-
ceptible to this disease (fig. 46).
Cause of black-rot: Black-rot is caused by the fungus
Guignardia bidwellii (Ell.) V. & R. The trouble begins in the
spring when two kinds of spores are liberated from their hiber-
nating quarters on the canes, tendrils or the mummied fruit,
including both that still hanging on the vines and that which
may be lying on the ground.. With the absorption of water, the
winter spores are discharged into the air with considerable
force and may be distributed about the vineyard by air currents.





Bulletin 178, Diseases of Grapes in Florida


Also in the spring the so-called summer spores, which have hi-
bernated in the pustules on the old canes, tendrils or hanging
clusters of mummied fruit, ooze out of these pustules in long
curled, gelatinous threads (fig. 52, a). These spores may be
washed or spattered by rain to the adjacent susceptible parts of
vines. Under favorable conditions the spores germinate and












C f


-4-v






d l, ad i nat.
Fig. 52.-Microscopic characters of the black-rot fungus: a, a magnified
portion of the epidermis of an affected berry, showing the pustules with
the spore masses oozing out in tortuous gelatinous threads; b, a section
thru the skin of an affected berry, showing the development of two
different forms of fruiting bodies (a spermogonium at left and a pyc-
nidium at right) and the mycelium, or vegetative part, of the fungus
developing thru the underlying tissues of the berry; c, a portion of a
pustule, or fruiting body, more highly magnified, showing the individ-
ual spores and the organs on which they are developed; d, three spores
germinating; e, a section thru the skin of an affected grape, showing
the development of the perfect, or winter, spore stage of the fungus, in
which the spores are borne in sac-like structures within the pustule; f,
two of the spore-bearing sacs (asci) more highly magnified, each con-
taining eight spores; g, a group of four of these spores still further
enlarged. (After F. Lamson Scribner, in Proc. New Jersey Hort. Soc.,
1886.)

readily infect the succulent green parts of the vines.. The first
infections in the spring occur on the leaves, shoots and tendrils:
Later in the season the berries become affected. Infection of
the young leaves, tendrils and shoots may occur repeatedly
thruout the growing season. After infection it is usually from





Florida Agricultural Experiment Station


8 to 14 days before the disease makes its appearance on the
fruit and from 10 to 21 days before it appears on the leaves, the
interval varying according to the weather conditions.
Control measures: Like anthracnose, black-rot can be effec-
tively controlled by a series of timely and thoro sprayings with
Bordeaux mixture, supplemented by an intelligent system of
vineyard sanitation. The control measures given for the con-
trol of anthracnose (page 88) apply also in the control of black-
rot.
DOWNY MILDEW
Distribution and economic importance: Downy mildew is
common to both the wild and cultivated grapevines of this
country, and from the former it doubtless was conveyed to the
latter in the earliest days of American grape culture. This dis-
ease is now of general occurrence in the United States east of
the Rocky Mountains, where it has been known since 1834. In
the drier sections west of the Rocky Mountains, however, it is
virtually unknown.
The greatest loss from downy mildew occurs in the Northern
states, especially about the Great Lakes, where in some locali-
ties it has been estimated that from 25 to 75 percent of the crop
has been destroyed by it. In certain seasons in this section
downy mildew causes more loss than black-rot, to which in gen-
eral it ranks second in importance as a grape disease. Within
this country downy mildew has proved even more destructive to
European varieties than to domestic ones.
Like black-rot, downy mildew develops most rapidly and
causes most injury during periods of humid, rainy weather and
is seldom troublesome in dry seasons. Other conditions being
equal, downy mildew is most abundant on wet land and on
vines that are on a very low trellis or trailing on the ground,
where the air drainage is-restricted. For this reason we often
have outbreaks of downy mildew on nursery stock, altho the
older trellised vines of the same variety may not be particularly
subject to it.
Symptoms: Downy mildew attacks not only the berries, but
all succulent green parts of the vine. It causes loss thru the
rotting and shelling of the berries, the partial-or even total-
destruction of the foliage, and the dwarfing and killing of the
young shoots. While the berries may be attacked at any time
during the growing season, the disease usually is most trouble-






Bulletin 178, Diseases of Grapes in Florida


some in early summer. The flower clusters, especially in species
of wild vines, may be attacked even before the fruit has set.
On the leaves, where the disease is found most frequently,
the first evidence of it is the appearance on the upper surface
of small, irregular, greenish-yellow spots, the margins of which
gradually blend into the darker green of the leaf. In the early
stages these spots are more easily distinguished if the leaves are
held up to the light, being more translucent than normal leaf
tissue. These yellow areas generally increase in size, unite with
one another, soon turn brown, and die out altogether (fig. 53).




















Fig. 53.-Downy-mildew on leaves of Cloeta grape, a variety very sus-
ceptible to this disease in Florida. The leaf at the left shows the
patches of frost-like mildew on the under side, while the other two
leaves show the greenish-yellow to blackish and eventually dead areas
on the upper surface, where a growth of mildew occurs on the under
side. % natural size.

The appearance of the disease on the lower surface of the leaf
is at first similar to that on the upper one. If the atmosphere
be sufficiently moist there soon develop, on those portions of
the lower surface corresponding to the spots on the upper sur-
face, glistening frost-like patches of white fungous filaments
reminding one of table salt (fig. 53). Except in very rare
cases, the downy growth of mildew is visible only on the under
surface of the greenish yellow spots already mentioned.
The amount of mildew on a leaf depends upon weather condi-





Florida Agricultural Experiment Station


tions and on the variety of vine. While the patches of down
are very apparent in moist, warm weather, they may be en-
tirely absent or but scantily developed in dry weather. Under
favorable conditions the infection frequently is so heavy that
many spots appear on a single leaf, uniting more or less and
giving a mottled appearance to the whole leaf. In advanced
stages of the disease, or after a heavy rain, the frost-like
patches of mildew often dis-
appear, leaving in their places
light brown discolorations cor-
responding in size and shape
with those on the upper sur-
face. Eventually the severe-
ly attacked leaves dry up, be-
come brittle and soon fall, usu-
ally dropping at their junction
with the stalk. In severe cases
of attack considerable portions
of the vine may be defoliated.
If this occurs early in the sea-
son the nutrition of the vine
may be so.interfered with that
the berries, even if they be
not attacked directly, may be
so checked in growth that they
fail to reach maturity and then
remain hanging on the vine as
brown, shriveled bunches. Not
only is the crop of the current
season injured but that of the
following season is seriously
compromised, since the pre-
mature defoliation prevents
the accumulation of reserve
food materials in the vine,
diminishing the number and
size of the bunches formed
the following season. Repeated
attacks of mildew may so
weaken the vitality of the vine Fig. 54.-Downymmildew on grape
as to result in its death. shoot. (Photo by courtesy of the
Department of Plant Pathology of
On the shoots, leafstalks and Cornell University.)





Bulletin 178, Diseases of Grapes in Florida


tendrils the affected portion at first has a water-soaked, shiny
appearance, which is accompanied by a local swelling of the
tissue. The lesion is bare at first but quickly becomes cov-
ered with the same whitish, downy growth of mildew as occurs
on the leaves. In older cases the white down disappears and
the affected area becomes brown or dead and slightly depressed
as a consequence of the collapsing of the diseased tissues. In
case of severe attack the leaves remain small and the shoots are
dwarfed and may die (fig. 54).
On the berries, which may be attacked at any time from flow-
ering until they begin to ripen, two forms of rot may result
from downy mildew. The so-called gray-rot form of downy
mildew appears on the berries only while they are quite small.
After they have become half or more grown the symptoms of
the disease are entirely different, the disease then being termed
brown-rot.
If attacked when quite small the berries rarely attain more
than a fourth of their full size, often remaining no larger than
small peas. The first indication of the disease is a change of
the normal green color to a bluish green or lead color. At the
same time these berries become much harder than normal ones.
In a short time the surfaces of the attacked berries become
covered with a growth of mildew similar to that on the leaves
and shoots, after which they appear grayish (fig. 55). The
further growth of such diseased berries is checked and, while
they remain plump for a time, they finally dry up and blacken.
This form of the disease is usually called gray-rot.
When the berries are not attacked until half or more grown
the character of the rot appears entirely different. The at-
tacked berries may be distinguished readily from the healthy
ones by having a grayish or less vivid color. Soon marked dis-
colorations appear here and there over the surface and at these
points the skin becomes more or less depressed by the shrink-
ing of the tissues beneath. The rot soon involves the whole
berry. The pulp of the berry becomes soft and often shrinks,
forming depressions over which the wrinkled but otherwise
smooth and unbroken skin is stretched. The diseased berries
become more and more withered and lifeless in appearance.
They ultimately turn dark brown and fall at the slightest jar
of the vine. This form of downy mildew is commonly termed
brown-rot. Berries attacked by the brown-rot form of downy
mildew present neither the sharp and prominent wrinkles of





Florida Agricultural Experiment Station


berries destroyed by black-rot nor the characteristic, small,
black pustules that appear on the surface in the case of the
latter.
Cause: Downy mildew of grapes is caused by the fungus
Plasmopara viticola (B. and C.) Berl. and De Toni. Unlike
most parasitic fungi, the mycelium or vegetative filaments of
the downy mildew do not grow thru the cells composing the
tissues of the vine but develop between them in all directions.


























Fig. 55.-The gray-rot form of the downy-mildew on young grape berries.
(Photo by courtesy of the Department of Plant Pathology of Cornell
University.)

At frequent intervals on these filaments, as they push their way
in between these cells, minute lateral projections are formed
that penetrate the walls of the adjacent cells of the host plant,
from which they absorb the nourishment for the support of the
parasite. These projections are termed haustoria or "suckers"
(fig. 56, B). The contents of the parasitized cells quickly turn
brown, ultimately effecting the outward changes in the colora-






Bulletin 178, Diseases of Grapes in Florida


tion of the leaf or other affected part. Upon this mycelium, at
different periods and in very unlike ways, two sets of spores,
or reproductive bodies are developed. The summer spores, or
conidia, as they are technically termed, are borne upon the ulti-
mate branches of slender filaments of the fungus which issue
thru the natural openings afforded by the stomata, or breathing


pores, of the leaves.
ca lled conidio-
phores, issues
from each breath-
ing pore of a dis-
eased area of
leaf. On the
branching tips of
these superficial
fungous fila-
ments are borne
myriads of sum-
mer-spores, the
general plan of
these spore-bear-
ing filaments be-
ing much like a
bunch of grapes
(fig. 56, A.).
The glistening,
frost-like patches
of mildew so
conspicuous o n
the under sur-
face of affected
leaves consist
wholly of this
growth of spore-
bearing fungous
filaments w i t h
their spores and
it is due to their
abundance that


A group of from 4 to 10 of these filaments,


Fig. 56.-Microscopic characters of the downy mil-
dew fungus; (A), section of portion of leaf
with group of spore-bearing, branching fila-
ments of the fungus emerging from a breathing-
pore on the lower surface; (B), greatly enlarged
view of "suckers" developed on the fungous fila-
ments within the tissues of the host; (C), pro-
gressive stages in the formation of swarm spores
in the germination of the summer spores, or con-
idia; (D), progressive stages in the formation
of winter spores by a special sexual process. All
highly magnified. (After Millardet).


the fungus becomes visible to the unaided eye.
The summer spores are produced in great numbers at re-
peated intervals thruout the spring and summer and serve for





Florida Agricultural Experiment Station


the immediate propagation and rapid distribution of the fun-
gus, which is effected by wind and water. In shape these
spores are ovoid, the narrower end being at the point of at-
tachment. One of these bodies, happening to lodge upon a sus-
ceptible part of a grapevine where tlere is moisture condensed
in the form of drops as a result of rain, dew or fog, will ger-
minate within a couple of hours, producing a number of swarm
spores (fig. 56, C), which in turn germinate and produce in-
fection under favorable conditions.
With the cessation of growth at the close of the summer the
downy mildew fungus develops, in the interior tissues of the
affected leaves that fall to the ground, an entirely different
spore form better adapted to carry the fungus thru the winter
season. These spores, which have greatly thickened walls, are
produced as a result of a special sexual process and are termed
oospores or, more popularly, winter spores. In the spring these
spores are set free by the disintegration of the leaves and may
start the initial infections of the season. It is believed that
these spores retain their vitality in the soil for years.
Control measures: It is desirable to destroy as many as pos-
sible of the old diseased leaves, shoots and berries, which may
contain the winter spores of the fungus. Since these spores
hibernate in old fallen leaves, it is commonly recommended that
these be plowed under early in the spring. It is even prefer-
able to collect and burn the fallen leaves, if practicable, since it
is not known how long the spores may remain viable in the soil.
In Florida it probably will not be necessary in most cases to
spray for downy mildew alone since the spray applications for
anthracnose and black-rot, which should always be made, ordi-
narily suffice to keep this disease under control.

POWDERY MILDEW
Distribution and economic importance: The powdery mil-
dew, or oidium, of the vine, which was once thought to have
originated on wild vines of the Eastern and Central United
States, is now known to be native to the Old World, originating
on native vines in Japan. In the United States powdery mil-
dew has a wide geographical distribution, occurring from
Massachusetts to Florida and westward across the continent to
the Pacific Coast. It is also found to some extent in Canada,
particularly Ontario. The first record of its occurrence in






Bulletin 178, Diseases of Grapes in Florida


America comes from California, it being known in that state as
early as 1859.
Powdery mildew attacks practically all wild species of grape-
vines and their cultivated varieties but shows a decided prefer-
ence for the European grape. There are, however, various de-
grees of susceptibility among the latter. In certain regions of
the United States, for example, in California, Oregon and the
Chautauqua grape belt of western New York, powdery mildew
ranks ahead of downy mildew, black-rot or anthracnose. This
is apparently due to the ability of the causal fungus to with-
stand dry atmosphere better than the fungi concerned in the


Fig. 57.-Powdery mildew on upper surface of grape leaf. (From Trans-
vaal Agricultural Journal, Vol. 7, pl. 31, 1909).

other diseases mentioned. For the United States as a whole,
however, powdery mildew causes much less damage to vine-
yards in the average season than downy mildew, ranking third
in importance among grape diseases.
The fungus causing powdery mildew is quite different from
that causing downy mildew. It differs quite radically from all






Florida Agricultural Experiment Station


other parasitic fungi which attack the vine in that the mycelium
or vegetative part, of the fungus does not penetrate the tissues
of the host plant. Instead it grows superficially over the sur-
face of the part attacked, simply sending into the epidermal,
or surface, cells little sucker-like organs, thru which it absorbs
its nutriment. The plant body of the parasite is, therefore,
fully exposed to the direct action of any fungicide which may
be applied to destroy it.
Symptoms: Powdery mildew attacks all green parts of the
vine, including the leaves, shoots, flowers, and fruit.
On the leaves, which are attacked when young, whitish or
greenish-white patches about a quarter of an inch in diameter
first appear on both the upper and lower surfaces, but most
abundantly on the upper. A mottled appearance is thus produced.
As the disease progresses these patches run together until a
large part of the surface of the leaf may be covered with a gray-
ish-white mildew (fig. 57). The leaf ceases to grow and curls.
A vine with severely attacked foliage has a wilted and dwarfed
aspect. This is particularly true in the earlier part of the sea-
son and in warm dry weather. A heavily attacked vine has a
moldy odor. Eventually numerous minute, black fruiting
bodies just visible to the unaided eye are seen scattered over
the mildewed areas.
On the shoots, which are attacked as they lengthen, the








Fig. 58.-Blackening of the canes caused by powdery mildew. (From
California Agricultural Experiment Station Circular 144).

patches of mildew usually appear near the bases and are in-
conspicuous at first. Later they acquire a grayish tint as the
mildew develops on the surface and the disease is then more
conspicuous. In mild attacks the mildew is confined to patches
but in severe cases of attack it may completely cover the sur-
face of the shoot. If these patches are rubbed the fungus
comes off completely. The places where it has been, however,
turn dark later, owing to injuries to the superficial cells of the





Bulletin 178, Diseases of Grapes in Florida


bark (fig. 58). These discolored areas, which are brown at
first and blackish later, are usually branching or fern-like in
form, showing the points of attack by the fungus. If the shoots
are attacked when young they fail to mature properly and often
become blackened over their entire surface.
On the blossoms the disease may also make its appearance if
conditions in the vineyard during blossoming are favorable to
infection. Attack of the blossom clusters occurs regularly in
France and often in California, but is not known to occur in
the Eastern United States. Affected blossoms fail to set fruit
or develop in an aborted fashion.
On the berries the disease may appear at any time during the
course of their development until they begin to color. If at-
tacked when very small they fail to develop and drop off. If
not attacked until they have attained a fairly good development
the fruit continues to develop, but in an irregular fashion. In-
fected berries take on a gray, scurfy appearance and become
flecked with brown. The parts of the epidermis injured by the
fungus become blackened and cease to grow. This results in
irregularity in the form of the berry and, in severe cases, in
cracking, which may be so extensive as to expose the seeds.
In moist seasons the berries which have cracked usually become
infected by blue mold and are then completely destroyed. The
diseased fruit does not become soft and shrunken as when at-
tacked by downy mildew.
After the fruit has lost its green color and has commenced
to ripen it is no longer subject to attack by powdery mildew.
The markings and blotches which are often seen on ripe grapes
are due to injuries in the skin caused by the presence of the
powdery mildew fungus on the fruit before it ripened. These
markings are very objectionable on table and raisin grapes and
decrease their value.
The stems of the clusters and stalks of the individual berries
may also be attacked by powdery mildew, the fungus very com-
monly making profuse growth on these parts. By harvest time
the berries are withered and dwarfed. The development of the
grayish mildew is followed by the appearance of the minute,
black fruiting bodies described for the other susceptible organs.
Cause: Powdery mildew is caused by the fungus Uncinula
necator (Schw.) Burr. This fungus produces two unlike sets
of spores, or reproductive bodies. The fine, white filaments of
the fungus, which constitute the vegetative portion of the para-





Florida Agricultural Experiment Station


site, spread over the surface of the leaves, shoots and fruit and
send up short, irregular branches, upon which the summer
spores are produced in short chains (fig 59, a). The details of
this formation, however, are evident only with a microscope.
Upon this superficial, cobwebby growth of fungus myriads of
summer spores may be produced, giving the attacked parts a
gray powdery, or mealy, appearance. The spores are ready to
germinate as soon as they have fallen from their supporting
filaments and, upon coming into contact with susceptible parts of
the vine, may start new infections. This process may be repeated
thruout the summer. As a result of this great spore produc-
tion the spread of the fungus during the summer is very rapid.
In late
summer
and a u-
tumn the
second
form of
spores,
the so-
called
t b a winter
spores, is
a, developed.
These are
fo r med
i n little
sacs (fig.
59, b and
c), which
Fig. 59.-Microscopic characters of the powdery mildew fun-
gus: (a), a fertile filament of the fungus dividing into a r e en-
a chain of summer spores, or conidia; (b), a spore-case closed in
.with the characteristically curled appendages, in which
the winter spores are produced in sacs; (c), a single sac m i n u t e,
containing the winter spores; (d), a single winter spore. b 1 a c k,
All highly magnified. (After Shear, in U. S. Dept. Agr. r o u n d,
Farmers' Bull. 1220.) r o u n d,
hard
fruiting bodies, from which radiate a number of appendages
which are curled at their tips (fig. 59, b). These black spore-cases
occur scattered more or less abundantly among the filaments of
the fungus on the mildewed areas but are so small that they are
just visible as minute, black specks with the unaided eye, altho
they are easily visible with the aid of a hand lens. The forma-






Bulletin 178, Diseases of Grapes in Florida


tion of these spore-cases appears to depend upon a peculiar
combination of weather conditions, they being developed in
some parts of the country more readily than others.
The spore-cases remain upon the leaves and shoots, or other
grape litter on the ground until the return of warm weather in
the spring. As soon as the temperature becomes sufficiently
high the walls of the spore-cases crack open and allow the sacs
to eject their spores. The spore-cases do not all eject their
spores at the same time, owing to the different conditions of the
place in which they have passed the winter. Some may even
remain in the soil until the following spring and spore-cases
have been found to contain spores capable of germination 18
months after their formation. Since the winter form appears
to be absent or very rare in certain districts, it appears prob-
able that the fungus, under some conditions, can also pass the
winter in the conidial, or summer, form.
Control measures: Powdery mildew, even more than other
fungi attacking the vine, can be held in check to a large extent
by cultural methods. In general any cultural practice which
permits the sun and air to reach all parts of the vines more
completely will lessen the danger from it. Drainage of the wet
places in vineyards and methods of pruning and training which
will tend to spread out the vine so that no part is surrounded
by still, moist air will tend to diminish the intensity of the dis-
ease. Where practicable, it is advisable to rake up the fallen
leaves and burn them before the growth starts in the spring.
Burying them by plowing in simply aids in the preservation of
the spore-cases and they are then ready to cause infection when
brought to the surface again by plowing next year.
For American varieties east of the Rocky Mountains, where
anthracnose, black-rot and downy mildew are usually present,
Bordeaux mixture is fairly suitable for the control of powdery
mildew and should be used as recommended for anthracnose
(page 88).
BITTER-ROT
Distribution and economic importance: For a number of
years prior to the discovery of the causal fungus, grape growers
in some sections of the eastern United States have recognized a
form of grape-rot under the name of bitter-rot on account of the
particularly bitter taste of the diseased berries. Bitter-rot is said
to have been observed by one grape grower in Virginia as early
as 1873.





Florida Agricultural Experiment Station


However long bitter-rot may have been known to grape
growers, the causal fungus was not discovered until 1887, in
which year grape diseases first received the serious attention of
American plant pathologists. In that year the fungus causing
bitter-rot was observed in North Carolina. Later in the same
year it was observed in Missouri, Texas and the District of
Columbia.
This disease, which appears to have originated in the United
States, is now known to range from Florida west to Texas and
north to Missouri, Minnesota and New Jersey. It is of by far
the most frequent occurrence, however, in the southern part of
its range.
Bitter-rot is essentially a rot of ripe grapes, usually not mak-
ing its appearance until the fruit has attained full size or is
beginning to ripen, but continuing its ravages until the perfect
maturity of the fruit and even after it has been picked and
packed for shipment. Thus the causal fungus is both parasitic
and saprophytic in its habit of growth.
Observations in a number of Southern states demonstrate
that bitter-rot may often cause considerable losses in seasons
favorable to its development and result in extensive damage in
a very brief period. Periods of humid, rainy weather are es-
pecially favorable to the development of the fungus causing
bitter-rot. In dry, hot weather this disease is able to make but
comparatively little progress. Practically all varieties of
American grapes, including the muscadine grapes, seem to be
susceptible.
Bitter-rot is a particularly dangerous and troublesome dis-
ease, since ripening or ripe grapes may be attacked more or less
seriously even after they may have escaped other diseases dur-
ing the early part of the summer; also in coming at a time when
further applications of Bordeaux mixture are no longer consid-
ered necessary for disease control nor, in fact, even desirable on
account of the chalky blotches of spray residue left on the fruit
when ripe.
Symptoms: Grapes attacked by bitter-rot present an ap-
pearance very similar to that produced by ripe-rot and it is often
confused with both this disease and the brown-rot form of the
downy mildew.
While most conspicuous in its action upon the berries, the
bitter-rot fungus also attacks the young shoots and the stem of




Bulletin 178, Diseases of Grapes in Florida


the fruit cluster and its branches. It does not appear to occur on
the leaves to any appreciable extent. On the young shoots it some-
times occurs at the junction of the cluster, where it appears as a
black spot which increases in size and becomes covered with little
sooty-black pustules like those developed on the berries. All the
branches of the fruit clusters may become diseased but the indi-
vidual stalks of the berries are more frequently attacked. The fun-
gus, however, is quite capable of spreading thru the stem of the
cluster and infecting the berries at various points, the attacked
parts often becoming dry and hard before there is any evidence
of the fungus in the berries. If the cluster be attacked in this
manner before the fruit
begins to ripen the dis-
eased stem fails to nour-
ish the berries, which
shrivel slightly and ap-
pear as if suffering from
sun-scald. Such berries
do not ripen but fall to
the ground. If the
bunch be almost ripe
when attacked only a
few of the berries may
be so affected but the
cluster is ruined for
shipping, since the stem
becomes dry and brittle
and the berries drop off
in transit.
On the berries, when
they are attacked direct-
ly, as is most frequently
the case, the disease is
at first quite inconspicu-
ous. A slight discolora-
tion, rosy on the varie-
ties with white or green
Fig. 60.-Bitter-rot on Herbert grapes, fruit and rose-brown on
showing the innumerable pustules with the varieties with red
their sooty-black spore-masses dotting fruit is the first mani-
the surface of the diseased berries and
the shriveling and collapsing of the ear- festation of the disease.
lier infected berries at the center of the Purple and black grapes
cluster. Natural size. Purple and black grapes




Florida Agricultural Experiment Station


show but little change of color when first attacked but later the
rotted areas acquire a brownish, water-soaked appearance
The discoloration begins on the diseased side of the berry and
rapidly spreads over it, often in concentric zones. Ultimately
the whole berry is involved and assumes a uniform livid-brown
color. Berries attacked while still green, however, often de-
velop a pronounced purplish discoloration.
During the early stages of the disease the affected berry re-
tains its original contour and remains plump, often becoming
more juicy than is normal. Soon numerous minute, slightly
elevated points dot the surface more or less thickly, indicating
that the fungus has commenced to produce its spores. Within
two or three days, under favorable weather conditions, these
developing pustules rupture the skin of the berry and push out
small, broadly rounded, sooty-black masses of spores (fig. 60).
These are usually larger and more prominent than those formed
in the case of black-rot and
are scattered more or less
evenly over the surface of
the berry instead of being
confined to a definite dis-
eased area as in the case of
black-rot. The size of these
spore-masses depends large-
ly upon the amount of mois-
ture available. Under dry
conditions they remain very
small and inconspicuous, but
under moist conditions they
may develop so abundantly
that spore-masses from ad-
joining pustules may unite
Fig. 61.-Bitter-rot on Moore Early and become continuous, ap-
grape, enlarged 21/2 times to show pearing like small blisters
the characteristic sooty-black spore-
masses exuded from the numerous in the skin (fig. 61). When
pustules dotting the surface of the the surface of such a berry
berry. becomes wet with dew or
rain, and it is touched with the fingers, the sooty-black spore-
masses become smeared. In case there was any free moisture
on the surface of the berry there will be a dark-colored smear
on the fingers, which contains literally thousands of spores of
microscopic size that have gone into suspension in the water.




Bulletin 178, Diseases of Grapes in Florida


Well-ripened berries begin to shrivel with the formation of
the spore-masses and soon appear more or less collapsed. The


S


Fig. 62.-Progressive stages in the decay of green Concord grapes at-
tacked by bitter-rot, showing the abundant sooty-black spore-masses
developed from the pustules dotting the surface of the berries and the
gradual mummification of the berries. 3/5 natural size.
diseased berries continue to shrivel and eventually closely re-
semble black-rot mummies in appearance (fig. 62). Berries at-
tacked by bitter-rot are further characterized by a bitter taste,


Fig. 63.-Shelling of berries on Thomas grapevine as a result of their at-
tack by bitter-rot.
which is more apparent in some cases than others. In advanced
stages of the decay, or even before spore production is well ad


I*



40


In





Florida Agricultural Experiment Station


vanced, the berries usually drop from their stalks, or "shell off"
(fig. 63). This ready shelling of the berries attacked by bit-
ter-rot is a very characteristic feature of the disease and one
that quickly attracts the attention of those who cut or sort and
pack the grapes. In many cases the dislodged berries lack any
superficial indication of the fungus but have a more or less
pronounced moldy or bitter flavor and soon develop the pus-
tules and the characteristic spore-masses when incubated in
a moist chanrber for one or two days.
In addition to attacking the fruit while on the vines, this
rapidly developing disease continues its activity after the grapes




I ... ., I' '1 I I '?' d
V i .. ,, ,
'- .! l '. '




*- c;. '.' 1 -- .
1--" .'-', ", '- ... i_ --- -;l -I

Fig. 64.-Section thru the skin of a grape attacked by bitter-rot, showing
the microscopic characters of a single, mature, spore-bearing pustule
that has burst thru the cuticle, cc. Below is the browned and dead
epidermis of the berry, dd, through which the filaments of the fungus
is growing. Above the cushion of mycelium a number of detached
spores are shown. At the right five of these spores are shown still
more highly enlarged. (After F. Lamson Scribner, in Report of the
Commissioner of Agriculture, 1887.)

are picked, if they are stored in a close place, or while on their
way to market. Under such conditions the spores of the fun-
gus produced on diseased berries can readily infect sound ber-
ries with which they come into contact, the rot developing in
the newly-infected berries within a few days. Upon the arrival
of the grapes on the market many of the diseased berries have
become dislodged from their clusters.
Cause: Bitter-rot is caused by the fungus Melanconium fuli-
ginewm (Scrib. & Viala) Cav. The mycelium of the fungus
penetrates in all directions the tissues of infected berries, even






Bulletin 178, Diseases of Grapes in Florida


entering their seeds. A compact growth, or cushion, of my-
celium develops at numerous points in the skin, rupturing the
latter and developing its spores on the free tips of the fungous
filaments (fig. 64). The superficially borne spores thus may
be disseminated readily by rain to other berries on the vine.
The writer has demonstrated repeatedly that the rot and the
initial stages of spore production can be reproduced regularly
in a week in the case of perfectly sound berries sprayed with
the spores and in still less time where the skin is first punctured
before spraying with the spores.
Control measures: Plowing the vineyard early in the spring
to bury the fallen mummied fruit, as has been recommended in
the case of anthracnose, black-rot and certain other fungous
diseases, is believed to be of equal value here. Likewise, any
cultural practices reducing the humidity or the stagnation of
the air in the vineyard will also be helpful.
Since bitter-rot, when present, develops so rapidly that it is
usually too late to control by spraying after it is observed, it
is desirable for growers who are troubled with a rotting of
their grapes just before or during the harvest season to make a
special effort to control this trouble the following year. In
case an application of Bordeaux mixture has been made a month
before picking time, a single finishing application of some fungi-
cide leaving a colorless residue, such as soda-Bordeaux mixture
or the copper acetates (see page 143) should prevent its destruc-
tion by bitter-rot and other associated ripe-rot fungi. In this
case it is only necessary to spray the fruit alone.

RIPE-ROT
Distribution and economic importance: Another decay of
ripe or ripening grapes, very similar to that of the bitter-rot
just described and usually termed ripe-rot, has been known in
this country for several years. The earliest record of the oc-
currence of this grape disease in the United States is in 1888,
when it was found on the grounds of the United States Depart-
ment of Agriculture in Washington, D. C. In 1890, when the
first report of its occurrence was published, ripe-rot was found
in Connecticut and New York. In this year the disease was
observed to occur in a number of vineyards and grape packing
houses in New York and appears to have occasioned quite a





Florida Agricultural Experiment Station


little destruction locally. While ripe-rot has proved quite de-
structive at times in some sections of the eastern United States,
it is less common and destructive than bitter-rot, with which
it may be associated. This disease is now known to extend
from Connecticut and New York south to Florida and west to
Illinois and Missouri.
Like bitter-rot, the development of ripe-rot is favored by a
high degree of humidity and hence is most to be feared when
such an atmospheric condition prevails during the ripening
period. Like bitter-rot again, ripe-rot appears when the fruit
is nearly mature and may, under favorable conditions, continue
its destruction of the fruit after it has been picked. It may
cause heavy loss in shipments.
Symptoms: On the berries the development and symptoms
of ripe-rot are very similar to those of bitter-rot. In fact these
two rots of ripening grapes are often confused. On white or
light colored
grapes a
small reddish-
brown spot

the attacked
side of the
berry. By
the time the
decay has
spread to
over half the
berr y the
spot becomes
Fig. 65.-Ripe-rot on Hicks grapes, showing the abun- darker in the
dant development of pustules and exuded spore-
masses, together with the shriveling of the berries, center, hav-
In the berry at the left the progress of the rot is ing a pur-
marked by a series of concentric zones. Enlarged lish center
three times. plish center
blending into
a light-brown border. With the progress of the disease the de-
cay soon involves the whole berry. In purple grapes no appre-
ciable change of color is caused by the rot unless the berries
be attacked before they color normally. Often, altho by no
means always, the advance of the rot is marked by a series of
concentric zones (fig. 65, left), as is commonly the case in bit-
ter-rot of apples caused by the same fungus.





Bulletin 178, Diseases of Grapes in Florida


In the earlier stages of its development ripe-rot can be dis-
tinguished from bitter-rot of grapes only by microscopic ex-
amination of the spores. By the time the rot has spread to the
whole berry the surface becomes more or less densely covered
with numerous, inconspicuous, slightly elevated pustules, from
which the spores ooze out in slimy masses, provided a favor-
able degree of humidity prevails. These spore-masses are pink-
ish, or flesh-colored at first but later become darker, even red-
dish-brown with age. Sometimes, especially during nights
when a heavy dew has fallen and there is an abundance of
moisture in the air, the spores will be discharged in the form
of tendril-like masses. Until the characteristically colored
spore-masses have exuded from the pustules it is impossible,
without microscopic examination, to identify the disease from
other closely related ripe-rot diseases with assurance.
With, or shortly after, the exudation of the spore-masses
from the pustules the diseased berries develop a sunken area
at the point of infection and gradually become more or less
shriveled and mummified. The pustules on the diseased grapes
often continue to produce spores and hence retain their flesh-
colored appearance even after the berry is nearly all dried up.
As in bitter-rot, however, the infected berries commonly "shell"
or drop off before the rot has progressed to this late stage.
While both fungi cause rots of ripe or ripening grapes, the one
causing the rot designated as ripe-rot does not impart a bit-
ter flavor to the attacked berries as does the one causing the
previously described rot designated as bitter-rot.
Cause: Ripe-rot of grapes is caused by the fungus Glomer-
ella cingulata (Atk.) Spauld. & v. Schrenk. This fungus also
causes the well-known bitter-rot of apples and the ripe-rot of
a number of other fruits and certain vegetables. The develop-
ment and behavior of ripe-rot is very similar to that described
for bitter-rot.
Control measures: The method of control of ripe-rot is iden-
tical with that given previously for bitter-rot (page 113).

ROOT-ROT

Distribution and economic importance: Root-rot of grape-
vines has long been known in Europe, where it has been care-
fully studied by French, German and Italian investigators, and





Florida, Agricultural Experiment Station


is known to occur in practically every grape-growing country
thruout the world. Grape vine root-rot was reported in this
country first from Missouri in 1887 and subsequently in the
same year was found in northeastern Texas and in Napa Valley,
California. During later years various writers have more or
less briefly reported a root-rot of grapevines in other parts of
California. Texas and Missouri, and in Arkansas, North Caro-
lina, Alabama, and Georgia. While apparently not reported pre-
viously from Florida, this disease is by no means unknown here.
Unlike the other diseases of grapevines already discussed, root-
rot is not of general occurrence over any part of the country
but is solely of local occurrence. It is nevertheless a fairly com-
mon vineyard disease in many localities, at least in the southern
portion of the country, where it ranges from coast to coast.
Some of the root-rots attacking the grapevines may also attack a
number of the more commonly cultivated fruit trees, as well as
many hardwood ornamental and forest trees, particularly the
oak.
Symptoms: The following description of the symptoms of
root-rot applies more or less equally well to grapevines regard-
less of the particular fungus causing the disease. Often, with-
out any cause apparent to the vineyardist, one or more vines
will suddenly exhibit a sickly appearance which is most evident
in midsummer, when the demand for water conduction is great-
est. At this time the margins of the leaves on diseased vines
suddenly brown, usually shortly before the ripening of the fruit.
Later the leaves may dry up entirely and the vines suddenly
die, leaving the fruit to dry and shrivel in the sun, or the crop
may mature and the vines linger along until fall, being found
entirely dead at the winter pruning. In other cases only a part of
the vine will die, some branches putting forth a feeble growth for
two or three seasons longer. In poorly drained sections of vine-
yards, where root-rot has become prevalent, the vines may con-
tinue to die out from year to year until but a small percentage
of the original stand may be left (fig. 66).
When vines attacked by root-rot are dug up and the outer
fibrous bark peeled off, the root-crowns and larger roots invari-
ably reveal a whitish to creamy-white or light tan-colored my-
celial coating or sheet. The marginal portions of this fungous
growth usually spread out in more or less of a fan-shaped man-
ner and the older parts often form a felt-like layer between




Bulletin 178, Diseases of Grapes in Florida


the outer bark and the wood (fig. 67). In the case of the mush-
room root-rots there is often, altho by no means always, pres-
ent beneath the bark a number of more or less flattened black
rhizomorphs. These are branching strands of the fungus which
facilitate its spread underground. The inner living bark will
be found to be more or less extensively invaded by the growth of





















Fig. 66.-Depletion of grapevines by Clitocybe root-rot in poorly drained
end of an 18-year-old vineyard where the vines continue to die out froa
year to year.

mycelium, which usually can be traced from one to three inches
above the ground-line and down onto the larger roots. In well-
advanced cases the fungus is most evident on the crown and
larger roots. In the mushroom root-rots there is usually com-
paratively little decay of the wood until after the death of the
vine, in which case transverse sections through these parts re-
veal radial streaks of more or less delignified wood. The ex-
tensive development of the mycelium soon leads to the forma-
tion of radial cracks in the wood, which become stuffed with
light tan-colored sheets or felt-like mats of mycelium often ex-
tending in to the pith.
When the mycelium has developed sufficiently thru the wood
and inner living bark to cut off either wholly or in part the
water supply, the vine dies more or less suddenly. If this oc-




118 Florida Agricultural Experiment Station
curs dur-
ing the
summer
the vine
may be
dead with-
in a few
days from
the time
the leaves
began to
wilt.
In the
case of
the mush-
r o o m
root rots
one often
finds i n
vineyard&
and or-.
chards
s u ff e r-
ing from
root rot,
9 clusters of
m u s h-
rooms or
toadstools
frui t-
ing from
the root-
crowns of
attack-
ed vines
o r trees
,(fig 68).
These
usual-
Fig. 67.-Rootstock of grapevine recently killed by Clito-
cybe root-rot. The outer, fibrous bark has been cut near ly are de-
the top of this picture and peeled away to show the whit- veloped
ish to isabelline mycelial mat and the black rhizomorphs
at the point marked R. The level at the top of the pic- during the
ture was but a short distance below the ground-line. % late sum-
natural size.




Bulletin 178, Diseases of Grapes in Florida


mer and autumn in years favorable to the development of the
fungus.
Cause of root-rot: Altho cases of grapevine root-rot have
been reported in various sections of the United States for many
years, little
eff ort has
Seen made to
demon-
strate the
causal organ-
ism, it hav-
ing been gen-
erally attrib-
uter to two
of the higher
fungi (Armil-
laria mellea
and Demato-
phora n e c a-
tri,). This,
however, was
done merely
o n assump-
tion rather
than on any
definite
grounds b e-
cause these
two fungi
were known
to commonly
cause roo t-
rot of grape-
Fig. 68.-A cluster of the mushrooms, or fruiting v i n e s and
bodies, of Clitocybe tabescens developed from the
root-crown of a 6-year-old peach tree attacked by other woody
root-rot. (Photo by courtesy of the Missouri State plants in Eu-
Fruit Experiment Station.)
rope. Root-
rot of grapevines and other woody plants in this country has
been shown to be caused by a number of different fungi, most
of which belong to that group known as mushrooms or toad-
stools. But two of this group are known to be of sufficient




Florida Agricultural Experiment Station


prevalence in the southeastern United States to justify mention
here.
The honey agaric (Armillaria mellea) is a cosmopolitan mush-
room which commonly causes a serious root-rot of many woody
plants in different sections of this country and is known to
cause root-rot of grapevines in Europe. While it is said to at-
tack grapevines in this country, this point has never been dem-
onstrated.
Another mushroom (Clitocybe tabescens), which frequently
causes a root-rot of fruit, forest and shade trees in the southern
states from Florida to Oklahoma and Texas, has been demon-
strated recently by the writer to cause a considerable amount
of root-rot of grapevines in Missouri. It seems likely that many
cases of this trouble reported in the Southern states are caused
by this fungus.
The mushroom root-rots are most prevalent in poorly drained
land and in newly cleared hardwood forest land. They may
either attack living woody plants or grow saprophytically on
stumps, roots and other wood left in the ground. The dissemi-
nation of these fungi may be accomplished both by the spores
produced in great numbers on the fruiting bodies, which are
usually developed in clusters at the bases of diseased vines dur-
ing the late summer and autumn in seasons favorable to the
growth of these fungi, and by means of strands termed rhizo-
morphs, which enable the fungus to spread thru the soil.
Control measures: A little attention directed to preventive
measures will obviate the necessity of applying remedial meas-
ures in combatting root-rot, which latter are, at best, but tem-
porary expedients. In selecting a site for a vineyard planting
newly cleared land, especially in a region of oak forests, should
be avoided since the fungus may live in the soil as a saprophyte
on dead wood. such as stumps, roots and pieces of these. The
character of the disease suggests the need for the thoro prepa-
ration of cleared lands, including the removal of all roots and
cultivation for at least three years in other crops before setting
out to grapevines or fruit trees. In any case land which prom-
ises poor natural drainage should be avoided unless artificial
drainage can be assured at a reasonable cost. In the cultiva-
tion of the vineyard care should be taken to prevent barking or
otherwise injuring the roots of the vines, since such injuries
favor infection by root-rotting fungi. Control of the grapevine
root-borer and root-worm is also essential for the same reason.





Bulletin 178, Diseases of Grapes in Florida


After root-rot appears in the vineyard the vines that have
been seriously attacked cannot be saved, altho measures can be
taken to check the spread of the disease and to save recently
attacked vines. Since an excess of moisture in the soil is one
of the chief conditions favoring the development of root-rot,
adequate drainage is the most valuable preventive and correc-
tive measure. Unless this precaution is undertaken all others
are useless, since vineyards that have become affected by root-
rot fungi are, unless drained, always subject to attack by it.
As soon as root-rot is discovered in a vineyard, all vines that
have been killed by it and all diseased vines should be removed.
These vines should be excavated carefully to remove all the
roots, which should be burned. Then, if the hole be left ex-
posed to the air and sun for a few weeks, or the disinfection
of the soil accomplished by the use of chemicals, it should be
safe to replant. A 3 percent solution of copper sulphate has been
used as a disinfectant with good results in European practice.

CROWN-GALL
Distribution and economic importance: This disease, which
is variously termed crown-gall, crown-knot, root-tumor, and
black-knot, apparently affects the grape wherever it is grown.
In the United States crown-gall has been found more particular-
ly in California, Arizona, New Mexico, Texas, Washington, Ore-
gon, Colorado, Nebraska, Missouri, Arkansas and Iowa. It was
common in California as early as 1880. The earlier records give
the impression that it was very destructive but now the disease
is not regarded as being of great economic importance on grape-
vines.
Symptoms: The disease manifests itself by the develop-
ment on the root-crown, stem or cane, of abnormal gall or
tumor-like structures. These are often of considerable size and
prominence in proportion to the diameter of the stem, as is
shown in figure 69, but at other times consist of numerous small
galls or warty growths united into elongated masses on the
stems and canes. The former type of gall is most frequent on
the European varieties of grapes, while the latter type is the more
common form on the American varieties. Young galls are com-
paratively small, greenish, relatively smooth or even spongy.
Mature galls are dark in color, with a roughened surface, and
usually are hard.





Florida Agricultural Experiment Station


Crown-gall is usually more common on the European varie-
ties than on American ones and, on the latter, does not generally
cause serious loss. The disease does not kill the vine outright
and occasionally,
if well rooted, at-
tacked vines ap-
pear to recover.
In severe cases
of attack, how-
ever, vines are
s t u n t e d, the
leaves become
smaller and chlo-
rotic, and even
unfr u itful-
ness has been ob-
served. In vine-
yards the disease
has been found
most frequently
in heavy or wet,
poorly drained
spots an d, in
some cases, ap-
pears to follow
winter injury of
the vine.
Cause: Crown-
gall is a disease
Fig. 69.-Crown gall developed at the root-crown gall is a disease
of an Ellen Scott grapevine. Natural size. caused by t h e
bacterial organ-
ism Bacteriutm tumefaciens Smith & Townsend. The same organ-
ism causes crown-gall in the almond, apricot, apple, peach, black-
berry, raspberry, English walnut, and a great variety of other
plants. The causal germ is a wound parasite which, after gaining
entrance to the root, stem or cane of the vine, stimulates the cells
to excessive multiplication. This abnormal development of the
attacked tissues manifests itself in the gall or tumor-like struc-
ture previously described. The bacteria may live independently
scattered thru the soil, or in old galls which may persist from
year to year. The bacteria may be transmitted by cuttings from





Bulletin 178, Diseases of Grapes in Florida


diseased plants and by insects, injuries in cultivation and prun-
ing, and by water of irrigation. Recent investigations have
shown that growths similar to crown-gall are often developed
on grafted plants where a poor union is made.
Control measures: Since the germ producing crown-gall
lives in the soil, this disease cannot be combatted by spraying.
Diseased plants showing galls at the root-crown or lower part
of the stem should be dug up and destroyed by burning. The
removal of such galls is not effective in controlling the disease,
since the bacteria occur within the stem at this point and new
galls may arise after the cutting out of the original one. Where
galls are confined to branches the latter should be cut off at
sufficient distance below the gall to include all diseased tissues.
In setting new plants care should be taken to see that they are
entirely free from any signs of galls on the roots, stems or
canes, for crown-gall is very frequently propagated in nur-
series. Since this disease also attacks various fruit trees, bushes
and other cultivated plants, soil where such diseased plants
have been found should be avoided in planting grapevines.

LEAF-BLIGHT

Distribution and economic importance: Leaf-blight is one of
the relatively unimportant grape diseases that has received but
little attention. In the United States it is found most abun-
dantly in the Southeastern states. It occurs on a great variety
of wild and cultivated vines. When prevalent, this disease may
cause considerable defoliation and consequent injury to the
vine. However, unless the season is a very wet one, leaf-blight
is not likely to do much damage, except, perhaps, in low or damp
situations, or upon vines improperly cared for.
Symptoms: In Florida grape leaf-blight does not develop
appreciably until after the middle of the summer. Occurring
at this time, after the fruit has been harvested and spraying
is no longer considered so necessary, considerable defoliation
of attacked vines may often result. On the lower and more
shaded leaves in particular, irregular or angular brown spots,
varying in size from one-sixteenth to one-eighth, or sometimes
one-fourth of an inch in diameter, occur, which have a clearly
defined and slightly thickened or elevated border. These dis-
colorations extend thru the thickness of the leaf, the diseased




Florida Agricultural Experiment Station


spots soon becoming black on both sides and dry and brittle
(fig. 70). On leaves near the ground, in close contact with
grass and weeds so that a high degree of humidity is maintained,
large marginal areas often become blackened. On the under
surfaces of these spots there can be seen by close observation,
but more readily with the aid of a hand-lens, numerous project-
ing, hair-like bristles, which are the fruiting bodies of the causal


Fig. 70.-A grape leaf, showing the characteristic appearance
of the leaf-blight disease. 2/3 natural size.
fungus. As the disease progresses the tissues of the severely
attacked leaves become generally affected, changing to a pale
green or yellow, and finally the whole leaf becomes so weakened
that it drops.
Cause: Grape leaf-blight is caused by the fungus Isariopsis


FJ






Bulletin 178, Diseases of Grapes in Florida


clavispora (B. & C.) Sacc. A microscopic examination of the
inconspicuous, black, hairlike processes developed so numer-
ously on the under sides of the spots shows them to consist of
a closely packed bundle of slender, unbranched fungous fila-
ments with free and somewhat irregular spreading tips (fig.


71). These short, thread-like fruiting
bodies vary in length from one- to
three-two hundred and fiftieths of an
inch in length. Upon the free and
spreading tips of these filaments are
borne elongated and somewhat club-
shaped spores, each rounded at its
apex and tapering into a slender stalk-
like base. These spores are olive
brown, like the fungous filaments upon
which they are borne, and are divided
by cross-walls into from 3 to about 10,
or rarely more, cells. The form of
this fungus described is the only stage
in its development yet known. The
spores apparently live over the winter
on the fallen leaves.
Control measures: It will rarely be
necessary to make an application of
Bordeaux mixture for the control of
leaf-blight alone. However, should the
disease be inclined to cause too heavy
premature defoliation, one or two ap-
plications made during the middle of
the summer will prove valuable in
maintaining the vigor of the vines. It
should be remembered that vines main-
tained in full vigor to the end of the
growing season are enabled to store up
a larger supply of reserve food mate-
rials and are in better position to de-


F i g. 7 1. Microscopic
characters of the
grape leaf-blight fun-
gus, showing one of
the spore-bearing or-
gans with the septate
spores borne on the
loose ends of the com-
pacted column of fun-
gus filaments. High-
ly magnified.


velop and carry fruit the following year. Applications of a
quickly available nitrogeneous fertilizer in mid-summer will
also aid in maintaining the vigor of the vines and help ward
off leaf-blight.






Florida Agricultural Experiment Station


LEAF-RUST

Distribution and economic importance: But little is known
concerning leaf-rust, which has been found to occur in Flor-
ida within recent years. The disease was first described on
leaves of Vitis vinifera from South Carolina but the specimens,
upon subsequent examination, are said to bear no rust what-
ever. In 1923 leaf-rust was reported in Santa Cruz County,
California.
In Florida grape leaf-rust is known to attack a number of va-
rieties of grapes, including Armalaga, Blondin, Carman, Champ-
anel, Fern, Goethe, Herbemont, Lenoir and Wapanuka. It also
occurs frequently on the most common native wild grape, Vitis
munsoniana. At present leaf-rust in Florida is known to occur
only in the central portion of the peninsula from Gainesville
south.
Cause: Leaf-rust is caused by the fungus Physopella vitis
(Thium.) Arth., a close relative to the fungus causing fig rust.
The cycle of development of this fungus is imperfectly known,
only two spore stages having been found thus far. The disease
appears in late summer and fall, at which time small, yellowish-
brown spore-masses (uredinia) or "rust-spots" appear on the
under sides of infected leaves. Later another and darker spore
stage teliaa) develops. More or less defoliation occurs as a re-
sult of attack by this rust but thus far this disease occurs so
late in the growing season that the damage to the vines appears
negligible.
Control measures: Spraying with fungicides for the control
of rust diseases of plants in general has not proved practical
and it is not expected that grape leaf-rust will prove any excep-
tion to the rule. In view of this and of our imperfect knowl-
edge of the life history of the causal fungus no definite meas-
ures can be recommended for the control of this disease.

INJURIES DUE TO PHYSIOLOGICAL CAUSES
NON-SETTING OF FRUIT

Distribution and economic importance: The failure of grape-
vines to set fruit, or of the berries to develop appreciably after
blossoming, is often a trouble of considerable economic impor-
tance that is very puzzling to the grower. This trouble has






Bulletin 178, Diseases of Grapes in Florida


been termed "coulure" by the French viticulturists, and is ex-
perierced thruout the range of grape culture.
Cause: The non-setting of grapes, or coulure if we accept
the more convenient term, has been studied by a large number
of investigators and a variety of causes assigned. These may
be either constitutional or accidental.
In the case of coulure as a result of constitutional causes, by
far the most important factor to be considered is the lack of
self-fertility of certain varieties due to imperfect development
of the flowers or to lack of functional activity of the pollen pro-
duced. The work of a number of investigators has shown that
a large number of grape varieties are more or less incapable
of setting fruit if planted alone but that, like the pistillate
strawberries, they must depend upon the pollen of other varie-
ties for perfect fertilization and fruitfulness. A striking ex-




















Fig. 72.-Failure of Moore Early grapes to set fruit as a result of the cold,
rainy weather that prevailed during the blooming period. A normal
cluster is shown at the left. 1z natural size.

ample of self-sterility is offered by the R. W. Munson grape often
grown in Florida. In other instances the flowers may seeming-
ly be perfect in their organs and yet fail to develop fruit. In
Europe this has been regarded as an inheritable character of
certain vines.
Coulure as a result of accidental causes has been shown to






Florida Agricultural Experiment Station


be due to such factors as unfavorable weather conditions or
fungous attacks occurring at flowering time, spraying while in
bloom, improper pruning, a deficiency in the supply of reserve
food materials in the canes due to its depletion by excessive vege-
tative growth or by overbearing the preceding year, unsuitable or
exhausted soil, and the absorption of excessive material from
soils extremely poor in nitrogen and phosphoric acid. The
first two of these factors probably are the ones most frequently
involved. A cold, rainy season alone at blooming time will suf-
fice to retard the fertilization of the flowers so that they may
drop in greater or less number without setting fruit, or the
fruit may develop for a time but quickly fall off before attain-
ing any appreciable size. This often results in more or less
straggly bunches (fig. 72), and the loss may amount to as high
as 50 percent of the crop in susceptible varieties.
Control measures: The application of remedial measures for
the prevention of non-setting of grapes obviouslyis futile where
caused by unfavorable climatic conditions. The failure of more
or less self-sterile varieties to set fruit can be overcome easily
by planting near them varieties noted for their ability to pro-
duce abundant and vigorous pollen and that bloom at the same
time as the variety to be pollinated.

SHELLING OF FRUIT
Distribution and economic importance: The dropping of
more or less fully developed grapes from the bunches shortly
before maturity has troubled many grape growers in certain
sections of the United States for at least half a century. This
trouble, which is commonly termed "shelling" or "rattles," has
been reported especially from Connecticut, Michigan, central
and western New York, and Pennsylvania. In severe cases it
may cause a loss of as high as 50 percent of the crop.
Symptoms: Grapes affected by shelling as a result of pure-
ly physiological derangements usually fall two or three weeks
before maturity, the normally fibrous connecting tissues of the
berry stalk cleaving smoothly at the point of junction with the
berry. The berries at the end or at the extremity of the shoul-
der of the cluster, as a rule, are the first to fall. The affected
berries, particularly of the green varieties, often exhibit a pe-
culiar, tho indistinct, mottling of the surface; the skin becomes
abnormally thick and the whole berry is harder than normal





Bulletin 178, Diseases of Grapes in Florida


berries of the same age. The interior of such a berry shows a
brown zone immediately beneath the skin and the taste is notice-
ably insipid as compared to the tart, astringent flavor of the
normal, unripe berries. Shelling is by no means always accom-
panied by discolorations of the foliage, nor is a browning of
the leaves a certain indication of the trouble.
Cause of shelling: Like non-setting, shelling is also due to
a variety of causes, most of which come under the category of
unbalanced nutrition and unfavorable climatic conditions. The
agencies that contribute to shelling generally are considered to
be the following: a weakening of the vines due to overbearing,
heavy vegetative growth in proportion to the root system, at-
tack of the vine by root-rot, root pruning caused by too deep
tillage, prolonged drought or excessive rain followed by drought,
poor drainage, and lack of sufficient nitrogen in the soil. It
has also been held that a lack of potash is the primary cause in
many cases, altho there is considerable evidence that this is not
a factor.
The shelling of mature or nearly mature grapes may occur
also as the result of certain fungous diseases of the fruit, altho
shelling, as understood in American literature, is limited to the
dropping of berries resulting from purely physiological dis-
orders.
Control measures: In order to prevent shelling of the more
or less fully matured fruit occurring as a result of purely phy-
siological disorders it is obvious that steps should be taken to
correct any cultural conditions that tend to result in a deficient
or unbalanced nutrition of the vines. The soil should receive
attention and the proper fertilizer which it needs should be
applied. Care should be taken to properly fertilize the vines
that have been allowed to overbear, as well as those that have
been allowed to carry an excessive amount of wood; such vines
require a greater food supply. Excessive cultivation, especially
of poorly nourished vines, seems to aggravate shelling, probably,
on account of the root pruning resulting from this operation.
Closer pruning, which tends to reduce the amount of fruit borne
by the vine, will help. In France the pinching off of the shoots
bearing fruit after the development of from six to eight leaves
beyond where the grapes are borne, or after the development of





Florida Agricultural Experiment Station


from 12 to 15 leaves on those shoots not carrying fruit, is said
to give satisfactory results in the control of shelling. By this
practice the material elaborated by the vine is carried to the
grape clusters instead of being utilized for greater growth of
the shoots.
CHLOROSIS

Distribution and economic importance: Chlorosis is the
term applied to that abnormal condition assumed by the leaves


Fig. 73.-Chlorosis on leaf of muscadine grapevine. Natural size.

of plants when they fail to develop the normal amount of green
coloring pigment and remain yellowish or whitish. Chlorosis,
then, does not denote a specific disease, the chlorotic condition
being merely the result or external symptom of a disturbance





Bulletin 178, Diseases of Grapes in Florida


in the physiology of the plant. Chlorosis of grapevines, which
has been reported from various sections of the United States,
occurs on both wild and cultivated vines, some varieties show-
ing this more than others.
Symptoms: Leaves on affected vines may exhibit chlorosis
to greatly varying degrees. In mild cases the leaves may show
slightly yellowed areas at points along the margin of the leaf.
In more severe cases these yellowed areas may extend inward
between the prominent lateral veins so that the leaves exhibit
a decided mottled or "frenched" appearance (fig. 73). In very
severe cases the yellow color may extend over the entire leaf.
In such cases brown, dead patches may appear and the leaf
may curl and eventually drop from the vine. One striking pe-
culiarity of chlorosis is that a badly affected vine may occur
by the side of a perfectly healthy one of the same variety.
Cause of chlorosis: Altho known and studied for many
years in Europe, grape chlorosis has received virtually no at-
tention in this country. It has been known for many years that
some plants become affected with chlorosis when they are grown
on soils containing very large amounts of carbonate of lime.
Other calcium salts and other carbonates do not seem equally
effective in causing chlorosis. Probably the best example of
grapevine chlorosis is to be found on certain highly calcareous
soils of France, in which country certain American stocks have
been found to be quite tolerant of such soils.
The favorable effect of salts of iron on plants affected with
lime-induced chlorosis was discovered before the middle of the
last century, when it was found that spraying a solution of an
iron salt on chlorotic leaves resulted in correcting the chlorotic
appearance. It has been generally concluded that the chlorotic
condition is brought about by the excessive amount of carbonate
of lime retarding the assimilation of iron by the plant. Chlo-
rosis, however, may be induced by deficient drainage, lack of
adequate nutrition, and other causes, so that all cases of chlo-
rosis of grapevines cannot be attributed to an excessively cal-
careous soil.
Control measures: Chlorosis of grapevines induced by ex-
cessive amounts of carbonate of lime in the soil has been suc-
cessfully treated in French vineyards by spraying affected
vines at intervals of a few weeks with about a 1 percent solu-
tion of ferrous sulphate copperass). Stronger applications often





Florida Agricultural Experiment Station


result in burning of the foliage under some conditions. Appli-
cations of this iron salt made to the soil have proved less effec-
tive than spraying the foliage with dilute solutions of the salt.

IRREGULAR WATER RELATIONS
A number of different types of dying vines or parts of vines
are sometimes observed in Florida vineyards where the cause
obviously is due solely to extremes of variation in the level of
the water table. One form of the dying of vines or parts of
vines occurs when the soil becomes saturated in rather low or
poorly drained portions of the vineyard as a result of heavy
rains. In such cases affected vines suddenly drop a large por-
tion, or even all, of their foliage shortly after the soil becomes
water-logged. This is followed by a more or less severe dy-
ing back of the shoots and often more or less of the canes and
arms in addition. After the lapse of a few weeks, sprouts are
developed from the lower trunk or arms of the vines, which re-
mained living. The dying back of the tops of any vine so af-
fected is the result of the natural balancing of the vine necessi-
tated by the reduction of the root system caused by the death
of many of the smaller roots.
Other and usually less conspicuous cases of dying of parts of
apparently healthy vines also occur at times, the cause of which
is less obvious. In some cases the leaves wilt, turn brown and
become dry; at the same time the green bark on the shoots
changes to a reddish-brown and shrivels. In severe cases even
canes or whole arms may succumb on affected vines without the
other canes or arms being affected. Such dying, as a rule, usu-
ally is not of general occurrence thruout vineyards exhibiting
this trouble but of a rather sporadic nature. Vines making a
vigorous, robust growth are more apt to suffer in this way than
weaker ones.
Such a sudden death of parts of healthy vines is regarded as
a physiological trouble in contradistinction to a disease. Such
a dying has long been looked upon as obscure but the usual ex-
planation is that it is the result of the disturbance of the equili-
brium between the water absorbed from the soil by the roots
and that transpired by the leaves. Climatic influences and the
relative position of the water table with regard to the roots
seem to have much to do with its occurrence. It is most fre-
quent when dry hot weather immediately follows a rainy or
humid spell, especially when there is abundant moisture in the





Bulletin 178, Diseases of Grapes in Florida


soil. During the rainy or humid weather transpiration is great-
ly reduced and the roots, becoming accustomed to sending up
a small supply of moisture, then fail to respond quickly enough
to the demand made upon them when dry, hot atmospheric con-
ditions suddenly follow. On the other hand, this trouble is
even more apt to occur in time of drought, particularly after
a period of abundant rain. At such times the water table may
drop so far below the range of the fibrous feeding roots that
the root system may be injured to such an extent that it is no
longer able to fulfill the transpiration demand made upon it.
Another form of this trouble may also be induced by the lack of
affinity between the stock and the scion.
Control measures: It is perfectly obvious that vine troubles
due to irregular water relations must be controlled by preven-
tion rather than cure. Those who have such troubles should
take the proper steps immediately to prevent their recurrence.
Before deciding upon the planting of an area to grapes the
grower would do well to investigate the land sufficiently to
thoroly acquaint himself with the general character and physical
properties of the soil, including, of course, the subsoil. He
should consider the topography in relation to natural drainage.
He should also consider the type of soil, its physical properties
and water-holding capacity, the relative amount of organic mat-
ter, the presence and proximity of hardpan and marl to the sur-
face, and the extremes in the variation of the water table during
the wet and dry seasons of the year. A little time devoted to an
investigation of these extremely important considerations should
eliminate subsequent losses and failures as a result of planting
on land that may ultimately prove unsuitable as a vineyard site.
Applications of a fertilizer rich in nitrogen are especially
beneficial in maintaining the vigor of the vines after a pro-
longed rainy period during the growing season. This is especi-
ally true on the lighter soils, from which the nitrogen is readily
leached.

INJURIES DUE TO METEOROLOGICAL CAUSES
AND ANIMALS
SUN-SCALD

Unless the clusters of grapes are protected from the direct
rays of the sun by an ample leaf canopy they are apt to become
scalded. Sun-scald of the berries is especially apt to occur on





Florida Agricultural Experiment Station


vines making a weak growth of foliage. It is also of common
occurrence on normally healthy vines that have been given a


Fig. 74.-Sun-scald of poorly shaded clusters on young Delicious vine.
more or less heavy summer pruning in the belief that the ad-
mission of more light will stimulate the fruit to ripen earlier.
The clusters of fruit that are exposed to the strong rays of





Bulletin 178, Diseases of Grapes in Florida


the sun, especially if suddenly exposed by summer pruning,
frequently acquire a coppery hue or become bronzed. Frequent-
ly they may become scalded on the exposed side, after which
the injured berries merely rot or shrivel up instead of ripen-
ing (fig. 74). Even in case the berries on one side of the clus-
ter merely become bronzed they ripen but slowly, requiring
even more time to attain the degree of ripeness at which they
are suitable for picking than those of clusters allowed to ripen
under the protection of ample shade. Even when apparently
well colored, such berries have more or less of an acid taste and
never become as sweet as those of the clusters protected from
the sun by ample shade. As a matter of fact, experimental evi-
dence indicates that the summer pruning of bearing grapevines
is never justifiable.

LIGHTNING INJURY

Lightning strokes, when occurring in vineyards, commonly
result in a very sudden dying of the vines, the cause of which
often remains a mystery to the grower. In case the lightning
strikes a trellis wire it may be conducted along the wire for
several rods before the discharge becomes grounded, and fre-
quently it may run the whole length of the trellis. The dis-
charge, which is communicated to all the living parts of the
vines in contact with the wire or wires over which it travels, is
greatly favored if the vines have first become drenched with
rain. If struck during the season of active growth the young
shoots and their leaves suddenly wither and die, the effect being
quite striking within a few days after the occurrence of the
stroke.
Where the main stem or arms of an affected vine remain un-
injured it may put forth new shoots so that the vine soon ap-
pears as vigorous as ever. In other cases, however, the injury
is by no means confined to the shoots that wither a few days
after the stroke, but the vines or parts of vines that are not
killed outright often continue to die during the next year or
two. In such cases the roots probably were injured, for it seems
likely that this may result from the conduction of the discharge
thru the soil. With the lapse of a few months or a year the ex-
tent of the injury to the vines becomes fully evident. Some
die entirely; others die only to the ground and later send up





Florida Agricultural Experiment Station


basal shoots (fig. 75), while still others may have two or three
arms yet alive. Upon the latter there is a weak production of
both foliage and fruit and whatever fruit is produced is sub-
ject to sunscald as a result of the insufficient protection afford-
ed by the scanty leaf canopy. As a result of their greatly de-
creased vitality the vines not killed outright are especially sus-
ceptible to attacks by various parasitic fungi.


Fig. 75.-Lightning injury to vine in row where most of the vines were
more or less completely killed.

Control measures: Vines in which even the roots are killed
should be dug up and replaced by others; those that are but par-
tially killed usually send up basal shoots which should be trained
to replace the old bearing vine. The latter should be cut back
if dead, or as soon as it becomes unprofitable.
As a preventive measure, the use of metal posts instead of
wooden ones for the trellis should serve to ground the discharge
before it can travel any appreciable distance along the trellis
wires.

HAIL INJURY
Grapevines, in common with fruit trees and other vegetation,
are often severely damaged by hail, the extent of the damage
depending upon the severity and duration of the storm and the





Bulletin 178, Diseases of Grapes in Florida


size of the stones. In some localities hail storms are of rare
occurrence while in others they may be expected almost every
year. In Florida, fortunately, they do not occur very often.
By far the greatest menace of hail to the vineyard is the dam-
age to the fruit crop in the course of development. If the fruit
is injured
when still
very imma-
ture, the in-
jured berries,
unless knock-
ed off com-
pletely, con-
tinue their
develop-

may become
variously
cracked or
split open,
even to the .
point of ex- Fig. 76.-Hail injury on grape berries. % natural size.
posing the
seeds (fig. 76). Each of the injured portions on the individual
berries develops a hard corky layer. Even aside from the un-
sightly splitting of the berries, these hardened, scarified places
on the injured berries render them unpalatable. Where the
berries of the clusters have been quite generally injured by hail
they are unmarketable as table grapes and, unless they can be
used in juice extraction, must be a total loss.
Besides the injury occasioned individual berries, the stem of
the fruit cluster may be so badly injured that it can no longer
conduct nourishment to the cluster, in which case it may dry
up without ripening. Considerable damage may also be done
to the young shoots and leafy parts; both may be broken off
more or less abundantly and the latter may be variously split
and torn. Injury to the older parts is rarely of much conse-
quence since the hard, fibrous bark is less apt to be knocked
off than in the case of fruit trees, and the injured places usu-
ally callus over quickly (fig. 77).
Control measures: While hail injury, of course, is not pre-
ventable without protecting the vines by supporting wire





Florida Agricultural Experiment Station


screening above them, as has been practiced in certain parts
of Europe where hail is prevalent, the effects of the injury may
often be mitigated. In less severe cases of injury to the devel-
oping fruit it would be possible to go thru the vineyard, at least
in the case of smaller ones, and pick off the injured berries. If
this be done
while the grapes
are young the
clusters will close
up again more
or less complete-
ly as the grapes
grow. Whi le
this task will be
laborious, it
would be prefer-
able to have well-
Sformed clusters
at picking time
than to have to
pick the injured
berries from the
harvested c 1 u s-
ters, which would
then leave them
ragged and un-
sightly.

ANIMAL
INJURIES

Birds and rac-
coons often de-
Fig. 77.-Hail injury on grape canes. Natural size.
stroy a consid-
erable amount of fruit in vineyards. They may be controlled
best by the use of a gun or traps. Where only a few vines are
grown, birds may take a large proportion of the fruit. In small
vineyards damage may be avoided by bagging the fruit after
the third or fourth spraying. Rabbits often damage young
grapevines by eating off their tender growth. The use of repel-
lent washes, or of dried blood as a fertilizer around the vines,





Bulletin 178, Diseases of Grapes in Florida


usually will prevent such injury. The planting of varieties mak-
ing an abundant foliage is of value in lessening depredations by
birds.

PREPARATION OF SPRAY MIXTURES
FUNGICIDES
Bordeaux Mixture
Spraying is the most valuable immediate means of preventing
the development of fungous diseases and insects. Bordeaux mix-
ture, the standard fungicide for vineyard spraying, is prepared
by mixing together a solution of copper sulphate (bluestone) and


5


Fig. 78.-Bordeaux injury on grape leaves.


2/3 natural size.


milk of lime. When a solution of copper sulphate and milk of
lime are mixed together in the right proportions a complex chem-
ical reaction results between these substances and copper is
thrown down in the form of a light blue, flocculent gelatinous
precipitate. The fungicidal efficiency of Bordeaux mixture de-
pends upon the particular physical and chemical properties of
this precipitate, which in turn are governed by the method of
mixing the solutions.





Florida Agricultural Experiment Station


For vineyard spraying during the growing season the 4-3-50
formula is recommended for making the Bordeaux mixture. In
such a formula, which expresses the proportions of the mate-
rials used, the first figure designates the number of pounds of
copper sulphate, the second the number of pounds of lime, and
the third the number of gallons of water. Of course, when us-
ing hydrated lime to prepare the Bordeaux mixture one-third
more lime should be used than in the case of stone lime.
Preparation of the solutions.-If large quantities are to be
used it is best to prepare stock solutions which contain one
pound of the bluestone or one pound of lime to each gallon of
water. For example, take a barrel containing 25 gallons of
water and suspend, just below the surface of the water, a
coarse sack containing 25 pounds of bluestone. The bluestone
will require a few hours to dissolve in this way. If a solution
is desired quickly, hot water may be poured on the crystals, al-
though a few minutes stirring in unheated water will suffice to
dissolve the crystals. In another container slake carefully 25
pounds of good quicklime. The proper slaking of quicklime con-
sists in sprinkling it with a little water and leaving it for a
while in order to absorb this moisture. A little more water
should be added gradually from time to time, but just enough
to keep the lime slaking and to prevent it from becoming dry
and "burning", altho not enough to quench the heat generated
in the process. When thoroly slaked, add water to make up to
25 gallons, stirring thoroly.
Bordeaux mixture may also be made by using the hydrated
lime instead of the quicklime (lump or rock lime), in which case
one-third more lime should be used. It is only necessary to mix
the hydrated lime with the required amount of water since it
is lime that has already been slaked.
Mixing the solutions.-Bordeaux mixture may be made in a
satisfactory manner by several different methods. Where the
old standard method of mixing the solutions is employed for the
making of 50 gallon lots of the mixture the operator should pro-
ceed as follows:
1. Stir up the stock solution of copper sulphate thoroly, dip
out 4 gallons, pour into a barrel, and dilute by adding 21 gallons
of water. For convenience the 25 gallon level may be marked
in some way and the dilution made by adding water until this
point is reached. If powdered copper sulphate be used, sift






Bulletin 178, Diseases of Grapes in Florida


slowly 4 pounds of copper sulphate into 25 gallons of water,
stirring until dissolved.
2. Stir the stock milk of lime thoroly, dip out 3 gallons (bet-
ter to use 4 if a good grade of lime was not used), pour into an-
other barrel and dilute by adding 21 gallons of water.
3. Pour the two diluted solutions simultaneously thru the
strainer into the spray tank, stirring thoroly.
When large quantities of Bordeaux mixture are to be used,
much time may be saved if a Bordeaux mixing plant, especially
designed for the convenient handling of the solutions and the
water needed, be constructed. The main feature of this plant
is to have the bluestone,
lime and water conveniently
arranged on platforms high
enough to permit the solu-
tions to flow by gravity into
the spray tank (fig. 79).
The water supply tanks
should be on the upper plat-
form and connected by two-
inch pipes to the dilution
tanks, which may be con-
nected by a three or four-
inch pipe with a flexible
hose connected to an outlet
valve at the center of this
pipe, thru which the diluted
bluestone solution and the
diluted milk of lime may be
conducted simultaneously in- Fig. 79.-Bordeaux mixing plant.
to the spray tank below. By (From U. S. Department of
Agriculture Farmers' Bulletin
the side of each of these di- 1220.)
lution tanks a 50-gallon bar-
rel, one containing stock solution of bluestone and the other
stock milk of lime, should be placed. Each gallon of stock solu-
tion should contain 1 pound of bluestone or 1 pound of lime.
To make 200 gallons of Bordeaux mixture of the 4-3-50 for-
mula with a mixing plant of this type, dip out 16 gallons of stock
bluestone solution into the bluestone dilution tank and 12 gal-
lons of the well-stirred stock milk of lime into the lime dilu-
tion tank. Then fill each of these tanks to the 100-gallon mark





Florida Agricultural Experiment Station


by running in water from the storage tanks above, or whatever
the most convenient source of water supply may be. The stop-
cocks of the dilution tanks may be opened then so that the di-
luted bluestone solution and the diluted milk of lime may run to-
gether thru the discharge pipe and into the spray tank, the open-
ing of which should be covered by a good brass wire strainer in
order to remove any sediment or dirt and avoid subsequent clog-
ging of the spray nozzles. Various modifications of this Bor-
deaux mixing plant can easily be devised to suit the conditions
and requirements in any particular case.
Where spray tanks are provided with an efficient agitator
the following modified method has been found the simplest in
field practice, and the mixture made in this way is entirely
satisfactory:
1. Fill the spray tank about three-fourths full of water,
pour in as much stock solution of copper sulphate as will be
required for the tankful of spray and then start the engine.
2. Stir up the stock milk of lime thoroly and pour the re-
quired amount slowly thru the screen while the weak copper
sulphate solution is being agitated vigorously.
3. When all the milk of lime has been added and thoroly
mixed, add the lead arsenate, or calcium arsenate, and calcium
caseinate spreader, if these are to be used. The latter sub-
stances can be added best by whipping them to a thin paste
With water before adding to the spray tank.
4. With the agitator still running, add sufficient water to
fill the tank to the top and begin spraying.
This method involves less work than any other method and
has given excellent results. It eliminates the need for large
dilution tanks or barrels for the two solutions and greatly sim-
plifies the preparation of Bordeaux mixture.
Combinations with Bordeaux Mixture.-Bordeaux mixture
itself is merely a fungicide and has no beneficial properties for
the control of insect pests other than acting as a repellent. In
order to make the spray effective also in the control of insects,
arsenate of lead, arsenate of lime (calcium arsenate), nicotine,
or soap should be added as required.
Use of Spreaders.-The spreading and adhesive qualities of
Bordeaux mixture may be increased by adding some spreader
such as rosin-fish oil soap (1 pound to 50 gallons) or calcium
easeinate (3/4 pound to 50 gallons)., The latter, which has





Bulletin 178, Diseases of Grapes in Florida


proved especially promising, is now put out commercially in
powder form under a number of trade names. When using a
calcium caseinate spreader with Bordeaux mixture, empty the
required amount into a bucket half full of water, stir or beat
vigorously for two or three minutes with a wire whip and then
pour thru the screen into the spray tank containing the Bor-
deaux mixture while the agitator is running.
NON-STAINING FUNGICIDES
When a fungicide leaving very inconspicuous spots on the
fruit or foliage is desired for a final application shortly before
the picking season, the copper sulphate may be neutralized
with some soluble alkali, as in the case of soda-Bordeaux mix-
ture, or an entirely different salt of copper requiring no neutral-
ization may be used. A good example of each of these fungicides
is given in the following. Ammoniacal copper carbonate and
Burgundy mixture are frequently used for this purpose but
sometimes result in more or less burning of the foliage.
Soda-Bordeaux Mixture
Soda-Bordeaux mixture is prepared by neutralizing copper
sulphate with caustic soda (lye) instead of with lime as in the
case of the ordinary Bordeaux mixture. While this makes a
very cheap and practical fungicide, it has not been extensively
used in the past. Soda-Bordeaux mixture may be prepared as
follows. Dissolve 4 pounds of copper sulphate in water and di-
lute to almost 50 gallons. Dissolve 11/2 pounds of caustic soda
(lye sold in grocery stores) in a small quantity of water and pour
into the copper sulphate solution, stirring thoroly. Add water
to make the volume 50 gallons. This amount of caustic soda
should make the mixture safely alkaline so that no burning
should result. This fungicide should be prepared by careful
weighing and not guesswork. It is somewhat caustic to the
skin.
Copper Acetates
The copper acetates may be considered under two headings:
1. Basic acetate of copper, or verdigris, of somewhat vari-
able composition but consisting mainly of bi-basic copper ace-
tate. The majority of the verdigris used in this country is im-
ported from France. The imported product usually occurs in
small lumps of a blue-gray color or else in granulated form. It





Florida Agricultural Experiment Station


dissolves readily in water, forming a pale, blue solution with a
finely divided precipitate in suspension. Verdigris has been
quoted by one wholesale chemical company as low as 22 cents
per pound in 220 pound barrels and 25 cents per pound in small
lots, both prices being f. o. b. shipping point.
2. The neutral or normal acetate of copper, a salt of more
recent introduction than verdigris. This is a coarse crystalline
salt resembling copper sulphate but with a greenish-blue color.
It dissolves readily and completely in cold water, forming a
clear greenish-blue solution. The price of this form of copper
acetate is much higher, however, ranging around 60 cents per
pound in small lots.
The adhesiveness and spread of the copper acetate spray solu-
tions can be increased greatly by the use of gelatine, the great-
est benefit resulting with the neutral acetate.
Preparation of spray mixtures.-Stock solutions of the cop-
per acetates containing 1 pound per gallon should be made up
according to the quantity of spray solution desired. If the
basic acetate or verdigris be used the spray solution can be pre-
pared in a few minutes by stirring the required amount of ver-
digris into the water. Solutions of the neutral acetate require
somewhat longer to make, as this salt occurs in coarse crystal-
line form like copper sulphate. It may be stirred in the water
until dissolved, or the crystals may be suspended overnight in
a burlap sack just below the surface of the water. No attempt
should be made to hasten the dissolution by means of hot water,
since the salts will decompose. The following amounts will be
required for 50 gallons of spray mixture:
W ater .......... ................................... .........................48 gallons
Stock solution of basic copper acetate (verdigris).... 2 gallons
When gelatine is added to increase the adhesiveness, which
is always required when the neutral acetate is used and which
is decidedly advantageous even when the basic acetate, or verdi-
gris, is used, the formula becomes:
W after .......... ....... .................... ....................... 47 gallons
basic copper acetate (verdigris)
Stock solution of or .... 2 gallons
S neutral copper acetate
Stock solution of gelatine ..................... ............ ......... .. 1 gallon
The stock solution of gelatine is made by dissolving four
ounces of an inexpensive grade of gelatine in a gallon of boil-
ing water. After cooling, this is added to the copper acetate
solution previously diluted to spraying strength, stirring thoroly.





Bulletin 178, Diseases of Grapes in Florida


An off-colored grade of gelatine known as "last run" gelatine
can be purchased for as low as 35 cents per pound. Solutions
of gelatine should not be made up very far in advance since
they are very subject to putrefaction. In case they are not used
shortly after their preparation it is well to stir in a small quan-
tity of the copper acetate stock solution, half a pint to each gal-
lon being a reasonable amount.*
INSECTICIDES
General Classification of Insecticides
The insecticides for use on grapevines may be grouped into
two series, as follows:
Insecticides for biting or chewing insects (stomach poisons).
-For the control of such insects attacking grapevines as adult
beetles and their grubs, leaf skeletonizer, grape root-worm,
berry moth, leaf-folder, various caterpillars, and the like, which
cut out particles of the leaves or other green parts and pass
these on as more or less solid particles to the food canal for di-
gestion, we rely upon the use of some stomach poison. In the
case of the grape we rely entirely upon such arsenical insecti-
cides as arsenate of lead and arsenate of lime (calcium arsenate)
for the destruction of this class of insects.
Insecticides for sucking insects (contact sprays).-For the
control of such insects attacking grapevines as aphids or plant
lice, leaf-hoppers, scale insects, and the like, which merely
suck the juices out of the green parts, we rely upon the use of
the so-called contact sprays which corrode the body or penetrate
the breathing pores or otherwise affect their destruction. In the
case of the grape we rely almost wholly upon nicotine solution
and soaps of various kinds, for the destruction of this class of
insects.
STOMACH POISONS
ARSENICAL INSECTICIDES
Arsenate of Lead
Arsenate of lead is the best known and most extensively used
stomach poison we have and the arsenical principally used in
spraying grapes. There are three different kinds of lead arsen-
ate, the basic, neutral, and acid. The latter is the most concen-

*A more detailed account of the copper acetates and their use may be
found in Florida Agricultural Experiment Station Press Bulletin 361.





Florida Agricultural Experiment Station


treated form and the one usually sold to growers. The paste
form, in which lead arsenate was formerly marketed; is now
largely supplanted by the more convenient dry form.
Arsenate of lead possesses good adhesive qualities and, owing
to its fineness, remains in suspension well in water. Moreover,
it can be safely combined, without reducing its effectiveness, with
the nicotine and soaps used as contact sprays, and with the Bor-
deaux mixture used for the control of fungous diseases, or it
may be used alone in water. In the latter case there should be
added to each 50 gallons of the spray mixture the milk of lime
from slaking 2 or 3 pounds of good stone lime, to eliminate the
danger of burning the foliage.
The powdered arsenate of lead is used on grapes mostly at
the rate of 11/2 pounds, and the paste form at the rate of 3
pounds per 50 gallons of water or the diluted spray mixture.
Before adding the paste arsenate of lead to the spray tank it
should first be mixed with a little water to make a thin paste.
Likewise, the powdered form should be mixed with a little water
or else slowly sifted into the spray tank, provided the tank has
been partly filled with water or the diluted spray mixture which
is being churned by the agitator.
Arsenate of Lime (Calcium Arsenate)
Arsenate of lime, or calcium arsenate, has recently come into
use as a substitute insecticide for arsenate of lead. It is a com-
pound somewhat similar to the latter, in which lime has re-
placed the lead. Arsenate of lime can be profitably used for the
control of biting or chewing insects upon grapes and other plants
whose foliage is not especially tender, but is more likely to burn
than arsenate of lead. Like the arsenate of lead, it may be
combined with the nicotine used as a contact spray and with the
Bordeaux mixture used as a fungicide. The paste form, in
which arsenate of lime was formerly marketed, is now largely
supplanted by the more convenient dry form. The directions
and strengths for mixing the arsenate of lime are the same as
those given for arsenate of lead.

CONTACT SPRAYS
TOBACCO OR NICOTINE INSECTICIDES
Nicotine, or tobacco extract, has long been recognized as an
effective agent for the destruction of many soft-bodied sucking





Bulletin 178, Diseases of Grapes in Florida


insects, particularly aphids, or plant lice, and the grape leaf-
hopper. Commercial nicotine extract is sold on the market in
various grades and strengths. Highly concentrated prepara-
tions containing 40 percent of nicotine and sulphate are,used ex-
tensively.
Nicotine solutions are especially valuable as contact sprays,
since they can be applied at the required insecticidal strength
without injury to the foliage. Moreover, nicotine extracts may
be combined with the Bordeaux mixture used as a fungicide,
or with the stomach poison without depreciating their value.
These combination sprays are much used when it is desired to
control, with the one spray application, certain sucking and
chewing insects and fungous diseases.
In vineyard spraying nicotine extract containing 40 percent
nicotine sulphate is used at the rate of 1 to 800, or 1/2 pint to
50 gallons of water of the diluted spray mixture. When spray-
ing with nicotine solutions in water alone their efficiency can
be increased by the addition of soap, preferably rosin fish--il
soap, as is discussed in the following section.

SOAP SPRAYS
Sprays made from several kinds of soaps are much used for
the destruction of various soft-bodied sucking insects, particu-
larly aphids, or plant lice. Soaps are also frequently combined
with other spray materials to cause them to spread and adhere
better to the foliage and fruit.

ROSIN-FISH OIL SOAP
Of the various soaps available the rosin-fish oil soap has proved
best and has come into extensive use in sprays for grapes and cer-
tain other small fruits. The soap is used at the rate of 2 or 3
pounds to 50 gallons of spray solution and may be added to a
spray solution composed of Bordeaux mixture, arsenate of lead
and nicotine sulphate, or used alone with any one of these, in
water. In the absence of rosin-fish oil soap, ordinary laundry
soap may be substituted.
Soap sprays may be applied alone for the destruction of vari-
ous soft-bodied insects such as aphids, or plant lice, leaf-hoppers,
etc. For vines in foliage the soap, according to its quality and
the insects to be treated, is used at the rate of 1 pound to 3 or
4 gallons of water, or even at greater dilutions.





Florida Agricultural Experiment Station


COMBINATIONS OF STANDARD SPRAY MATERIALS FOR

SUMMER SPRAYING

Vineyards are invariably troubled with different classes of
pests, as fungous diseases, chewing insects and sucking in-
sects, each of which requires for its control a different kind of
spray material. Fortunately it is possible to combine the neces-
sary materials for the simultaneous control of these pests, thus
avoiding separate applications. In the following table the cor-
rect combinations of spray materials are given for the control
of fungous diseases, chewing insects and sucking insects alone,
and for the various combinations of these that it may be desired
to combat simultaneously. To illustrate the use of this table,
the pest or combination of pests to be controlled is located in
the left-hand column and by reading to the right of the desired
one we find the correct combination of spray materials classi-
fied as fungicide, stomach poison, contact spray, and stabilizer
to eliminate the likelihood of arsenical burning.

TABLE 1.-COMBINATIONS OF STANDARD SPRAY MATERIALS FOR SUMMER
SPRAYING.


Pests to be
Controlled
Fungous diseases

Chewing insects

Sucking insects


Fungicide
Bordeaux
mixture


Chewing and
sucking insects
Fungous diseases]
and chewing in- Bordeaux
sects mixture
Fungous diseases
and sucking in- I Bordeaux
sects ] mixture
Fungous diseases]
and both chewing
and sucking in- Bordeaux
sects mixture


S Stomach
I Poison


Arsenate of
lead or ar-
senate of limej


Contact
Spray


Stabilizer


Milk of
lime


SNicotine
__I and soap
Arsenate of
lead or ar- Nicotine Milk of
senate of lime and soap lime
Arsenate of
lead or ar-
senate of lime
INicotine
with or
without soap

Arsenate of Nicotine
lead or ar- with or
senate of lime without soapj





Bulletin 178, Diseases of Grapes in Florida


SPRAY DILUTION TABLE FOR READY REFERENCE

Table 2 shows the amount of spray material required for a
number of different quantities of spray solution. The rate at
which the materials have been computed will be found in the
lefthand column. The figures at the top of the table represent
the total number of gallons of diluted spray desired, and the
figures in the vertical columns give the amount of spray mate-
rial required.

POWDERED SPRAY MATERIALS FOR DUSTING

The materials employed for vineyard dusting are mostly
finely ground, dehydrated copper sulphate, arsenate of lead, ar-
senate of lime, sulphur, and tobacco. The sulphur, and some-
times others of these dusts, often contain a filler such as hy-
drated lime or gypsum. Various ready-mixed combinations of
fungicides and insecticides in dust form are now on the market.
The copper-lime dusts have given good control of grape dis-
eases in dry seasons but it is not known how effective they will
prove during wet seasons. Sufficient experimental work, how-
ever, has not yet been done with the dust materials, other than
sulphur for powdery mildew and nicotine sulphate-lime dusts
for aphids, to show definitely their value as compared with the
liquid sprays in the control of various diseases and insects in
vineyards under variable weather and climatic conditions. The
conservative vineyardist, therefore, under ordinary circum-
stances, should continue to use liquid sprays until the status of
the dust sprays has been more fully determined.

SPRAYING OUTFITS

The equipment for spraying should be consistent with the
size of the vineyard. A bucket, small compressed-air, or wheel-
barrow pump will be sufficient for a few vines. A small vine-
yard may be sprayed effectively with a barrel pump. Commer-
cial vineyards of a few or more acres, however, necessarily
must be provided with power sprayers of a dependable type that
can be handled conveniently in the field. The essential features
of each of these five types of spraying outfits are considered
briefly in the following.





Bulletin 178, Diseases of Grapes in Florida


SPRAY DILUTION TABLE FOR READY REFERENCE

Table 2 shows the amount of spray material required for a
number of different quantities of spray solution. The rate at
which the materials have been computed will be found in the
lefthand column. The figures at the top of the table represent
the total number of gallons of diluted spray desired, and the
figures in the vertical columns give the amount of spray mate-
rial required.

POWDERED SPRAY MATERIALS FOR DUSTING

The materials employed for vineyard dusting are mostly
finely ground, dehydrated copper sulphate, arsenate of lead, ar-
senate of lime, sulphur, and tobacco. The sulphur, and some-
times others of these dusts, often contain a filler such as hy-
drated lime or gypsum. Various ready-mixed combinations of
fungicides and insecticides in dust form are now on the market.
The copper-lime dusts have given good control of grape dis-
eases in dry seasons but it is not known how effective they will
prove during wet seasons. Sufficient experimental work, how-
ever, has not yet been done with the dust materials, other than
sulphur for powdery mildew and nicotine sulphate-lime dusts
for aphids, to show definitely their value as compared with the
liquid sprays in the control of various diseases and insects in
vineyards under variable weather and climatic conditions. The
conservative vineyardist, therefore, under ordinary circum-
stances, should continue to use liquid sprays until the status of
the dust sprays has been more fully determined.

SPRAYING OUTFITS

The equipment for spraying should be consistent with the
size of the vineyard. A bucket, small compressed-air, or wheel-
barrow pump will be sufficient for a few vines. A small vine-
yard may be sprayed effectively with a barrel pump. Commer-
cial vineyards of a few or more acres, however, necessarily
must be provided with power sprayers of a dependable type that
can be handled conveniently in the field. The essential features
of each of these five types of spraying outfits are considered
briefly in the following.





Bulletin 178, Diseases of Grapes in Florida


SPRAY DILUTION TABLE FOR READY REFERENCE

Table 2 shows the amount of spray material required for a
number of different quantities of spray solution. The rate at
which the materials have been computed will be found in the
lefthand column. The figures at the top of the table represent
the total number of gallons of diluted spray desired, and the
figures in the vertical columns give the amount of spray mate-
rial required.

POWDERED SPRAY MATERIALS FOR DUSTING

The materials employed for vineyard dusting are mostly
finely ground, dehydrated copper sulphate, arsenate of lead, ar-
senate of lime, sulphur, and tobacco. The sulphur, and some-
times others of these dusts, often contain a filler such as hy-
drated lime or gypsum. Various ready-mixed combinations of
fungicides and insecticides in dust form are now on the market.
The copper-lime dusts have given good control of grape dis-
eases in dry seasons but it is not known how effective they will
prove during wet seasons. Sufficient experimental work, how-
ever, has not yet been done with the dust materials, other than
sulphur for powdery mildew and nicotine sulphate-lime dusts
for aphids, to show definitely their value as compared with the
liquid sprays in the control of various diseases and insects in
vineyards under variable weather and climatic conditions. The
conservative vineyardist, therefore, under ordinary circum-
stances, should continue to use liquid sprays until the status of
the dust sprays has been more fully determined.

SPRAYING OUTFITS

The equipment for spraying should be consistent with the
size of the vineyard. A bucket, small compressed-air, or wheel-
barrow pump will be sufficient for a few vines. A small vine-
yard may be sprayed effectively with a barrel pump. Commer-
cial vineyards of a few or more acres, however, necessarily
must be provided with power sprayers of a dependable type that
can be handled conveniently in the field. The essential features
of each of these five types of spraying outfits are considered
briefly in the following.












TABLE 2.-SPRAY DILUTION TABLE FOR READY REFERENCE.


Spray material and usual rate of
concentration

(A) for vines in foliage.
Fungicides
Bordeaux mixture (4-3-50), copper
sulphate and stone lime..................
Copper acetate (basic or neutral),
2 Ibs. to 50 gals...................... .........

Insecticides (stomach poisons)

Arsenate of lead or arsenate of
lime powder, 1% Ibs. to 50 gals.....
Arsenate of lead or arsenate of
lime paste, 3 lbs. to 50 gals............

Insecticides (contact sprays)

Nicotine sulphate (40%), 1-800 or
% pt. to 50 gals........... .......... ...
Rosin-fish oil soap, 2 Ibs. to 50 gals...

(B) for dormant vines.
Fungicides
Copper sulphate, 4 lbs. to 50 gals.....


200



S16 lbs.*
12 lbs.

8 lbs.



6 lbs.

12 lbs.



1 qt.
8 lbs.


16 lbs.


Total gallons of spray material desired.


150



12 lbs.*
9 lbs.

6 Ibs.



4%/ lbs.

9 lbs.



1% pts.
6 Ibs.


12 lbs.


*Upper figure refers to copper sulphate; lower to stone lime.


100 50



I8 lbs.* J 4 lbs.*
S6 lbs. | 3 lbs.

4 lbs. 2 lbs.


3 lbs.

6 lbs.



1 pt.
4 lbs.


8 lbs.


1 V lbs.
3 lbs.



2 pt.
2 lbs.


4 lbs.


25



S2 lbs.*
1' lbs.

1 lb.



% Ibs.

1 lbs.



14 pt.
1 lb.


2 Ibs.






Bulletin 178, Diseases of Grapes in Florida


BUCKET PUMPS


Bucket pumps (fig. 80), which are
convenient for spraying small gardens
and shrubs, or a few small trees, should
be made of brass or other non-corrosive
metal and preferably equipped with an
agitator. Agitation is provided for in
some of these pumps by means of a
small jet of liquid that is forced from
the bottom of the pump thru the mix-
ture as the pump is operated. For con-
venience in use these pumps may be
clamped to a bucket or used free in a
tub or other vessel containing the spray
material. They should be equipped with
a spray rod and sufficient hose to reach
conveniently to all parts of the plants
to be sprayed.

WHEELBARROW PUMPS

The wheelbarrow pump (fig. 81) is
an exceedingly handy outfit for small
spraying operations. These may be
had with high pressure barrel spray
pumps. The pump is fastened in a
heavy galvanized can holding about a


Fig. 81.-Wheelbarrow sprayer for
small spraying operations. (After
Hayes Pump & Planter Co.)


PATENT AGITATOR
BRASS BALL VALVES
Fig. 80.-Bucket pump,
which is placed in a
bucket or other small
vessel of spray mate-
rial and steadied by
means of the foot-rest.
(Cut by courtesy of
the Bean Spray Pump
Co.)


fourth of a barrel,
the can being mounted
on a steel wheelbar-
row frame. The out-
fit thus can be readily
wheeled anywhere.





Florida Agricultural Experiment Station

SMALL COMPRESSED-AIR PUMPS


Compressed-air
in small fruit
gardens and are
preferred to the
bucket and knap-
sack pumps by
those who do not
wish to pump
while e applying
the spray, are
made of brass or
galvanized sheet
metal and have
a capacity of
from three to
four gallons.
They are carried
by means of a
shoulder s t r a p.
In the better
ty p e s agitation
is provided for
by the entrance
of the air at the


Fig. 83.-Barrel pump suit-
able for spraying the
small vineyard or home
orchard. (After Goulds
Mfg. Co.)


pumps (fig. 82), which are frequently used


Fig. 82.-Compressed air sprayer. (From U. S.
Department of Agriculture Farmers' Bulletin
1220.)


bottom of the tank. After the spray
material is poured into the tank and
the opening closed by an air-tight
cap, air is pumped until the liquid is
under sufficient pressure. Three or
four pumping of a dozen strokes
each usually suffice to empty the
tank.

BARREL PUMPS

The barrel hand-pump outfit (fig.
83) having a capacity of about 50
gallons is widely used for the home
orchard, small vineyard or fruit gar-
den. It should be provided with an





Bulletin 178, Diseases of Grapes in Florida


efficient agitator, either of the paddle or rotary type. To in-
sure adequate pressure and a uniform rate of discharge of the
spray material, the pump ,
should be provided with an
air chamber to which a pres-
sure gauge may be attached
if desired. The pump may
be mounted on either the
head or side and the whole
outfit placed on a wagon *
or sled. Outfits in which
barrel sprayers are mount-.
barrel spra es are m ot Fig. 84.-Barrel cart spraying outfit
ed on light hand carts may suitable for spraying the small vine-
also be obtained and are yard or home orchard where a horse
desirable where a horse is is not available. (After The Deming
not available (fig. 84). Co.)

GASOLINE POWER SPRAYERS

Power spraying outfits operated by gasoline engines (fig. 85)
are by far the most commonly used type of sprayer for large
vineyards. Those operated by gasoline engines are made in
various sizes and styles to suit almost any requirement. Special
outfits have also been designed for vineyard spraying.
For spraying commercial vineyards of several acres a depend-
able type outfit that can be handled conveniently in the field
should be selected. Such a machine should have a capacity of
from four to seven gallons per minute, according to the number
of nozzles it is
desired to oper-
I ate. An engine
S.. of two or three
S. d *H. P. rating will
__ be required to
S :-, = 'maintain suitable
pressure (about
200 pounds) with
-- a pump of such
Fig. 85.-Gasoline power sprayer designed for capacity. The ca-
spraying large vineyards or groves. (Cut by pacity of the tank
courtesy of the Bean Spray Pump Co.)





Florida Agricultural Experiment Station


may range from 100 to 200 gallons but the larger the tank the
less time lost in refilling.
Assuming that the engine and pump of any standard machine
will give satisfactory service, the manner in which the entire
outfit is assembled and mounted is the important consideration.
The outfit should be compact and the center of balance low. The
front axle should be equipped with a flexible fifth wheel or bol-
ster and preferably with complete cut-under construction to per-
mit short turning. There should also be a good strainer between
the tank and pump. Orchard power sprayers, when they con-
stitute a part of the farm equipment, may well be used for vine-
yard spraying.
DUSTING OUTFITS
Outfits of various styles adapted to a wide range of use for
applying insecticidal and fungicidal dusts are available on the
market. The small hand-duster types (fig. 86), which are suit-
able for a small vineyard, are supported by shoulder straps and
the nozzle directed by hand. Power dusters of various sizes
are also available for larger operations.
SPRAYING ACCESSORIES
TRAILERS
The use of stationary nozzles attached at either side at the
rear of the power sprayer is not advised. To do a thoro job
of spraying bearing vineyards it is necessary to use an outfit
operated with trailers, that is, long leads of hose attached to the
rear of the outfit, having the nozzles directed by hand (fig. 87).
One lead of hose is generally used with a small power outfit. Two
leads may be employed with a pump of suffi-
cient capacity to keep up the necessary pres-
sure. The hose for the trailers should be of
sufficient length to permit convenient spraying
and to allow the nozzle men to take advantage
of tho wind in order to prevent the
spray mixture from being blown on
them. Usually lengths of hose rang-
Fig. 86 -Ha plying ing from 25 to 50 feet are used.
dust mixtures in the home
vineyard or fruit garden. Af- SPRAY RODS
tc.r Dunn Machinery Co.)
ter Dunn Machinery Co.) Spray rods should preferably be
brass rods contained within bamboo poles. Some growers use





Florida Agricultural Experiment Station


may range from 100 to 200 gallons but the larger the tank the
less time lost in refilling.
Assuming that the engine and pump of any standard machine
will give satisfactory service, the manner in which the entire
outfit is assembled and mounted is the important consideration.
The outfit should be compact and the center of balance low. The
front axle should be equipped with a flexible fifth wheel or bol-
ster and preferably with complete cut-under construction to per-
mit short turning. There should also be a good strainer between
the tank and pump. Orchard power sprayers, when they con-
stitute a part of the farm equipment, may well be used for vine-
yard spraying.
DUSTING OUTFITS
Outfits of various styles adapted to a wide range of use for
applying insecticidal and fungicidal dusts are available on the
market. The small hand-duster types (fig. 86), which are suit-
able for a small vineyard, are supported by shoulder straps and
the nozzle directed by hand. Power dusters of various sizes
are also available for larger operations.
SPRAYING ACCESSORIES
TRAILERS
The use of stationary nozzles attached at either side at the
rear of the power sprayer is not advised. To do a thoro job
of spraying bearing vineyards it is necessary to use an outfit
operated with trailers, that is, long leads of hose attached to the
rear of the outfit, having the nozzles directed by hand (fig. 87).
One lead of hose is generally used with a small power outfit. Two
leads may be employed with a pump of suffi-
cient capacity to keep up the necessary pres-
sure. The hose for the trailers should be of
sufficient length to permit convenient spraying
and to allow the nozzle men to take advantage
of tho wind in order to prevent the
spray mixture from being blown on
them. Usually lengths of hose rang-
Fig. 86 -Ha plying ing from 25 to 50 feet are used.
dust mixtures in the home
vineyard or fruit garden. Af- SPRAY RODS
tc.r Dunn Machinery Co.)
ter Dunn Machinery Co.) Spray rods should preferably be
brass rods contained within bamboo poles. Some growers use






Bulletin 178, Diseases of Grapes in Florida


a -- -.-
-.i-. -i.
-- S -;


Fig. 87.-Gasoline power sprayer, illustrating the so-called trailer method
of applying the spray. (From U. S. Department of Agriculture Farm-
ers' Bulletin 1220.)

ordinary brass pipe but the lighter weight spray rods are prefer-
able. A suitable length for vineyard spraying is three feet, but
this may vary slightly either way.
SPRAY NOZZLES
Angle nozzles of the disk-whirlpool type are recommended for
use with vineyard outfits. These nozzles are provided with
interchangeable disks, each having a different sized opening to
give fine, medium or coarse spray. The holes in the disks may
vary according to the pressure used but in every case should be
small enough to break up the mixture into a fine mist. The
rate of discharge at 175 or 200 pounds pressure should average
about five quarts per minute per nozzle. If the discharge is
much less, the work will be slow. If it is much greater, the
spray will be too coarse. For rapid spraying with outfits
having sufficient capacity and pressure, two nozzles, connected
by means of a Y, may be used on each spray rod after the vines
are in foliage. For dormant spraying, however, a single nozzle


~Bs-T

?~ -
~"
'''
~c- L-^i b-






Florida Agricultural Experiment Station


on a rod is about all the average man will handle without an
undue waste of material.
It is important that all of the entire surface of the foliage,
shoots, canes and fruit be thoroly coated, but the vines should
not be oversprayed. In spraying vines in foliage it is important
that the spray should be directed upward from the nozzle held
beneath the vine, as well at directly at the vine.

SPRAY SCHEDULE


PURPOSE


MATERIALS


In the spring before Control of anthracnose Copper sulphate (4
buds begin to swell, so and for general sanita- lbs. to 50 gallons.)
as to make a dormant tion.
application.
I Control of anthrac- Bordeaux mixture (4-
nose, black-rot, downy 3-50) for diseases,
mildew, and other fun- adding lead arsenate
When shoots are from gous diseases, leaf skel- or calcium arsenate
10 to 18 inches long. etonizer and flea beetle. (11 lbs. dry form or
3 lbs. paste form) if
f -needed for insects.
Control of anthrac-
nose, black-rot, downy Same as for preced-
Just before blooming, mildew and other fun- ing application.


After blossoms have fal- I
len and fruit is about
the size of buckshot.



10 to 14 days later.




2 weeks later and re-
peated at equal intervals
thereafter until about
May 15 to June 15, or
until within about 4
weeks of maturity.


As fruit is just begin-
ning to ripen, so as to
make a final finishing
application.


gous diseases, leaf skel-
etonizer, flea beetle and
berry moth.
Control of anthrac-
nose, black-rot, downy
mildew, and other fun-
gous diseases, berry
moth, leaf skeletonizer
and other leaf-eating
insects.
Control of anthrac-
nose, black-rot, downy
mildew and other fun-
gous diseases, leaf skel-
etonizer, berry moth,
leaf folder, and other
insects.
Control of anthrac-
nose, black-rot, downy
mildew, and other fun-
gous diseases, leaf skel-
etonizer, berry moth,
leaf folder, leaf hop-
per, aphids, and other
insects.


Control of various ripe-
rot fungi.


Same as for preced-
ing application.




Same as for preced-
ing application.



Same as for preced-
ing application, add-


ing /2 pint of 40%"
nicotine sulphate to
each 50 gallons of
spray if aphids or
leaf hoppers be pres-
ent.
Use a fungicide leav-
ing a colorless resi-
due, such as soda-
Bordeaux mixture or
the copper acetates
(See page 143.)


Note:-Subsequent applications of Bordeaux mixture and insecticides
should be made as needed after the harvest in order to maintain the vines
in a healthy condition.


TIME


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