• TABLE OF CONTENTS
HIDE
 Title Page
 Credits
 Table of Contents
 Introduction
 Diseases caused by nutritional...
 Diseases caused by bacteria
 Diseases caused by fungi
 Disease and injuries due to other...
 Control measures
 Acknowledgement
 Literature cited














Group Title: Bulletin - University of Florida. Agricultural Experiment Stations ; no. 439
Title: Diseases of beans in southern Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027350/00001
 Material Information
Title: Diseases of beans in southern Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 56 p. : ill., chart ; 23 cm.
Language: English
Creator: Townsend, G. R ( George Richard ), 1905-
Ruehle, George D
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1947
 Subjects
Subject: Beans -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 55-56.
Statement of Responsibility: by G.R. Townsend ; rev. by Geo. D. Ruehle.
General Note: Cover title.
General Note: "A revision of Bulletin 336"--T.p.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00027350
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000925516
oclc - 18253889
notis - AEN6167

Table of Contents
    Title Page
        Page 1
    Credits
        Page 2
        Page 3
    Table of Contents
        Page 4
    Introduction
        Page 5
        Page 6
        Page 7
    Diseases caused by nutritional disorders
        Page 8
        Page 9
        Page 10
        Page 11
    Diseases caused by bacteria
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
    Diseases caused by fungi
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
    Disease and injuries due to other causes
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
    Control measures
        Page 51
        Page 52
        Page 53
        Page 54
    Acknowledgement
        Page 55
    Literature cited
        Page 55
        Page 56
Full Text




(A Revision of Bulletin 336)


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
HAROLD MOWRY, Director
GAINESVILLE, FLORIDA








DISEASES OF BEANS

IN SOUTHERN FLORIDA

By G. R. TOWNSEND
Revised by GEO. D. RUEHLE


Fig. 1.-Applying sulfur to a crop of beans with a dusting machine operated
by a power take-off from a tractor.



Single copies free to Florida residents upon request to
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA


Bulletin 439


December, 1947


S,' .









BOARD OF CONTROL

J. Thos. Gurney, Chairman, Orlando
N. B. Jordan, Quincy
Thos. W. Bryant, Lakeland
M. L. Mershon, Miami
J. Henson Markham, Jacksonville
J. T. Diamond, Secretary, Tallahassee


EXECUTIVE STAFF
J. Hillis Miller, Ph.D., President of the
University3
H. Harold Hume, D.Sc., Provost for Agr.3
Harold Mowry, M.S.A., Director
L. O. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifleld, M.S., Asst. Dir., Admin.
J. Francis Cooper, M.S.A., Editors
Clyde Beale, A.B.J., Associate Editors
Jefferson Thomas, Assistant Editors
Ida Keeling Creeap, Librarian
Ruby Newhall, Administrative Manager'
K. H. Graham, LL.D., Business Managers
Claranelle Alderman, Accountants


MAIN STATION, GAINESVILLE
AGRICULTURAL ENGINEERING
Frazier Rogers, M.S.A., Agr. Engineer"
J. M. Johnson, B.S.A.E., Asso. Agr. Engineer3
J. M. Myers, B.S., Asso. Agr. Engineer
R. E. Choate, B.S.A.E., Asst. Agr. Engineer3
A. M. Pettis, B.S.A.E., Asst. Agr. Engineer3

AGRONOMY
W. E. Stokes, M.S., Agronomist'
Fred H. Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Agronomists
G. B. Killinger, Ph.D., Agronomist
H. C. Harris, Ph.D., Agronomist
R. W. Bledsoe, Ph.D., Agronomist
M. E. Paddick, Ph.D., Agronomist
W. A. Carver, Ph.D., Associate
Fred A. Clark, B.S., Assistant

ANIMAL INDUSTRY
A. L. Shealy, D.V.M., An. Industrialist'
R. B. Becker, Ph.D., Dairy Husbandman'
E. L. Fouts, Ph.D., Dairy Technologist'
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian'
L. E. Swanson, D.V.M., Parasitologist
N. R. Mehrhof, M.Agr., Poultry Hush.'
G. K. Davis, Ph.D., Animal Nutritionist
R. S. Glasscock, Ph.D., An. Husbandman3
P. T. Dix Arnold, M.S.A., Asst. Dairy Husb."
C. L. Comar, Ph.D., Asso. Biochemist
L. E. Mull, M.S., Asst. in Dairy Tech."
Katherine Boney, B.S., Asst. Chem.
J. C. Driggers, B.S.A., Asst. Poultry Husb.3
Glenn Van Ness, D.V.M., Asso. Poultry
Pathologist
S. John Folks, B.S.A., Asst. An. Husb.3
W. A. Krienke, M.S., Asso. in Dairy Mfs.
S. P. Marshall, Ph.D., Asso. Dairy Husb.3


ECONOMICS, AGRICULTURAL

C. V. Noble, Ph.D., Agri. Economist' a
Zach Savage, M.S.A., Associates
A. H. Spurlock, M.S.A., Associate
D. E. Alleger, M.S., Associate
D. L. Brooke, M.S.A., Associate


Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr. Economist
J. C. Townsend, Jr., B.S.A., Agr. Statisticiap
J. B. Owens, B.S.A., Agr. Statistician'
W. S. Rowan, M.S., Asst. Agr. Statisticians


ECONOMICS, HOME
Ouida D. Abbott, Ph.D., Home Econ.1
R. B. French, Ph.D., Biochemist


ENTOMOLOGY
A. N. Tissot, Ph.D., Entomologist'
H. E. Bratley, M.S.A., Assistant

HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturist'
F. S. Jamison, Ph.D., Truck Hort.
Byron E. Janes, Ph.D., Asso. Hort.
R. A. Dennison, Ph.D., Asso. Hort.
R. K. Showalter, M.S., Asso. Hort.
R. J. Wilmot, M.S.A., Asst. Hort.
R. D. Dickey, M.S.A., Asst. Hort.
Victor F. Nettles, M.S.A., Asst. Hort."
F. S. Lagasse, Ph.D., Asso. Hort."


PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist1
Phares Decker, Ph.D., Asso. Plant Path.
Erdman West, M.S., Mycologist and Botanist
Lillian E. Arnold, M.S., Asst. Botanist

SOILS
F. B. Smith, Ph.D., Microbiologist1
Gaylord M. Volk, Ph.D., Chemist
J. R. Henderson, M.S.A., Soil Technologist
J. R. Neller, Ph.D., Soils Chemist
Nathan Gammon, Jr., Ph.D., Soils Chemist
C. E. Bell, Ph.D., Associate Chemist
L. H. Rogers, Ph.D., Biochemist
R. A. Carrigan, B.S., Asso. Biochemist
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, M.S., Asso. Microbiologist
R. E. Caldwell, M.S.A., Soil Surveyor
J. B. Cromartie, B.S.A., Soil Surveyor
Ralph G. Leighty, B.S., Asso. Soil Surveyor
V. W. Cyzycxi, B.S., Asst. Soil Surveyor


1 Head of Department.
2 In cooperation with U. S. D. A.
3 Cooperative, other divisions, U. of F.
*In Military Service.
0 On leave.










BRANCH STATIONS


NORTH FLORIDA STATION, QUINCY

J. D. Warner, M.S., Vice-Director in Charge
R. R. Kincaid, Ph.D., Plant Pathologist
W. H. Chapman, M.S., Asso. Agron.
R. C. Bond, M.S.A., Asso. Agronomist
L. G. Thompson, Ph.D., Soils Chemist
Prank S. Baker, Jr., B.S., Asst. An. Hush.
Kelvin Dorward, M.S., Entomologist

Mobile Unit, Monticello
R. W. Wallace, B.S., Associate Agronomist

Mobile Unit, Marianna
R. W. Lipscomb, M.S., Associate Agronomist

Mobile Unit, Wewahitchka
J. B. White, B.S.A., Associate Agronomist

Mobile Unit, DeFuniak Springs
R. L. Smith, M.S., Associate Agronomist

CITRUS STATION, LAKE ALFRED

A. F. Camp, Ph.D., Vice-Director in Charge
W. L. Thompson, B.S., Entomologist
J. T. Griffiths, Ph.D., Asso. Entomologist
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, M.S., Plant Pathologist5
J. E. Benedict, B.S., Asst. Horticulturist
R. K. Voorhees, M.S., Asso. Horticulturist
C. R. Stearns, Jr., B.S.A., Asso. Chemist
James K. Colehour, M.S., Asst. Chemist
T. W. Young, Ph.D., Asso. Horticulturist
J. W. Sites, M.S.A., Horticulturist
H. 0. Sterling, B.S., Asst. Horticulturist
J. A. Granger, B.S.A., Asst. Horticulturist
H. J. Reitz, M.S., Asso. Horticulturist
Francine Fisher, M.S., Asst. P1. Path.
I. W. Wander, Ph.D., Soil Chemist
A. E. Willson, B.S.A., Asso. Soil Phys.
R. W. Jones, Asst. Plant Path.
J. W. Kesterson, M.S., Asso. Chemist
C. W. Houston, Ph.D., Asso. Chemist
R. H. Cotton, Ph.D., Supervisory Chemist
R. Hendrickson, B.S., Asst. Chemist

EVERGLADES STA., BELLE GLADE

R. V. Allison, Ph.D., Vice-Director in Charge
F. D. Stevens, B.S., Sugarcane Agron.
Thomas Bregger, Ph.D., Sugarcane
Physiologist
B. S. Clayton, B.S.C.E., Drainage Eng.2
J. W. Randolph, M.S., Agricultural Engineer
W. T. Forsee, Jr., Ph.D., Chemist
R. W. Kidder, M.S., Asso. An. Husb.
T. C. Erwin, Assistant Chemist
Roy A. Bair, Ph.D., Agronomist
C. C. Seale, Asso. Agronomist
N. C. Hayslip, B.S.A., Asso. Entomologist
J. C. Hoffman, M.S., Asso. Hort.
C. B. Savage, M.S.A., Asst. Hort.
D. L. Stoddard, Ph.D., Asso. Plant Path.
W. A. Desnoyles, B.S., Asst. Hydrologist


SUB-TROPICAL STA., HOMESTEAD

Geo. D. Ruehle, Ph.D., Vice-Director in
Charge
D. O. Wolfenbarger, Ph.D., Entomologist
Francis B. Lincoln, Ph.D., Horticulturist
Robt. A. Conover, Ph.D., Asso. Plant Path.
R. W. Harkness, Ph.D., Asst. Chemist

W. CENT. FLA. STA., BROOKSVILLE

C. D. Gordon, Ph.D., Geneticist in Charge2

RANGE CATTLE STATION, ONA

W. G. Kirk, Ph.D.. Vice-Director in Charge
E. M. Hodges, Ph.D., Associate Agronomist
D. W. Jones, B.S., Asst. Soil Tech.
H. J. Fulford, B.S.A., Asst. An. Hush.

CENTRAL FLORIDA STATION, SANFORD
R. W. Ruprecht, Ph.D., Vice-Director in
Charge
A. Alfred Foster, Ph.D., Asso. P1. Path.
J. W. Wilson, Sc.D., Entomologist
Ben F. Whitner, Jr., B.S.A., Asst. Hort.

WEST FLORIDA STATION, MILTON

H. W. Lundy, B.S.A., Asso. Agronomist


FIELD STATIONS

Leesburg

G. K. Parris, Ph.D., Plant Path. in Charge

Plant City

A. N. Brooks, Ph.D., Plant Pathologist

Hastings

A. H. Eddins, Ph.D., Plant Path. in Charge
E. N. McCubbin, Ph.D., Horticulturist

Monticello

S. 0. Hill, B.S., Asst. Entomologist' '
A. M. Phillips, B.S., Asso. Entomologist2

Bradenton

J. R. Beckenbach, Ph.D., Horticulturist in
Charge
E. G. Kelsheimer, Ph.D., Entomologist
David G. Kelbert, Asso. Horticulturist
E. L. Spencer, Ph.D., Soils Chemist
Robert 0. Magie, Ph.D., Gladioli Hort.
J. M. Walter, Ph.D., Plant Path.
Donald S. Burgis, M.S.A., Asst. Hort.

Lakeland

Warren O. Johnson, B.S., Meteorologist2

1 Head of Department.
2 In cooperation with U. S.
a Cooperative, other divisions, U. of F.
In Military Service.
SOn leave.















CONTENTS


PAGE
INTRODUCTION .................. ---...-...--- .....--.....------ ---- -- 5
DISEASES CAUSED BY NUTRITIONAL DISORDERS ...............-------------------- 8
Copper Deficiency .......8... .......... .. 8
Manganese Deficiency ....-.......-.- .... ... ---- --- 9
Zinc Deficiency ..... ...........-..-............. ...... ----- .. 11
DISEASES CAUSED BY BACTERIA .........-...- ........ -.. ....--- --- .---- --12
Halo Blight ....................- ...--.. -....--. 12
Common Bacterial Blight .-.....--------------.....--.--.--------- 17
DISEASES CAUSED BY FUNGI ..-...........-.. ...... -------------- ---- 18
Powdery Mildew -.. .......... ..---------- --- ...........- -18
Rust ....-......... ------..--...... --..........-------..------ 21
Angular Leaf Spot ..................................--.... ... 27
Sclerotiniose ....---.....-.....-..-..-.--- .--------------- 27
Anthracnose ...-....-.... ....-..-....-.-..-- .. .. ------ ----- 30
Rhizoctonia Disease -....---... ..........-... ...-- -- ...----- .. 33
Southern Blight ......... ... .. ...... --......- --- 37
W eb-blight ................ .... -.. ... ..- .. -.. --- -.. --- 39
DISEASE AND INJURIES DUE TO OTHER CAUSES ..--...~.....---..--.. ----.....-- 40
Root-Knot ...........~... .-. ....- ..- --..... 40
Baldheaded Beans .--......--.... ----.-.-.-.--..--- ... ......... 45
Wind Injury ...-....-................------.. ---.--.- -------.------- 46
Low Temperature Injury --........-...... -- ------ --- -- ---------- 47
Water Injury ......---..-..-....... .... --------- -------------- 47
Fertilizer Injury ......-.........-.--.. --------------------------. 48
Copper Injury --... -..-.... ..- .......-. ..----- .------------ 49
Sulfur Spray ............. --.--- .. -- .-- --..... 50
CONTROL MEASURES ....--..--..--....------.-------- -------------------------- 51
Exclusion .... --- -..-....-...--..--.- -- .. ------- -------- 51
Eradication ......-........-......---....--....----------------. 51
Immunization .....--......------- ----------------------------- 51
Protection -..........-....-- ---..- --------------------------- 52
ACKNOWLEDGMENTS -.......-------- ------------ ---------.... 55
LITERATURE CITED ....................------------------------------. 55









DISEASES OF BEANS IN SOUTHERN FLORIDA

By G. R. TOWNSEND
Revised by GEO. D. RUEHLE

INTRODUCTION
In recent years the average acreage of snap beans harvested
in Florida has been approximately 80,000 acres. More than 90
percent of this acreage has been in southern Florida. Palm
Beach County in 1945-46 led with 48,800 acres of snap beans.
It was followed by Broward County with 20,200 acres and Dade
County with 3,100 acres. The farm value of this crop in Florida
was a little over S18,000,000 in 1945-46.1
The production of beans in southern Florida is centered in
2 important and somewhat different agricultural areas-the
peat and muck soils of the Everglades near the eastern and
southern shores of Lake Okeechobee and the sandy soils along
the lower East Coast.
Soils.-The peat and muck soils of the Everglades are rich in
total nitrogen and usually contain an abundant supply of avail-
able nitrogen except immediately after periods of heavy leaching
rains. In their virgin state these soils usually are deficient in
phosphorus, potassium, copper, manganese, and in some cases
zinc and boron. Higher residual levels of these elements usually
are found after several years of intensive cropping and fertiliz-
ing. A deposit of marl at depths of 3 to 10 feet below the soil
surface charges the soil water with alkaline salts and prevents
the organic soil from becoming too acid. These soils are not
alkaline except where they have been burned extensively, where
marl has been mixed with the top soil, or when frequent flooding
has been practiced. The peat soils have high water-holding
capacities and usually have adequate moisture for crop needs.
The muck soils are slightly higher in elevation and become
rather dry during periods of prolonged drouth. Good water
control for both drainage and irrigation is necessary on both
these soil types.
The sandy soils of the East Coast bean-growing area are classi-
fied in several soil series. These soils are low in most of the
nutrient elements and may require additions of some of the
minor elements as well as nitrogen, phosphorus and potassium.
Statistics from reports of Bureau of Agricultural Economics, USDA.







Florida Agricultural Experiment Station


The acid sands are deficient in calcium and magnesium. The
latter element also may be low in the more neutral sands. Or-
ganic matter usually is quite low. Because sandy soils gener-
ally have low exchange capacities, they are subject to serious
leaching losses of applied fertilizers. Proper water control for
drainage and irrigation is necessary on the sandy soils.
Climate.-The climate of southern Florida is suitable for
growing beans during 9 months of the year. Owing to its loca-
tion south of the 27th parallel of North Latitude, and its prox-
imity to the Atlantic Ocean, the southern portion of the Florida
peninsula enjoys a subtropical climate. The rainfall is heavy
during the summer and early fall months, but is very light during
the rest of the year. Temperatures favorable for growing beans
occur throughout the year but the heavy rains and the intensity
of solar radiation during the summer months are injurious to
beans. Temperatures low enough to injure beans may be ex-
pected in the Everglades from December to March. Along the
lower East Coast there is less danger from low temperature.
Figs. 2 and 3 illustrate the mean temperatures, rainfall and
evaporation over a 12-year period at the Everglades Experiment
Station. These records fairly represent the Everglades farm-
ing area. On the lower East Coast winter temperatures are not
quite so low and frosts are less frequent.
Cropping System.-Beans are planted from early September
until about the first of April in southern Florida. Shipments of
beans to Northern markets begin 6 or 7 weeks after the plant-
ings are made. The growing period is somewhat longer with
certain varieties and during colder months. The production of
beans in the Everglades reaches peaks in November and April.
Fewer beans are grown in the Everglades during December,
January and February because of the frost hazard. Along the
East Coast the production of beans is highest during winter.
Forty-five to 60 pounds of seed are required to plant an acre
of beans. It is a common practice to apply the fertilizer in the
row either before the seeds are planted or at the same time.
The general fertilizer practice with beans on organic soils is to
use little or no nitrogen and to apply mixtures containing phos-
phorus, potash, copper, manganese and sometimes sulfur and
zinc. There is considerable variation in formulas of fertilizers
commonly used, but it is recognized that potash is generally
needed in larger amounts than phosphorus and that the secondary
nutrients may be needed in special cases.









Diseases of Beans in Southern Florida


MEAN TEMPERATURES FOR FIVE DAY PERIODS


77
76
75
74
73
72
71
70
69.
68 EVERGLADES EXPERIMENT STATION
67 BELLE GLADE, FLORIDA
66.
65 _..-. 12 YEAR AVERAGE \, /, '
64 ESTIMATED NORMAL -\ r'
b3

bi
3 13 23 2 1 22 1 11 21 1 11 21 31 10 2030 10 20 3 9 19 29 8 18 28'b 20 30 9'I 299 19 29 8 1 28
JULY AWUST SEPTEMBER OCTCER NOVEMBER ECEMBERJANUARY FEBRURY MARCH APRIL MAY JUNE

Fig. 2.-Average temperatures at the Everglades Experiment Station
for 12 years.


Avere Monthly Prectptatlon and Evaporatlon at the Everg(ades Expernent Station
(/924 /93b)


July Aug. Sept. Oct


Nov Dec Jan Feb Mar Apr May


Fig. 3.-Average precipitation and evaporation at the Everglades
Experiment Station for 12 years.


---b--- ojn -
/'
//
,/







Florida Agricultural Experiment Station


Most beans grown on the sandy soils are planted on raised
beds. This system removes the crop from the danger of flood
waters after heavy rains and allows for irrigation through the
furrows between the beds. Because there are fewer rows to
the acre, less seed is required. It is necessary to include nitro-
gen in the fertilizer for beans on sandy soils and to use larger
amounts of phosphorus and potash. Lime should be applied to
some of the more acid sands. Manganese and magnesium have
been used to advantage on some sandy soils.
Most varieties of beans planted in southern Florida for mar-
ket production are of the dwarf or bush type. Their pods are
not stringy and they snap well. The Bountiful, a flat green-
podded variety, is the most popular. Stringless Black Valentine,
Giant Stringless Green Pod and Tendergreen are popular oval
to round-podded 'green beans. When wax beans are grown the
variety is usually Golden Bountiful Wax or Sure-Crop Wax.
Bean seed usually is obtained from Northern or Western seed
producers, but some growers save seed from their own fields
when it has not been profitable to sell the snap beans. Although
home-grown seed is cheap, usually it is poor. Growers should
insist that seed purchased from other states be disease-free.
As a result of diseases, injurious physiological processes de-
velop in the plant. Those described here are caused by a variety
of agents such as fungi, bacteria, nematodes and the deficiency
of nutrients. Several physical injuries to the bean plant are
described also.
Pod and leaf spots, root rots, root galls, chlorosis and stunting
are some of the symptoms in which the abnormal physiology of
diseased beans is expressed. The diagnosis of some diseases is
simplified if the bodies of the fungi, bacteria or nematodes can
be found on or in the plant.
Although usually possible to find a single factor which may
be named as the cause of a disease, it should be emphasized that
the plant cannot be separated from its environment. It is natural
that such factors as rainfall, temperature, humidity, air move-
ment, soil fertility and soil reaction act inseparably with the
chief causal factor in the production of the disease.

DISEASES CAUSED BY NUTRITIONAL DISORDERS
COPPER DEFICIENCY
The sawgrass soils in the Everglades were very unproductive
when first reclaimed. Applications of the usual fertilizer ma-







Diseases of Beans in Southern Florida


trials failed to make these soils productive for beans and other
crops. Potatoes could be grown if sprayed with bordeaux mix-
ture. This observation, together with other facts known about
raw organic soils, led to experimentation with copper sulfate
and other minerals. It was found that the soils became pro-
ductive when treated with copper sulfate (1).2 Slight responses
to other minerals were noted also in the first experiments.
Symptoms of copper deficiency in beans have never been fully
described and are not well known even today. However, it has
been noted that when beans were planted on raw sawgrass soil
without the copper treatment the crop was a failure. After the
nutrients in the cotyledons have been exhausted the plants fail
to grow on copper-deficient soils. The result is a stunted plant
which eventually becomes chlorotic, withers and dies.
Copper deficiency probably has been confused to some extent
with the lack of manganese and zinc in similar soils. The symp-
tom patterns for the other deficiency diseases of beans are better
known. Before it can be determined that there is need for cop-
per the plants should be examined carefully for symptoms of the
other nutritional disorders, although it is a safe assumption that
the copper sulfate treatment will be needed on most of the saw-
grass land in the Everglades at the time it is brought into pro-
duction. The soil should remain productive after the initial
copper treatment.
Fifty to 100 pounds of copper sulfate are required to bring
an acre of unproductive sawgrass soil into production. Better
results are obtained when the raw land is plowed and partially
fitted for cropping several months before it is to be used. If
the copper treatment is made at that time the soil will be fertile
when it is time to plant the crop. The copper sulfate should
be broadcast and disked in. If an early treatment with copper
sulfate has not been made, this material should be included in
the fertilizer. Some growers use a little copper in their fer-
tilizer even after the first year. Beans sometimes show an
increased yield following the application of copper fungicides
which cannot be assigned to the control of fungous diseases,
and may be a nutritional effect.

MANGANESE DEFICIENCY
This trouble occurs on mineral and organic soils where the
soil solution is not sufficiently acid to dissolve manganese com-
SItalic figures in parentheses refer to "Literature Cited."







Florida Agricultural Experiment Station


Fig. 4.-A normal leaf of a Bountiful be
in contrast with a leaf showing early sym
manganese deficiency.

or mixed with marl have reactions al
to be deficient in available manganes
The symptoms of manganese defic
pear after the beans have been grove


pounds. It has
not been reported
as a factor in
bean production
on the more acid
soils in Florida,
but is common on
slightly acid to
neutral peats and
mucks and on the
alkaline sands
and marl soils
along the coast.
The solubility of
manganese com-
pounds is very
low in soils
where the reac-
tion is higher
than pH 6.0 and
the manganese is
not available for
S( the growth of
an (left)
ptoms of crops. Peat and
muck soils which
have been burned
)ove pH 6.0, and are liable


e.
iency in
ving for


beans usually ap-
2 or 3 weeks. A


chlorosis, developing in the areas between the small veins of the
leaf, gives the leaf a mottled appearance when viewed closely
and a general light green color when seen at a little distance
(Fig. 4). Plant growth slows down when the green color begins
to fade from the leaves. If corrective applications are not made
the leaves soon become golden yellow and the plants become very
stunted. Dark dead spots occur on the leaves. Severly affected
plants shed many leaves, bud growth ceases and root systems
are very sparse and frequently affected by fungi and nematodes.
Yields are reduced in proportion to severity of the disease.
Beans grow normally on manganese-deficient soils when man-
ganese sulfate is included in the fertilizer (28). A fertilizer







Diseases of Beans in Southern Florida


which supplies 50 to 100 pounds of manganese sulfate to the
acre is sufficient for most soils.
Sulfur is sometimes added to fertilizers to increase the soil
acidity and the solubility of manganese compounds applied with
the fertilizer or naturally present in the soil. Applications of
50 to 100 pounds of sulfur to the acre in the row are required
to alter the soil reaction sufficiently to accomplish this result.
The reaction change is not permanent and the treatment has
to be repeated with each crop. The practice is not recommended
for deep marl soils of the lower East Coast.
Spraying manganese solutions on the plants is a very effec-
tive corrective for manganese deficiency. Frequently this is
done even when manganese has been included in the fertilizer
and it can be a complete substitute for the use of manganese
in fertilizers. Fifty gallons of a solution containing 4 pounds
of manganese sulfate is sufficient to spray an acre of beans. It
may be necessary to spray the beans 2 or 3 times if the chlorosis
is likely to be severe. The plants respond by becoming green
in 2 or 3 days after spraying. Possibility of combining man-
ganese sulfate and other spray materials is discussed later.
ZINC DEFICIENCY
Some response to zinc was noted on the raw sawgrass soils
in the Everglades in the early experiments with minerals. It
is now known that zinc is essential for the production of beans
on certain peat soils. A response to zinc by beans on the East
Coast sandy soils has not been noted.
Symptoms of zinc deficiency do not show in beans as early
as do copper and manganese deficiencies. The beans may grow
normally on zinc-deficient soils for 4 or 5 weeks, and may even
appear to be luxuriant. In their later growth the plants are
retarded and sometimes develop thick stems and look rather
stiff. Older leaves are thick and tough, while younger leaves
are likely to be rather thin and narrow. Some distortion of the
leaves also is noted. A chlorosis sets in which later involves all
the leaf area between principal veins and is not segregated by
smaller veins as in manganese chlorosis. Tissue along the prin-
cipal veins remains green longest (Fig. 5). The chlorotic area
does not become a brilliant yellow but may be dull yellow, brown
or even white in older leaves. Chlorotic areas in younger leaves
sometimes wilt suddenly so that beans in an affected field may
have a blighted appearance. Zinc-deficient plants shed leaves
prematurely and do not blossom or bear heavily.







Florida Agricultural Experiment Station


Fig. 5.-Bountiful bean leaf (left) showing early symptoms of zinc
deficiency in contrast with a normal leaf.

Beans can be produced successfully on zinc-deficient peat soils
when zinc sulfate is added to the fertilizer or is sprayed on the
plants. Fifty to 100 pounds of zinc sulfate added to a ton of
fertilizer is a helpful corrective. If the zinc sulfate is applied
separately 10 to 20 pounds should be applied to an acre. The
response is obtained most effectively by spraying the plants
with a solution containing 2 pounds of zinc sulfate in 50 gallons
of water (25). About 50 gallons of this spray should be applied
to the acre. Seldom is it necessary to make more than 2 appli-
cations. Response from zinc is slower than from manganese,
but should be evident in from 5 to 7 days. Combinations of zinc
sulfate with other spray materials are discussed later.

DISEASES CAUSED BY BACTERIA
HALO BLIGHT
Halo blight affects snap and dry shell beans, scarlet runner
beans, lima beans and kudzu (8, 19). Other legumes and non-
leguminous crops are not susceptible to this disease.







Diseases of Beans in Southern Florida


No varieties of dry shell or snap beans are known to be highly
resistant or immune to halo blight. The Refugee, Scotia, New
Stringless Green Pod and Tendergreen have been found to be
either somewhat resistant to or tolerant of this disease (7, 30).
The varieties grown in Florida-Bountiful, Stringless Black
Valentine, Sure-Crop Wax, Tennessee Green Pod and Giant
Stringless Green Pod-are very susceptible to halo blight.
Halo blight was first recognized as a distinct disease of beans
in 1924 (7). Its known distribution is now world wide. It
caused heavy crop losses in the seed growing areas of Wyoming,
Colorado and Montana in 1927, 1928, 1937 and 1938 (23).
Florida and the other Southeastern states have had serious out-
breaks in seasons following its occurrence in the seed fields.
Heaviest losses occur when young plants are affected (Fig. 6).
Entire plantings sometimes are destroyed in this way. Older
plants may be affected only slightly or may be killed, the degree
of severity depending largely on environmental factors. The
reduction in yield of snap beans in Florida due to bacterial dis-
eases, chiefly halo blight, has been about 5 percent from 1927
to 1938 (23). In an average year this loss amounts to 250,000
hampers of beans.
Small dead spots on the leaf surrounded by yellow halos are
a characteristic symptom of halo blight. The halo is several

Fig. 6.-Bean plants (center) affected with halo blight which has spread
alcng a row from one plant. (Photo by G. F. Weber.)







Florida Agricultural Experiment Station


times broader than the dead center of the spot. Isolated spots
generally are circular in outline. Adjacent halo spots sometimes
merge and produce a larger spot of an irregular shape.
While the halo spot usually is apparent, it is not the most
common symptom of the disease. The dead spots on the leaf
may be so numerous that all of the remaining tissue is more
or less yellow. These spots originate as small water-soaked
areas which are first visible on the under side of the leaves.
Some affected leaves are small and distorted. They soon wither
and die. Other leaves on the same plants may not be spotted
but are so affected by systemic toxins that they cease to func-
tion normally and are dull grayish in color.
Stems of badly diseased plants are swollen near the lower leaf
nodes. The swollen tissue appears to be water-soaked at first,
and then turns red or brown. Eventually it dries out and longi-
tudinal brown cracks form on the stem. There may be smaller
brown cracks on the lower and unswollen parts of the stem.
Some affected plants are so weakened that they are easily broken
over at the first or second node by the wind.
Pods on affected plants usually are few in number and poor
in quality. They are likely to be spotted if conditions are favor-
able for the occurrence of secondary infection when they are
forming (Fig. 7). The pod spots are 1/8 to 1 inch in diameter
and have a greenish water-soaked appearance. When the spots










-t


Fig. 7.-Halo blight spots on bean pods.







Diseases of Beans in Southern Florida


dry out they have a reddish brown color. Other organisms
which invade these spots at certain times may cause a soft
decay which spreads through the pod.
Seeds produced on severely blighted plants are small and
wrinkled. On less severely affected plants the seeds sometimes
show yellow spots around the hilum or even an entirely yellow
seed coat. (This symptom is not seen in the dark-seeded vari-
eties.) Some seeds from diseased plants show no evidence of
infection. It is therefore impossible to determine by inspecting
the seed whether a particular lot is diseased.
The bacteria may accumulate in the plant in such numbers
that some of them are forced to the surface of the affected
stem or pod while the spots are in the water-soaked stage. The
bacterial exudate may be seen protruding from the diseased
tissue in the form of gelatinous masses, drops, coils or films.
The exudate is a viscid grayish white material. Where the
exudate has dried in a mass it appears to be of an amber color,
but thinner films are silvery. It is never yellow as is similar
exudate from plants affected with common bacterial blight.
Halo blight of beans is caused by the bacterial organism,
Pseudomonas medicaginis var. phaseolicola (Burkh.) Stapp and
Kotte. The bacteria within the tissues of the stems, leaves and
pods (35) have entered the plant through the cotyledons or
through the pores on the leaves, stems and pods. Those present
in infected seeds are lodged under the seed coat and do not infect
the young embryos until the seeds swell and start to grow.
The bacteria multiply so rapidly in the stem cortex that its
cells are torn apart and disintegrated. Pockets containing
masses of bacteria are thus formed in the stem. The bacteria
secrete toxins which enter the vascular system, weaken the plant
and cause chlorosis in the terminal bud.
Secondary infections occur when bacteria are transferred from
the exudate on diseased plants to healthy parts of the same or
other plants. Many plants besides those from diseased seed
become infected in this way. The bacteria gain entrance through
pores or wounds in leaves, stems and pods. The cycle of bac-
terial development after the organism enters the plant is similar
to that for the primary infections. There may be several subse-
quent cycles of development on new host plants.
Halo blight bacteria in diseased plants reach the soil through
crop debris. Whether these bacteria can later infect beans of
a new planting on the same soil has not been fully determined.







Florida Agricultural Experiment Station


Experiments seem to show that while the blight bacteria can
infect beans from the soil they do not survive in Florida soils
as long as 30 days.
Environmental factors play a large part in the development
of halo blight. If the soil is dry and the weather fair when
infected seeds sprout, blight may not appear in the crop. The
greatest trouble occurs when infected seeds are planted in wet
soils and the weather is showery and humid during the period
of germination and early growth. A few plants infected from
seed can inoculate an entire field during a driving rainstorm.
Heavy rains and hail batter the bean leaves so that the tissue
is water-soaked and sometimes torn. The disease symptoms
appear sooner on such leaves and the damage is greater.
Temperatures favorable to halo blight development occur in
Florida from October to May. Although the disease is said
to reach its maximum development at moderate to cool tem-
peratures, there have been severe outbreaks of halo blight in
the early fall and late spring as well as in the cooler months.
Halo blight may develop on shipped beans if they are not
properly refrigerated. It is unsafe to pack any spotted pods
for shipment. Beans from infected fields may be infected but
not show spots at time of shipment. These will develop pod
spots in transit if they are not refrigerated. The cars should
be precooled to 450 F. and standard refrigeration should be main-
tained en route to market.
Direct measures for the control of halo blight never have been
successful. The bacteria in the seed are lodged under the seed
coat so that usual methods of seed treatment are not effective.
Research eventually may yield some sort of seed treatment for
disease control, but at present none is recommended.
Although spraying beans with copper and sulfur fungicides
is commonly practiced, there has never been any convincing
evidence that fungicides applied to the foliage will help to con-
trol the disease. Experimental work in other states also has
indicated the ineffectiveness of fungicidal sprays.
Planting disease-free seeds is the best protection against halo
blight. Test plantings of clean seeds have indicated that this
is a reliable method. There appears to be no danger that a crop
from clean seeds will become infected from bacteria in the soil
if a month intervenes between a diseased crop and the date of
the new planting. There is some danger that a crop from clean
seeds will become infected from a nearby diseased crop.







Diseases of Beans in Southern Florida-


Seeds free from the halo blight bacteria can be secured only
from fields where the disease did not occur. For this reason
most of the major seed companies conduct their bean seed grow-
ing operations in the semi-arid sections of the West. In some
seasons it is possible to produce blight-free seeds in certain
sections of Idaho, Wyoming, Colorado and Montana but, un-
fortunately, in other seasons this is not true. Above normal
precipitation occurred in these states in the 1937 and 1938
growing seasons and considerable blight was reported from
there (23). The fact that bean seeds are produced in those
states is not a guarantee that they will be disease-free, but they
are more likely to be so than seed from more humid sections.
While halo blight may occur in California, Nevada, New
Mexico, Washington, and Oregon, it rarely causes enough loss
to be of any economic importance (18) in these states. Inspec-
tion and certification of bean fields for freedom from diseases
would solve the halo blight problem for Florida growers.

COMMON BACTERIAL BLIGHT
It is not necessary to describe this disease in detail because
it is so similar to halo blight. Some of the differences between
the 2 diseases will be mentioned.
Leaf spots of common blight are larger and more irregular
in shape than those of halo blight. There is no definite broad
halo around the isolated spots (8) but sometimes these leaf
spots have a narrow yellow border. The bacteria which some-
times exude in masses from the infected stems and pods are
yellow instead of white or grayish. Common blight is con-
sidered a warm weather disease, although this has not been a
distinguishing character in Florida. The disease is more often
found to occur in crops grown from seed produced in the East
or in Colorado than in crops from seed produced in Idaho,
Wyoming, Montana, and other far Western states.
Common bacterial blight is caused by the bacterial organism,
Xanthomonas phaseoli (E. F. Sm.)Dowson. This organism is
closely related to the halo blight bacterium but can be distin-
guished in culture by its color, which is yellow instead of white,
and by some of its physiological reactions with nutrient materials.
Recommendations for control of common bacterial blight are
the same as for halo blight. Seed treatments and spraying are
not effective. The planting of clean seed is the best assurance







Florida Agricultural Experiment Station


of obtaining a clean crop. This practice has the same limita-
tions mentioned in discussing the control of halo blight.

DISEASES CAUSED BY FUNGI

POWDERY MILDEW
Powdery mildew, sometimes called white mold, is a disease
common to beans and many other species. Some plants reported
to be susceptible to the powdery mildew of beans are peas, cow-
peas, clover, vetch, cabbage, carrots, tomatoes and turnips.
Different bean varieties vary in susceptibility to powdery
mildew. Bountiful and Hodson Wax are very susceptible in
Virginia (10), but Refugee is quite resistant. In Florida String-
less Black Valentine and certain strains of Kentucky Wonder
are more resistant to mildew than the Bountiful.
Powdery mildew occurs in many states where beans are grown,


Fig. 8.-Powdery mildew on bean leaves.







Diseases of Beans in Southern Florida


but is most prevalent in the Southeastern states from Virginia
to Florida. It occurs annually in Florida during the late fall,
winter and early spring.
Rather heavy losses may be caused by the mildew if pre-
ventive measures are not employed. The vines do not mature
a crop or yield only a few beans of inferior quality when mildew
is severe. Losses due to other diseases of the pods which follow
mildew injury may occur in shipped beans.
Powdery mildew is first seen as small, dark green spots on
the upper surfaces of the older leaves. Later these spots are
covered with a powdery or cobweb-like growth and are from
1/16 to 1/3 inch in diameter. The mildew eventually occurs
on the lower surfaces of the leaves and on young leaves, stems
and pods. It may become so widespread on the leaf that the en-
tire leaf surface is covered with the powdery growth. On stems
and petioles the spots are more often elongated streaks or collars.
Affected leaves curl downwards when mildew injures the
veins or midribs. Shortly after mildew appears the tissue be-
neath the spots becomes withered and brown. If the powdery
growth is brushed off these spots resemble the spots caused by
common bacterial blight. When the mildew is severe the leaves
turn yellow, wither and die. Dead leaves fall; a few younger
leaves at the top, which are less affected and still green, remain.
The tissue beneath the powdery spots on the pods, petioles
and stems becomes reddish brown or brownish purple. Badly
mildewed pods have a rusty appearance and the disease therefore
sometimes erroneously is called rust. Affected pods do not
have deep lesions like those caused by the bacterial blights,
anthracnose and soil rot.
This disease is caused by the fungus, Erysiphe polygoni DC.
Unlike many parasitic fungi, this one confines its activity to the
surface cells of its host plants. It sends a few minute threads
or suckers into the epidermal cells of the plant from which it
obtains its sustenance.
This fungus produces only single-celled, non-sexual spores
under Florida conditions. These spores are borne on short erect
branches of the mycelium from which they are detached easily.
New infections result when these spores are transferred to other
plants under suitable conditions. The longevity of the spores in
Florida is not known, nor is it known how this fungus survives
the long Florida summers when conditions are unfavorable for
infection and few of its host plants are growing.







Florida Agricultural Experiment Station


Powdery mildew is most prevalent during cooler parts of the
growing season but may occur at almost any time when beans
are grown in southern Florida. It is most likely to be present
and to damage the crop in the period from November to March.
The spores of the fungus are able to germinate in a humid
atmosphere. Night fogs and heavy dews, common during win-
ter in southern Florida, are especially favorable to development
of the disease.
Air currents readily disseminate the very light spores and
the fungus spreads over wide areas in this way. Because of
the universal occurrence of the spores through the bean grow-
ing area, during periods when the fungus is active protective
measures must be employed to save the crop.
Plants which have grown slowly because of cool weather, rust
infection, dry soil or lack of nutrients seem to be particularly
susceptible to the disease. The same is true of the older shaded
foliage and of old plants when they are declining after harvest.
Powdery mildew is controlled easily by the application of
protective fungicides (Table 1). Sulfur dusts and wettable
sulfur sprays have given good control when applied prior to the
occurrence of infection. Two or 3 applications of some form
of sulfur generally are considered adequate. The possibility of
injuring beans with sulfur fungicides is discussed in a later
paragraph. Unless the mildew becomes very threatening and
the plants have not been protected previously, it is not well to
apply sulfur fungicides after the plants come into bloom.

TABLE 1.-EFFECT OF FUNGICIDES IN THE CONTROL OF POWDERY MILDEW
OF BOUNTIFUL BEANS.

Treatment Hampers per Acre
A B C D Average

None .........-........ ............ 120 167 144 95 131
Black sulfur dust .................. 143 176 150 135 151
15-50 Wettable sulfur spray-- 150 162 150 137 150
4-4-50 Bordeaux spray ......... 150 173 173 138 157

Bordeaux mixture also may be used for the control of this
disease. Bordeaux spray applied to young beans for a possible
nutritional effect on the crop will be effective against mildew.
It probably is advisable to follow such an application with one
of sulfur within a week or 10 days.







Diseases of Beans in Southern Florida


RUST
It was thought for many years that bean rust was identical
with the rust of cowpeas and several wild legumes. However,
experiments in Virginia and elsewhere (13, 17) have shown that
cowpeas and certain wild legumes are not susceptible to bean
rust. Plants now considered susceptible to bean rust are varieties
of the common bean, lima bean, sieva bean and tepary bean.
Susceptibility to rust varies not only with the variety of bean
but with the strain of rust fungus. Beans commonly grown in
Florida, such as Bountiful, Stringless Black Valentine, Giant
Stringless Green Pod, Sure-Crop Wax and Tendergreen, are very
susceptible to the forms of rust which have occurred in Florida in
recent years. Most of these varieties had been listed (17) as
fairly resistant to rust in other parts of the United States.
Certain rust-resistant strains of Kentucky Wonder have been
found to resist the rust in Florida. These are useful for home
garden but not commercial production in this state. They are
useful also in breeding work for the production of new varieties
of rust-resistant beans. Fordhook and Henderson Bush lima
beans never have been observed to be seriously affected with
rust in Florida, although a few pustules sometimes occur on their
foliage and they have been reported (17) to be susceptible in
other states. Several varieties of beans which have been adver-
tised as "rust-proof" or rustlesss" are not rust-resistant. These
terms have been applied erroneously to varieties of beans re-
sistant to anthracnose, a very different disease of beans.
Bean rust occurs in many of the countries of North and South
America and Europe. In the United States it has been particu-
larly prevalent in certain years in Virginia (34), West Virginia,
Tennessee, Georgia, Florida, Alabama, Louisiana, Texas, Colo-
rado and California. In Florida the most recent severe out-
breaks occurred on winter and spring crops in Broward and
Palm Beach counties during the 1935-36 and 1936-37 seasons.
First symptoms of rust infection on beans is the development
of pale yellow spots on the under sides of affected leaves. These
spots are circular in form and are generally less than 1/16 inch
in diameter. There may be only a few spots or as many as
several hundred on each leaf. A day or 2 after the yellow spots
appear the surface of the spots becomes raised and somewhat
later the epidermis of the leaf is broken and a pustule of red
spores is exposed. The spores are so small that a single pustule
contains thousands of them. If there are many spots on a leaf







Florida Agricultural Experiment Station


the spores fall from the pustules as a reddish brown dust which
collects on the leaves and stems and even may be seen on the soil
under heavily rusted plants. The clothing of persons who walk
through a rusted field may be reddened by spores brushed from
plants.
Rust pustules occur also on the upper surface of the leaf but
their formation there is later and less abundant than on the
lower surface. Usually the spots on the upper surface are
directly over ones on the lower surface, and are part of the same
infection. There may be a yellow halo around the spots on the
upper leaf surface. This symptom varies somewhat with the
variety of bean and the form of the rust fungus present. When
infections are very numerous the whole leaf becomes yellow
and later withers and dies. Many leaves fall prematurely.
In southern Florida the disease rarely has been observed on
stems and pods. Sometimes the pods have a rusty color from
numerous spores which have fallen from the leaves.
Damage to the crop is caused when the leaves are so heavily























L_ _
Fig. 9.-Rust on bean leaves, showing comparative symptoms on the
lower (left) and upper leaf surfaces.







Diseases of Beans in Southern Florida


rusted that they become chlorotic, wither and die. This inter-
feres with the production of carbohydrates and causes few, or
poorly filled, pods to be produced. Yield reductions are propor-
tionate to the earliness and severity of the attack.
Bean rust is caused by the fungus, Uromyces phaseoli typical
Arthur. This fungus belongs to the group causing rust diseases
of cereal crops, but is not identical with any other rust fungus.
More than a dozen biological forms of the bean rust fungus are
being studied by various workers in the United States at this
time and research is still adding to their number.
In southern Florida the only spores produced by the rust
fungus are the uredospores which occur as a reddish brown
powder in the pustules on bean leaves. Since bean rust does
not occur during the summer in southern Florida and since the
uredospores are rather short-lived, it is believed that uredospores
produced on plants in areas to the northward are carried by air
currents to southern Florida where they initiate new cycles of
infection during the winter and spring.
The uredospores germinate on the bean leaves and send
thread-like branches into the leaf tissue. Most of the spores
on a leaf can germinate and enter the leaf in a period of 8 to 10
hours under favorable conditions. The yellow spots which are
the first evidence that infection has occurred appear in 4 to 6
days. Seven to 10 days pass before the mature spore pustules
rupture the leaf surface. These spores are immediately capable
of initiating new infections.
The mature uredospores fall from the pustules and are dis-
seminated through the field by air currents. Similar spores of
the cereal rust fungi are believed to be carried by air currents
for hundreds of miles (20).
The spores germinate on the bean leaves only when the rela-
tive humidity is high or when there is water on the leaves.
Temperatures near 600 F. were found to be the most favorable
for the development of infection following artificial inoculation.
Infection has been known to follow incubation periods in which
the temperature was as low as 480 F. and as high as 980 F.
No infection occurred in 1 test in which the temperature rose
to 103c F. during the incubation period. As a rule, infection
was obtained more readily at temperatures below 750 F.
The fact that bean rust has not been observed to occur in
southern Florida from the latter part of May until November
is attributed to the prevalence of temperatures considerably








Florida Agricultural Experiment Station


TABLE 2.-NUMBER OF RUST PUSTULES ON SPRAYED AND DUSTED PLANTS
ARTIFICIALLY INOCULATED.
Wet- IBlack
Treatment Basic Bor- None table Sulfur Sulfur
Copper deaux Sulfur Dust Dust

Pustules per plant ..... 30.3 50.4 62.3 6.2 5.3 0.4

Percent control ........- 51.4 19.1 -. 90.1 91.4 99.4


TABLE 3.-COMPARATIVE EFFECT OF COPPER AND SULFUR IN THE CONTROL
OF RUST ON BOUNTIFUL BEANS IN 1936.


Treatment
A

None ......-...........-.... --..-.......- 187

Three applications of sulfur dust ...... 280

Two early applications of sulfur dust 209

Two late applications of sulfur dust.. 197

Three applications of bordeaux spray 199


Hampers per Acre
B [ C D Average

194 206 199 196

255 270 260 265

236 232 256 233

190 220 231 209

146 178 196 180


TABLE 4.-COMPARATIVE EFFECT OF COPPER AND SULFUR FUNGICIDES IN
THE CONTROL OF RUST OF BOUNTIFUL BEANS IN 1938.*

Treatment A B Average


None ................... .... ..... ... ..-- ........ 89 97 93

Three applications of wettable sulfur .........-.. 138 147 142

Four applications of wettable sulfur ........-.. 170 172 171

*Five applications of wettable sulfur ......... ... 144 167 155

*Six applications of wettable sulfur ..--....-..... 155 155 155

Three applications of bordeaux spray ......- 95 92 94

Five applications of bordeaux spray ............ 128 141 134

Four applications of sulfur paste .................... 164 160 162

Note that in this experiment the yield was not increased by making more than four
applications of wettable sulfur. Injury to the blooms and young pods probably accounted
for the lower yields on the plots sprayed 5 and 6 times.

above the optimum and near the maximum for infection. On
the other hand, during winter and spring the temperatures are
favorable for rust development, and night fogs are most preva-







Diseases of Beans in Southern Florida


lent. Even on nights without fog during winter the relative
humidity is usually 100 percent, and the foliage is wet with dew.
Sulfur fungicides are required for the control of bean rust
(Table 2). These materials have given very satisfactory con-
trol of the disease and the yields of beans have been increased
as much as 78 hampers per acre (84 percent) on experimental
plots (Tables 3 and 4). Growers who have used the recom-
mended methods also have obtained good control of the disease.
The amount applied seems to be more important than the
kind of sulfur. A few soluble sulfur fungicides have a very
low sulfur content and should not be used for the control of
rust because it is not possible to apply enough sulfur at 1
application. Good results have been obtained by applying dust-
ing sulfur or wettable sulfur sprays. It is recommended that
the sulfur have a fineness of at least 325 mesh. The purity of
the sulfur is not important if the proper adjustment of the
rate of application can be made without the use of exceptionally
heavy applications of materials. Good control of bean rust
has been obtained by the application of sulfur at the rate of
15 to 25 pounds per acre. In general, more material is used
when dusting than when the sulfur is applied as a spray.
The frequency with which applications should be made de-
pends upon the severity of rust in the vicinity and the prevalence
of weather conditions favoring its development. If rusted fields
are nearby and the weather is humid and moderately cool, it
is well to start the applications 2 or 3 days after the beans
emerge and to continue them at intervals of 5 or 6 days until a
few days before the plants bloom. This may require as many as
6 applications. The rate of application may be reduced if the
frequency is increased. The important feature is thorough
coverage of the foliage with a light application of sulfur at all
times when there is a threat that rust will develop. The bean
plant produces new foliage very rapidly and this factor necessi-
tates frequent applications to keep all the foliage protected. The
material applied in the early applications remains on the older
leaves and protects them after it is no longer possible to reach
them with fungicides because of the heavy growth of new foliage.
At times when rust is not present in the vicinity the grower
should be on watch for its first development. It is a waste of
material and labor to start applying fungicides to a field of
beans after rust has made much progress. Plants which have
30 or 40 pustules to the leaf and are becoming yellow from







Florida Agricultural Experiment Station


the effects of rust are not likely to be saved by any control
measures. Such plants usually have many more infections de-
veloping than there are pustules at the time of observation.
Since the infection occurs a week or 10 days before the pustules
appear there is nothing that can be done to prevent the rust
from developing when many pustules are evident.
There is little reason for a grower allowing the rust to catch
him unawares, since an outbreak of rust does not begin so sud-
denly as it sometimes seems. A few pustules of rust can be
found on the leaves for 2 or 3 weeks before there is a general
outbreak. The appearance of these pustules should be the signal
to begin applying sulfur fungicides and the frequency of the
applications should increase as the number of pustules on un-
protected plants increases. Even better results can be obtained
when one watches for the first development of the yellow spots
on the under sides of the leaves, since these will warn of an ap-
proaching outbreak several days sooner than will mature pustules.
The sulfur fungicides may be applied with hand-operated
machines, power equipment or by airplane. Dusting is prefer-
able if only hand equipment is available. Either dusting or
spraying is satisfactory with traction and power-driven field
equipment.
Applications of sulfur should not be made to bean plants
that are in bloom or that have small beans on them. It has
been found that when sulfur is applied during or after bloom-
ing the yield is reduced slightly and there is an increase in the
number of scarred beans. Plants well protected up to the bloom-
ing period should remain in good health for 2 or 3 weeks.
Copper fungicides have no value for the control of bean rust.
They are not only less efficient in preventing infection, but after
infection has occurred copper sprayed plants suffer more than
unprotected ones. Experiments have shown that the yield may
be reduced considerably where copper fungicides have been ap-
plied as a protection against rust.
To a limited extent control of bean rust is possible through
the use of rust-resistant varieties. A few rust-resistant strains
of Kentucky Wonder are available for home garden planting.
These can be used to advantage wherever rust prevents the
growing of other types of beans in Florida. As a result of
several years of breeding and selection of rust-resistant types
of beans at the Everglades Experiment Station in cooperation
with the United States Department of Agriculture, the Florida







Diseases of Beans in Southern Florida


Belle (a green-podded bush bean) and the Florida White Wax
varieties were released to seedsmen in 1943. They are resistant
to some forms of rust and mildew and are of good quality and
market type. Other rust-resistant types are being tested and
it is likely that other desirable varieties possessing resistance
to rust will be developed as this work is continued.

ANGULAR LEAF SPOT
This disease has been observed only on snap beans in Florida,
although it has been reported on peas (9) in other states. It
has been seen most often on Bountiful beans, but other varieties
seem to be susceptible. It is not a common disease of beans in
southern Florida.
Angular leaf spot is characterized by angular brown spots
on the leaves of affected plants. The maximum width of these
spots varies from 1/16 to 1/4 inch. There may be as many
as 100 of these spots on a leaf. A gray fungous growth is seen
on the under sides of the dead spots. The fruiting structures
of the fungus appear as black spines bearing a crown of grayish
spores. These appear in the center of the spots as they become
old and begin to dry out.
Angular leaf spot is caused by the fungus Isariopsis griseola
Sacc., which is seen as the gray growth on the under sides of
the leaf spots. The black spines are composed of several strands
of the fungous mycelium which are united in a column and bear
spores at their free ends. These large 2- to 4-celled spores are
disseminated by wind and rain and can cause new infections
Angular leaf spot has occurred so infrequently that experi-
ments for its control never have been conducted. Bordeaux
mixture has been suggested (9), but its use on beans in Florida
should be confined to 1 or 2 early applications.

SCLEROTINIOSE
This disease has been found attacking to some degree prac-
tically all vegetable crops except onions, and different names
have been applied to it on various hosts. It is commonly known
as watery soft rot, sclerotinia rot, sclerotinia wilt or white mold
on beans, tomatoes, potatoes and cabbage; as pink rot on celery;
and as drop on lettuce. In addition to the commercial vegetable
crops, the disease has been found on a number of wild hosts,
particularly ragweed. Since powdery mildew sometimes is
called white mold, that name should not be used for this disease







Florida Agricultural Experiment Station


on beans, although it is descriptive of certain of its symptoms.
The disease has become of increasing importance on beans
during recent years in several sections of Florida, particularly
the lower third of the peninsula. It varies is severity from one
soil type to another. It is fairly general and severe in the better
drained marl soils of Dade County; it is widely distributed but
severe only on low fields in the sandy soils between Miami and
West Palm Beach, and it has been found only to a slight extent
in a few instances in the muck soils around Lake Okeechobee.
No varieties grown commercially in Florida are resistant and
none have been reported as immune (18). The disease is grad-
ually increasing in severity in potato fields in Dade County (11)
as well as on tomatoes in this same area.
Scterotiniose is caused by Sclerotinia sclerotiorum (Lib.) DBy.,
a soil-inhabiting fungus which is dormant in Florida during
the summer and at other seasons when the weather is warm and
dry. It survives in the form of small black bodies called sclerotia
in old plant debris or in the soil. During cool, moist weather,
these sclerotia germinate to tiny mushroom-like structures which
bear hundreds of spores. The spores are discharged forcibly
and are carried by air currents. If deposited on growing bean
or other susceptible host plants when conditions are suitable,
they infect these plants. Spore infections can take place readily
through dead areas, whether caused by fungi, spray burn or
mechanical means, but the spore germ tubes are unable to estab-
lish infection in healthy tissues under normal conditions. Once
a mycelium is formed, it can infect healthy tissue readily
through contact. The sclerotia also may produce mycelial threads
which grow in or on the surface of the soil and plant parts and
initiate infections through contact with susceptible parts.
Since sclerotiniose is essentially a cool weather disease, it
causes its greatest damage to Florida vegetables during the win-
ter months when periods of intermittent rains and heavy dews
occur. It may attack bean plants during early stages of growth
and kill them outright. More often, heaviest infections occur
when the plants are in full bloom, when there is heavy foliage,
resulting in damage to the main stem and branches, the foliage
and the developing pods.
Initial infections appear as irregular, water-soaked spots
which enlarge gradually, causing a somewhat soft watery rot
of the affected parts. Leaves on a branch above an infection
wilt when their water supply is cut off. Infection is always







Diseases of Beans in Southern Florida


accompanied within a few days of warm wet weather by a heavy
growth of white cottony fungous mycelia on the diseased parts
(Fig. 10). A few days later the irregular black sclerotia begin
forming and frequently occur in large numbers.
Infection may cause a total loss of plants in individual fields,
although scattered diseased plants are the general rule. The
heaviest losses on beans from this disease usually are sustained
during transit. A few infected pods in a packed basket may
cause all of the beans in the container to become infected within
a period of 2 or 3
days. Many cars of
beans have been ship-
ped from Florida in
apparently good con-
dition only to be re-
jected at destination
because of sclerotinia
rot.
Cool, rainy weath-
er, fogs or heavy
dews, and poor drain-
age during the grow-
ing season favor
development of
sclerotiniose. Factors
which tend to reduce
air circulation about
the individual plants,
such as too thick
planting and a luxuri-
ant growth of weeds,
also increase the in-
cidence of the dis-
ease. It has been Fig. 10.-Sclerotinia sclerotiorum on bean pods.
(Photograph by W. D. Moore, USDA.)
shown (21) that the
fungus attacks bean pods in transit most vigorously at tempera-
tures ranging from 66 to 75 F. Temperatures lower than
500 F. retard its development considerably.
Research work looking to a satisfactory control for sclero-
tiniose is now under way in southern Florida but definite recom-
mendations are not available as yet. Cyanamid treatment has
given good control in muck and marl soils in some seasons (6).







Florida Agricultural Experiment Station


The amount of cyanamid recommended for killing sclerotia is
750 to 1,000 pounds per acre for these soils. Cyanamid should
be applied uniformly with a lime distributor or a special broad-
caster and immediately disked into the soil 3 to 5 inches deep.
Cyanamid is toxic to sclerotia and plant growth when freshly
applied and it contains nitrogen in a form not immediately avail-
able to plants. It should be applied far enough in advance of
planting a crop for the toxicity to disappear and for the nitrogen
to be converted into nitrate nitrogen which can be used by
plants. Time required for completion of these reactions varies
with the temperature, moisture content and type of soil treated.
The cyanamid treatment has not given as good results in sandy
soils. Furthermore, since the disease is spread by spores, it will
become re-established in treated fields of any soil type within
a few years from spores blown in from neighboring, non-treated
fields.
Flooding the land with water and leaving it immersed for
a period of 4 to 5 weeks during late spring or summer has killed
the sclerotia and controlled the disease in celery fields (5). This
method may be applicable to bean fields situated so that the land
can be flooded readily at low cost.
Fungicides applied to the foliage and to the soil immediately
around the growing plants have not given satisfactory control
of sclerotiniose in Florida.
From investigational work done to date, a few general prac-
tices may be followed that will aid in reducing the amount of
disease losses on beans grown in infected soils. They are as
follows: (1) Make seedings where possible to avoid bean harvest
during late December and January, the heaviest disease period
in the year; (2) avoid seeding too heavily and keep the rows
at maximum width to promote better aeration; (3) keep the
fields well drained during the growing season; (4) harvest beans
only when dry from fields where sclerotiniose is present and
grade carefully before packing to remove all infecter pods;
and (5) pre-cool cars of beans to 480 F. or lower as rapidly as
possible before shipping and maintain this temperature by
standard refrigeration while the cars are en route to market.
Very little spoilage of beans can result from sclerotinia rot
under these conditions.
ANTHRACNOSE
Anthracnose of beans has been known for many years and is
world wide. In the United States it is most prevalent in the







Diseases of Beans in Southern Florida


Northeastern states. It occurs in Florida and the other Southern
states during the cooler seasons of the year.
The common bean, lima bean and sieva bean are the principal
species affected by anthracnose. It has been reported (4) that
few species outside the genus Phaseolus are susceptible to the
bean anthracnose fungus and that no plants except varieties of
the common bean are so susceptible that the disease becomes
severe on them.
Some varieties of beans are resistant to anthracnose, but not
all of them are resistant to all forms of the fungus.
Low germination, death of seedlings, low yields, poor quality
in the harvested crop, and spoilage of beans en route to market
are some of the ways in which the disease causes economic losses.
It has been known to cause heavy losses in Florida, although
in recent years it has not been of importance in southern Flor-
ida. During the 10-year period 1928-38 the loss due to this
disease in Florida has been estimated at from nothing to 11
percent of the crop (23).
Anthracnose produces distinctive symptoms on leaves, stems,
pods and seeds of infected plants. Veins on the under sides of
the leaf are darkened and the adjacent leaf tissue withers.
Petioles severely affected show brown streaks and may become
so weak that they permit the leaf to droop. Dark streaks and
cankered areas are produced on the stems. This is especially
serious in seedlings, since it may cause them to break over and
wither. Dark cankers appear on the cotyledons of seedlings
from diseased seed.
If conditions are favorable for secondary infection, deep
cankers are produced on the pods of affected plants. The pod
spots are nearly circular in form except where 2 or more have
joined (Fig. 11). Color of the cankers varies from shades of
brown to nearly black. Some spots reach a diameter of a half
inch and penetrate through the pod wall into the underlying
seeds. Diseased seeds are shrivelled and darkened.
Anthracnose is distinguished from the bacterial blights by
the presence of masses of flesh-colored spores at the center of
the pod spots. If the spore masses have dried they appear as
gray, brown or black pimples. Similar spore masses occur on
the infected cotyledons during wet weather.
Anthracnose is caused by the fungus Colletotrichum lindemu-
thianum (Sacc. and Magn.) Bri. and Cav. There are several







Florida Agricultural Experiment Station


biologic forms of this fungus, each restricted in parasitism to
certain varieties of beans.
Spores produced on the cotyledons of infected seeds are re-
sponsible for infections on seedling beans. These spores are
transferred from the cotyledons to the leaves and stems by
splashing rain. They infect the seedlings by sending slender
germ tubes into the epidermal cells of the plant. The mycelium
of the fungus grows within the plant, penetrating cells and
killing them as it progresses. This is the cause of the collapsed
tissues and the dark streaks which appear on infected plants.
A mat of the mycelium forms in the collapsed tissue and from
this structure a new crop of spores is borne. These spores in
their turn cause new infections on leaves, stems and pods, or
on other nearby plants to which they may be carried.
Some infections may occur from spores in the soil or from
diseased parts of plants remaining in the field. Infected seed
is the most important source of infective material in all parts
of the country, and is probably the only source of the disease
here because our climatic conditions are unfavorable for summer
survival of the spores in the soil or in trash.
Temperature and humidity are controlling factors in the de-
velopment of anthracnose. In Florida humidity is generally

Fig. 11.-Anthracnose spots on bean pods.






^S.o^^^^ -







Diseases of Beans in Southern Florida


high during the growing season and seldom limits infection.
Night fogs and heavy dews provide adequate moisture for its
development.
Temperature is the factor which limits bean anthracnose to
the cooler seasons in Florida. In Louisiana (12) the disease
does not develop on beans during summer months because pre-
vailing temperatures are too warm. This is true in Florida for
even more of the year and as a consequence anthracnose has
been known to occur only on the winter crop in this state.
Anthracnose is likely to develop on beans which have been
shipped to market if they were picked while wet with dew or
rain. A few spores spread from diseased plants in this way
can cause a great deal of damage at a time when it is particu-
larly costly to the grower. If the temperature of the beans is
reduced to 450 F. as quickly as possible practically no spoilage
due to anthracnose will result.
The use of clean seed produced in disease-free fields is the
best guarantee that the bean crop will be free of anthracnose,
even when the weather becomes favorable for its development.
The reduction in occurrence of anthracnose in Florida in recent
years may be due to an increasing use of Western-grown seed.
Spraying experiments were conducted in New York State
from 1908 to 1916 to determine whether this disease could be
controlled with fungicides. In these experiments (4) bordeaux
mixture controlled anthracnose. Good results also were obtained
with lime-sulfur solution. Because of improvements in spray-
ing equipment and in copper and sulfur fungicides since that
time, it is probable that anthracnose could be controlled well with
fungicidal sprays in Florida. The disease has not been preva-
lent enough in southern Florida in recent years to provide an
opportunity for testing newer materials and methods.

RHIZOCTONIA DISEASE
Rhizoctonia attacks many vegetable crops grown in Florida.
Beans, peas, cabbage, lettuce, celery, tomatoes and potatoes are
most often affected. It also affects many species of ornamental
plants and native weeds.
All varieties of beans seem to be equally susceptible, although
no experiments have been performed to substantiate this state-
ment. There is evidence that certain biological strains of the
Rhizoctonia fungus (24) are more active parasites than others.
This fact might make it appear that there are varietal differ-







Florida Agricultural Experiment Station


ences in the resistance of beans to this fungus, when the real
differences are in the strains of the fungous parasite.
The Rhizoctonia disease is common wherever beans are grown.
It is sometimes referred to as stem canker, damping off, and
stem rot (18). It appears whether the crop is planted on virgin
soil or on land that has been cultivated for many years, and on
sands and marls as well as peats. Fortunately, the disease is
less destructive than it is common. Usually it affects only a
few plants scattered through the field. At certain times it may
appear suddenly and threaten to destroy large acreages of
beans, but its ravages
,are checked quickly by
a return to conditions
more favorable to the
bean crop.
Average losses due to
this disease are small,
but losses may be quite
heavy in certain fields.
Such losses are of par-
S ticular concern to the
,* small grower, since he
may lose a considerable
part of his planting.
in shipment is due to this
disease.
The Rhizoctonia dis-
Sease is almost as varied
in its symptoms as it is
in the species of plants
Fig. 12.-Roots and stems of beans affected it affects. Beans are sus-
with Rhizoctonia root rot (right) contrasted
with a normal root (left). ceptible to the disease
from the time the seeds
are planted until the snap beans are marketed. Symptoms vary
with the age and part of the plant affected.
Bean seeds sometimes rot in the ground before or during
germination. Some seedlings emerge which have been twisted
and stunted by the disease. Reddish brown lesions occur on the
stems of affected seedlings and may be so numerous that the
entire stem is girdled for several inches at or near the soil line
(Fig. 12). Very young seedlings topple over and "damp-off"







Diseases of Beans in Southern Florida


when affected in this way, but older plants remain erect, grad-
ually becoming yellow and withered. Sometimes it is the roots
which are affected and become brown and rotten. The foliage
turns yellow and then withers in this case just as when the stem
is girdled. A few plants recover sufficiently to produce new
roots directly from the stem at a point above the infection and
near the soil line. Even though these plants remain alive they
are not as vigorous and productive as healthy plants.
Leaves of affected plants wilt when the infection destroys the
water absorbing and conducting tissues in the roots and stems.
Leaves, stems and pods which touch the soil or have been
splashed with soil become infected and decay. Infected leaves
have water-soaked lesions of indefinite shape and size and
eventually disintegrate completely. The ends of pods touching
or near the soil are affected by the phase of the disease known
as soil rot. The pod lesions may be only a few scattered spots
which are rather deep and are concentrically ringed, or the lesion
may be quite large and involve the entire width of the pod. In-
fected parts of the pods have a dark brown color.
The fungous mycelium can be found on all affected parts of
the plant. It is sometimes visible to the unaided eye as delicate
brown threads running over the surface of lesions and adjacent
sound tissues. The fungus produces sclerotia, which are drouth-
and heat-resistant structures for the perpetuation of the fungus
on other host plants, but these organs have not been found on
affected beans in southern Florida. It appears that here the
fungus is in the vegetative state throughout the year.
The mycelium of the fungus is best seen when it causes a form
of nesting in beans which have been packed for shipment. The
mycelia are neither so white nor so abundant as those of Sclero-
tinia rot. They occur as a spider-web growth among the beans
in the hamper and occasionally cause the development of definite
concentric lesions (21) on some pods.
The Rhizoctonia fungus which causes root rot is a very com-
mon soil-inhabiting organism. It is able to live on organic mat-
ter in the soil as well as to parasitize beans and other plants.
The specific form of the fungus is generally said to be Rhizoctonia
solani Kuehn (Pellicularia filamentosa (Pat.) Rogers).
Soil temperatures ranging from 750 to 850 F. are particularly
favorable to the rapid development of Rhizoctonia and to the
infection of beans by it. Soil temperatures in this range occur
in the early fall and late spring in southern Florida. Such tem-







Florida Agricultural Experiment Station


peratures may occur in the soil after a week or more of unusually
warm weather in winter. Stem and root rots of beans are preva-
lent during such periods and particularly in the early fall. When
soil temperatures are lower than 70 F. there is little root rot.
Moist soils favor the development of this disease of beans.
The trouble frequently arises following showers heavy enough
to cause water to stand in low places in the fields for several
hours. However, in peat and muck soils lack of moisture seldom
limits the disease. In drier soils infections are found on the
roots and lower parts of the stem, while in wetter soils infec-
tions are higher on the stem and in wet weather may reach the
leaves, branches and pods. Loose peat soils are more likely to
give trouble from this disease than are the more compact soils.
Recent additions of crop refuse, cover crops and weed growth
stimulate the development of the fungus in the soil. The damage
caused by the Rhizoctonia disease is greater where such addi-
tions of available organic matter have not had time to decom-
pose before the beans are planted.
A summer cover crop or weed growth should be plowed under
in time to decompose before the beans are planted. A period
of 3 to 6 weeks should intervene between plowing under a heavy
growth of weeds, a cover crop, or an earlier vegetable crop and
the planting of the bean seed. During this period the land
should be disked several times to hasten the decomposition of
the organic debris and to compact the soil.
Experiments have shown the advantage of having the organic
matter decomposed and the soil compact. There was a 24 per-
cent reduction in the stand of beans where grass was turned
under on the day the seeds were sown, but no reduction where
the grass had been turned under 312 weeks before. Yields of
beans on these plots varied in the same manner. Where the
soil was compacted by rolling there was a 6.5 percent increase
in stand over that of a plot with loose soil.
Cultural practices must be utilized for the control of the
Rhizoctonia disease of beans. When good practices are followed
the disease causes very little damage, while certain poor prac-
tices are likely to result in heavy losses from root rot.
Beans for an early fall crop are planted when soil tempera-
tures are high enough to be very favorable for the development
of this disease. It is therefore important that more than ordi-
nary precautions be taken to see that other factors are adjusted
properly.







Diseases of Beans in Southern Florida


Water control is essential in the production of beans for
several reasons besides the assistance it renders in the control
of root rot. The soil must be neither too wet nor too dry in
a properly managed field. The field must be provided with
ditches and pumping facilities and should be sufficiently level
that water does not stand in low places during heavy rains. Pro-
vision for subsurface irrigation will save many beans from root
rot, since it would obviate the necessity of planting the seed
so deeply in dry soil. Deep planting is a poor practice because
the bean stems have to grow through so much soil that they
frequently are rotted. This is especially true when showers and
warm weather follow deep planting in dry soils.
Seed treatments for snap beans have been tested in several
experiments, but better stands have resulted in only 1 of them.
An organic mercury treatment of the bean seed may be used
with safety and may result in slight increases in stand on very
wet soils, but should not be expected to increase the stand of
beans in soils having an optimum amount of water.
The nesting of shipped beans caused by the Rhizoctonia dis-
ease can be controlled by grading out the pods showing soil rot
when the beans are packed and by shipping the beans in re-
frigerated cars or trucks. Infection of bean pods by the Rhizoc-
tonia fungus (21) is negligible at temperatures below 50 F.

SOUTHERN BLIGHT
This disease is similar to the one caused by the Rhizoctonia
fungus. It affects many species of plants, including all of the
vegetable crops and many weeds and ornamentals. No varieties
of beans are known to be resistant to it.
Southern blight occurs throughout Florida and the other
Southern states. The disease is not limited to any soil type
but often is more prevalent on soils which have been under
cultivation for a long time.
The disease is only a little less important than Rhizoctonia
because of the poor stands of beans due to root rot and the
damping-off of young plants. Some of the loss caused by nesting
in shipped beans is due to this disease.
Sudden wilting of affected bean plants usually is the first
symptom noticed, and this is followed quickly by their death.
Few, if any, plants recover from this disease because the roots
and the lower part of the stem are affected with a dry rot. The






Florida Agricultural Experiment Station


rotten stems do not turn brown but are gray and have a papery
texture and are hollow.
The disease can be identified positively by the occurrence of
a coarse white fungous mycelium attached to the stem at the
soil line and spreading over and into the soil around the plant.
If the plant is pulled a considerable amount of soil bound to-
gether with the white mycelium adheres to the stem. The fun-
gus produces numerous sclerotia on its mycelium both on the
plant and in the soil. The sclerotia at first appear as white
nodules on the mycelium, but turn brown later. These organs
of the fungus are about the size of mustard seed (Fig. 13).
The fungus is sometimes found on the ends of pods which
have touched the soil or have been splashed with wet soil. In-


rt 3Irt.,


AiJ

r r


Fig. 13.-Southern blight of bean plants. Note the white fungus on
the soil around the standing plant and binding the soil to the roots of
plants which have been pulled.







Diseases of Beans in Southern Florida


fected pods in a hamper of shipped beans may produce a fungous
nest similar to that caused by the sclerotinia rot fungus.
Southern blight is caused by Sclerotium rolfsii Sacc. This
is a common fungus which, like Rhizoctonia, lives in the soil
on organic debris or on such plants as happen to be there.
Sclerotia serve to keep the fungus alive during periods too
dry or too cold for mycelium development. They are so resist-
ant to unfavorable environmental conditions that they can sur-
vive for several years. The sclerotia also serve to disseminate
the fungus since they are carried easily by moving water, in
soil on farm machinery, or with crop refuse. When conditions
are favorable the sclerotia germinate by producing mycelia
which can grow in the soil or parasitize new plants.
Southern blight is a warm weather disease. It occurs on
beans in early fall and late spring when soil temperatures are
highest. The fungus occurs throughout the summer on other
host plants.
It is most prevalent in fields where the soil is quite wet. As
the soil surface becomes drier the disease is seen less frequently.
A period of warm, wet weather in the winter may bring about
a development of the disease even at that season.
Nesting of shipped beans caused by Southern blight is most
common at temperatures near 85 F. (21). Infection of pods
by the Southern blight fungus does not occur at temperatures
lower than 43 F.
No fungicides are known to control Southern blight. A plant-
ing schedule that uses heavily infested soils during the cooler
and drier seasons of the year is advisable. Losses in shipped
beans should be prevented by grading the beans and by refriger-
ation of the shipments so that a temperature around 45 F. is
maintained in the cars or trucks.

WEB-BLIGHT
The occurence of web-blight was reported in Florida in 1937
(31). It has been found here most frequently during the sum-
mer rainy period when the daily maximum temperatures were
about 90 F. and minimum about 700 F. (33). In many in-
stances it was found very destructive on the late spring crop
in June when the summer rains began early, and in the early
fall crop in November when the rainy season was prolonged.
The disease is more or less prevalent in central Florida from
the Suwannee River to Lake Okeechobee (33). While it has







Florida Agricultural Experiment Station


been found in some of the principal bean-growing areas and
has been very destructive in the few instances observed there,
it has not become a serious disease in the lower third of the
peninsula, probably because few beans are grown in this area
during the period when the fungus is most active.
The disease is caused by Corticium microsclerotia (Matz)
Weber (32), first described as Rhizoctonia microsclerotia Matz
as the cause of a disease of figs in Florida (22). The fungus
survives from one season to the next on plant debris in culti-
vated fields and on living plants, including a number of wild
and cultivated annuals and perennials.
The fungus produces small, circular, water-soaked spots on the
leaf and under favorable conditions spiderweb-like mycelia on
stems, pods and foliage, tying them together with a mat of
tenacious mycelial strands. In this stage the disease is char-
acterized by the presence of many small brown sclerotia em-
bedded in the mycelial web. Under favorable environmental
conditions sclerotia are produced in great numbers and have
been observed to cover the entire surface of leaves, petioles,
stems and even the soil surface for several inches around in-
fected plants where they appear as a coarse brown dust (33).
Pods are attacked at all stages in their development. On young
pods, early infections are light tan in color and irregular in
shape, becoming dark brown, more or less circular, slightly
zonate and sunken on mature pods. Nesting may occur in
packed containers if infected pods are packed with healthy ones.
It has been suggested (33) that damage from the disease may
be reduced by not planting beans during the period between
June 1 and September 1 in fields where the disease has occurred
previously. Other suggestions for control include rotation with
tobacco, corn, grasses or other nonsusceptible crops; the use
of bordeaux mixture up to blooming time; and the destruction
of infected plants as soon as possible after they are abandoned.
No resistance in bean varieties has been observed.

DISEASE AND INJURIES DUE TO OTHER CAUSES

ROOT-KNOT
The root-knot disease occurs on nearly 900 species of plants
(29). All of the principal vegetable crops of Florida are more
or less severely affected. A few can be grown on infested soils
under certain conditions.







Diseases of Beans in Southern Florida


Beans are very susceptible to this disease. No resistant vari-
eties are available at present. Two resistant varieties have
been selected by Alabama workers (3) and may some day prove
to be a valuable contribution.
The nematode (Heterodera marioni (Cornu) Goodey) which
causes root-knot is strictly parasitic, dying unless it has roots
on which to feed. It is widely distributed in tropical and semi-
tropical soils and even in some more temperate parts of the
United States. It occurs throughout Florida, and may be very
troublesome on both sandy and organic soils in the southern part
of the state. Losses caused by root-knot are due to the reduction
in stand of beans and to the stunting of many plants which are
not killed. Less than 1 percent of the beans grown in southern
Florida are destroyed by root-knot, but the problem is some-
times very acute for a few growers.
The most noticeable symptom of the disease is the knots
which are found on the roots of affected plants (Fig. 14). These
differ from the nitrogen nodules on legume roots in that the
swelling involves the entire circumference of the root, whereas,
the legume nodules occur as growths attached to the side of the
smaller rootlets. Nematode galls also occur on the larger roots
and even on the underground portions of the stems. When
the infestation of bean roots is heavy the entire root may be-
come one large gall. The gall on small rootlets may enlarge
the root to 5 or 10 times its normal diameter.
Root-knot galls appear to be composed of normally healthy
but overgrown tissues in their early development and may
reach considerable size before there is any evidence that the
tissues are breaking down. Most galls become soft and begin
to disintegrate before the plants die. Old galls are brown and
have the appearance of rotten cork.
If the galls are dissected carefully the bodies of mature nema-
todes can be found in them. Mature female nematodes are
about the size of a common pin head. They are pear-shaped
and have a pearly white color. The tissue immediately around
them may be brown in the older galls.
The bean plants may not show other symptoms if the infec-
tion occurred late in the growth of the crop, or if the develop-
ment of the nematodes has been slow. Plants which are severely
infected in their early growth become stunted and have few
branches. They may become chlorotic or may simply wilt and
die. The death of the plants does not occur until the galled







Florida Agricultural Experiment Station


roots begin to break down. This may be caused by the activity
of other organisms infecting the diseased roots as much as by
the nematodes.
The young nematodes hatch from eggs present in old root
galls or which have been left in the soil by the disintegration of
such galls. Larvae move actively in the soil until they locate
the root of a susceptible plant. They then burrow into the root
tip and embed
their heads near
the conducting
tissues (16). A
Ssecretion pro-
duced by the lar-
vae causes the
root cells to grow
Abnormally large.
It is from these
enlarged cells
S, that the nema-
tode obtains its
food. The loss of
food materials by
the root is not as
important a cause
S" of death of the
plant as is the dis-
ruption of the nor-
mal anatomy and
Fig. 14.-Nematode galls on the roots of a n n
bean plant, functioning of
the root tissues.
Nematodes grow considerably as they feed in the roots and
it is necessary for the female nematodes to moult before they
complete their development. The females grow rapidly after
moulting and become motionless. Their bodies change from
the long slender form of a worm to that of a globose or pear-
shaped sack. The internal organs of the female nematode at
maturity are displaced by eggs which are extruded in gelatinous
masses, sometimes to the extent that they rupture the root gall
and are deposited in the soil. Female nematodes commonly
produce hundreds of eggs (29). The larvae which hatch from
these eggs invade roots of susceptible plants where the cycle
of development is repeated.







Diseases of Beans in Southern Florida


Several factors affect the rate at which nematodes develop
and hence the severity of their attack on the host plants. Soil
temperature is the most important (26). Only 1 generation of
nematodes develops during the growth of a crop of beans when
the mean soil temperature is 72' F. or lower. Unless the initial
infestation was extremely heavy, this rate of development does
not affect the bean plant seriously. When the mean soil tem-
perature is 800 F. or higher it is possible for 2 generations of
the nematodes to mature while the bean crop is growing. This
may result in a very heavy infestation and in severe damage or
even death to the plants.
Nematodes may be killed by the extremely low temperatures
which occur in Northern states, but in Florida their develop-
ment is merely slowed down by winter temperatures. They
are not likely to be killed by high temperatures in the summer
except in the dry surface layer of soils where temperatures of
100 F. or higher may occur for a few hours on some days.
The larvae and eggs of nematodes cannot stand desiccation.
Even the eggs in root galls are killed by drying for a few days.
The larvae are the most sensitive to drying and are killed by
a 3-minute exposure to an unsaturated atmosphere (15).
Larvae in the soil are able to invade roots and produce galls
when there is enough water for growth of the bean plant. Root
galls will form on plants in soils at less than 40 percent or more
than 80 percent of their water-holding capacity (14). Flooding
the soil kills most of the nematodes in 6 months (29), but a few
remain alive in flooded soils even after a year.
Nematodes fail to reproduce and their population gradually
decreases in fallow soils, since the larvae must have living roots
upon which to feed or they will starve. Some eggs continue to
hatch in fallow soil for a time and the nemic population does
not decrease rapidly at first. The numbers of nematodes in
soils planted to root-knot-resistant crops decreases in the same
manner and for the same reason. Nematode numbers increase
in soils where susceptible crops or weeds are growing.
The application of chemicals to the soil for the control of
nematodes has a limited field of usefulness. Most usable ma-
terials are very expensive and reinfestation of Florida soils is
so rapid that chemical treatments are not recommended, except
for special purposes, such as seedbed soils, small gardens and
potting or bedding soils for ornamental plants. The control







Florida Ai, ij, tinral Experiment Station


of root-knot of beans on the extensive acreages of this crop in
southern Florida must depend upon cultural practices.
Beans should not be planted on infested soil from March to
December. Infested soils should be kept fallow and well disked
during April and May. They can then be planted with a re-
sistant cover crop when the rains begin in June. Iron cowpeas,
velvet beans or crotalaria should be planted in rows so that all
weed growth can be controlled by cultivation. The native
grasses of the Everglades are resistant to root-knot and can
be used as summer cover crops, but they are not recommended
because of other problems associated with them. The cover
crop should be plowed under in August or September and the
land should be kept well disked until planted to beans about
the first of November. The land can be returned to normal
cultural practices after the winter bean crop has been harvested,
if there was no root-knot damage to that crop.
When the soil is so heavily infested with nematodes that
these practices do not result in control, the land should be kept
cultivated from March to November. During this time it should
be disked regularly to kill all weeds that might harbor nema-
todes and to expose the nematode larvae and eggs to the sun
and dry air. The land might be used during the winter for
some of the less susceptible vegetable crops such as cabbage,
potatoes, lettuce, carrots or radishes. After the winter crop
has been harvested the land should be returned to fallow or
planted to a resistant cover crop during the second summer
and it should then be safe for planting beans in the fall.
Very susceptible crops such as okra, tomatoes, peppers, egg-
plants, beans or peas should never be planted during the warmer
months on land which is known to be infested. To do so is the
surest way to build up a heavy infestation of nematodes.
The practices which have been discussed are methods for
ridding the land of heavy infestations of nematodes. A few
nematodes occur in all soils, although they may be doing no
apparent damage. It is therefore wise not to encourage their
development by growing susceptible crops in the summer and
the practice of growing a root-knot-resistant cover crop during
the summer should be adopted generally. Aside from the bene-
fit these crops give in preventing heavy infestations of nema-
todes, there are other advantages of cover crops which more
than offset the cost of growing them.







Diseases of Beans in Southern Florida


BALDHEADED BEANS
"Baldheaded" or "snakeheaded" beans are young bean plants
which do not have an apical bud after the cotyledons expand
(Fig 15). This condition occurs commonly and may affect less
than 1 percent to more than 10 percent of the beans in certain
lots of seed. Most baldheaded beans fail to grow after the
seedling has emerged and the cotyledons have expanded. New
buds develop on the stem near the cotyledons in some cases, but
the growth from these lateral buds usually is very weak. Such
plants are stunted and the neighboring plants outgrow them
so that they are hidden in older plantings of beans.







I








Fig. 15.-Baldheaded bean plants. (Photo by G. F. Weber.)

Baldheaded beans are caused by any of 3 factors which injure
or destroy the growing apex of the stem in the embryo or the
germinating seedling. Most baldheaded beans are the result
of injuries to the embryo when the seed is being threshed.
The violent shocks due to improper threshing methods cause the
stem of the embryo to break just below the apical growing point.
Reducing the speed of operation of the threshing machines,
using rubber-roller instead of steel-toothed threshers, and thresh-
ing before the seeds are too dry are some of the ways in which
this type of injury can be minimized. These factors are gener-
ally beyond the control of the grower or retail seedsman unless
he has contracts with producers which specify conditions under
which the bean seed is to be threshed. When seeds are purchased
they should be examined for split seeds and cracked seedcoats,






Florida Agricultural Experiment Station


since these are signs that the seeds were improperly threshed
and may produce a high percentage of baldheaded beans. Trial
plantings of a few hundred seeds will determine whether the lot
will produce many baldheads. Seed lots which have been im-
properly threshed are not inferior to other lots if the rate of
seeding is increased and a price adjustment can be obtained.
Diseases and insects sometimes cause beans to be baldheaded.
Seeds heavily infected with blight bacteria may produce many
baldheaded beans if conditions are favorable for infection at
time of germination. Other seedlings become baldheaded when
root rot fungi attack them before they emerge from the soil.
In some parts of the country the seed corn maggot destroys
the buds in beans as they are sprouting.

WIND INJURY
Bean plants are easily injured by winds. This occurs most
frequently during winter when cold northwest or north winds
may blow continuously for several days. The margins of the
leaves become whipped and frayed by rubbing against the stems
and other leaves. Injured tissues turn brown and dry out.
When growth at the margins ceases, the leaves become wrinkled
and rolled downward due to continued growth at the center.
Leaves of wind-whipped plants have a coarse, scarred appear-
ance, and growth of the entire plant is retarded while the con-
dition causing the injury persists. With return of more favor-
able growing conditions the plants recover and new growth
appears to be normal. These plants produce pods later but the
yield may be reduced.
Pods and stems of wind-injured beans are marked with brown
spots and scars where they have been rubbed by other parts
of the plant. Scars on pods may be large and deep enough
to cause some twisting of the pods. Such beans are of poor
quality and are sold with difficulty.
Windbreaks provide some protection from this type of injury.
Corn, sunflowers and Japanese cane sometimes are planted in
rows at right angles to the direction of the damaging winds.
The windbreak crops are planted several weeks before the beans
are to be planted so that they will offer some protection to the
beans as they grow. The windbreaks are spaced 121/2 to 221/2
feet apart and 4 to 8 rows of beans are planted between them.
Drilling the beans in rows closer than 30 inches helps sometimes,







Diseases of Beans in Southern Florida


since the vines are closer and tend to support each other so that
they move less with the wind.
Corn probably is the least effective windbreak, but it some-
times produces roasting ears which can be sold at considerable
profit. Insects often damage the corn considerably and some-
times destroy its effectiveness as a windbreak. Sunflowers make
effective windbreaks in a short time and are used more than
corn in the Everglades. As they mature, the sunflowers fre-
quently become infected with a rust. This is not the bean rust
and will not injure beans in any way. It probably could be
controlled on the sunflowers by sulfur dusting. Japanese cane
is used as a windbreak on the East Coast. It is planted in rows
at wider distances than are corn and sunflowers or may be used
as a border around a field.

LOW TEMPERATURE INJURY
Beans are affected considerably by temperatures well above
the freezing point. After a cold night when the temperature
drops below 45 F. the bean leaves droop and appear slightly
water-soaked. The chilled plants wilt temporarily, if they are
exposed to strong sunlight in the morning. Part of the damage
caused by cold winds may be due to the permanent wilting of
chilled tissues. The plants recover from the chilling and sub-
sequent wilting when adequate soil moisture and more favorable
temperatures prevail.
A frost deposit on bean leaves will kill them. Some lower
leaves protected by those above may escape a frost in which the
temperature does not fall below 31 F. at the plant level. All
leaves are killed if the temperature falls to 30 F.
There is no effective protection against frost for large fields
of beans. Small plots can be protected against temperatures
as low as 280 F. by overhead sprinklers. The sprinklers must
be operated while the subfreezing temperatures prevail and
afterwards until the ice has been melted from the leaves.

WATER INJURY
A part of the space in the soil must be occupied by air so
that plant roots and soil microorganisms can obtain the oxygen
they require. The air supply is reduced in wet soils and air is
excluded from flooded soils. When the soil is too wet the roots
cannot obtain enough oxygen and do not form enough small
feeding roots to support maximum growth. If the air is en-







Florida Agricultural Experiment Station


tirely excluded from the soil by flooding the roots die in a few
hours. After short periods of flooding, and where the water
table is continuously within a few inches of the surface of the
soil, new roots may be formed on the stems just below the soil
line. Plants which recover from flooding in this way usually
are weak and unproductive.
Very wet soils contribute to several other troubles of beans.
The activity of soil organisms maintains the soils in a fertile
state. If the oxygen supply is too limited, these organisms
cannot function and the plants suffer because of a lack of avail-
able nitrogen and other nutrients. The availability of man-
ganese seems to be at a minimum in wet soils, and the yellowing
of beans due to its deficiency is worse on such soils. Most fungi
which cause seed decay and rots of the root and stem of beans
are favored by wet soils.
Some of the injury occurring on wet and flooded soils can be
prevented by the use of adequate field ditches, mole drains and
pumps. A grower, particularly in the Everglades, should have
equipment for removing 3 or 4 acre-inches of water in 24 hours.
He would then have protection against all but the heaviest rains.
Most of the heavier rains occur in the summer months when
beans are not being grown.
FERTILIZER INJURY
High concentrations of certain chemical fertilizers are some-
times injurious to beans. This type of injury occurs more fre-
quently in the drier soils, but can occur in wet soils where
extremely heavy applications of chemical fertilizers have been
made. Bean seeds fail to sprout in soils which have been fertil-
ized too heavily. The seeds may not be killed immediately, but
usually rot if they have not sprouted within 2 weeks after being
planted in a moist soil. Where the concentration of the chemi-
cals is injurious but does not inhibit germination, the seeds
sprout slowly and produce stunted plants.
No reduction in the stand of beans in the fertilizer experi-
ments on peat soil at the Everglades Experiment Station has
been noted with various sources of nitrogen and phosphorus.
The stand of beans on plots fertilized with potash has varied
with the salt used. Kainit applied in the row and mixed with the
soil 2 to 5 days before the seed were planted has caused consider-
able injury. The reduction in the stand of seedlings on kainit-
treated plots as compared with the plots fertilized with the
sulfate of potash are shown in Table 5.







Diseases of Beans in Southern Florida


TABLE 5.-REDUCTION IN THE STAND OF BEAN SEEDLINGS ON KAINIT-
TREATED PLOTS.

Year KO (0) 60 Pounds per Acre K2O @ 180 Pounds per Acre
1933 2.0 percent 34.9 percent
1934 3.7 percent 36.2 percent
1935 11.8 percent 44.1 percent
Average 1 5.8 percent 38.4 percent

Kainit contains large amounts of sodium chloride and an ex-
periment at the Everglades Station clearly indicated the in-
jurious effects of chloride salts on the germination of bean seed
and the growth of seedlings.
The extreme effects of these salts demonstrated in these ex-
periments are not encountered often in the field because suffi-
ciently high applications of potash seldom are made to beans.
The loss of some seed as the result of applications of 300 to 500
pounds of chemical fertilizers containing potassium and sodium
chlorides is to be expected on the basis of these experiments.
This loss can be held at a minimum by any practices which will
reduce the concentration of chemicals in the soil around the
seed, such as special placement methods for fertilizer, use of
a minimum amount of fertilizer, and maintenance of a high
moisture content in the soil.
Heavy applications of ground sulfur for acidifying the soil
may be injurious to beans planted too soon afterwards. The
injury is not in proportion to the increase in acidity but seems
to be due to contact of the roots and stems of the beans with
undissolved sulfur practices. Roots and underground portions
of bean plants decay as though affected with Rhizoctonia root
rot. The injury can be avoided by distributing sulfur several
weeks before planting. Small quantities of sulfur included in
the fertilizer are not particularly injurious to beans.
COPPER INJURY
Experiments with fungicides over an 8-year period have
shown that copper sprays and dusts are injurious to beans when
the foliage has been injured by cold winds, bean leaf-hoppers
or bean rust. The damage has occurred irrespective of the
proportions of copper and lime in bordeaux mixture and even
with such neutral copper fungicides as basic copper sulfate and
copper hydroxide. Bountiful beans which had been injured by







Florida Agricultural Experiment Station


the bean leaf-hopper and cold winds in March, 1932, were injured
so severely by applications of bordeaux mixture and copper-lime
dust that the plants shed some of their leaves. Yields were
about 25 percent less than from nontreated plots.
In April, 1932, plots of beans sprayed with bordeaux mixture
and dusted with copper-lime dust were injured severely when
the application of these materials coincided with a period of
cold windy weather. These plants recovered with the return
of more favorable growing conditions. In the same experiment
no injury was noted following the application of other materials.
Yields on the copper fungicide plots were reduced about 10
percent as a result of the injury.
Yields of beans were reduced by insignificant amounts in 4
other experiments where copper fungicides were applied. In 3
experiments the yields of beans were increased by 5 to 15 per-
cent where copper-lime dust and bordeaux mixture were applied.
These yield increases were obtained in experiments conducted
in the early fall or late spring when none of the factors which
contribute to copper injury were present.

SULFUR SPRAY
Beans are injured by too heavy or untimely applications of
sulfur fungicides. When mildew or rust is present the injury
caused by sulfur may not be so apparent because the control
of these fungous diseases improves the crop and increases the
yield more than enough to offset the injurious effects of the
sulfur. There is no appreciable injury due to the proper use
of sulfur fungicides.
Bean plants which have been sulfured too heavily have coarse,
weather-beaten leaves. They are marked by brown or gray
scars and show considerable injury along the leaf margins.
Applications of sulfur while the plants are in bloom seem to
affect pollination and pod setting, and may reduce yields. Bean
pods which have been sprayed or dusted with sulfur are more
susceptible to wind scarring.
Some data obtained from an experiment in the fall of 1934,
when no diseases occurred on beans, reflect the injurious action
of sulfur. The last of 3 applications of the fungicides in this ex-
periment was made when the vines were in full bloom. The
data in Table 6 give the average yields and percentages of scar-
red pods for 6 replications of the experiment. The beans were
picked twice.







Diseases of Beans in Southern Florida


TABLE 6.-YIELDS OF BEANS AND PERCENTAGES OF SCARRED PODS IN THE
1934 FUNGICIDE EXPERIMENT.

Material Rate of Application Hampers Percent
per Acre Scarred
N one ...................... ....... 264 43
Sulfur dust A .................. @ 26 pounds per acre 258 53
Sulfur dust B ............... @ 36 pounds per acre 256 54
Sulfur dust C .................... @ 38 pounds per acre 258 53
Wettable sulfur spray A @ 100 gallons per acre 261 52
Wettable sulfur spray B (@ 100 gallons per acre 248 48


CONTROL MEASURES

EXCLUSION
The feasibility of excluding all diseased bean seed from the
state may well be questioned. However, the individual grower
can obtain some measure of protection from the seed-borne dis-
eases if he is able to look into the sources of his seed and to
purchase seed known to have been produced on disease-free
plants. At least 1 Western state is contemplating a certification
system which would give growers the benefit of field inspections
and a certificate on each bag of seed.

ERADICATION
The treatment of seed or soil for the eradication of disease-
producing organisms has never offered much promise as a meas-
ure for the control of bean diseases. The halo blight bacteria in
bean seed are not killed by any of the chemicals frequently used
for the treatment of vegetable seeds. A new treatment reported
effective in another state has not proven so in Florida. Chemical
treatment of the soil for the control of nematodes has been
discussed under the root-knot disease. Except for gardens and
seedbeds, this is not considered economical for the control of
root-knot on beans.

IMMUNIZATION
Utilization of the immunity from or the resistance to certain
diseases which are inherent in a few varieties of beans has been
the object of a breeding program at the Everglades Experiment







Florida Agricultural Experiment Station


Station for several years. This program has resulted in the
development and release of 2 new varieties of bush snap beans,
the Florida Belle and the Florida White Wax (2, 27). Plants
of both of these varieties are resistant to some forms of rust
and mildew, resistant to common bean mosaic, and tolerant of
heat and drought. Both are now being used in commercial
plantings. Selections are being continued with the hope that
other varieties suitable for commercial use may be developed.

PROTECTION
Many measures for the control of bean diseases utilize the
principle of protection. Chemicals applied to the crop as fungi-
cides or supplementary nutrients protect it from several diseases.
Fungous diseases cannot be controlled by protectants applied
after the disease has affected the plants seriously. Nutritional
disorders can be corrected to some extent even after the plants
have gone into a serious decline, but it should be recognized
even here that early diagnosis and prompt treatment of the
trouble have much to do with the success of the treatment.
There is a great variety of protective chemicals, but most of
those used on beans are compounds of copper or elemental sulfur.
The choice of applying the materials as sprays or dusts depends
upon relative costs of the different forms and availability of
either spraying or dusting equipment. Applications of dusts
usually can be made more rapidly than sprays and sometimes
this is an important consideration.
Often it is advantageous to combine insecticides or secondary
nutrients with fungicides to reduce the cost of application. The
arsenical poisons can be added to bordeaux mixture, insoluble
copper sprays, wettable sulfur sprays, copper-lime dusts and
sulfur dusts. Rotenone and pyrethrum insecticides should not
be added to bordeaux or any other material which contains lime,
since the alkaline reaction will cause them to decompose rapidly.
These materials can be mixed with the sulfur fungicides. The
solutions of manganese and zinc sulfates can be combined with
each other or with any of the fungicides. Manganese sulfate can
be combined with sulfur dust in the proportion of 1 part of the
manganese salt to 9 parts of dusting sulfur. The zinc sulfate is
generally too coarse and heavy to be combined with a dust.
The simplest machines for applying fungicides are the hand-
operated sprayers and dusters. Knapsack sprayers are satis-
factory for the application of the nutritional sprays, but it is







Diseases of Beans in Southern Florida


unwise to rely upon them for the protection of large acreages
of beans against fungous diseases. Bordeaux mixture is handled
to better advantage than wettable sulfur sprays by the knap-
sack sprayers.
When hand equipment must be used for the protection of large
acreages, the dusters are more satisfactory. Dust guns can be
adjusted to deliver various amounts of dust per acre. The dust
is blown out in a cloud which covers all of the plant. Better
coverage of the lower surfaces of the leaves is obtained when
the blower is directed towards the soil and at each side of the
row. The nozzle outlets should not be held so close to the plants
that heavy deposits of the fungicide form at any place on the
plant. A thin but even distribution of the dust is much better
than a heavier application which is spotty.
Several types of traction or power-operated sprayers are on
the market. These machines give the best distribution of fun-
gicides and are economical in operation. Good sprayers should
handle a 6-row boom with 3 nozzles per row and should deliver
the spray at a pressure of 300 pounds or higher. The volume
of spray applied per acre will vary with the speed of operation
but should be not less than 50 gallons. More dilute spray sus-
pension can be used if the volume of spray delivered per acre
exceeds the minimum requirement.
Power dusters are efficient machines for the application of
fungicidal dusts. Since dusting can be done more rapidly than
spraying, it is more frequently the choice of large operators.
However, dusting operations must be performed when there is
little wind and, for copper-lime dusts at least, when there is
dew on the foliage. This restricts the operation of dusters
as compared with sprayers. Dusters which deliver the fungi-
cide through a large blower are better than those which have
a set of nozzle outlets for each row of the crop.
Airplane dusting is a spectacular method for the application
of fungicides. However, it can be done very efficiently by good
pilots operating over large open fields as in the Everglades.
It is not recommended for fields smaller than 10 acres. Long
fields are handled more effectively than square ones. The
absence of hedgerows, trees or power lines on the borders of
the field also helps to make the application by plane easier and
better. This type of dusting is subject to the same criticism
and has the same advantages over spraying as have been men-
tioned for dusting with land machines.








Florida Agricultural Experiment Station


A regular schedule for the application of fungicides and
supplementary nutrients is advisable. The schedule outlined
here (Table 7) is not necessarily the best for all conditions, but
should receive consideration by everyone who raises beans until
he can work out a better one for his particular conditions. Some
growers may find it necessary to increase the number of appli-
cations to 5 or 6 at certain seasons but 4 applications should
carry the average bean crop to maturity and permit at least 2
pickings. While 4 applications of fungicides is often more than
is needed, the grower has no way of knowing beforehand what

TABLE 7.-A SCHEDULE OF SPRAY AND DUST APPLICATIONS FOR THE
PROTECTION OF BEANS.


Days from
Planting




9 to 12






14 to 18



21 to 28






28 to 40


Application


4-3-50 Bordeaux mixture for its nutritional effects and the
control of powdery mildew, except when the beans are
being injured by leaf-hoppers or cold winds and when rust
is prevalent
or
10-50 Wettable sulfur or dusting sulfur for the control of
mildew and rust; add manganese, zinc or insecticides to
either if necessary.*


15-50 Wettable sulfur to which manganese, zinc and insecti-
cides have been added if necessary
or
Dusting sulfur with manganese and insecticides added if
necessary.


Same as second application, except that manganese, zinc
and insecticides may be omitted if not needed.


15-50 Wettable sulfur
or
Sulfur dust.

Manganese, zinc and insecticides probably will not be added
in this application if they have been given before.
This application should precede the opening of the first
blooms by a day or two.


Ordinarily no fungicides should be applied in this post-
bloom period. The pre-bloom application should protect
40 to 50 the plants until the time of the second picking. If rust
and mildew are very severe in nearby fields a light sulfur
dusting may be made.
See cautions concerning the use of pyrethrum and rotenone on p. 53.








Diseases of Beans in Southern Florida


diseases he may have to contend with nor of the probable
severity of those diseases. It is therefore wise to insure the
crop by protecting it with a minimum of 4 applications of fungi-
cides. Insecticides and nutritional sprays usually can be com-
bined with these applications.

ACKNOWLEDGMENTS
Grateful acknowledgment is made to Dr. W. D. Moore, USDA, B.P.I.,
S. and A.E., for Fig. 10 and for suggestions regarding revision of the
section on Sclerotiniose; and to Dr. W. T. Forsee for revision of the para-
graphs 3 and 4 in the introduction.

LITERATURE CITED
1. ALLISON, R. V., O. C. BRYAN and J. H. HUNTER. The stimulation of
plant response on the raw peat soils of the Florida Everglades
through the use of copper sulphate and other chemicals. Fla. Agr.
Exp. Sta. Bul. 190: 35-80. 1927.
2. ANDERSON, E. M., J. R. BECKENBACH, A. H. EDDINS, E. N. MCCUBBIN,
R. W. RUPRECHT, F. S. JAMISON and E. C. MINNUM. Commercial
vegetable varieties for Florida. Fla. Agr. Exp. Sta. Bul. 405:
1-30. 1944.
3. BARRONS, K. C. Varietal differences in resistance to root-knot in
economic plants. Plant Dis. Reporter Sup. 109: 143-151. 1938.
4. BARRUS, M. F. Bean anthracnose. Cornell Univ. Agr. Exp. Sta.,
Memoir 42: 97-209. 1921.
5. BROOKS, A. N. Control of celery pink rot. Fla. Agr. Exp. Sta. Press
Bul. 567. 1942.
6. BROOKS, A. N., W. D. MOORE and H. I. BORDERS. Sclerotiniose of vege-
tables and tentative suggestions for its control. Fla. Agr. Exp.
Sta. Press Bul.'613. 1945.
7. BURKHOLDER, W. H. A new bacterial disease of the bean. Phytopath.
16: 1915-927. 1926.
8. The bacterial diseases of the bean. A comparative
study. Cornell Univ. Agr. Exp. Sta. Memoir 127: 3-88. 1930.
9. CHUPP, CHARLES. Manual of vegetable garden diseases. New York.
1925.
10. COOK, H. T. Powdery mildew diseases of beans. Va. Truck Exp. Sta.
Bul. 74: 931-940. 1931.
11. EDDINS, A. H., GEO. D. RUEHLE and G. R. TOWNSEND. Potato diseases
in Florida. Fla. Agr. Exp. Sta. Bul. 427: 1-96. 1946.
12. EDGERTON, C. W. The bean anthracnose. La. Agr. Exp. Sta. Bul. 119:
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13. FROMME, F. D. The rust of cowpeas. Phytopath. 14: 67-79. 1924.
14. GODFREY, G. H. Effect of temperature and moisture on nematode root-
knot. Jour. Agr. Res. 33: 223-254. 1926.








Diseases of Beans in Southern Florida


diseases he may have to contend with nor of the probable
severity of those diseases. It is therefore wise to insure the
crop by protecting it with a minimum of 4 applications of fungi-
cides. Insecticides and nutritional sprays usually can be com-
bined with these applications.

ACKNOWLEDGMENTS
Grateful acknowledgment is made to Dr. W. D. Moore, USDA, B.P.I.,
S. and A.E., for Fig. 10 and for suggestions regarding revision of the
section on Sclerotiniose; and to Dr. W. T. Forsee for revision of the para-
graphs 3 and 4 in the introduction.

LITERATURE CITED
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14. GODFREY, G. H. Effect of temperature and moisture on nematode root-
knot. Jour. Agr. Res. 33: 223-254. 1926.








56 Florida Agricultural Experiment Station

15. GODFREY, G. H., and H. T. MORITA. Effects of some environmental
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