Front Cover
 Front Cover
 Table of Contents
 Diseases caused by nutritional...
 Diseases caused by bacteria
 Diseases caused by fungi
 Disease and injuries due to other...
 Control measures
 Literature cited

Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 336
Title: Diseases of beans in southern Florida
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00015115/00001
 Material Information
Title: Diseases of beans in southern Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 60 p. : ill., charts ; 23 cm.
Language: English
Creator: Townsend, G. R ( George Richard ), 1905-
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1939
Subject: Beans -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 59-60.
Statement of Responsibility: by G.R. Townsend.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00015115
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000924566
oclc - 18214637
notis - AEN5193

Table of Contents
    Front Cover
        Page 1
    Front Cover
        Page 2
    Table of Contents
        Page 3
        Page 4
        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
        Page 18
    Diseases caused by fungi
        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
        Page 40
        Page 41
        Page 42
    Disease and injuries due to other causes
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 54
    Control measures
        Page 55
        Page 56
        Page 57
        Page 58
    Literature cited
        Page 59
        Page 60
Full Text

September, 1939





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

Singles copies will be sent free to Florida residents upon request to

Bulletin 336

John J. Tigert, M.A., LL.D., President of
the University3
Wilmon Newell, D.Sc., Directors
Harold Mowry, M.S.A., Asst. Dir., Research
V. V. Bowman, M.S.A., Asst. to the Director
J. Francis Cooper, M.S.A., Editors
Jefferson Thomas, Assistant Editor3
Clyde Beale, A.B.J., Assistant Editors
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Managers
K. H. Graham, Business Managers
Rachel McQuarrie, Accountant3

W. E. Stokes, M.S., Agronomist'
W. A. Leukel, Ph.D., Agronomist3
G. E. Ritchey, M.S., Assoicate3
Fred H. Hull, Ph.D., Associate
W. A. Carver, Ph.D., Associate
John P. Camp, M.S., Assistant
Roy E. Blaser, M.S., Assistant

A. L. Shealy, D.V.M., Animal Husbandman' a
R. B. Becker, Ph.D., Dairy Husbandman3
L. M. Thurston, Ph.D., Dairy Technologist3
W. M. Neal, Ph.D., Asso. in An. Nutrition
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian3
N. Mehrhof, M.Agr., Poultry Husbandmana
0. W. Anderson, M.S., Asst. Poultry Husb.3 4
W. G. Kirk, Ph.D., Asso. An. Husbandmans
R. M. Crown, B.S.A., Asst. in An. Husb.3
P. T. Dix Arnold, M.S.A., Assistant Dairy
L. L. Rusoff, M.S., Asst. in An. Nutrition3

R. V. Allison, Ph.D., Chemist' 3
F. B. Smith, Ph.D., Microbiologists
C. E. Bell, Ph.D., Associate Chemist
H. W. Winsor, B.S.A., Assistant Chemist
J. Russell Henderson, M.S.A., Associate3
L. H. Rogers, M.A., Asso. Biochemist
Richard A. Carrigan, B.S., Asst. Chemist

C. V. Noble, Ph.D., Agricultural Economist'
Bruce McKinley, A.B., B.S.A., Associate
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Assistant

Ouida Davis Abbott, Ph.D., Specialist'
Ruth Overstreet, R.N., Assistant
R. B. French, Ph.D., Associate Chemist
J. R. Watson, A.M., Entomologist1
A. N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
G. H. Blackmon, M.S.A., Horticulturist'
A. L. Stahl, Ph.D., Associate
F. S. Jamison, Ph.D., Truck Horticulturist3
R. J. Wilmot, M.S.A., Specialist, Fumigation
R. D. Dickey, B.S.A., Assistant Horticulturist
J. Carlton Cain, B.S.A., Asst. Horticulturist
Victor F. Nettles, M.S.A., Asst. Hort.
W. B. Tisdale, Ph.D., Plant Pathologist'1
George F. Weber, Ph.D., Plant Pathologists
L. O. Gratz, Ph.D., Plant Pathologist
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Assistant Botanist

R. P. Terry, Chairman, Miami
Thomas W. Bryant, Lakeland
W. M. Palmer, Ocala
H. P. Adair, Jacksonville
Chas. P. Helfenstein, Live Oak
J. T. Diamond, Secretary, Tallahassee

J. D. Warner, M.S., Agronomist Acting in
R. R. Kincaid, Ph.D., Asso. Plant Pathologist
Jesse Reeves, Fhrm Superintendent
A. F. Camp, Ph.D., Horticulturist in Charge
John H. Jefferies, Superintendent
Michael Peech, Ph.D., Soils Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Asso. Entomologist
W. W. Lawless, B.S., Asst. Horticulturist
R. K. Voorhees, M.S., Asst. Plant Path.
J. R. Neller, Ph.D., Biochemist in Charge
J. W. Wilson, Sc.D., Entomologist
F. D. Stevens, B.S., Sugarcane Agronomist
Thomas Bregger, Ph.D., Sugarcane
Frederick Boyd, Ph.D., Asst. Agronomist
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, B.S., Asst. An. Husbandman
W. T. Forsee, Ph.D., Asso. Chemist
B. S. Clayton, B.S.C.E., Drainage Engineer2
W. M. Fifield, M.S., Horticulturist Acting in
S. J. Lynch, B.S.A., Asst. Horticulturist
Geo. D. Ruehle, Ph.D., Asso. Plant Pathologist
W. F. Ward, M.S., Asst. An. Husbandman
in Charge2

M. N. Walker, Ph.D., Plant Pathologist in
K. W. Loucks, M.S., Asst. Plant Pathologist
Plant City
A. N. Brooks, Ph.D., Plant Pathologist
R. N. Lobdell, M.S., Asst. Entomologist
A. S. Rhoads, Ph.D., Plant Pathologist
A. H. Eddins, Ph.D., Plant Pathologist
Samuel O. Hill, B.S., Asst. Entomologist2
Jos. R. Beckenbach, Ph.D., Truck Horticul-
turist in Charge
David G. Kelbert, Asst. Plant Pathologist
R. W. Ruprecht, Ph.D., Chemist in Charge,
Celery Investigations
W. B. Shippy, Ph.D., Asso. Plant Pathologist
E. S. Ellison, Meteorologist2
B. H. Moore, A.B., Asst. Meteorologist2
1Head of Department.
2In cooperation with U.S.D.A.
3Cooperative, other divisions, U. of F.
40n leave.


INTRODUCTION ..............................------------ 5
DISEASES CAUSED BY NUTRITIONAL DISORDERS ......-..........------.........------ 8
Copper D efficiency ........................... .. .. ........................ ............ ..... 8
Manganese Deficiency ........-..----......------.. --------------------------. 9
Zinc Deficiency ......... ............... ... ......... .... ...----- ...... 10
DISEASES CAUSED BY BACTERIA ---................... ---..............------- -- -- 12
Halo Blight .......--.. ...........................-- -- ---............ --- 12
Common Bacterial Blight ......................... .......---..-- --. 19
DISEASES CAUSED BY FUNGI ..................................... ----------------- 19
Powdery Mildew ............. ...... .......................-------- 19
Rust ....... ........ ...-- .. -- ------.. ...... .... ................------ ----.. ---. 23
Angular Leaf Spot .................................. .... ... ------- 31
Watery Soft Rot .........--.....-------..... -. ...............---.-- 32
Anthracnose ........-.....---..--.......---.... ---.... ---------- 34
Rhizoctonia Disease ...................--....- ..........-..- ...----- --- 37
Southern Blight ........................................ ..... .. ... .--- ----- 41
DISEASES AND INJURIES DUE TO OTHER CAUSES ........................................ 43
Root-Knot ....................--........ ----- .... ....... .....- ---- 43
Baldheaded Beans ........................................ ....................... 48
W ind Injury ..--............ .......--- --.......... .... ............... 49
Low Temperature Injury ....... .................... ....- ...--- .............. 50
W after Injury .....-- ... --.... ----........ ----.... .........-.. ---.....- ..--....- .- 51
Fertilizer Injury .......--- ....--....-...-..-- ..................... 52
Copper Injury ............................. ................ ....................... 54
Sulfur Injury ..... ............................. -- ........- ......-.. ... 54
CONTROL M EASURES .......-..............---- ...... ......... ....... ........ 55
Exclusion --.................................--------------.... ..-- 55
Eradication ........................................ --- ----- --- .----- 56
Immunization ....--......................--...--------...------ 56
Protection .............-..... .. ......... .... .--- -. ... ............ 56
LITERATURE CITED --........--.........-------.........------- -----....... 59

65. ---. 12 YEAR AVERAGE
60 .


3 13 23 2 12 22 I II 21 1 II 21 31 10 20 30 10 2030 9 19 29 8 18 28 10 20 40 0 13 29 9 19 29 8 18 28

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

Aerage Monthly Precipitation and Evaporation at the Everglades Expenment Station
(1924 -/936)

July Aug. Sept. Oct.

Nov Dec Jan Feb Mar Apr May June

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



In recent years the snap bean crop in Florida has occupied
approximately 60,000 acres annually. More than 85 percent of
this acreage has been in southern Florida. Palm Beach County
in 1937-38 led with 26,000 acres of snap beans. It was fol-
lowed closely by Broward County, where 23,500 acres of beans
were grown. The farm value of this crop in Florida was a little
over $6,000,000 in 1937-38.1
The production of beans in southern Florida is centered in
two important and somewhat different agricultural areas. Many
beans are produced on the peat and muck soils of the Everglades
near the eastern and southern shores of Lake Okeechobee. The
other important center of production is on the sandy soils along
the lower East Coast.
The peat and muck soils of the Everglades are rich in nitro-
gen, but contain very small amounts of phosphorus and potash.
They are generally deficient in copper, manganese and zinc. The
more mineralized custard apple muck soil close to Lake Okee-
chobee is more fertile than the highly organic sawgrass peat
soils which lie farther from the lake. A deposit of marl at
depths of three to 10 feet below the soil surface charges the
soil water with calcium and magnesium.' However, these soils
are not alkaline except where they have been burned extensively
or where marl has been mixed with the top soil. Peat and
muck soils have high water-holding capacities and good capillary
action. They generally have adequate moisture for crop needs.
The sandy soils of the East Coast bean growing area are
classified in several soil series. Sands of the Leon and Bladen
series and other flatwoods soils are the ones most often used
for the production of snap beans in this area. These soils are
not rich in the primary nutrient elements, nitrogen, phosphorus,
and potash, but generally have adequate supplies of copper and
zinc. Available manganese may be deficient in neutral and
alkaline sands which overlie deposits of marl or are affected
by tidal waters. The acid sands are deficient in calcium and

'These statistics were obtained from reports of the Bureau of Agricul-
tural Economics, U. S. Department of Agriculture, and from reports of
the Marketing Bureau of the Florida Department of Agriculture.

Florida Agricultural Experiment Station

magnesium. Because sandy soils have low water-holding ca-
pacities leaching of applied fertilizers may occur during heavy
rains. At times irrigation is necessary.
The climate of southern Florida is suitable for growing beans
during nine months of the year. Owing to its location south
of the 27th parallel of North Latitude, and its proximity 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
during the winter months. 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 farming area. On the lower East
Coast winter temperatures are not quite so low and frosts are
less frequent.
Beans are planted from early September until about the first
of April in southern Florida. Shipments of beans to Northern
markets begin six or seven weeks after the plantings 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 the winter months.
Forty-five to 60 pounds of seed is 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
phosphorus, potash, copper, manganese and sometimes sulfur
and zinc. There is considerable variation in formulas of fer-
tilizers 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.
Most beans grown on the sandy soils are planted on raised
beds. This system removes the crop from the danger of flood

Diseases of Beans in Southern Florida

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
nitrogen 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 mag-
nesium 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 Valen-
tine, 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 is usually 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. The production
of high quality seed is a specialized business for which most
growers have neither the time nor the training and equipment.
Growers should insist that seed purchased from producers in
other states be disease-free.
The writer wishes to reserve his judgment on the production
of bean seed as a specialized business in Florida. Seeds of
certain new varieties which are being developed at the Ever-
glades Experiment Station are being produced here now and
it may be possible to work out a program for the production
and certification of these varieties within the state.
Diseases are injurious physiological processes occurring in the
plant. Those described here are caused by a variety of agents
such as fungi, bacteria, nematodes and the deficiency of nutri-
ents. Several physical injuries to the bean plant are described
Pod and leaf spots, root rots, root galls, chlorosis and stunt-
ing 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. Since
this is so, it is natural that we should find such factors as rain-

Florida Agricultural Experiment Station

fall, temperature, humidity, air movement, soil fertility and
soil reaction acting inseparably with the chief causal factor
in the production of the disease.

The sawgrass soils in the Everglades were very unproductive
when first reclaimed. Applications of the usual fertilizer ma-
terials failed to make these soils productive for beans and other
crops. Potatoes could be grown if they were sprayed with
bordeaux mixture. This observation, together with other facts
which were known about raw organic soils, led to experimenta-
tion with copper sulfate and other minerals. It was found that
the soils became productive when treated with copper sulfate
(1).2 Some slight responses to other minerals were noted also
in the first experiments.
The 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 saw-
grass 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
Copper deficiency probably has been confused to some ex-
tent with the lack of manganese and zinc in similar soils. The
symptom patterns for the other deficiency diseases of beans
are better known. Before it can be determined that there is
need for copper the plants should be carefully examined 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 sawgrass land in the Everglades at the time it
is brought into production. 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
'Italic figures in parentheses refer to "Literature Cited" in the back
of this bulletin.

Diseases of Beans in Southern Florida

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.
This trouble occurs on mineral and organic soils where the
soil solution is not sufficiently acid to dissolve manganese com-
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

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
the growth of
crops. Peat and Fig. 4.-A normal leaf of a Bountiful bean (left) in contrast
with a leaf showing early symptoms of manganese deficiency.
muck soils which
have been burned or mixed with marl have reactions above pH
6.0, and are liable to be deficient in available manganese.
The symptoms of manganese deficiency in beans usually ap-
pear after the beans have been growing for two or three weeks.
A chlorosis, developing in the areas between the small veins
of the leaf, gives the leaf a mottled appearance when viewed

Florida Agricultural Experiment Station

closely and a general light green color when seen at a little
distance. Plant growth slows down when the green color begins
to fade from the leaves. If corrective applications are not made
at this stage the leaves will soon become golden yellow and the
plants become very stunted. Dark dead spots occur on the
leaves in this stage. Many leaves are shed from severely af-
fected plants and growth of the buds ceases. The root systems
of affected plants are very sparse and are frequently affected
by fungi and nematodes. Yields are reduced in proportion to
the severity of the disease.
Beans grow normally on manganese-deficient soils when man-
ganese sulfate is included in the fertilizer (21). A fertilizer
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.
Spraying manganese solutions on the plants is a very effec-
tive corrective for manganese deficiency. This is frequently
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 four pounds
of manganese sulfate is sufficient to spray an acre of beans.
It may be necessary to spray the beans two or three times
if the chlorosis is likely to be severe. The plants respond to
the spray by becoming green in two or three days after the
application. The possibility of combining manganese sulfate
and other spray materials is discussed in a later paragraph.
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 where copper and manganese sulfate do
not correct the unproductivity completely. 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

Diseases of Beans in Southern Florida

normally on zinc-deficient soils for four or five 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. The older leaves are thick and tough, while the younger
leaves are likely to be rather thin and narrow. Some distortion
of the leaves also is noted. A chlorosis sets in which later in-
volves all the area of the leaf between the principal veins and
is not segregated by the smaller veins as in the manganese
chlorosis. The tissue along the principal veins remains green
the longest. The color of the chlorotic area does not become
a brilliant yellow but may be dull yellow, brown or even white
in the older leaves. The chlorotic areas in the younger leaves
sometimes wilt suddenly so that beans in an affected field may
have a blighted appearance. Leaves of zinc-deficient plants are
shed prematurely and the plants do not blossom or bear heavily.

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

Florida Agricultural Experiment Station

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 gal-
lons of water (19). About 50 gallons of this spray should be
applied to the acre. It seldom is necessary to make more than
two applications on a crop. The response from zinc is slower
than from manganese, but it should be evident in from five
to seven days. Combinations of zinc sulfate with other spray
materials are discussed in a later paragraph.

Halo blight affects snap and dry shell beans, scarlet runner
beans, lima beans and kudzu (5, 14). Other legumes and non-
leguminous crops are not susceptible to this disease.
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
(4, 23). 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 (4). 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 (17). Flor-
ida and the other Southeastern states have had serious out-
breaks of the disease in seasons following its occurrence in
the seed fields.
Heaviest losses occur when young plants are affected. Entire
plantings are sometimes 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 re-
duction in yield of snap beans in Florida due to bacterial dis-
eases, chiefly halo blight, has been about 5 percent in the last
11 years (17). 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
times broader than the dead center of the spot. Isolated spots

Diseases of Beans in Southern Florida

are generally 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 yellow in color.
Stems of badly diseased plants are swollen in the region of
the lower leaf nodes. The swollen tissue appears to be water-
soaked at first, and then turns red or brown. Eventually the
affected tissue dries out and longitudinal 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. The pod spots are 1/8 to 1/4 inch in diameter and
have a greenish water-soaked appearance. When the spots 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. This exudate is never yellow

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


Diseases of Beans in Southern Florida

as is the similar exudate from plants affected with the common
bacterial blight.
Halo blight of beans is caused by the parasitism of the
bacterial organism, Phytomonas medicaginis var. phaseolicola
(Burkh.) Link and Hall. The bacteria within the tissues of

'""*'*<*,, >A- ^ ., -- FyS natf

Fig. 7.-Halo blight spots on bean pods.
the stems, leaves and pods (26) 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. Conditions are then favorable for
growth of the bacteria and the cotyledons are invaded by these
organisms. The bacteria move through the cotyledons to the
stems and the vascular systems, or under some conditions they
infect the unfolding leaves which \are in contact with the in-
fected cotyledons during germination.
The bacteria multiply so rapidly in the stem cortex that its
cells are torn apart and disintegrated by bacterial action.
Pockets containing masses of bacteria are thus formed in the
stem. The bacteria secrete toxins which enter the vascular
system of the plant, weaken the plant and cause chlorosis in
the terminal bud.
Secondary infections occur when the bacteria are transferred
from the exudate on diseased plants to healthy parts of the
same or other plants. Many plants besides those from diseased

Florida Agricultural Experiment Station

seed become infected in this way. The bacteria gain entrance
to the plants through pores or wounds in leaves, stems and pods.
The cycle of bacterial development after the organism enters
the plant is similar to that for the primary infections. There
may be several subsequent cycles of development on new host
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 deter-
mined. In some sections of the country it is thought they do,
and a few experiments have been reported seeming to show
that the bacteria can survive from one year to the next either
on crop debris on the soil surface or free in the soil. Very
little crop debris remains either on or in the soil of old bean
fields in Florida from one season to the next, and it is doubted
that the bacteria can survive our summer conditions. There
is more reason to believe that these bacteria may reach the soil
from a diseased crop and infect a second bean crop in the same
season. However, no observations that would prove this have
been made in several years' study of the problem. Beans have
been planted in fields where the disease destroyed a crop two
or three months earlier, and have shown no signs of the trouble.
Two experiments have been performed to determine whether
the bacteria survive long in our soils. Severely blighted bean
plants were added to peat soil in large jars. Some of these
plants were exuding masses of bacteria when incorporated in
the soil. Bean seeds were planted in the soil in some of these
jars when the vines were added and in other jars at weekly
intervals after the addition of the vines. Halo blight did not
develop on the bean seedlings which grew on these soils. There
was some seed decay and damping-off in the soils to which the
vines had been added, but this appeared to have been caused
by Rhizoctonia sp. and other fungi.
In another experiment a broth culture of the blight bacteria
was added to jars of peat and heavy sand soils. Clean Bounti-
ful bean seeds were planted in some of the jars on the day
the bacteria were added to the soil and in others a month later.
Typical halo blight infection occurred on the beans planted
when the soils were inoculated. No infection occurred on the
plants from seeds sown a month after the soils were inoculated
or on plants in soils which had not been inoculated. The experi-
ment seems to show that while the blight bacteria can infect

Diseases of Beans in Southern Florida

beans from the soil they do not survive in these 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. Under these conditions a
number of infected plants develop in the field after a period
of two or three weeks. Only a few infected plants scattered
through the field may be noticed if the weather remains fair
and the humidity low. However, under humid or rainy condi-
tions there usually is considerable spread of the disease to other
plants in the field and losses may become great. The severity
of an outbreak of halo blight depends upon the duration of
rainy weather, the amount of rainfall and the wind velocity,
since the bacteria are easily spread through a field by splashing
and wind-driven rain. After a hard shower which splashes
bacteria in all directions from the infected plants, a field may
be marked by circular areas, five to 25 feet in diameter, where
the plants are dying with halo blight. A strong wind blowing
from one direction during a rainstorm drives bacteria-laden
raindrops over a fan-shaped area to the leeward from infected
plants, and the plants in this area begin to show symptoms of
halo blight a week or more after the storm. Instances have
been observed where apparently the bacteria had been carried
300 feet in this manner. A few plants infected from the seed
can serve to inoculate an entire field during a driving rain-
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

Florida Agricultural Experiment Station

be precooled to 450 F. and standard refrigeration should be
maintained enroute to market.
Direct measures for the control of halo blight have never
been successful. The bacteria in the seed are lodged under the
seed coat so that the usual methods of seed treatment are not
effective. Experimental work with new types of seed treat-
ments is being continued and a way may be found to control
the disease by chemical treatment of the seed. No treatment
is recommended at this time.
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.
SPlanting 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 period of 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.
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 (17). 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 sec-
Halo blight has never been reported from California, and
tests of the practicability of raising snap bean seed in certain
California districts have been started. Because of peculiar con-
ditions in that state it is expected that seed produced there
will be more expensive than from the present sources.
Inspection and certification of bean seed fields for freedom
from diseases would solve the halo blight problem. California

Diseases of Beans in Southern Florida

issues certificates of inspection for dry bean seeds, but has not
been called upon to certify the seeds of green beans. This
could be arranged if the service is desired by a sufficient num-
ber of growers. There is also some interest in certification in
the other Western states where bean seed is produced.
It is not necessary to describe this disease in detail because
it is so similar to halo blight. Some of the differences between
the two 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 (5) 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 and Montana. The seed producing companies moved
their production operations from the East to the more arid
parts of the West to escape this disease and anthracnose several
years ago.
Common bacterial blight is caused by the parasitism of the
bacterial organism, Phytomonas phaseoli E. F. Smith. This
organism is closely related to the halo blight bacterium but
can be distinguished 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
of obtaining a clean crop. This practice has the same limita-
tions mentioned in discussing the control of halo blight.

Powdery-mildew, sometimes called white mold, is a disease
common to beans and many other species of plants. While
there are distinct differences between the mildew diseases of
beans and some non-leguminous host plants, it is doubtful

Florida Agricultural Experiment Station

whether this is true of the powdery mildew diseases of legumes
and certain other crops. Some of the plants which have been
reported to be susceptible to the powdery mildew of beans are
peas, cowpeas, clover, vetch, cabbage, carrots, tomatoes and
Different bean varieties vary in susceptibility to powdery
mildew. Bountiful and Hodson Wax are very susceptible in
Virginia (7), but the Refugee is quite resistant. It has been
observed that in Florida the Stringless Black Valentine and
certain strains of Kentucky Wonder are more resistant to mil-
dew than the Bountiful.
Powdery mildew occurs in many states where beans are
grown, 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 fol-
low mildew injury may occur in shipped beans. Part of the
cost of control measures which are effective for mildew as well
as for other bean diseases should be charged to this disease.
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 surface of the leaves and on the younger leaves,
stems and pods. It may become so widespread on the leaf that
the entire leaf surface is covered with the powdery growth of
the fungus. On the stems and petioles the spots are more often
in the form of 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 is there-
fore sometimes erroneously called rust. Affected pods do not

Diseases of Beans in Southern Florida

have deep lesions like those caused by the bacterial blights,
anthracnose and soil rot.
This disease is caused by the parasitism of the fungus, Ery-
siphe polygoni D C. Unlike many parasitic fungi, this one
confines its activity to the surface cells of its host plants, on
which it is seen as the powdery growth already described. It
sends a few minute threads or suckers into the epidermal cells
of the plant from which it obtains its sustenance.

Fig. 8.-Powdery mildew on bean leaves.
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 easily detached.
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 un-

Florida Agricultural Experiment Station

favorable for infection and few of its host plants are growing.
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, and free water on the surface of the leaf or stem
is not required for successful inoculation of the plant. Night
fogs and heavy dews, common during winter in southern Flor-
ida, are especially favorable to the 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 the lack of nutrients seem to be particu-
larly susceptible to the disease. The same is true of the older
shaded foliage on the plant and of the old plants when they
are declining after harvest. Such plants sometimes become
gray with the mildew, and are a menace to younger beans in
the area because of the immense crops of spores which they
produce daily.
Powdery mildew is controlled easily by the application of
protective fungicides (Table 1). Sulfur dusts and wettable
sulfur sprays have given good control of the disease when ap-
plied prior to the occurrence of the infection. Two or three
applications of some form of sulfur are generally considered
adequate. The possibility of injuring beans with sulfur fungi-
cides is discussed in a later paragraph and should .be borne
in mind in determining the advisability of making applications
for the control of mildew. 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.
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.
Mildew was the only disease which occurred on the beans in
an experiment in the fall of 1937. It was observed quite gen-

Diseases of Beans in Southern Florida

erally on stems and leaves of plants on plots not protected with
fungicides, but was much less severe than usual during late
winter. The disease did not occur on plants which had been
protected with four applications of the fungicides. Each of
the treatments was made in quadruplicate on 1/45 acre plots.
Beans were harvested from these plots in two pickings and the
yield in hampers per acre is given in Table 1.

Treatment I Hampers per Acre
A B C I 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

Progress is being made in the breeding of mildew-resistant
beans at the Everglades Experiment Station.
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 (9, 13) have shown that
cowpeas and certain wild legumes are not susceptible to bean
rust. The writer also has been unsuccessful in his attempts to
infect cowpeas, wild cowpeas, and a species of wild bean from
northern Florida with the bean rust fungus. Plants now con-
sidered 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 several strains of the rust fungus. Some
varieties which had been reported resistant to rust were found
to be very susceptible to the forms of rust occurring in Florida
in 1936 and 1937. The varieties of beans commonly grown in
Florida, such as the 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 (13) as fairly resistant to rust in other parts of the
United States.

Florida Agricultural Experiment Station

There are certain rust-resistant strains of the Kentucky
Wonder bean which have been found to resist the rust in Florida.
These varieties are useful for home garden production in this
state, but are not adaptable to commercial production because
of market preferences. These varieties are also useful in breed-
ing work for the production of new varieties of rust-resistant
beans. Fordhook and Henderson Bush lima beans have never
been observed to be seriously affected with rust in Florida,
although a few pustules sometimes occur on their foliage and
they have been reported (13) to be susceptible in other states.
Several varieties of beans which have been advertised as "rust-
proof" or rustlesss" are not rust-resistant. These terms have
been applied erroneously to varieties of beans resistant to an-
thracnose, 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, West Virginia, Ten-
nessee, Georgia, Florida, Alabama, Louisiana, Texas, Colorado
and California. In Florida the most recent severe outbreaks of
bean rust occurred on the winter and spring crops of beans in
Broward and Palm Beach counties during the 1935-36 and
1936-37 seasons.
This disease is said to be one of the most destructive to
beans in Virginia (25), sometimes completely destroying the
crop. In the spring of 1936 rust was so destructive in southern
Florida that many hundreds of acres of beans were plowed under
without being harvested. The loss at that time was estimated
at from 40 to 80 percent of the late crop in Palm Beach and
Broward counties. The losses were heavy again the following
year and would have been larger except for the general practice
of control measures in Palm Beach County.
F first symptom 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 two after the yellow
spots appear the surface of the spots becomes raised and some-
what later the epidermis of the leaf is broken and a pustule
-afredspres is exposed. The spores are so very small that a
single pustule contains thousands of them. If there are many
spots on a leaf the spores fall from the pustules as a reddish
brown dust which collects on the leaves and stems and may even

Diseases of Beans in Southern Florida

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 also occur 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
from rusted plants.
In southern Florida the disease has not been observed on
stems and pods. Sometimes the pods have a rusty color due
to the presence of numerous spores which have fallen from the
Damage to the crop is caused when the leaves are so heavily
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 caused by
rust are proportionate to the earliness and severity of the
Bean rust is caused by the parasitism of the fungus, Uromyces
phaseoli typical Arthur. This fungus belongs to the.group caus-
ing 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
In_ southern Florida the only spores produced by the rust
funguasareAthe urfedospores-which occur as a reddish brown
powder in the pustules on bean leaves. This fungus also pro-
duces a-black spore form in colder climates. These black spores
carry the fungus through the winter in the North, but are
apparently not needed in the far South. Here the fungus ap-
parently perpetuates itself with the red or summer type spores.
It has been found that the uredospores do not live long under
Florida conditions. Most of those collected for testing the
duration of their viability were not alive two weeks after they
were collected, and none were able to infect bean plants after
being stored for three months. The storage conditions included

26 Florida Agricultural Experiment Station

a variety of moisture and temperature conditions but none were
found which would lengthen the period of survival of the spores.
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

: ;'
I ~.`;'
"`; ''"
11' ~4
.S I
t : ~





".'' :- "
A' 4
: .ah:: ~ :Ii;.
4'.; 5t

Fig. 9.-Rust on bean leaves, showing comparative symptoms on the lower (left) and
upper leaf surfaces.
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 eight
to 10 hours under favorable conditions. The yellow spots which
are the first evidence that infection has occurred appear in four
to six days. Seven to 10 days* pass before the mature spore
pustules rupture the leaf surface. These spores are immed-
iately 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

Diseases of Beans in Southern Florida

the cereal rust fungi are believed to be carried by air currents
for hundreds of miles (15).
The spores germinate on the bean leaves only when the rela-
tive humidity is high or when there is water on the leaves. In
some inoculation experiments with plants in the greenhouse it
has been found that few infections occur on plants standing on
a greenhouse bench where the air is relatively dry. When the
inoculated plants are placed in a closed chamber where the
humidity is high, infection occurs normally. Infections are
very readily obtained on inoculated plants when the foliage is
wet and the plants are kept in a closed chamber overnight.
Similar conditions frequently occur in the field in southern
Florida where dews and night fogs are common during most
of the growing season.
Temperatures near 60 F. were found to be the most favbr-
able for the development of infection following artificial inocu-
lation. 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 one test in which the tem-
perature rose to 1030 F. during the incubation period. As a
rule infection was more readily obtained at temperatures below
750 F. than at higher temperatures.
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
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-
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 have also 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 one
application. Good results have been obtained ,by applying dust-
ing sulfur or wettable sulfur sprays. It:is recommended that

Florida Agricultural Experiment Station


Treatment Basic Bor-
_Copper deaux

Pustules per plant ....... 30.3 50.4

Percent control .............. 51.4 19.1







Sulfur Sulfur
Dust Dust

5.3 0.4

91.4 99.4



None ...........---..-------- ...--

Three applications of sulfur dust ......

Two early applications of sulfur dust

Two late applications of sulfur dust

Three applications of Bordeaux spray

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



None .......-........ ------..----------

Three applications of wettable sulfur ............

Fourapplications of wettable sulfur ..............

Five* applications of wettable sulfur ...........

Six* applications of wettable sulfur ..............

Three applications of Bordeaux spray ...........

Five applications of Bordeaux spray ...........

Four applications 'of sulfur paste ..................



























*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 five and six times.

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

Diseases of Beans in Southern Florida

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 two or three days after the
beans emerge and to continue them at intervals of five or six
days until a few days before the plants bloom. This may re-
quire as many as six applications. The rate of application may
be reduced slightly if the frequency is increased. The im-
portant 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 necessitates 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
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. The only
hope is that sufficient control of new infections can be obtained
to make the use of fungicides worth while. There is little rea-
son for a grower allowing the rust to catch him unawares,
since an outbreak of rust does not begin so suddenly as it some-
times seems. A few pustules of rust can be found on the leaves
for two or three weeks before there is a general outbreak. The
appearance of these pustules should be the signal to begin apply-
ing sulfur fungicides and the frequency of the applications
should increase as the number of pustules on unprotected plants
increases. Even better results can be obtained when one

Florida Agricultural Experiment Station

watches for the first development of the yellow spots on the
under sides of the leaves, since these will warn the grower of
an approaching outbreak of the rust several days sooner than
will the 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. While sulfur dust
applied with a hand duster has given adequate control of rust,
wettable sulfur sprays applied with knapsack sprayers have
failed to do so. Either dusting or spraying is satisfactory with
traction and power-driven field equipment. More farmers have
power-driven sprayers than dusters, and the cost of spraying
is somewhat less than dusting. Some growers prefer to dust
with airplanes. There are no objections to this method when
it is done by an experienced flier who can cover all parts of
a field equally. The method is particularly applicable when
large fields must be covered rapidly, but the cost is higher than
where a grower uses his own 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 slightly reduced and there is an increase in the
number of scarred beans. There probably is no reason for
applying fungicides at this time if sufficient sulfur has been
applied previously. Plants which have been well protected up
to the blooming period should remain in good health for two
or three 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. When the rust pustules rupture the leaves
the plant loses water more rapidly and tends to dry up. It is
believed that copper fungicides increase the water loss from
rusted leaves and actually hasten the plant's death. Experi-
ments have shown that the yield may be reduced considerably
where copper fungicides have been applied 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 beans are available for home garden plant-

Diseases of Beans in Southern Florida

ing. These can be used to advantage wherever rust prevents
the growing of other types of beans in Florida. There is some
hope that rust-resistant strains of Bountiful and other market
types of snap beans may some day be available. The Ever-
glades Experiment Station and several seed companies are
breeding and selecting rust-resistant types of beans, but none
of these are likely to be available for commercial planting for
several years.
This disease has been observed only on snap beans in Florida,
although it has been reported on peas (6) in other states. It
has been seen most often on Bountiful beans, but other varieties
seem to be susceptible.
Angular leaf spot is not a common disease of beans in south-
ern Florida. It occurs sparingly in some fields during the
winter. Severe outbreaks have been observed in only a few
fields. At such times losses in affected fields have been heavy.
It is estimated that the loss for the entire crop in southern
Florida would be less than 1/ of 1 percent.
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 Cercospora col-
umnaris Ell. and Ev., 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
two-celled spores are disseminated by wind and rain and are
capable of causing new infections.
Angular leaf spot has occurred so infrequently that experi-
ments for its control have never been conducted. Since beans
are generally protected against mildew and rust with sulfur
fungicides, it may be that these materials help to control the
angular leaf spot fungus, and thus account for its infrequent
occurrence. Bordeaux mixture has been suggested for the con-
trol of this disease (6), but its use on beans in Florida should
be confined to one or two early applications.

Florida Agricultural Experiment Station

Many names have been applied to this disease on various
hosts, and even on different parts of the bean plant. In addi-
tion to watery soft rot, the disease is sometimes spoken of as
white mold and Sclerotinia rot of beans. Since powdery mildew
often is called white mold by growers, that name should not
be used for this disease, although it is quite descriptive of
certain of its symptoms.
Watery soft rot occurs on celery where it is known as pink
rot, and on lettuce as drop. It attacks a large number of other
cultivated plants and weeds. No varieties of beans have been
reported to be resistant to this disease.
Watery soft rot is found on beans quite generally in the Ever-
glades at certain seasons. It is most prevalent in the crop in
fields where beans have been grown continuously for several
years. Beans following celery with pink rot or lettuce with
drop are also quite likely to be affected to some extent with
watery soft rot.
Losses occur through the destruction of young plants in the
field when they are a week or 10 days old, rotting of branches
and pods of older plants and a decay of beans while en route
to market. The loss of young plants in the field seldom affects
the yield seriously. However, there may be small losses when
it attacks the older plants and rots some of the pods. The most
serious losses occur in shipped beans.
When the disease attacks young bean plants it causes a watery
soft rot of the stem near the cotyledonary node or in the bud.
Plants attacked at this early stage are always killed. The dis-
ease can be distinguished from other seedling diseases by the
presence of a white fungous growth on the affected parts and
by the fact that the lower part of the stem and the root are
not affected.
On older plants infections occur on branches, pedicels and
pods. Leaves on a branch above an infection wilt when their
water supply is severed. The pods decay with a watery soft
rot. A cottony white fungus is seen frequently on the affected
branches and pods. This white mycelium also forms within
affected pods and hollow stems or branches.
Nesting of shipped beans is sometimes caused by this disease.
This results when a few infected pods are included in the pack-
age of beans and cause other beans in the package to rot. The

Diseases of Beans in Southern Florida

affected beans are bound together by the white mycelium of the
Watery soft rot is caused by the fungus Sclerotinia sclero-
tiorum (Lib.) de Bary. This is the fungus which is seen so
frequently on the pods and branches of beans as a cottony
growth. Infections occur when the mycelium of the fungus
grows from soil particles blown or splashed onto the plant.
This fungus produces sclerotia in the tissues of the plants
it attacks. The sclerotia serve to perpetuate the fungus in the
same way that seeds and tubers maintain the life of plants
through conditions unfavorable for vegetative growth. When
the infected tissues rot the sclerotia are left in the soil where
they are ready to initiate a new cycle of fungous development
when beans or other susceptible crops are grown under suit-
able environmental conditions.
Precipitation is the most important factor contributing to
the development of watery soft rot. The disease is most preva-
lent and destructive in fields where heavy rains have splashed
soil particles onto the buds of young plants or onto the branches
and pods of mature plants. It is seen most frequently in the
fall crop, probably because more heavy rains occur at that
It has been shown (16) that the fungus attacks bean pods
most vigorously at temperatures ranging from 660 to 750 F.
Temperatures lower than 50 F. retard its development con-
siderably. Mean daily temperatures in southern Florida are
within the optimum range for the development of this disease
from the middle of October to December 1 and from March 20
to the end of the season.
Fungicides effective in the control of watery soft rot have
not been found. The disease occurs on beans which have re-
ceived protective applications of sulfur and copper fungicides
for other purposes. Whether more frequent or heavier applica-
tions of these fungicides would be effective is not known, but
it is doubtful that they would be profitable.
A rotation system in which beans do not follow beans or other
susceptible crops, particularly in the early fall crop, would help
in controlling this disease. An experiment in 1936 showed the
relation of the disease to the previous cropping practice. In
this test-the loss of young bean plants due to'watery soft rot
was 18 percent in an area where beans followed beans, 17 per-

Florida Agricultural Experiment Station

cent following peas, 3 percent following carrots and 2 percent
following fallow.
Beans should be picked only when dry from a field where
watery soft rot is present and should be very carefully graded
before packing in order to remove all infected pods. A few
infected pods left in a hamper may be the cause of so much
spoilage while the beans are en route to market that the entire
shipment is endangered. Pre-cooling of cars of beans from
affected fields is advisable to reduce the temperature of the
beans to 45' F. or lower as rapidly as is possible. This tem-
perature should be maintained by standard refrigeration while
the cars are en route to market. Very little nesting and spoilage
of beans can result from the watery soft rot disease under these
The common bean, the lima bean and the sieva bean are the
principal species of plants affected by the anthracnose disease.
It has been reported (3) 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 sus-
ceptible that the disease becomes severe on them.
Some varieties of beans are resistant to anthracnose. How-
ever, since there are several physiologic forms of the anthrac-
nose fungus, not all of these varieties are resistant to all the
forms of the fungus. Some workers have attempted to hybridize
various resistant and susceptible varieties of snap beans to ob-
tain one resistant to all forms of the fungus. This work has
not progressed to the point where anthracnose-resistant snap
beans similar to our commercial varieties have been produced.
Anthracnose of beans has been known for many years and is
world wide. In the United States it is most prevalent in the
Northeastern states. It occurs in Florida and the other Southern
states during the cooler seasons of the year.
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 last 10 years the loss due to this disease in
Florida has been estimated at from nothing to 11 percent of
the crop (17).

Diseases of Beans in Southern Florida

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 two or more
spots have joined. The 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 under-
lying seeds. Diseased seeds are shrivelled and darkened.
Anthracnose is most readily 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. As has been men-
tioned above, there are several biologic forms of this fungus.
Each form is restricted in its 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 the leaves, stems and pods
of the plant, or other nearby plants to which they may be
Some infections may occur from spores in the soil or from
diseased parts of plants remaining in the field from an earlier
diseased crop. These sources of spores have been shown to be

Florida Agricultural Experiment Station

responsible for part of the infection of beans with anthracnose
in the Northern states. It is improbable that they are of im-
portance in southern Florida. Infected seed is the most im-
portant 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 the humidity is generally
high during the growing season and seldom is a factor which
would limit infection. The night fogs and heavy dews provide
adequate moisture for the development of this disease.
Temperature is the factor which limits bean anthracnose to
the cooler seasons in Florida. It has been shown (8) in Louis-
iana that the disease does not develop on beans in that state
during summer months because prevailing temperatures are too
warm. This is true in Florida for an even greater part 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.
Although it is possible to detect shrivelled and discolored seed
in infected seed lots, this is not a good criterion for selecting
seed. Some seeds which are neither shrivelled nor darkened
carry the fungus. It is safer to purchase seed grown in a semi-
arid region or at least from a field which was declared disease-
free by some reliable authority. Bean seed which has been
grown in some of the Western states is preferred because the
anthracnose disease is seldom found there. The reduction in
the occurrence of anthracnose in Florida in recent years may
be due to an increasing use of Western-grown bean 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 (3) bordeaux

Diseases of Beans in Southern Florida

mixture controlled the anthracnose. Good results also were
obtained with lime-sulfur solution. Because of improvements
in spraying 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 prevalent enough in southern Florida in recent years to
provide an opportunity for testing the newer materials and
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 (18) are more active parasites than others.
This fact might make it appear that there are varietal differ-
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 appears whether the crop is planted on virgin soil or on land
that has been cultivated for many years, and on sands as well
as peats. Fortunately, the disease is less destructive than it is
common. It usually 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
Average losses due to this disease are small, but losses may
be quite heavy in certain fields. Such losses are of particular
concern to the small grower, since he may lose a considerable
part of his planting. Some spoilage of beans in shipment is
due to this disease.
The Rhizoctonia disease is almost as varied in its symptoms
as it is in the species of plants it affects. Beans are susceptible
to the disease from the time the seeds are planted until the
snap beans are marketed. The symptoms of the disease vary
with the age and part of the plant affected.
Bean seeds sometimes rot in the ground before or during
the process of germination. Some seedlings emerge which have
been twisted and stunted by the disease. Reddish brown lesions

Florida Agricultural Experiment Station

occur on the stems of the affected seedlings and may be so
numerous that the entire stem is girdled for several inches at
or near the soil line. Very young seedlings topple over and
"damp-off" when they are affected in this way, but the older
plants remain erect, gradually 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
I the infection and near
the soil line. Even
though these plants re-
main alive they are not
Sas vigorous and produc-
tive as healthy plants
should be.
Leaves of affected
plants wilt when the in-
fection destroys the wa-
ter absorbing and con-
ducting tissues in the
roots and stems. Leaves,
stems and pods which
touch the soil or have
been splashed with soil
become infected and de-
cay. Infected leaves have
Fig. 10.-Roots and stems of beans affected with
Rhizoctonia root rot (right) contrasted with a nor- water-soaked lesions of
mal root (left). indefinite shape and size
and eventually disintegrate completely. The ends of pods touch-
ing 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. Infected 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

Diseases of Beans in Southern Florida

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 mycelium is neither so white nor so abundant as that of
the watery soft rot. It occurs as a spider-web growth among
the beans in the hamper and occasionally causes the develop-
ment of definite concentric lesions (16) on some of the pods.
Another type of Rhizoctonia disease has been reported (24)
and has been observed in the Everglades. This fungus appears
to be different from the Rhizoctonia sp. which causes the root
and stem rotting disease. The new form has been described
as an aerial Rhizoctonia because it attacks the upper leaves
and pods. It has been very destructive in the few instances
where observed. This form of the fungus produces numerous
minute sclerotia on the affected leaves and pods and even on
the soil under the diseased plants. Another distinctive symp-
tom of this form of the disease is the way in which the affected
leaves and pods are held together by the fungous mycelium.
The Rhizoctonia fungus which causes root rot is a very com-
mon soil-inhabiting organism. It is one of those organisms
which is able to live on organic matter in the soil as well as
to parasitize beans and other plants which may be grown there.
The specific form of the fungus is generally said to be Rhizoc-
tonia solani Kihn.
Soil temperatures ranging from 750 F. to 850 F. are particu-
larly 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
temperatures may occur in the soil after a week or more of un-
usually warm weather in the winter. Stem and root rots of
beans are prevalent during such periods and particularly in the
early fall. When the soil temperatures are lower than 700 F.
there is very little root rot.
Moist soils favor the development of this disease of beans.
The trouble frequently arises following showers which have
been heavy enough to cause water to stand in low places in the
fields for several hours. However, peat and muck soils usually
are wet enough that moisture is not a factor which limits the
disease. In drier soils infections are found on the roots and
lower parts of the stem while in wetter soils infections are

Florida Agricultural Experiment Station

higher on the stem and in wet weather may reach the leaves,
branches and pods.
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.
Loose peat soils are more likely to give trouble from this
disease than are the more compact soils. This is because there
is an abundant supply of oxygen which can be used in the
respiration process of the fungus. Part of the trouble follow-
ing the addition of large quantities of organic matter to the
soil is due to the aerating effect of the organic matter on the
soil. The greater prevalence of root infections in the drier
soils and stem infections in the wetter soils is also related to
the presence of more oxygen at greater depths in the dry soils
and its exclusion from the root zone in the very wet soils.
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.
The beans for an early fall crop are planted at a time when
the soil temperatures are high enough to be very favorable
for the development of this disease. It is therefore important
that more than ordinary precautions be taken to see that other
factors are adjusted properly.
A summer cover crop or weed growth should be plowed under
in time to decompose before the beans are planted. A period
of three to six 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 decomposi-
tion 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 three and one half weeks before
the seeds were planted. 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.

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. This means that 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. Provision 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 of beans have resulted in only
one of these experiments. An organic mercury treatment of
the bean seed may be used with safety and may result in slight
increases in the stand of beans 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 but the pods showing soil rot
when the beans are packed and by shipping the beans in refrig-
erated cars or trucks. Infection of bean pods by the Rhizoctonia
fungus (16) is negligible at temperatures below 500 F.
This disease is similar to the one caused by the Rhizoctonia
fungus. If affects many species of plants, including all of the
vegetable crops and many weeds and ornamentals. No vari-
eties 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 nest-
ing 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

Florida Agricultural Experiment Station

and the lower part of the stem are affected with a dry rot. The
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.
The fungus is sometimes found on the ends of pods which
have touched the soil or have been splashed with wet soil. In-


,A y '- .

Fig. 11.-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.

j~I ~F~:~""


Diseases of Beans in Southern Florida

fected pods in a hamper of shipped beans may produce a fun-
gous nest similar to that caused by the watery soft 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 a mycelium
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 the 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. (16). Infection of pods
by the Southern blight fungus does not occur at temperatures
lower than 430 F.
Recommendations for the control of Southern blight are the
same as for the Rhizoctonia disease. A planting schedule that
uses heavily infested soils during the cooler and drier seasons
of the year is advisable. No fungicides are known to-control
this disease. Losses in shipped beans should be prevented by
grading the beans and by refrigeration of the shipments so
that a temperature around 45 F. is maintained in the cars
or trucks.

The root-knot disease occurs on nearly 900 species of plants
(22). 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.

Florida Agricultural Experiment Station

Beans are very susceptible to this disease. No resistant vari-
eties are available at present. Two resistant varieties have
been selected by Alabama workers (2) and may some day prove
to be a valuable contribution.
The nematode which causes the root-knot disease is widely
distributed in tropical and semi-tropical soils. It is even found
in soils of some of the more temperate parts of the United
States. The nematode and the root-knot disease occur through-
out 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 by the dis-
ease. 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. 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 galls on small rootlets may enlarge
the root to five 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

Diseases of Beans in Southern Florida

roots begin to break down and this may be caused by the
activity of other organisms infecting the diseased roots as
much as by the nematodes.
Minute soil-inhabiting worms (Heterodera marioni (Cornu)
Goodey), commonly known as nematodes, are the cause of the
disease. They are strictly parasitic, since they die when they
cannot feed on
the roots of sus-
ceptible plants.
The young
nematodes hatch
from eggs pres-
ent in old root
galls or which
have been left in ..
the soil by the ,
disintegration of ?.
such galls. Lar- "
vae move active-
ly in the soil un-
til they locate the
root of a suscept-
ible plant. They
then burrow into
the root tip and
embed their
heads near the Fig. 12.-Nematode galls on the roots of a bean plant.
conducting tis -
sues (12). A secretion produced by the larvae causes the root
cells to grow abnormally large. It is from these enlarged cells
that the nematode obtains its food. The loss of food materials
by the root is not as important a cause of death of the plant
as is the disruption of the normal anatomy and 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

Florida Agricultural Experiment Station

and are deposited in the soil. Female nematodes commonly
produce hundreds of eggs (22). The larvae which hatch from
these eggs invade roots of susceptible plants where the cycle
of development is repeated.
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. The number of generations
of nematodes which can develop in a given time is directly
related to the temperature of the environment where they are
developing (20). Only one generation of nematodes develops
during the growth of a crop of beans when the mean soil tem-
perature is 720 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 temperature is
800 F. or higher it is possible for two generations of the nema-
tode 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
1000 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 three-minute exposure to an unsaturated atmosphere (11).
The larvae in the soil are able to invade roots and produce
galls when there is enough water for the 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
(10). Flooding of the soil kills most of the nematodes in six
months (22), 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 a 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 that they decrease in fallow

Diseases of Beans in Southern Florida

soils. Nematode populations 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
of root-knot of beans on the extensive acreages of this crop
in southern Florida must depend upon cultural practices which
utilize the facts that nematodes starve in fallow soils or where
resistant crops are grown and that they multiply least rapidly
during the cooler months.
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. If planted at this time there should
be very little root-knot damage to the bean crop because it will
be growing when soil temperatures are low enough to retard
nematode development. 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.

Florida Agricultural Experiment Station

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.

"Baldheaded" or "snakeheaded" beans are young bean plants
which do not have an apical bud after the cotyledons expand.
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 de-
velop on the stem near the cotyledons in some cases, but the
growth from these lateral buds is usually very weak. Such
plants are stunted and the neighboring plants outgrow them
so that they are hidden in o:der plantings of beans.

Fig. 13.-Baldheaded bean plants. (Photo by G. F. Weber.)

Diseases of Beans in Southern Florida

Baldheaded beans are caused by any of three 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
threshing before the seeds are too dry are some of the ways
in which this type of injury can be minimized. These factors
are generally beyond the control of the grower or retail seeds-
man unless he has contracts with producers which specify con-
ditions under which the bean seed is to be threshed. When
seeds are purchased they should be examined for split seeds and
cracked seedcoats, since these are signs that the seeds were im-
properly threshed and may-produce a high percentage of bald-
headed beans. Trial plantings of a few hundred seeds will
determine whether the lot will produce many baldheads. Seed
lots which have been improperly threshed are not inferior to
other lots if the rate of seeding is increased and a price adjust-
ment 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.

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

Florida Agricultural Experiment Station

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 are sometimes 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 four to eight rows of beans are planted between
them. Drilling the beans in rows closer than 30 inches helps
sometimes, 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 seldom used in the Everglades as a windbreak, but is used
on the East Coast for this purpose. It is planted in rows at
greater distances than are corn and sunflowers or may be used
as a border around a field.

Beans are affected considerably by temperatures well above
the freezing point. After a cold night when the temperature
drops below 450 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 favor-
able temperatures prevail.

Diseases of Beans in Southern Florida

A frost deposit on bean leaves will kill them. Some of the
lower leaves which are protected by those above may escape
a frost in which the temperature does not fall below 310 F. at
the plant level. All leaves on the plant are killed if the tem-
perature falls to 30 F. Some cases have been observed in
which plants that had lost all of their leaves in a frost would
develop new growth from buds which had not been killed. This
cannot occur when the frost has been severe enough to affect
the stem and branches of the plants. Pods which have been
affected by frost appear to be water-soaked as the frost leaves
them, but they soon dry and shrivel.
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.

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-
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

Florida Agricultural Experiment Station

injury is not in proportion to the increase in acidity produced
by the sulfur but seems to be due to contact of the roots and
stems of the beans with undissolved sulfur particles. Roots
and underground portions of bean plants decay as though
affected with Rhizoctonia root rot. In this case the fungus is
not present and the color of the decayed tissue is a lighter shade
of brown. The injury can be avoided by distributing sulfur
several weeks before planting. Small quantities of sulfur in-
cluded in the fertilizer are not particularly injurious to beans.
Experiments with fungicides over an eight-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
the bean leaf-hopper and cold winds in March, 1932, were so
severely injured by applications of bordeaux mixture and
copper-lime dust that the plants shed some of their leaves.
Yields of beans from these plots were about 25 percent less
than from non-treated plots.
In April, 1932, plots of beans sprayed with bordeaux mixture
and dusted with copper-lime dust were severely injured 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 ma-
terials. 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
four other experiments where copper fungicides were applied.
In three experiments the yields of beans were increased by 5
to 15 percent where copper-lime dust and bordeaux mixture
were applied. These yield increases were obtained in experi-
ments conducted in the early fall or late spring when none of
the factors which contribute to copper injury were present.
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

Diseases of Beans in Southern Florida

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 too heavily sulfured 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 three applications of the fungicides in
this experiment was made when the vines were in full bloom.
The data in Table 7 give the average yields and percentages of
scarred pods for six replications of the experiment. The beans
were picked twice.
I Hampers I
Material Rate of Application per Percent
Acre Scarred
None .......... ---...... ...... 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

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 one Western state is contemplating a certifica-
tion system which would give our growers the benefit of field
inspections and a certificate on each bag of seed.

SFlorida Agricultural Experiment Station

The treatment of bean seed or the soil for the eradication
of disease-producing organisms has never offered much promise
as a measure for the control of bean diseases. The halo blight
bacteria in bean seed are not killed by any of the chemicals fre-
quently used for the treatment of vegetable seeds. A new treat-
ment reported effective in another state has not proven so in
Florida. Chemical treatment of the soil for the control of nema-
todes 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.

The utilization of the immunity from or the resistance to
certain diseases which are inherent in a few varieties of beans
is the object of a breeding program at the Everglades Experi-
ment Station. Crosses have been made which combine resistance
to powdery mildew and resistance to certain physiologic forms
of the bean rust with market quality in garden beans. It is
expected that new varieties of disease-resistant bush snap beans
will be the outcome of this work within a few years. The suc-
cess of this breeding work will eliminate most of the fungicidal
program which is now necessary for the protection of beans
from the fungous diseases.

fp 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 dis-
eases. Fungous diseases cannot be controlled by protectants
applied after the disease has affected the plants seriously. Nu-
tritional disorders can be corrected to some extent even after
the plants have gone into a serious decline, but it should be
recognized that even here the early diagnosis and prompt treat-
ment of the trouble have much to do with the success of the
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 avail-
ability of either spraying or dusting equipment. Applications

Diseases of Beans in Southern Florida

of dusts usually can be made more rapidly than sprays and
sometimes this is an important consideration.
Very often it is advantageous to combine insecticides or the
secondary nutrients with fungicides so that the cost of applica-
tion will be reduced. The arsenical poisons can be added to
bordeaux mixture, insoluble copper sprays, wettable sulfur
sprays, copper-lime dusts, and sulfur dusts. The rotenone and
pyrethrum insecticides should not be added to bordeaux or any
other material which contains lime, since the alkaline reaction
of the medium will cause them to decompose rapidly. These
materials can be mixed with the sulfur fungicides. The solu-
tions 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 sul-
fate 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 where it
is not necessary to have as complete coverage of the plant as
with the fungicides, but it is unwise to rely upon these for the
protection of large acreages of beans against fungous diseases.
They do not develop sufficiently high pressures to atomize the
spray, and do not deliver an adequate volume of the fungicide
to protect the crop. Bordeaux mixture is handled to better
advantage than wettable sulfur sprays by the knapsack 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 six-row boom with three nozzles per row and should
deliver the spray at a pressure of 300 pounds or higher. The

Florida Agricultural Experiment Station

volume of spray applied per acre will vary with the speed of
operation but should be not less than 50 gallons. More dilute
spray suspensions 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

Days from 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
9 to 12 or
S10-50 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
14 to 18 or
Dusting sulfur with manganese and insecticides added if

21 to 28 Same as second application, except that manganese, zinc
and insecticides may be omitted if not needed.

15-50 Wettable sulfur
Sulfur dust.
28 to 40 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. 57.

Diseases of Beans in Southern Florida

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 help 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.
A regular schedule for the application of fungicides and
supplementary nutrients is advisable. The schedule which is
outlined here (Table 8) is not necessarily the best one for all
conditions, but it 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 applications to five or six at certain seasons,
but the schedule of four applications given here should carry
the average bean crop to maturity and permit at least two pick-
ings of beans. While four applications of fungicides is often
more than is needed, the grower has no way of knowing before-
hand what diseases he may have to contend with nor of the
probable severity of those diseases. It is therefore wise to in-
sure the crop by protecting it with a minimum of four applica-
tions of fungicides. Insecticides and nutritional sprays usually
can be combined with these applications.

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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. BARRONS, K. C. Varietal differences in resistance to root-knot in eco-
nomic plants. Plant Disease Reporter Supplement 109: 143-151.
3. BARRUS, M. F. Bean Anthracnose. Cornell University Agr. Exp. Sta.
Memoir 42: 97-209. 1921.
4. BURKHOLDER, W. H. A new bacterial disease of the bean. Phytopath.
16: 915-927. 1926.

Florida Agricultural Experiment Station

5. The bacterial diseases of the bean. A comparative
study. Cornell University Agr. Exp. Sta. Memoir 127: 3-88. 1930.
6. CHUPP, CHARLES. Manual of vegetable garden diseases. New York.
7. COOK, H. T. Powdery mildew diseases of beans. Va. Truck Exp. Sta.
Bul. 74: 931-940. 1931.
8. EDGERTON, C. W. The bean anthracnose. La. Agr. Exp. Sta. Bul.
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SExp. Sta. Press Bul. 488. 1936.
20. Development of the root-knot nematode on beans as
affected by soil temperature. Fla. Agr. Exp. Sta. Bul. 309: 3-15.
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disease affecting beans. Fla. Agr. Exp. Sta. Bul. 300: 3-23. 1936.
22. TYLER, JOCELYN. The root-knot nematode. Calif. Agr. Exp. Sta.
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