U UNIVERSITY of
2006 Florida Plant Disease Management Guide: Beans1
Aaron Palmateer and Ken Pernezny2
Specific Common Diseases
Alternaria Leaf and Pod Spot (Alternaria spp.)
Symptoms: Symptoms are generally confined to
older leaves. Lesions tend to become circular,
dark-brown and zonate with advanced age and size.
Centers of older spots may appear gray and often fall
out, leaving a dark-brown, lesion border and a
shot-hole effect on the leaf. Petioles and stalks may
also become infected, developing dark-brown
elongated spots. The most conspicuous symptom is
small, raised black pimples on pods that throw
produce out of grade.
Alternaria infections of bean plants occur
throughout the season in the winter vegetable areas of
southern Florida. This disease is often found on
plants that have been injured by spider mites or
Cultural Controls: Avoid nutrient stress that can
weaken bean plants. Control insect problems.
Chemical Controls: See fungicides listed for
anthracnose control in PPP-6.
Symptoms: Anthracnose affects all above-ground
portions of the bean plant. The most noticeable
symptoms are on the pods, especially on lima or
butter beans, where the fungus causes
yellowish-brown or purple-colored, irregular, sunken
spots with dark reddish-brown borders. These spots
vary in size and often coalesce. Infections may occur
on the underside of the leaf veins, causing a dark,
brick-red to purplish color which later turns to dark
brown. Elongated dark-red or blackened lesions also
may be found on the stems.
Under moist conditions, masses of flesh-colored
spores are borne on the surface of the lesions. These
small spores are easily spread to other plants by rain
or mechanical means. Fields of anthracnose-affected
beans should not be cultivated or worked while plants
are wet. The spores of the anthracnose fungus bear a
sticky substance causing them to adhere to hands and
clothing of farm workers and to the bodies of insects
and other animals. Disease development is favored by
cool, wet weather.
1. This document is PDMG-V3-33, one of a series of the Department of Plant Pathology, 2006 Florida Plant Disease Management Guide, Florida Cooperative
Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised December 2005. Please visit the EDIS Web site at
2. Aaron Palmateer, assistant professor, Plant Pathology Department, Tropical Research and Education Center, Homestead, FL; Ken Pernezny, professor,
Plant Pathology Department, Everglades Research and Education Center, Belle Glade, FL ; Florida Cooperative Extension Service, Insitute of Food and
Agricultural Sciences, University of Florida, Gainesville, FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products
named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and
other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex,
sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry
2006 Florida Plant Disease Management Guide: Beans 2
Cultural Controls: Purchase anthracnose-free
seed or seed grown in arid regions of the country as
the causal fungus can be seedborne. Rotate fields out
of beans for at least three years where disease has
been a problem. The pathogen can survive in soil for
Chemical Controls: See PPP-6.
Ashy Stem Blight (Macrophomina
Symptoms: Seedling infection may occur before
or after emergence and appears as small, dark sunken
lesions at the base of the cotyledon. The disease
progresses quickly into the petioles of primary leaves
and then into the shoot tip. Strong winds or
cultivation result in the breakage of many infected
plants at the soil line. Older plants develop a root and
stem rot with sunken lesions. Plants exhibit a
one-sided wilt and leaf yellowing prior to plant death.
A diagnostic sign is the presence of small, black
sclerotia in or on stem and root tissue.
This disease is most severe under very hot
growing conditions or when adverse soil moisture or
fertility shortens the normal maturity of the crop. The
fungus survives as sclerotia and/or mycelium on
debris and in the soil. Avoid depositing soil on stems
Cultural Controls: Plant only certified,
disease-free seed. Maintain adequate nematode
control so plants are not prematurely stressed.
Balanced soil fertility and moisture will lessen
disease incidence. Rotation is not a satisfactory
control measure due to the wide host range of this
fungus. Do not deposit soil on stems during
Bacterial Blights (Xanthomonas campestris
pv. phaseoli, Pseudomonas syringae pv.
Symptoms: There are two bacterial blights
occurring in Florida, halo blight caused by
Pseudomonas syringae pv. phaseolicola and common
blight caused by Xanthomonas compestris pv.
phaseoli. The symptoms and controls for each are
These diseases may attack the seed, seedlings,
leaves and pods. Many seedlings from infected seed
may die before or soon after they emerge, but some
may continue to live. In either case, they serve as a
source of inoculum for nearby plants. During wet
weather, lesions on these infected plants produce
slimy masses of bacteria that are spread by
wind-blown rain or mechanical means. On older
plants, the first evidence of infection of the leaves
appears in the form of water-soaked spots. In the case
of halo blight, these are often surrounded by a yellow
halo. Later, the spotted leaf tissue turns brown and
dies. The spots on the pods start as water-soaked
(greasy) areas and later become surrounded by a
Cultural Controls: The most effective control is
to plant certified blight-free seed. If the disease
appears, pickers and cultivators should be kept out of
the field while the plants are wet to reduce the amount
of spread in the field. Common blight has been found
to survive in the soil from one growing season until
the next. Beans should not be planted in infested
fields for at least three years.
Chemical Controls: See PPP-6.
Cercospora Leaf Blights (Cercospora
canescens, C. cruenta)
Symptoms: These diseases occur on Phaseolus,
Dolichus, and Vigna species of beans, with the fungus
surviving in crop debris and on or in seed. The
disease is fairly uncommon in beans in Florida, but
they occur on southern peas commonly. Cercospora
canescens produces a circular to slightly angular leaf
spot with a gray center and a reddish border. Lesions
are smaller on lima beans than other species and have
more intense red borders.
Cercospora cruenta infects stems, leaves, and
pods of mature and senescent plants. Brown to
rust-colored lesions (irregular in size and shape)
develop on the leaves. These lesions are patch-like in
appearance, angular, and form a checkerboard
pattern. The leaf undersurface characteristically
exhibits the dark, fuzzy growth of the causal fungus.
The lesion centers often drop from the dried, necrotic
tissue giving a shot-hole appearance.
2006 Florida Plant Disease Management Guide: Beans 3
Cultural Controls: Plant only disease-free,
certified seed. Plow up and bury all infested crop
debris to reduce the survival of the causal fungi in the
Chemical Controls: See PPP-6.
Cladosporium Pod Spot (Cladosporium
Symptoms: Pod lesions start as small, narrow,
brown-black spots with a slight yellow halo. Spots
enlarge irregularly, turning purplish-black in color.
Young pod infection results in pod distortion and
some pod drop. Older pod lesions develop a dark
border and a light brown center of dead tissue. Leaf
infection is less common and is characterized by a
brownish-purple mold growth on the undersides of
leaves. This is primarily a disease of southern pea.
Cultural Controls: Plant only disease-free seed
since this disease is commonly seedbome. Black-eye
varieties of Southern peas are more susceptible than
Damping-off and Root Rots (Pythium spp.,
Symptoms: Several soilbome pathogens will rot
bean seed and seedlings from planting time through
emergence. Later stages of infection by these fungi
often produce root rots. Infected seeds become soft
and discolored. Diseased roots are characterized by
colorless to dark brown water-soaked lesions.
Infected tissue is soft and watery and easily separated
from the central cylinder of the stem by pulling the
root. Sometimes, the stem is girdled. Further, when
beans are grown under irrigation or exposed to heavy
rainfall, pods touching the soil are infected. They
become water-soaked and covered with a fluffy white
fungal growth. Symptoms of Pythium root rot and
Rhizoctonia root rot may resemble one another, so
laboratory examination may be necessary to
differentiate between the two diseases. This
condition is aggravated by deep planting, excess
moisture and by the presence of newly incorporated
green plant material such as weeds or cover crops.
Cultural Controls: Control of root rots and
damping-off can be aided by preventing saturation of
the soil and by chopping all cover crops and allowing
them to dry thoroughly before disking or plowing
under. Green cover crops should be turned under 6 to
8 weeks before planting time, and the land should be
kept disked in order to prevent a new grass/weed
cover from developing.
Chemical Controls: Seeds should be treated with
a fungicide. See PPP-6.
Fusarium Root Rot (Fusarium solanif. sp.
Symptoms: Symptoms of infection appear as a
reddish discoloration on the taproot as early as 1-2
weeks after plant emergence. Root lesions enlarge
and turn dark brown in color. Clusters of roots
develop above the lesion and below the soil line as
the main taproot becomes riddled with longitudinal
cracks, then hollows and dries. In dry seasons, plants
will be stunted with poor pod and seed set. Disease
symptoms in wet years may be limited to some leaf
yellowing due to compensatory surface root
development. This common soil fungus, Fusarium
solani, produces a dry root rot in green beans, limas,
southern peas and English peas. This disease is most
prevalent in hot weather, in acidic, low nutrient soils.
Cultural Controls: Practice crop rotation and
maintain adequate nematode control. Insure the
complete decomposition of crop debris or the cover
crop by land preparation at least 4-6 weeks prior to
Mosaic (Bean Common Mosaic Virus, Bean
Golden Mosaic Virus)
Symptoms: These diseases are caused by viruses.
The leaves of diseased plants become mottled with
light and dark green areas, the greener portion of the
pattern often becomes decidedly puckered. Bean
golden mosaic is now the most common and
destructive virus of the snap bean. A striking yellow
mottling of leaves occurs with this disease. Plants are
severely stunted and little yield is obtained. The virus
may cause a downward curling of the leaf margins,
and in some varieties extreme malformation of the
leaves occurs. The whole plant may become stunted
and have a pale yellow appearance. Flowers may shed
freely, resulting in late and irregular setting of the
2006 Florida Plant Disease Management Guide: Beans 4
pods. Usually the earlier the plants become infected,
the greater will be the reduction in yield. Bean
common mosaic is spread via seed and aphids. Bean
golden mosaic virus is spread by whiteflies.
Cultural Controls: Purchase virus-free seed. The
best seed is produced in the dry areas of the United
States (Idaho, Oklahoma, Wyoming, Colorado, etc.).
The use of resistant varieties offers the only other
practical means of control. Seed treatment or
eradication of the aphid or whitefly populations has
not been successful on a commercial scale. However,
control of the virus-bearing weeds in and around the
field and the vectors that spread the virus will help in
Powdery Mildew (Oidium sp.)
Symptoms: The first evidence of the disease is
the presence of small, dark-green areas in a mottled
pattern over the leaf. These develop into white
talcum-like spots that increase in size and run
together to form a whitish, powdery growth,
primarily over the upper surface of the plant. If
infection is severe, the diseased leaves curl downward
and become distorted and pale yellow. The pods
become mottled or blotched with purple and have
little direct evidence of mildew growth.
This disease is usually most severe during cool,
humid weather or following application of irrigation
water during cool weather. In Florida, these
conditions normally occur during late fall and early
Cultural Controls: Avoid late spring plantings.
Chemical Controls: See PPP-6.
Red node (Tobacco streak virus)
Symptoms: Red node is caused by a strain of the
tobacco streak virus (TSV). It is a sporadic problem,
but has occurred in several seasons in the Belle
Glade, FL farming region. The initial symptom is
usually a characteristic reddening of the node of bean
stems. Veins of leaves may also be reddish and turn
necrotic. Sunken, reddish lesions may form on pods.
Cultural Controls: Plant disease-free seed. Control
leguminous weeds that may be source of TSV.
Rhizoctonia Root, Stem, and Pod Rot
Symptoms: Rhizoctonia is a soilbome fungus that
can rot bean seeds prior to emergence from the soil.
Young seedlings develop brick-red to brown, sunken
lesions on the tap root and basal stem. When the
disease is severe, the tips of branch and tap roots may
rot off leaving reddish-brown stubs. Such plants are
weakened and may not survive. Above-ground
symptoms appear as lower-leaf chlorosis with leaf
marginal and tip bum and stunting. Older plants are
affected similarly to seedlings.
In addition, leaves and pods can be affected.
Leaves become irregularly blighted with
reddish-brown spots. During moist, warm weather,
the tan strands of the causal fungus can be seen
matting leaves together or spanning the distance from
the soil to the lowest leaves. Pods develop typical
sunken, brick-red lesions both in the field and during
shipment, especially near tips close to the ground.
This disease is so common on beans in Florida
that 100% field infections are not rare in spring or
fall. Stand losses up to 75% have been reported,
which makes it one of the most economically
important root diseases of beans. Rhizoctonia solani
has a broad host range that includes most annual and
many perennial plants.
Cultural Controls: Turn under summer
vegetation 3-4 weeks before planting, practice
rotation, plant disease-free seed, maintain good
drainage and plant not deeper than 1-1.5 inches. At
harvest, cull out all pods showing the disease to
prevent its spread in transit.
Chemical Controls: Use Chloroneb or Vitavax
Rust (Uromyces appendiculatus)
Symptoms: Occurs on the leaves and rarely on
the pods in Florida. The first evidence of the disease
is the presence of small, pale-yellow spots on the
upper side of the affected leaves. Usually, 2-3 days
later, cinnamon-brown pustules about 1/16 inches in
2006 Florida Plant Disease Management Guide: Beans 5
diameter appear in the yellow spots and break open,
exposing the spores. Under severe conditions, the
rust pustules may be so numerous that the whole leaf
becomes yellow, withers and dies. This loss of
foliage can greatly reduce the yield. Conditions most
favorable for severe rust infections in South Florida
usually occur during the late winter-spring months,
beginning in February or March. Crop losses are
greater when rust pustules are numerous before
blossoming, rather than when the disease appears
after the blossoms have formed. Traditionally, this
disease has been most severe on pole beans in South
Cultural Controls: For bush and pole beans,
plant resistant or tolerant varieties where they are
adapted. Avoid late spring plantings.
Chemical Controls: See PPP-6.
White Mold (Sclerotinia sclerotiorum)
Symptoms: Most infections begin on flower
petals that have fallen onto plants. Young plants
diseased by this fungus have a watery soft rot of the
stem beginning near the soil line and extending up to
the primary leaves. Older plants may be invaded on
any growing part, including the pods. A day or two
after infection, a white fungal growth appears over
the diseased parts. Later, black sclerotia (irregularly
shaped, hard bodies) ranging from 1/4 to 1/2 inch in
length are produced by the fungus. The presence of
these sclerotia is an identifying characteristic that is
unmistakable. Most of the infections occur when the
plants are at or near blossoming time.
In addition to being called white mold, this
disease is known as watery soft rot, sclerotinose, and
sclerotinia rot of beans. During periods of cool
weather accompanied by frequent rains, fogs or heavy
dews, epidemics of white mold can be expected. The
disease will develop after 20 or more days, with a
mean temperature of 70 degrees F or below, in an
area in which the soil is infested with the sclerotia of
the fungus. The lower temperatures stimulate the
production of small mushroom-like, spore-bearing,
fruiting bodies. The spores ascosporess) from these
are discharged into the air and are disseminated by
wind and splashing rain. Virtually all inoculum in
Florida is ascosporic.
Cultural Controls: Turn soil at least 6 inches
deep where possible. Flooding fields for 5-6 weeks
during summer months will effectively reduce the
number of sclerotia in the soil. Before using flooding
as a control measure, find out from local authorities if
drainage into a given body of water after flooding
agricultural fields is permissible. Plant seed farther
apart (2-3 in) within bean rows to allow for adequate
air circulation when plants mature.
Chemical Controls: See PPP-6.
Southern Blight (Sclerotium rolfsii)
Symptoms: Infection by the southern blight
fungus usually produces a sudden wilting as the first
symptom, followed by the appearance of a collar of
fan-like, white fungal mycelium. This band of white
fungus threads is attached to the stem at the soil line
and may spread over and into the soil for a radius of
one or more inches. Death of the plant follows soon
thereafter. If an infected plant is pulled, it brings with
it soil which adheres to the mycelium around the
In the white mycelium, numerous sclerotia are
produced both on the plant and on the mycelial
threads on the soil. The sclerotia first appear as white
nodules, but later turn tan and are about the size of
cabbage seed. Under favorable conditions, the
sclerotia germinate by producing mycelial threads,
which can live for long periods on organic material in
the soil. It occurs throughout Florida and is especially
prevalent in soils that have been cultivated for many
years. Southern blight is a warm weather disease and
occurs on beans in early fall and late spring plantings.
The fungus is preserved over periods of unfavorable
environmental conditions in the form of sclerotia and
is disseminated in water, in soil, and on farm
Cultural Controls: Long crop rotations with
grass crops are best. Turn under cover crops and
weed cover at least 6 inches deep as far ahead of
planting as possible to allow decomposition of the
plant material before bean seeds are planted. A
minimum of a week or 10 days for lower Florida east
coast, to several weeks further north should elapse
between turning under weeds (or cover crops) and
2006 Florida Plant Disease Management Guide: Beans 6
planting. The ground should be kept clean of
subsequent grass/weed growth until planting.
Wet Rot (Choanephora cucurbitarum)
Symptoms: This disease has been reported
throughout Florida on beans and southern peas. It is
found on bean foliage, blossoms and pods. On the
foliage, symptoms begin as water-soaked areas
without external white mycelium; these lesions then
enlarge, darken and dry with age. Signs of the fungus
become evident on both surfaces of the leaf as well as
on blossoms and pods. These consist of whitish
fungal growth tipped with numerous black
spore-bearing structures, giving the appearance of
"whiskers". It can be expected during periods of
excessive rainfall and high temperatures.
Cultural Controls: Avoid excessively high plant
populations that may favor disease incidence. Some
data exists to indicate that disease severity is
correlated with high populations of cowpea cuculio
on southern pea plants.
Chemical Controls: The fungicides such as
Botran when used to control other diseases will
provide control of this disease.