Title: Florida plant disease management guide
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Permanent Link: http://ufdc.ufl.edu/UF00053871/00025
 Material Information
Title: Florida plant disease management guide
Alternate Title: Ornamentals and turf
Fruit and vegetables
General plant pathology, field crops and pasture grasses, fungicides, adjuvants and application techniques
Physical Description: v. : ; 28 cm.
Language: English
Creator: University of Florida -- Dept. of Plant Pathology
Florida Cooperative Extension Service
Publisher: The Extension
Place of Publication: Gainesville Fla
Frequency: annual
regular
 Subjects
Subject: Plant diseases -- Periodicals -- Florida   ( lcsh )
Pesticides -- Periodicals   ( lcsh )
 Notes
Statement of Responsibility: Plant Pathology Dept., University of Florida and Institute of Food and Agricultural Sciences, Florida Cooperative Extension, University of Florida.
Numbering Peculiarities: Issued in three volumes: v. 1, General plant pathology, field crops and pasture grasses, fungicides, adjuvants and application techniques; v. 2, Ornamentals and turf; v. 3, Fruit and vegetables.
General Note: Description based on: 1999-2000.
General Note: "SP-52"
 Record Information
Bibliographic ID: UF00053871
Volume ID: VID00025
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 44549741
lccn - 00229071
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Preceded by: Florida plant disease control guide

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PDMG-V3-53
U UNIVERSITY of

UF FLORIDA
IFAS Extension



2006 Florida Plant Disease Management Guide: Tomato 1


Tim Momol and Ken Pernezny2


Specific Common Diseases

Anthracnose (Colletotrichum coccodes, C.
gloeosporoides, C. dematium)

Symptoms: This is primarily a disease of ripe to
overripe fruit that can cause serious losses in home
gardening but seldom in commercial fields due to the
mature green harvest nature of Florida's industry.

Fruit infection may occur during green stages but
disease development is linked to ripening. Small
lesions are circular and depressed, but can enlarge to
greater than 12 mm in diameter with zonate
markings. The lesion surface may appear
salmon-colored due to spore production and be dotted
with black specks (microsclerotia). Infected fruit
have a short shelf life.

Cultural Controls: Home growers should rotate
the location of tomatoes in the garden whenever
possible to avoid soil survival of the causal fungi.
Avoid stress on tomatoes from nematodes, insects,
and other diseases that will predispose plants to fruit
rot. Collect and destroy infected fruit as they appear.
Avoid overhead irrigation where possible. Staking


plants and mulching helps to reduce losses to
anthracnose.

Chemical Controls: Use of a fungicide to control
other diseases will reduce incidence of anthracnose.
Specific fungicides for anthracnose must be used
before fruit ripen. See PPP-6.

Bacterial Soft Rot and Hollow Stem (Erwinia
carotovora pv. carotovora)

Symptoms: The most important aspect of this
disease is post-harvest infection of the fruit.
Symptoms are soft watery decay of fruit, starting at
one or more points, as very small spots. These spots
enlarge, often very rapidly until the entire fruit may
become a soft watery mass. Usually leakage occurs as
the decay develops.

The causal bacterium may infect stems, petioles
and pedicels producing a dark green-to-black,
water-soaked canker. Affected stem areas become
soft and hollow.

Cultural Controls: Tomato varieties differ in
their resistance to bacterial soft rot disease of fruit.


1. This document is PDMG-V3-53, 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 http://edis.ifas.ufl.edu.
2. T. M. Momol, associate professor, Plant Pathology Department, North Florida Research and Education Center, Quincy, FL; K. L. 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, 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
Arrington, Dean






2006 Florida Plant Disease Management Guide: Tomato 2


To reduce disease incidence and severity, avoid
harvesting plants while they are wet. Avoid
wounding fruit and avoid exposing harvested fruit to
the sun. Use chlorine in the first water immersion in
the packinghouse. Avoid deep or prolonged
immersion of tomato fruit in water. Fruit should not
be packed with wet stem ends nor should green fruit
be chilled below 550 F. See Plant Pathology Fact
Sheet PP-12.

Chemical Controls: See PPP-6.

Bacterial Speck (Pseudomonas syringae pv.
tomato)

Symptoms: Foliar infection due to this disease is
difficult to distinguish from leaf spots caused by
bacterial spot. Fruit infection caused by bacterial
speck appears as numerous, tiny, dark brown lesions
less than one-sixteenth of an inch in diameter, and
sunken. Speck lesions do not usually extend deeper
than the epidermis of the fruit.

Large speck lesions may be mistaken for those of
bacterial spot since both diseases can occur on the
same fruit. Speck lesions are more restricted in size
on the fruit and do not exhibit the raised, scab-like
appearance or cause the epidermis to rupture as with
bacterial spot-infected fruit. This bacterial pathogen
is seedborne and is apt to be more severe during
particularly cool, wet growing seasons that favor
plant-to-plant spread. See Plant Pathology Fact Sheet
PP-10.

Cultural Controls: Start with clean, disease-free
seed or transplants. This disease, like bacterial spot,
is very difficult to control once it is established in a
field situation.

Chemical Controls: See PPP-6.

Bacterial Spot (Xanthomonas axonopodis
pv. vesicatoria)

Symptoms: Spots on the leaves and fruit spurs
are brown, water-soaked circular and rarely more
than 1/8 inch in diameter. They can be confused with
young early blight, gray leaf spot and target spot
lesions on the leaves. Later, spots may coalesce and
large blighted areas appear. Lesions caused by the
race T3 of the pathogen often tear out leaving a


"shot hole" appearance. However, the bacterial
spot lesions usually lack the concentric zones of early
blight and usually they are darker and less uniformly
distributed on a leaflet than gray leaf spot lesions.
Often the lesions tend to be elongated on the leaf
margins; occasionally, after a heavy rain during
which the leaves have become saturated with water,
entire interveinal areas will become infected.

On the fruit, the early symptom is a very minute
black speck surrounded by a slightly lighter area. As
the spot enlarges it becomes brownish in color,
scab-like, slightly raised on the edges, and sunken in
the center. The epidermis of the fruit finally ruptures
and curls back from the center of the spot. This is the
most characteristic symptom of the disease on the
fruit. The bacterial spots are very seldom deeper than
halfway through the outer fleshy layer of the tomato.

Cultural Controls: Do not place seedbeds in the
area of an abandoned field where bacterial spot was
present the previous season. Set only disease-free
transplants. This disease is difficult to control once it
is established. Protect against mechanical
transmission by frequent hand washing with a
bactericidal soap.

Biological Controls: Bacteriophages (phages)
have been found as an effective biocontrol agent for
the management of bacterial spot on tomato. Phages
are viruses that infect bacteria. Recently, protective
formulations were developed to increase longevity of
phages on plant surfaces in the field conditions. A
Powdered Skim milk formulation may be
recommended for field application because it is easy
to prepare and apply. Evening (before sunset)
application of phages resulted in better bacterial spot
control compared to morning application. Formulated
phages could be applied twice a week at sunset for the
management of bacterial spot. As for any new
product, first test on a limited acreage.

Chemical Controls: See PPP-6. Recently,
alternative chemical control approaches have been
investigated in which chemicals are applied that
activate plant defense responses. Plants can activate
protective mechanisms upon detection of invading
pathogens. It is a similar concept to immunity in
animals. If this protection is expressed locally at the
site of primary inoculation and also systemically in






2006 Florida Plant Disease Management Guide: Tomato 3


tissues remote from the initial treatment, it is called
systemic acquired resistance (SAR). Chemical SAR
inducers are active against a broad range of
pathogens, including fungi, bacteria, and viruses.
Acibenzolar-S-methyl (Actigard 50WG, Syngenta),
an SAR inducer, has now been registered for
commercial use in Florida against bacterial spot of
tomato.

Bacterial Wilt (Ralstonia solanacearum)

Symptoms: A diseased plant is characterized by
rapid wilting with the foliage remaining green.
Affected plants rapidly wilt and die without
appreciable yellowing of the lower leaves. Plants that
are attacked by this pathogen frequently appear
stunted before wilting occurs. The pith near ground
level is dark colored and has a water-soaked
appearance. If the stem is cut near the base, a slimy,
gray material may exude from the cut.

In later stages, the pith decays and the stem
becomes hollow. The vascular tissue becomes brown,
and adventitious root formation may be enhanced.
The rapidity of wilting and death, the lack of foliage
yellowing, and the pith decay and hollowness
distinguish this wilt disease from the Fusarium and
Verticillium wilts. This is a hot-weather and wet-soil
disease.

Rapid diagnosis can be made in the field. Cut the
lower three-inch stem section from soil line upwards.
Suspend this section in water for 15-30 seconds.
Observe immersed stem end for streams of bacteria
that will be extruded into the water. Visibility of
bacteria is enhanced when viewed in front of a strong
source of light.

Cultural Controls: Bacterial wilt is a very
difficult disease to control. The only way to totally
control bacterial wilt is to not plant in fields infested
with the pathogen. Do not plant seedbeds on land
where this disease has been a problem. Infested fields
should be rotated to non-susceptible crops (long term
rotation might reduce pathogen populations). Avoid
movement of water, equipment, or soil from infested
fields to non-infested ones. In south Florida, late fall
planting (October in the Ft. Pierce area) reduces the
incidence of this disease. Fields should not be
over-irrigated, because excess soil moisture favors


disease build-up. Increase of soil pH and available
calcium might reduce the disease incidence.

Chemical Controls: See PPP-6. Please note that
these broad spectrum soil fumigants chloropicrinn)
will contribute to the management of this disease
either through reduced disease incidence or the delay
of the initial disease onset.

Black Shoulder (Undetermined)

Symptoms: Fruit approaching maturity appear
most susceptible. Dark gray to blue-black areas
develop on the shoulders of fruit. Those areas are
irregular in size and shape. The discolored areas may
undergo tissue collapse with the subsequent
production of sunken lesions. The affected tissue in
these lesions will harden and shrivel but further lesion
enlargement normally does not occur.

Cool, rainy weather that occurs, especially when
fruit are mature, has been associated with the
incidence of this problem.

Cultural Controls: Choose varieties that are
more tolerant of this disorder.

Blossom-end Rot (Calcium deficiency)

Symptoms: The blossom ends of fruit turn pale
green to brown. These affected areas enlarge into
sunken spots. The discolored fruit portion will shrivel
into a dry rot unless the tissue is invaded by
secondary organisms that often extend the area of rot
throughout the fruit.

This condition can result from a number of
situations that limit available calcium to the plant.
Poorly limed, sandy soils may suffer from a
deficiency of calcium in the soil. Calcareous soils
seldom have this problem. Extremes in soil moisture
can limit calcium availability to roots regardless of
the amount present in the soil. Since calcium is not
freely mobile in the plant, short periods of calcium
deficit will affect rapidly growing fruit tissues.
Competition from other cations (e.g. Mg) can lead to
and exacerbate blossom-end rot.

Cultural Controls: Follow a program of soil
testing and liming according to soil test results. Soil
should contain adequate calcium (=> 300 ppm).






2006 Florida Plant Disease Management Guide: Tomato 4


Supplement erratic rainfall with irrigation during fruit
development to avoid blossom-end rot problems.

Buckeye Rot (Phytophthora nicotianae var.
parasitica)

Symptoms: On fruit that are touching soil, the
fungus enters at the point of contact, causing a slight
brownish spot. As the fungus develops and the spot
enlarges, a series of irregular, brown-to-light-colored
concentric bands are produced, forming a typical
buckeye effect. Fruits decay very rapidly and break
down in a soft-rot.

All stages in the growth of the tomato fruit can
be infected by the fungus. In some instances when the
fruit remain damp and moist for a day or two, the
concentric zoning effect may be indistinct and
invasion of the fruit by the fungus exceedingly rapid.
Under these conditions the invaded areas become dull
brown, and the fruit collapse without the production
of the marked concentric zones. In some cases where
the epidermis is ruptured the mycelium of the fungus
can be distinguished.

Cultural Controls: Drain fields well. Stake
plants. Use of full-bed plastic mulch will limit fruit
contact with the ground and therefore limit disease
incidence.

Chemical Controls: See PPP-6.

Cucumber Mosaic (Cucumber Mosaic Virus)

Symptoms: This aphid-vectored virus has a wide
host range within Florida that includes many plant
species among agronomic, vegetable, ornamental
crops as well as weeds. Plants in the Solanaceae and
Cucurbitaceae are particularly susceptible. The virus
is not seed-transmitted. Infection results in a
'shoestring' like symptom on leaves as the interveinal
tissue is reduced. Infected plant appears stunted and
bushy while fruits may exhibit ring or line patterns
during ripening.

Cultural Controls: Sanitize surrounding crop
fields to prevent over-seasoning of the virus and/or
the aphid vector. Eliminate stands ofdayflower in
and around the tomato field.


Chemical Controls: Manage aphid populations
according to the latest recommendations in the Insect
Management Guide.

Damping-off (Various fungi, species of
Pythium and Rhizoctonia often implicated)

Symptoms: Dying or poor growth of seedlings in
seedbed. Seedling death may also occur after plants
are set in the field.

Chemical Controls: Plant only fungicide-treated
seed.

Employ an appropriate soil fumigant for seedbed
treatment as well as in-row treatment in the field
depending on previous disease history and other
production practices. See PPP-6.

Early Blight (Alternaria solani)

Symptoms: Early blight is first observed in the
field as small brownish-black lesions on the older
foliage. The spots enlarge rapidly, and by the time
they are 1/4 inch in diameter or larger, concentric
rings may be distinguished on the dark brownish
portion of the spots. The tissue surrounding the spots
may become yellow in color, and when spotting is
abundant the entire leaf may yellow.

Stem lesions on seedlings are small, dark, and
slightly sunken. These lesions enlarge, forming
circular or elongated lesions with concentric rings
and light centers. If stem-infected seedlings are set in
the field, the lesions continue to enlarge at the ground
line and partially girdle the plants. These plants often
die, but if they do survive, their growth and yields are
reduced.

The fruit become infected, generally through the
calyx or stem attachment, either in the green or ripe
stage. The fruit lesions attain considerable size, often
involving nearly the entire fruit, and usually show
concentric ringing. The diseased areas appear leathery
and may be covered by a velvety mass of black
spores. Infected fruit frequently drop, and losses of
50% of the immature fruit may occur.

Chemical Controls: Pursue fungicide
applications as needed in the transplant production
system as well as in the field. See PPP-6.






2006 Florida Plant Disease Management Guide: Tomato 5


Fusarium Crown Rot (Fusarium oxysporum
f.sp. radicis-lycopersici)

Symptoms: Disease first appears during cool
seasonal periods when fruit are setting or sizing.
Symptoms indicate lower leaf marginal yellowing
and a slow-to-rapid wilt syndrome that kills the plant.
The lower stem at soil line exhibits vascular
discoloration and pith necrosis for a variable distance
upward in the stem.

Cultural Controls: As the pathogen is soilbome,
incidence tends to increase with the direction of
movement of infested soil. Several cultivars with
resistance are now available.

Chemical Controls: Use of soil fumigation will
aid in pathogen suppression.

Fusarium Wilt (Fusarium oxysporum f. sp.
lycopersici races 1-3)

Symptoms: Infected seedling plants are stunted,
the older leaves droop and curve downward, and the
plants frequently wilt and die. Symptoms on older
plants generally become apparent during the interval
from blossoming to fruit maturation. The earliest
symptom is the yellowing of the older, lower leaves.
These yellow leaves often develop on only one side
of the plant, and the leaflets on one side of the petiole
frequently turn yellow before those on the other side.
The yellowing process gradually includes more and
more of the foliage and is accompanied by wilting of
the plant during the hottest part of the day.

The wilting becomes more extensive from day to
day until the plant collapses and dries up. The
vascular tissue of a diseased plant is dark brown in
color. This browning often extends far up the stem
and is especially noticeable in a petiole scar. This
browning of the vascular system is characteristic of
the disease and generally can be used for its
identification. Fruit infection occasionally occurs and
can be detected by the vascular tissue discoloration
within the fruit.

Cultural Controls: Use resistant varieties where
available for Race 1 or 2. A 5-7 year crop rotation
will greatly reduce losses on infested land.


Prevent the movement of infected plants and/or
infested soil clinging to machinery, hand tools,
vehicles, trellising and staking implements, and field
crates into areas free of this pathogen.

Do not flood land, since this will spread fungus.
Do not overhead irrigate with ditch water that may be
contaminated with the fungus. Do not use infested
land for seedbeds.

Chemical Controls: Use pre-plant soil
fumigants.

Gray Leaf Spot (Stemphylium solani)

Symptoms: Gray leaf spot first appears as
minute, brownish-black specks on the lower leaves.
The spots are circular to oblong. Occasionally the
spots are marginal and in such cases are somewhat
elongated or irregular in outline. The spots enlarge to
about 1/12 inch in diameter, turn in color from a
brownish-black to a grayish-brown, and become
somewhat shiny and glazed. By this time, a definite
yellow area may be apparent around the spots.

Lesions rarely exceed 1/12 inch in diameter,
although on the very oldest leaves near the base of
the plant individual spots may obtain a diameter of
1/6 inch or more. On the older leaves the spots may
coalesce, killing large areas of the leaf blade. As the
centers of the spots dry out, they often crack with a
yellowing of the entire leaf. The leaves then die
rapidly, become brown, and drop. Serious infections
in the seedbeds result in marked defoliation without
conspicuous yellowing. Most globe tomatoes
developed for Florida are resistant to this disease.
Commercially, most gray leaf spot outbreaks have
been noted in cherry tomatoes. Homeowners may
experience problems if older, "up-north" cultivars
or heirlooms are planted.

Cultural Controls: Plant resistant varieties.

Chemical Controls: See PPP-6.

Gray Mold (Botrytis cinerea)

Symptoms: On the stems, gray mold is
characterized by large, elliptically shaped,
water-soaked lesions that during cool, wet weather






2006 Florida Plant Disease Management Guide: Tomato 6


soon become covered with the grayish-brown
mycelium and spores of the fungus.

The lesion produced on the fruit is a watery area
with a light brown or tan-colored central region. The
decay develops rapidly, and the fruit is converted into
a soft, watery mass within a few days. If the skin is
broken, the grayish mycelium and spore clusters
develop within a few hours.

Occasionally, following abortive infections,
small whitish rings approximately 1/6 inch in
diameter develop on young green fruit. These "ghost
spots" are usually single rings but may be solid white
spots; the center of which contain dark-brown specks.
The spots are superficial on the pericarp of the fruit,
do not increase in size, and do not affect fruit eating
quality. Infected leaves, which develop gray lesions
that are often wedge-shaped, soon wither and die.
During cool, wet weather the diseased leaves become
covered with the gray mycelium and spores of the
fungus.

Cultural Controls: To avoid gray mold, crop
tomatoes on soil limed to pH = 6.5 or higher.

Chemical Controls: See PPP-6.

Gray Wall (undetermined)

Symptoms: Dark-brown tissue develops around
the vascular bundles of the outer fruit wall.
Sometimes this browning also occurs in the middle
column and septa of the fruit. Outward appearance of
the fruit shows blotchy gray (sometimes yellow)
areas with indistinct margins. Occasionally the tissue
of the gray areas shrinks and sunken spots develop.
On green immature fruit, symptoms are more
difficult to see, but by careful examination the dark
areas and streaks can be seen through the translucent
skin. Plants infected with Tobacco Mosaic Virus
(TMV) have higher incidence of gray wall. However,
plants free of TMV and those resistant to the virus
can also develop gray wall.

Cultural Controls: Use resistant varieties.


Late Blight (Phytophthora infestans)

Symptoms: The lesions produced on the leaves
are rather large, irregular, greenish, water-soaked
areas. These areas enlarge rapidly and become brown
and paper-like. During moist weather or periods of
heavy dew, a fine, white mold may develop near the
margin of the diseased tissue on the lower surface of
the leaf.

Stem lesions may occur anywhere on the stem,
and appear as water-soaked brown to gray areas that
may girdle and kill the plant. Severely diseased plants
often appear to have been frozen.

Fruit lesions appear as large, green to mahogany
colored, irregular water-soaked blotches. These
lesions most commonly appear on the upper half of
the fruit, are firm in texture, and may occasionally
become zonate. Often soft rot organisms invade
blighted fruit and cause rapid deterioration of the
fruit.

Chemical Controls: Apply fungicides
preventively. See PPP-6. See Plant Pathology Fact
Sheet PPP-6.

Leaf Mold (Fulvia fulvum)

Symptoms: Leaf mold is usually first observed
on the oldest leaves closest to the ground where
ventilation is poorest and the period of excessive
moisture is most uniform. It is detected on a leaf by
the appearance of small, light-colored spots which
turn to a distinct light yellow color followed by the
browning, drying, and death of the cells in the area.
Often when the infection is severe these spots
coalesce, and the foliage is rapidly killed.

The causal fungus sporulates on the lower
surface of the leaf but very rarely is found producing
spores on the upper surface. Careful examination of a
yellow-spotted leaf will reveal an olive-green mold
on the lower surface almost exactly coinciding with
the yellow area. Traditionally, this disease has been
more of a problem on greenhouse crops.

Cultural Controls: Choose resistant varieties
where possible. The practice of staking and pruning
plants, along with proper plant spacing, will ensure






2006 Florida Plant Disease Management Guide: Tomato 7


adequate ventilation and discourage disease
development.

Chemical Controls: Apply fungicides when
needed. See PPP-6.

Phoma Rot (Phoma destructive)

Symptoms: On the foliage, small black spots first
appear on either surface of the leaf. These spots are
round or irregular in shape, slightly sunken, and as
they rapidly enlarge, become typically zonate as in
early blight. They enlarge and often coalesce, causing
the leaves to become yellow and curl upward. The
pycnidia, or fruiting bodies, which are produced in
these spots on the foliage, are imbedded or sunken in
the leaf tissue with only a small opening to the
outside. Thus, they are very difficult to observe, and
without a hand lens it is almost impossible to make a
definite diagnosis.

On the stems the lesions are black, elongate, and
zonate. The damage to young seedlings may be
extremely severe, since they are often completely
girdled by the stem lesions. Plants are attacked from
the seedling stage to maturity.

On the fruit, the spotting takes place only where
the fruit have been injured, and in most cases the
fungus enters through growth cracks, the stem scar,
and other mechanical injuries around the stem end,
although in some cases it enters through punctures
made by insects. When it enters any skin rupture it
produces a distinctly sunken spot almost black in
color which enlarges rapidly and involves large
portions of the fruit.

The disease is readily distinguished from other
rots by the black color of this spot which is speckled
with small, black, pimple-like eruptions. These
specks are the pycnidia or fruiting bodies of the
fungus.

Chemical Controls: Use only fungicide-treated
seed. Apply fungicides in the seedbed or field as
needed. Use ofchlorothalonil to control other
diseases will aid in control of Phoma rot. See PPP-6.


Potato Y Disease (Potato virus Y)

Symptoms: The young leaflets cup inward
slightly and curl downward. The petioles also curl
downward and give the plant a drooping appearance.
The vein areas of the leaflets are banded with yellow.
Dark-brown necrotic areas develop on the young
leaves, especially on the terminal leaflets. The stem
tips and petioles are usually streaked with purple.
Entire shoots may be killed. Infected plants are
stunted, unthrifty, and yield poorly, but the fruit do
not show symptoms. Laboratory assays are required
to accurately diagnose this disease.

This virus is transmitted to tomato plants by
aphids during feeding. A number of weed hosts of
this virus occur in Florida and include the ground
cherries and nightshades.

Cultural Controls: Eradicate wild host plants
and volunteer tomato plants before the crop is
planted. Avoid planting subsequent crops next to
diseased early plantings until after the early plantings
have been destroyed. Avoid tomatoes in close
proximity to potatoes. Applications ofJMS Stylet Oil,
exactly as the label directs, will reduce virus spread
by aphids in the field.

Chemical Controls: See PPP-6.

Pseudo-curly Top (Pseudo-curly top virus)

Symptoms: Primarily a disease of young plants,
but fruiting-sized plants can become infected. The
first symptom is severe upward rolling and curling of
leaflets. Later the plant turns rather yellow and
becomes brittle and often the veins of the leaflets turn
purple. Branches and stems are stiff and erect and the
entire plant stunted. After infection, little or no fruit is
set.

Cultural Controls: Destroy nightshade and
ragweed growing in and around the field before
planting the crop. If the disease appears in the field,
spray the margin of the field with an approved
insecticide to kill the treehoppers that transmit the
virus. Consult the Insect Control Guide for
recommendations.






2006 Florida Plant Disease Management Guide: Tomato 8


Sclerotinia Stem Rot (Sclerotinia
sclerotiorum) (White mold)

Symptoms: The seedling disease occasionally
caused by this fungus is a typical damping-off,
resulting in a quick, wilting death of the seedlings.
The fungus usually attacks older plants at or slightly
above the soil line.

The grayish-white mycelium covers the surface
of infected tissues and the plant shows a marked
wilted condition and eventually withers and dies. An
examination at this time will show a large canker at
the base of the plant, which girdles the stem and
causes the softer tissue to disintegrate. Stems are
generally quite soft, later turning to a white "dried
bone" appearance. This disease is most prevalent in
Miami-Dade County.

Splitting of the stem will reveal cavities filled
with the black, large, hard sclerotia and the
grayish-white fungal growth characteristic of this
fungus. Infected fruit may develop a watery soft rot.
Occasionally the leaves are affected; however, if
petioles become infected the fungus generally grows
into the stem. See Plant Pathology Fact Sheet PP-22.

Cultural Controls: Flooding fields for five to six
weeks during summer months will reduce the number
of sclerotia in the soil. However, flooding may spread
other soilbome pathogens such as those causing
Fusarium wilt and bacterial wilt. Adequate drainage,
sanitation and crop rotation are important in the
control of this disease. Plant tomatoes in well-drained
fields. Do not plant tomatoes immediately following
Sclerotinia-diseased crops of beans, cabbage, celery,
lettuce, potato, or any other susceptible crop.

Chemical Controls: Apply fungicides to the
transplant production system or field as needed when
disease occurs. See PPP-6.

Soil Rot (Rhizoctonia solani)

Symptoms: This fungus causes the fruit to decay
in all stages of development. It penetrates the fruit
through wounds or the unbroken epidermis and
invades the tissue, causing numerous small, brown,
sunken spots on the side of the fruit that is in contact
with the soil.


Usually there is a single point of invasion by the
fungus, and as this spot enlarges it becomes zonate
with concentric brown rings, somewhat typical of
buckeye rot. This marking may be distinguished from
buckeye rot in most instances by the narrowness of
the concentric zones. With this disease, the zoning is
extremely definite and more pronounced than in
buckeye rot. In most cases, the epidermis is ruptured
at the center of the spot in soil rot, whereas in
buckeye rot the epidermis is very seldom broken. See
Plant Pathology Fact Sheet PP-41.

Cultural Controls: This disease is seldom of
importance in fields where the plants are staked,
pruned and/or grown on plastic mulch. Fruit losses in
transit can be controlled by careful grading.

Chemical Controls: See PPP-6.

Southern Blight (Sclerotium rolfsii)

Symptoms: Mature plants are attacked just below
the soil surface and are completely girdled. The tops
wilt and die rapidly. The mycelium often grows over
the diseased tissue and surrounding soil forming a
white mat of mycelial threads with the typical
tan-to-brown, mustard-seed-sized sclerotia. Often the
entire root system is destroyed. This is a hot weather
disease.

The fungus is exceedingly destructive on ground
crops and attacks the fruit where they contact the soil.
Slightly sunken, yellow spots develop on invaded
fruit, which rapidly decay, collapse, and become
covered by a white fungal mass with numerous
sclerotia.

Seedling invasion occurs rapidly, and the
seedlings die quickly. As the plants grow older they
become more woody and more resistant to attack.

Cultural Controls: Sanitation will provide good
protection against southern blight. Whenever
diseased fruit or plants are found in a field they should
be collected and disposed of, preferably by burying 2
or 3 feet deep or by burning. In this way, the
distribution of the sclerotia throughout the field will
be prevented, and to a large extent the disease will be
controlled.






2006 Florida Plant Disease Management Guide: Tomato 9


Since these sclerotia are so large that they are not
carried by the wind and since their numbers are
comparatively small, sanitation is an effective control
measure.

The careful regulation of water by means of a
well-designed irrigation-drainage system to prevent
excessive soil moisture will help prevent the
occurrence of the disease.

Plants in a field where the disease has been
prevalent should be staked. This will keep the fruit
from touching the ground and thus prevent infection
of the fruit. Also, turn soil at least 6 inches deep when
plowing.

Chemical Controls: Use of preplant soil
fumigation will aid in the control of this disease.

Target Spot (Corynespora cassiicola)

Symptoms: Leaf spots start as small brown spots
and as each increases in size, a sunken area, dull green
in color, surrounds the spot. In older leaves the center
of the spot is white.

Fruit rot is most often on the shoulder or sides
and starts as small white, circular spots with a definite
border. Later the spots enlarge or coalesce up to 1/2
inch, become noticeably sunken, and are brown to
black.

Chemical Controls: See PPP-6.

Tobacco Etch Disease (Tobacco etch virus)

Symptoms: Effects of this virus on tomatoes is
somewhat like those of potato virus Y, except plants
are more stunted by tobacco etch virus. Leaves of the
terminal shoots are cupped and petioles are bent
downward. Fruits are not mottled or deformed.
Spread of this virus is somewhat slower than potato
virus Y. Laboratory assays are required to accurately
diagnose this disease.

This virus is transmitted by aphids during
feeding. A number of weed hosts (ground cherry,
nightshade) serve to overseason the virus in Florida.

Cultural Controls: Eradicate wild host plants
and volunteer tomatoes before the crop is planted.
Avoid planting subsequent crops next to diseased


early plantings until after the early plantings have
been destroyed. Control aphids as needed.
Applications of JMS Stylet Oil will reduce virus
spread by aphids in the field.

Chemical Controls: See PPP-6.

Tomato Chlorosis Disease (Tomato
Chlorosis Closterovirus)

Symptoms: This virus has been fairly restricted
to the acreage of greenhouse tomato production. The
virus is vectored by four whiteflies: the sweet potato,
silverleaf, cotton and greenhouse species. Host range
information is being researched along with important
weed hosts in Florida. Onset of disease appears to
occur during the short day-length period of late
December-February. Lower leaves develop a
progressive, interveinal chlorosis, often with necrotic
flecking. Symptoms resemble these caused by
magnesium deficiency in tomato but are less uniform
within a leaflet or among leaflets on a leaf. No fruit
abnormalities have been observed. Fruit size and
number appear reduced by virus infection.

Cultural Controls: Raise clean transplants in a
whitefly-free production site. Tighten greenhouse
facilities to prevent ingress of whiteflies from the
field. Use of insect screening can dramatically reduce
virus incidence but will seriously limit cooling
capabilities, unless houses are structurally
redesigned.

Chemical Controls: Judicious vector control
with legally available insecticides will slow disease
onset and reduce severity. See the latest
recommendation in the Insect Management Guide.

Tomato Little Leaf Syndrome (physiological
disorder)

Symptoms: Interveinal chlorosis in the young
leaves could be the first sign of this disorder.
Subsequent top growth could become severely
distorted with leaflets along the midrib failing to
expand properly, resulting in a "little-leaf'
appearance. In addition, these symptoms may include
cessation of terminal growth, leaflets with twisted
and brittle midribs and auxiliary buds with distorted
growth. Fruits that set in mildly affected plants are






2006 Florida Plant Disease Management Guide: Tomato 10


distorted with radial cracks extending from the calyx
to the blossom scar. In more severely affected plants,
blossoms are distorted and fail to set fruit. Affected
plants can resume normal growth and set marketable
fruit, if conditions no longer support the development
of this syndrome.

Cultural Controls: Avoid waterlogged situations

Tomato Mottle (Tomato mottle virus)

Symptoms: Tomato mottle virus was the first
begomovirus known to infect tomato in Florida. It
was first found in 1989 and is widespread throughout
the state. The virus is transmitted by the silverleaf
whitefly, Bemesia argentifolii. Once the whitefly
acquires the virus, it is retained for the remainder of
its life. These viruses are not seedborne and are not
mechanically transmitted in the field.

Virus symptoms on tomato have been variable
but all varieties observed have been susceptible. One
symptom type (least common) is a bright golden
mosaic accompanied by leaf curling and plant
stunting. The more widespread appearance is an
interveinal chlorosis and mottle that is accompanied
by a downward arching of leaves, leaflet curl, and
plant stunting. Damage to yield appears to be a
reduction in fruit numbers and size.

Cultural Controls: See Tomato Yellow Leaf Curl
Virus.

Chemical Controls: See Tomato Yellow Leaf
Curl Virus.

Tomato Mosaic (Tomato mosaic virus)

Symptoms: The ordinary green strains of tomato
mosaic virus cause mottled areas of light and dark
green on the leaves. The dark green areas are usually
raised and crinkled.

Plants may be somewhat stunted and yields
reduced if infected while small, but little harm is
incurred if the plants are not infected until after one or
two clusters of fruit have set.

There may be no fruit symptoms, or fruit may be
deformed or marked with spots or streaks. Certain
strains of tomato mosaic virus cause a yellow mottling


of the leaves and occasionally a mottling of the stems
and fruit.

The yellow mosaic is more severe than the green
and may cause pronounced stunting of the plants and
large yield reductions.

Cultural Controls: Before handling plants and
during staking, pruning, or tying operations, wash
hands thoroughly in soap and running water or in
70% alcohol. This will wash off or inactivate the
virus. Do not use tobacco when working with tomato
plants. If seedbeds are used, periodically remove
diseased plants. Do not carry diseased plants to the
field. Eliminate all volunteer tomato plants. Sterilize
equipment before each growing season.

Tomato Pith Necrosis (Pseudomonas
corrugata)

Symptoms: This is a sporadic bacterial disease
that was first reported in greenhouses in Europe, but
has now been found in greenhouses in North America
and in several field situations in Florida.

Initial symptoms include chlorosis of young
leaves, followed by wilting of plants. A brown
discoloration of the surface of the lower stem may be
evident. The most diagnostic characteristic is the
appearance of a hollow or chambered ("laddered")
pith in the lower stem evident when lower stems are
cut open longitudinally. The intact pith tissue is often
a dark-brown color. Proliferation of adventitious
roots is common.

Cultural Controls: Little can be done for this
disease once it appears in fields. It appears to be
worse when nighttime temperatures are low, nitrogen
fertilization is excessive, and humidity and rainfall
are high.

Tomato Spotted Wilt (Tomato Spotted Wilt
Virus)

Symptoms: Tomato spotted wilt virus (TSWV)
(genus Tospovirus), has a large host range and is
vectored by thrips. The western flower thrips
(Frankliniella occidentalis) is the main vector
although the tobacco thrips (F. fusca), and other
thrips can also vector this virus. The immature insect
stages acquire the virus, the virus multiplies in its






2006 Florida Plant Disease Management Guide: Tomato 11


vector, and the insect remains infective throughout its
life cycle. TSWV can infect some 35-plant families
including the Solanaceae, Asteraceae, Leguminaceae,
Brassicaceae, and Bromiliaceae. This virus is not
easily mechanically transmitted in the field.

Symptoms on tomato include chlorotic and
necrotic ringspots, leaf bronzing, stem necrosis,
stunting, meristem necrosis, and fruit spotting.
Distinctive circular patterns often appear on the fruit
and leaves. These symptoms vary with the strain of
virus involved, time of year, and whether other
viruses exist in a plant.

Cultural Controls: Use virus-free transplants.
Weed control in and around production field is
encouraged. Use of UV-reflective plastic mulch
metalizedd mulch) will reduce TSW incidence. In
north Florida, UV-reflective mulch could be used in
spring and fall seasons, except early plantings in the
spring. Cut infected plants as they appear in the field
before secondary spread. Avoid overlapping crop
(peanut, pepper, tobacco) acreage nearby that can act
as both a virus and vector reservoir. Monitor for
thrips and manage populations with recommended
insecticides. In north Florida, integration of
metalized mulch with Actigard and insecticides
reduced TSW incidence up to 75 % compared to
black plastic mulch untreated plots.

Tomato Yellows (Tomato yellows virus)

Symptoms: Infected plants develop a stunted
appearance with a general foliar chlorosis. There have
been no typical viral symptoms of mosaic associated
with this disease. Fruit do not express symptoms. It
traditionally has been more of a problem in
Southwest Florida.

The virus is transmitted by aphids to the tomato
crop. Aphids pick up the virus from such wild hosts
as nightshade, ground cherry, and Datura spp.

Cultural Controls: Maintain weed control as
well as control of volunteer tomatoes prior to setting
the next crop. Avoid planting subsequent crops next
to diseased earlier plantings until these earlier
plantings have been destroyed. Control aphids as
needed.


Tomato Yellow Leaf Curl (Tomato yellow leaf
curl virus)

Symptoms: Tomato yellow leaf curl virus
(TYLCV-Is) is a whitefly-transmitted begomovirus
virus that is native to the eastern Mediterranean. It
was discovered in the eastern Caribbean in the early
1990s and was identified in Florida in July 1997.
TYLCV-Is has been found throughout Florida. The
disease is difficult to control, and management of
whitefly populations at both the beginning and end of
seasons is critical.

Two or three weeks after infection, mottling and
distortion can be seen on the newest leaves. At this
stage TYLCV symptoms are difficult to distinguish
from TMoV. However, subsequently emerging
leaves will be markedly reduced in size, upwardly
cupped, mottled and have yellow margins. Infected
plants are severely stunted. Flowers drop
prematurely, leading to poor fruit set. Fruit
production after infection may be reduced 90%.

Cultural Controls: Promptly remove sources of
TYLCV and whiteflies. Do not locate new fields near
infested crops. Promptly destroy fields. Keep fields
clean of volunteers and resprouts during off-seasons.
Create as long a crop-free period as economically
practical. Use virus-free transplants. Reflective
mulches will disorient whitefly adults, reducing
numbers of infected plants. Rogue infected plants at
first sign of disease. Scout fields for whiteflies and
apply insecticides accordingly.

Chemical Controls: Chemical controls are
centered on management of the whitefly vector. Use
imidacloprid (Admire) in the transplant water. Rates
recommended are Admire, 16 oz/A. See the insect
control guide for suggestions for spray treatment of
whiteflies if population becomes high later in the
season. Do NOT use Pravado if plants were treated
with imidacloprid or similar insecticide at
transplanting. Insect growth regulator insecticides can
be applied when scouts find nymphal densities to
exceed 5 to 10 per leaflet by standard sampling
procedures. Repellants (e.g. crop oil, UV-reflective
mulch) can be used to interfere with secondary virus
spread.






2006 Florida Plant Disease Management Guide: Tomato 12


Verticillium Wilt (Verticillium albo-atrum)

Symptoms: The first symptoms generally do not
occur until the beginning of fruit set, and consist of
the diurnal wilting and recovery of the lower leaves.
Initially, the leaves are green, but yellow areas
develop along the margins or between veins of the
leaflets. Fan-shaped necrotic lesions develop as the
yellowing progresses, and the affected leaves
gradually wither. The wilting and yellowing may
involve only a few terminal leaflets, or it may occur
on most of the bottom leaves, sometimes causing a
50% loss of foliage. Diseased plants, although not
killed by the fungus, are stunted, do not respond to
fertilizer, and produce only small fruit.

A lengthwise cut of an infected plant near the
base reveals a light tan discoloration of the vascular
tissue. The discoloration, in Florida, is typically
lighter than that of Fusarium wilt and usually does not
extend far up the stem before fruit are mature. There
is no decay of the pith typical of bacterial wilt, nor
dark-colored vascular bundles at the base of the
petiole typical of Fusarium wilt.

Cultural Controls: Choose varieties with
resistance or tolerance to this disease. Locate
seedbeds on soil free of the Verticillium fungus.
Practice sanitation and crop rotation.

Chemical Controls: Employ soil fumigants to
assist in control of Verticillium wilt in the seedbed
and in the field.




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