Controlling Bacterial and
Fungal Diseases in Tomato
Sally Miller
Ohio State University
Department of Plant Pathology
Early Blight

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Very common disease
Leaf spots, stem
cankers, fruit rot
Often defoliates
plants
Starts on older leaves
and moves up
Septoria Leaf Spot
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Usually appears after
mid-July
Favored by rainy
conditions
Spots appear on
leaves and stems at
any stage of plant
growth
Plants may lose
leaves
Tiny, dark fruiting
bodies in lesions
No fruit symptoms
Late Blight

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Favored by cool, wet
conditions
All above - ground
parts of the plant are
susceptible: lesions
are brown-black
Disease can progress
very quickly
Early sources of the
pathogen:

Transplants (?)
Timber Rot (Sclerotinia White
Mold)
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Stem necrosis, plant
death
Favored by cool, rainy
conditions
Soilborne pathogen,
wide host range, long
survival of sclerotia
No resistance
Powdery Mildew

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Potentially serious
problem
Already serious in
several states
Signs are white
powdery mycelium
and spores on the
surface of plants
May see plant
deformation and
death
Anthracnose

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
Favored by warm, wet
weather
Symptoms mainly on
fruit
Symptoms generally
occur on ripe or
ripening fruit
Buckeye Rot
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Phytophthora
capsici
Occurs occasionally
in Ohio
Requires hot, wet
conditions
Symptoms occur on
fruit; root rot also
poossible
Botrytis
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All above-ground plant
tissues susceptible
Olive-green/grey spores
produced rapidly
Ghost spots on fruit
Primarily a greenhouse
problem
Favored by cool
temperatures, high
relative humidity, free
moisture
Bacterial Canker

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Very serious disease
Causes burning
(“firing”) of the foliage,
fruit lesions, stunting,
plant death
Stunting, plant death
more often observed
under stress conditions
Seedborne
No resistant varieties
Bacterial Spot
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Spots w/chlorotic
haloes and firing of
leaves, defoliation, fruit
spots
Favored by hot, humid
conditions and driving
rainstorms
Seedborne
No resistant varieties
available
Bacterial Speck

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Foliar symptoms similar
to bacterial spot
Smaller spots
(“specks”) on fruit
Favored by cool, humid
conditions and driving
rainstorms
Seedborne
Limited resistant
varieties available
Bacterial Stem Rot/Pith
Necrosis
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Stunting, plant death
Pith shows brown
discoloration
Favored by hot, wet
weather
Increased by excessive
nitrogen fertilization
Soilborne
No resistant varieties
available
Tomato Disease Management

Use IPM approach - multiple tactics

Select best possible site

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Improve soil quality
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Open (good air movement), well-drained
Organic amendments
Cover crops
Practice appropriate rotations

Rotate away from solanaceous crops at least
three years
Tomato Disease Management

Manage water properly

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Trickle/drip irrigation better than overhead
Use raised beds
Choose varieties with best resistance
available

“Mountain” series: moderate resistance to early
blight (Mountain Pride, Supreme, Gold, Fresh and
Belle)
Use Clean Seed

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To control bacterial diseases
Tomato seed are acid treated during
processing/de-fuzzing

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Not fully effective in sanitizing seed
Other options
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Clorox treatment (surface sanitation)
Hot water treatment (surface & internal)
Hot water seed treatment
Seed
°F
Minutes
Brussels sprouts, eggplant, spinach,
122
cabbage, tomato
Broccoli, cauliflower, cucumber*, carrot, 122
collard, kale, kohlrabi, rutabaga, turnip
Mustard, cress, radish
122
25
Pepper
125
30
Lettuce, celery, celeriac
118
30
* Cucurbit seeds may be damaged by hot water treatment
20
15
Effect of Hot Water Treatment on
Bacterial Disease in Tomato
Disease incidence and yield of organic
tomato plants raised from seed treated with
hot water or not treated
Treatment
% Foliar
Bacterialmature
fruit (T/A)
Anthracnose
(T/A)
Marketable
Yield (T/A)
Fruit Size
(kg/fruit)
Healthy
immature
fruit (T/A)
Hot water
2.4 a
0.9 a
3.1 a
23.3 a
1.9 a
10.6 a
Untreated
66.6 b
2.4 b
12.6 b
16.7 b
1.6 b
0.9 b
Hot Water Treatment -Disadvantages
Figure 1. Effect of Hot Water
Treatment on Germination of
Tomato Seed
40
20
CMM treated
120
Percent Germination

Florida 47
untreated
Florida 47
treated
Peto 696 SM
untreated
Peto 696 SM
treated
CMM untreated
100
80
60
0

May reduce seedling vigor

May reduce seed longevity
XCV untreated
Day 3
Day 5
Day 6
XCV treated
Days after Sowing
Figure 2. Effect of Hot Water Seed Treatment
on Tomato Seedling Height

12.00
10.00
Height (cm)
May delay or reduce seed
germination, especially in old
or poor quality seed lots
8.00
6.00
Not compatible with other
seed treatments (pelleting,
priming etc.)
4.00
2.00
V
XC
te
d
ea
tr
V
XC
un
tr
e
tr
e
at
at
ed
ed
ed
M
CM
un
M
CM
SM
tr
e
tr
e
at
at
ed
at
ed
69
6
to
Pe
69
6
to
Pe
re
un
t
SM
47
id
a
or
Fl
Fl
o
rid
a
47
un
t
tr
e
re
at
ed
at
ed
0.00

Too damaging to largeseeded vegetables
Seed Treatment Cautions

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Use new, high quality seed
Treat a small sample first and test for
germination
Treat close to time of planting (within weeks)
Treat only once
More information:
 OSU Extension Bulletin 672 - Vegetable Production
Guide
 Miller, S. A. and Lewis Ivey, M. L. 2005. Hot water and
chlorine treatment of vegetable seeds to eradicate
bacterial pathogens. Ohio State University Extension
Fact Sheet HYG-3085-05

http://www.oardc.ohio-state.edu/millerlab
Produce Clean Transplants
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Practice good sanitation
in the greenhouse
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Use new or sanitized
plug trays or flats and
pathogen-free mixes
Sanitize equipment
Install solid flooring; raise
seedling trays
Limit movement of
personnel and equipment
between greenhouses
Clean benches,
greenhouse structure
thoroughly after the crop
Produce Clean Transplants
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Do not raise exotic or experimental
vegetable varieties, or plants from saved
seed, in the same greenhouse with
commercial seedlings unless all seeds are
treated
Avoid raising or holding ornamental plants
and vegetables in the same greenhouse
Exclude insects (may carry viruses)
Produce Clean Transplants

Maintain conditions in the greenhouse that do
not favor disease development
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Maintain relative humidity as low as possible
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Good air circulation
Proper temperatures
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Do not overwater
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Handle plants as little as possible
Seedling Treatments for Bacterial
Disease Management

Objective is to reduce or eliminate bacterial
pathogen populations on seedlings
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Copper/Manzate
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Bacteriophage - Omnilytics
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Good results in Florida
Apply in overhead irrigation water
Other biocontrols, e.g Serenade + Copper
In the Field - Cultural Tactics
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Mulches

Plastic or plant-based
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Reduce splash dispersal of pathogens
Protect fruit from soilborne pathogens
Row orientation

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Maximize air movement
Minimize leaf wetness periods
In the Field - Sanitation
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Destroy tomato tissue post-season
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Remove diseased plants and weeds inseason
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Removes sources of inoculum
esp. for late blight, bacterial diseases
Sterilize plant stakes between crops
Clean tools, equipment frequently
Prohibit tobacco use
Management with Fungicides

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Regular program of fungicide application
Mancozeb or Manzate or Bravo standard protectants (P)
Alternate with Quadris, Cabrio, Tanos or Flint (S)

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e.g. P-P-S-P-S-P-S-P-P
Strobilurin resistance in potato early blight - consider S+P tank
mix instead of S alone
Include copper material in tank mix with mancozeb or
manzate if bacterial spot or speck a concern
Other fungicides may be necessary for specific problems:

Topsin M for timber rot
GH Tomatoes - New
Fungicide Registrations

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Decree
Scala

Botrytis management