MANAGING BACTERIAL
DISEASES OF TOMATOES
Sally A. Miller
Department of Plant Pathology
The Ohio State University
Ontario Tomato Day
March 5, 2013
Bacterial Diseases - Great Lakes Region
Disease
Tomato
Bacterial spot
Bacterial speck
Bacterial canker
Syringae leaf spot
Bacterial soft rot
Pith necrosis
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√ (m)
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√
(m) = minor disease
Pepper Seedborne
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√ (m)
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Bacterial Disease Life Cycle
Bacteria are dispersed by irriga;on water and wind driven rain Infected seedlings are introduced into produc;on Bacteria survive on alternate hosts Seedlings become infected from infested seed Bacteria survive on fruit or foliar debris or in seed Disease Cycle for Seed‐borne Bacterial Diseases of Tomato Occurrence of secondary infec;ons Bacterial Leaf Spot
•  Xanthomonas spp.
•  Formerly X. campestris pv.
vesicatoria (4 races)
•  Re-classified:
•  X. vesicatoria
•  X. euvesicatoria
•  Only species affecting pepper
•  10 races
•  X. perforans
•  X. gardneri
•  Pathogen is highly variable
•  Resistance to copper,
antibiotics develops
commonly
•  Quickly overcomes
disease resistance
•  Favored by hot, moist
conditions
•  Relatively short-lived in soil
in cool climates
•  Seedborne
Bacterial Spot Symptoms
Tomato
•  Necrotic spots w/
chlorotic halos on
leaves, stems,
peduncles
Pepper
Bacterial Leaf Spot
•  Crusty/scabby spots
on fruit
Bacterial Leaf Spot
•  Defoliation
Bacterial Spot – Processing Tomato
Epidemic
•  2009 – 2012
–  Bacterial spot epidemic –
OH, MI, IN processing
tomatoes
•  Some fields have low foliar
severity
•  Some varieties in a field
more severely affected than
others
–  Foliar severity not
obviously/consistently
increased
•  Mainly X. gardneri
Northwest Ohio Processing Tomatoes
Fruit Symptoms
Peeling Problem
Bacterial Canker of Tomato and Pepper
•  Clavibacter
michiganensis subs.
michiganensis
•  Devastating disease of
tomatoes
•  Foliar and vascular
pathogen
•  Minor problem of pepper
•  Foliar only in pepper
•  Seedborne
•  Long-lived in soil in
northern climates
Bacterial Canker Symptoms
•  Foliar necrosis
•  Marginal necrosis (firing)
•  Defoliation
•  Silvering
Tomato
Bacterial Canker Symptoms
•  Wilting and plant
death
Vascular necrosis
Bacterial Canker Symptoms
•  Bird’s eye lesions on
tomato fruit
•  Necrotic lesion
surrounded by white
halo
•  Pepper symptoms
Not bacterial canker– but looks like it!
Two-spotted spider mite outbreak - 2012
Bacterial Speck of Tomato
•  Pseudomonas syringae
pv. tomato
•  Favored by cool,
moist conditions
•  High humidity
•  Not as variable as
•  Splashing water
bacterial spot pathogens
•  Seedborne
•  Resistance to copper,
antibiotics common
•  Limited to tomato
•  Survives in soil longer
in northern climates
than Xanthomonas
Bacterial Speck Symptoms
•  Necrotic spots on
leaves and stems,
surrounded by
chlorotic halo
•  Small, circular,
almost flat lesions
(“specks”) on fruit
6-Step Integrated Management Program
1.  Use clean seed
2.  Choose a resistant variety
3.  Use pathogen-free transplants
4.  Choose the best site and rotate
5.  Use appropriate cultural practices
6.  Use crop protectants as needed
1. Use Clean Seed
•  Check with seed provider –
have seed lots been tested
for bacterial spot, speck and
canker?
•  Are you saving your own
seed, e.g. heirloom varieties?
•  If not tested and shown to be
negative, or are saved seed:
•  Treat seed with dilute Clorox or
hot water
•  http://ohioline.osu.edu/hyg-fact/
3000/3085.html
Sanitizing Seed Treatments
2. Choose Resistant Varieties
•  Tomato
•  Bacterial disease resistance is rare
•  Resistance to race 0 – bacterial speck
•  Pepper
•  Resistance to bacterial spot is available
•  Multiple races of the pathogen – resistance may be overcome but so far
is not common
•  http://vegetablemdonline.ppath.cornell.edu/Tables/
PepperTable.html
3. Use Pathogen-Free Transplants
•  The goal is to keep bacterial populations low on seedlings
•  Use new or sanitized plug trays/flats and pathogen-free mixes
•  Sanitize equipment and tools regularly; install solid flooring/raise
seedlings from floor
•  Restrict movement of personnel, tools and equipment between
greenhouses
•  Thoroughly clean and sanitize house after each crop
3. Use Pathogen-Free Transplants
•  Prohibit the production of exotic or experimental pepper or
tomato varieties unless seed was treated
•  Scout regularly and destroy plants with symptoms and
surrounding flats
•  Minimize moisture – “dry growing”
•  Use only municipal or well water – avoid surface water unless it
is treated to kill bacteria
•  Apply one or two copper treatments (with mancozeb- tomatoes)
and one application of Agri-Strep before plants leave GH
Effect of Bactericides on Tomato
Seedlings Exposed to X. gardneri
7
6
5
4
3
2
1
0
388 cell trays
Log Xg/g
Lesions/plant
4. Choose the Best Site and Rotate
•  Site selection
•  Well-drained
•  Good air movement
•  Sunny
•  Rotate rotate rotate
•  Bacterial spot – 1-2 years
•  Canker, speck >3 years
•  Rotate out of the tomato/pepper/eggplant family
5. Use Best Cultural Practices
•  Avoid handling plants when they are wet
•  Sanitize hands, boots and tools between fields
•  Maintain reduced-stress growing conditions
•  Well-drained soil
•  Appropriate fertilizer (adequate but not excessive N)
•  Regular irrigation if needed
•  Improved organic matter content – cover crops, compost
•  Clean and sanitize equipment between fields
Equipment Sanitation Plans – Tomato
Grower Survey
90.0%
70.0%
62.5%
80.0%
76.5%
60.0%
70.0%
50.0%
60.0%
40.0%
50.0%
40.0%
30.0%
25.0%
30.0%
20.0%
20.0%
12.5%
14.7%
8.8%
10.0%
0.0%
10.0%
0.0%
Yes
No
I don't know
Before the season starts
Yes
No
Within the season
I don't know
6. Use Crop Protectants
•  If bacterial diseases have been a problem and/or
conditions favor bacterial diseases…
•  Begin early – within 7 days after transplanting recommended.
•  Include mancozeb (EBDC) with copper sprays until flowering
(tomatoes). Mancozeb + copper should stand in the tank 90
minutes before spraying.
•  Concentrate anti-bacterial treatments early season through fruit
set to keep bacterial populations low.
•  Apply copper on a 5-7 day schedule until fruit are set and approx.
¼ - ½ full size. Apply Actigard within 14 days of transplanting and
continue to apply on 10-14 day intervals through fruit set.
Some Points about Copper
•  Activity is affected by pH
•  The lower the pH (more acidic) the more active copper
ions
•  BUT pH < 6.5 may cause phytotoxicity
•  Copper is a protectant – it must be applied before
bacteria land on the plant and when populations are
relatively low; copper is ineffective once bacteria enter
the plant
•  Copper should be applied before it rains but in time for
plants to dry
Some Points About Copper
•  Residual drops quickly
on leaves
•  Florida – after 5 days, little
detectable residue
•  Ontario – residues at 25%
6-8 days after treatment (in
some samples were near
zero 6 days after
treatment)
•  Ohio - residues drop very
quickly within days after
application to seedlings in
the greenhouse
Disease Severity (%)
Do Surfactants Increase Bacterial
Disease Incidence or Severity?
100
90
80
70
60
50
40
30
20
10
0
*
*
*
*
No Activator 90
Plus Activator 90
Summary – Surfactant Study 2012
•  2012 was a hot dry
year
•  Activator 90 did not
affect:
•  Foliar disease severity
•  Number of lesions/fruit
•  Percentage of large
lesions
Thank you
•  Presentation will be posted on
www.oardc.osu.edu/sallymiller
•  Acknowledgments
•  OSU Vegetable Pathology Lab
•  Jhony Mera, Fulya Baysal-Gurel,
Melanie Ivey, Xiulan Xu, Xing Ma,
Nagendra Subedi
•  OSU NCARS
•  Matt Hofelich
•  OARDC Wooster Farm
•  Bill Bardall
•  OSU Muck Crops
•  Rick Callendar
OSU Vegetable Pathology Lab