Minnesota High Tunnel Disease Survey

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© 2012 Regents of the University of Minnesota. All rights reserved.
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High Tunnel Disease Survey
Summary of results, management recommendations, and future research
DR. ANGELA ORSHINSKY
ASSISTANT PROFESSOR AND EXTENSION SPECIALIST
DEPARTMENT OF PLANT PATHOLOGY
UNIVERSITY OF MINNESOTA

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TODAY’S TALK
 The MN High Tunnel Network Survey
– What it is
– What we found
 Management of disease in high tunnels
– IPM
– Fungicides
 Future of high tunnel disease research

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MN HIGH TUNNEL NETWORK SURVEY
 MN High Tunnel Network Survey
 USDA-MDA Specialty Crop Block Grant
 Initially subsidized sample submissions to the
PDC – low response rate
 Starting summer 2014 – sample 15+ high
tunnels across MN 3 times per year
 Tomato, pepper, eggplant only
 >200 samples collected and diagnosed this
summer

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Diagnosis of plant pathogens:
 Macroscopic symptoms
 Microscopy (fungi only)
 Isolation of bacteria and fungi
 Electron microscopy (viruses)
 Test strips (viruses)
 DNA isolation and sequencing

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2013 results:
– Only 10 samples sent in to PDC despite
subsidy
Found:
– Impatiens necrotic spot virus on pepper (1)
– Leaf mold (5)
– Unknown (1)
– Fusarium root and crown rot (1)
– Herbicide injury (3)
– Early blight (1)

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2014 results:
> 200 samples
• 100 % had leaf mold
• 100 % had early blight
• 90 % had gray mold
• Phoma fruit rot (1)
• Anthracnose (2)
• Bacterial spot (4)
• Bacterial speck (1)
• TMV/ToMV (3)
• White mold (3)
• Powdery mildew (5)
• Fusarium crown and root rot
(5)
• Septoria leaf spot (3)
• Late blight (1)

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MFVGA 2014: Is leaf mold a problem in your high
tunnels?

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2015: Is leaf mold a problem in your high
tunnels?
58%23%
10%
9%
I see it every year I see it some years
I have never seen it I am unsure

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2014 high tunnel results
• Every high tunnel visited had
at least some leaf mold
• Many tunnels experienced
severe defoliation
• Severe cases had fruit
infection
• Seen as early as June in
northern Minnesota

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• Severe cases often
ended up with multiple
pathogens
• Leaf mold  Botrytis 
Trichothecium

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TOMATO LEAF MOLD – PASSALORA FULVA
• Spore germination at 58 % RH,
optimal 75 – 90 %
• Sporulates 10-12 days after
infection
• Conidia survive “up to” one year
• Transmitted on seed, wind, rain,
equipment
• Survives as tiny bundles of cells
in leaf debris

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Diagram from Dhou and Zhou. 2012.Cell Host and Microbe. 12: 484

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Symptoms - Early

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UMN Research
 Research to determine
– What pathogen races are here = Cultivar recommendations
– Seed infection and treatment = heirloom growers
– Organic options and high tunnel fungicide options
– Timing of fungicide sprays
– Fungicide resistance
 Research is only possible because of your
support!

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2014: Has early blight been a problem in your
high tunnels?

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MN high tunnel Network survey
2015: Has early blight been a problem in your high
tunnels?

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• Found at every high tunnel
• Two different Alternaria species –
both were found.
• Stem infection, fruit infection, leaf
infection all found
• Found on tomato, pepper, and
eggplant

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EARLY BLIGHT – SYMPTOMS

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EARLY BLIGHT – SYMPTOMS

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EARLY BLIGHT – ALTERNARIA TOMATOPHILA,
ALTERNARIA SOLANI
 Very common disease
 Some resistant varieties
(resistance not complete)
 Can cause severe yield loss
(fruit infection, defoliation)
 Will infect nightshade weeds
 Temperatures of 59-86 F
 90 % humidity
 Survives in soil, seed, debris

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Gray Mold – Botrytis cinerea
 First observed in June
 Severe damage by September
 Loss of fruit, defoliation of
plants, stem lesions
 Spores infect in 5 h with free
water, temperatures 65 – 75 F

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Powdery Mildew
 Three types, only found one
type in MN this year.
 Late season disease
 Severe in overcrowded tunnels
 Defoliation
 Very aggressive pathogen
 Wide host range including
weeds

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Fusarium Root and Crown Rot
Fusarium oxysporum fsp. radicis
lycopersici (FORL)
 Up to 60 % loss at two
locations
 Plants lost early in the season
 Cool temperatures favor
disease

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Fusarium Root and Crown
Rot
 3 + years tomatoes
 Found on young pepper
plants at one location
 No fungicide options
 Resistant varieties
 Need rotation!

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Fusarium Root and Crown Rot
 Survives many years as chlamydospores in soil
 VERY difficult to eliminate
 Spread by water, people/clothing, infected pruning
tools
 There are no fungicides for crown and root rot!
 Cultural practices become that much more
important!

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Tobacco/Tomato Mosaic Virus
 Leaves - mottled, small,
curled/distorted, plants stunted
 Fruit - Distorted, uneven color, ripening
delay, brown discoloration of inner
walls
 Common on ornamentals and weeds
 Transmitted mechanically, seed,
survives tobacco curing and burning!
Photos: apsnet.org

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Photos: apsnet.org

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Tomato Spotted Wilt Virus
 Leaf bronzing
 Small darks spots on leaves
 Streaks on petioles & stems
 Spread by thrips
Photo: apsnet.org

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Photo: apsnet.org
Photo: apsnet.org

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Bacterial Spot, Xanthomonas spp.
 Dark, water-soaked lesions on leaves that turn red-brown
 Lesions often bound by leaf veins and on leaf edges/tips
 Fruit lesions are raised, brown, ¼ inch diameter
 Secondary fungal infections on fruit

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On our radar - Bacterial canker
 Seed transmitted (5 yr survival)
 Survives 2-3 yr in plant debris
 Causes wilt of the plant
 Causes fruit lesions (bird eyes)

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Other issues
 Russetting of peppers
 Caused by mites

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Other Issues
Herbicide Damage
• Cupped leaves
• Twisted growth
• Thick leaf veins
• Veins close together
• New leaves most severely affected
• Survives composting process,
volatilizes

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Other issues – Stink bug Damage

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Insect/Vector Management

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Management of High Tunnel
Diseases
SO WHAT DO WE DO WITH ALL OF THESE DISEASES?

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Pathogen
Host Environment
No Disease
No DiseaseNo Disease
No DiseaseNo Disease
No Disease
THE DISEASE TRIANGLE

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Integrated Pest Management (IPM)
Exclusion: Certified seed; seed
disinfestation; clean transplant; farm
traffic management
Plant Health: Site selection; choose appropriate
varieties; proper fertility
Cultural Management:
Sanitation, Humidity
control, rotation, mulch
Fungicides

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PLANT HEALTH
 Site selection/preparation
– Light requirements
– Soils: pH, drainage,
organic matter
 Variety selection:
– Disease resistance
– Temperature sensitivity

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PATHOGEN EXCLUSION
 Do not let the pathogens into your crop
 Use certified, disease-free seed
 Treat harvested seed
– Fermentation
– Hot water treatment
– Disinfectants
 Transplants from trusted sources
 Compost and mulch from trusted sources
 Manage insect vectors
 Physical barrier – plastic mulch

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CULTURAL MANAGEMENT
 Varieties with disease resistance
 Sanitation
– Remove diseased plants or plant parts
– Disinfest tools, equipment
– Boots and clothing for your farm only
– Remove plant debris regularly
 Humidity
– Allow for air flow by rolling up sides, vents, use fans
– Prune out lower canopy in the afternoon
 Crop rotation
– Reduce the build up of pathogens

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SCOUTING BASICS
 Pick a day and time each week
 What is your disease history?
 Know the biology of likely
pathogens
– What is a tolerable level?
– How fast can it progress?
 Bring a tool kit
 Establish a route for scouting
 Inspect entire plant – flip leaves,
look at soil line and up

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SCOUTING TOOL KIT
 Camera/smartphone
 Notepad
 Flagging tape
– Mark plants of interest
 Bags
– Remove diseased plants
– Collect samples for diagnosis
 Hand lens
 Disinfectant
– Disinfect pruning tools and hands as you go
 Disposable gloves
– If viruses a problem, don’t touch symptomatic plant then healthy one

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 Typical IPM recommendations: when you achieve
an economic threshold
 When you don’t have a threshold:
– What amount of the disease can you tolerate?
– Does this disease cause yield losses?
– Will the disease kill the plant?
– How quickly will the disease spread?
 Fungicide resistance management:
– DO NOT wait until you have massive sporulation
 Fungicides do not actually kill, they reduce growth
WHEN TO USE A FUNGICIDE

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 Diagnose the disease
– Pdc.umn.edu; smartphone apps; compendia (apsnet.org)
 You cannot treat abiotic, bacteria, and viral
diseases with fungicides!
 Fungicides don’t work the same on all fungi
HOW TO CHOOSE A FUNGICIDE
pdc.umn.edu

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 Once you have a
diagnosis:
– UMN Extension specialist
– Midwest Vegetable Production
Guide for Commercial
Growers
HOW TO CHOOSE A FUNGICIDE
mwvegguide.org

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 Understand the label
 What is the fungicide class?
 What is a FRAC code?
 Cross resistance
 Adhere to restrictions on:
– # applications in a row
– Total # applications
– Suggested tank mixes
FUNGICIDE RESISTANCE
MANAGEMENT

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 Fungicide rotation
– Rotating between fungicides from different classes.
 Tank mixing
– Spraying two fungicides of different classes at the same time
– include one penetrant and one multisite, contact fungicide.
– Some combinations are phytotoxic and could result in plant injury.
 Label restrictions reduce fungicide resistance,
environmental, and health hazards
– maximum numbers of consecutive applications
– maximum number of applications per season
– maximum amount of product applied per season.
FUNGICIDE RESISTANCE MANAGEMENT

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 Mode of action
– What cellular targets does the fungicide attach to?
– Mitosis, nucleic acid synthesis, cell wall synthesis
 Mobility
– Contact: Don’t move from landing spot
– Penetrant: Moves past the cuticle into the plant
– Local penetrant, Acropetal penetrant, Systemic penetrant
FUNGICIDE CHARACTERISTICS
Contact Local Penetrant Acropetal Penetrant Systemic Penetrant

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GENERAL GUIDELINES FOR DISEASE
MANAGEMENT
What if you find something?
 Diagnosis is key:
– Email or call a specialist or educator!
– Plant Disease Clinic: pdc.umn.edu
– Tomato MD
– UMN Extension website: www.extension.umn.edu

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ORGANIC OPTIONS
 Biocontrols not tested at UMN yet
 Will be tested in the next few years
 Cultural management
 Clean seed
 ROTATION

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FINAL WORDS ON DISEASE
MANAGEMENT
 Rotate out of Solanaceae to prevent disease build up
 Remove heavily sporulating plant material
 Reduce density of plants to reduce disease
 Cultural management is worth the effort

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WHAT’S NEXT FOR HIGH TUNNEL
RESEARCH?
 Last year of the survey is 2015
 Continuing with leaf mold disease
research (2015-2017)
– What races are here?
– Resistant cultivars?
– Survival in high tunnels & sanitation practices
– Organic options? Fungicides?

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 We depend on you for input and support:
 We need your help to gather information to
help us help you!
– Participate in our survey (sign up)
– Let us know what your disease problems are!
Angela Orshinsky – aorshins@umn.edu
612-625-9274
WHAT’S NEXT FOR HIGH TUNNEL
RESEARCH?

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The University of Minnesota is an equal opportunity educator and employer. In accordance with the Americans with Disabilities
Act, this PowerPoint is available in alternative formats upon request. Direct requests to the Extension Store at 800-876-8636.
Thank you!
Acknowledgements:
Michelle Grabowski
Terry Nennich
Vince Fritz

Minnesota High Tunnel Disease Survey

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