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Managing diseases in greens
Southern WI Vegetable Workshop
February 1, 2013 – 9:45-11:00AM
Dane Co. Extension Office, Madison, WI
Amanda J. Gevens
Extension Plant Pathologist
University of Wisconsin-Madison
Logistics
This presentation offers a general discussion of
most common diseases of greens and their
management across production systems
Factors influencing specific management:
Field grown vs. high tunnel/greenhouse
Conventional vs. organic
Raw-consumed (lettuce/endive/escarole) vs.
Cooked (mustard/collard) greens
Susceptible Host
Virulent Pathogen Favorable Environment
Disease
Triangle
High tunnels
extend growing
season for plants
and can
extend favorable
conditions for
pathogens
What can
you do?
Susceptible Host
Virulent Pathogen Favorable Environment
Disease
Triangle
High tunnels
extend growing
season for plants
and can
extend favorable
conditions for
pathogens
Manage:
1) Air temp
2) Humidity
3) Air flow
4) Start with
healthy plants
5) Resistant
varieties
6) Preventative
fungicides
7) Plant-free
periods
8) Sanitation
High Tunnel Disease Management
vs.
Disease Management in the Field
High Tunnel Field
Crop rotation No difference
Fungicides Restricted usage __
Windborne spores Little or no difference
Splash dispersed diseases
Some protection __
Leaf wetness Higher humidity plus leaf wetness
__
Courtesy Dan Egel, Purdue University
Cultural disease management practices
are essential
Fungicides are a final piece of disease control,
but critical for some diseases
Considerations include:
-coverage is critical
-repeated application may be needed
-selection of fungicides for greenhouses
may be limited
-consider materials with broad crop label
-organic vs conventional
Utility of Fungicides
A high tunnel is a greenhouse for federal
fungicide labeling. Fungicide labels may:
1. Have a section listing special rates and GH instructions
2. Mention that a fungicide can be used in GH but with no
special instructions
3. Have no mention of whether the fungicide can be
used in GH or not
4. Specifically prohibits greenhouse use
(ie: Kocide specifies allowable use in GH, Dithane allows
use in GH, Endura not for use in GH, Bravo label specifies
NO use in GH)
Fungicides in the high tunnel
Managing diseases in greens
2 groups of “greens”
1) RAW-CONSUMED: lettuce, endive, radicchio,
escarole, chicory Primary disease concerns: bottom rot (Rhizoctonia),
drop (Sclerotinia), damping-off (Pythium), downy
mildew (Bremia)
2) COOKED: mustards, turnips, collards, kales, crucifers Primary disease concerns: Alternaria, downy mildew
(Peronospora), black rot (Xanthamonas), club root
(Plasmodiophora), blackleg (Phoma), Rhizoctonia
or wirestem (Rhizoctonia)
• Diseases may cause losses by reducing stands, making plants
unthrifty, and by lowering the quality of marketable leaves
• Rotate greens with crops that are not in their plant family
• mustard family: broccoli, brussels sprouts, cabbage,
cauliflower, collard, kale, kohlrabi, leaf mustard, radish, turnip,
and water cress
• lettuce family: asteraceae (daisies, chamomile, tarragon),
endive
Do not plant in fields with a history of club-root (mustards)
Obtain high quality seed that have been grown under disease-
free conditions and treated by the seed producer to reduce
damping-off
Destroy weeds in the field and those bordering the field early in
the spring
General Disease Control Management
Strategies for “Greens”
Lettuce Rhizoctonia or Bottom Rot
Gerald Holmes
Soilborne pathogen
Favored by cool,
wet soil conditions
Lettuce Pythium or Damping-off
Soilborne pathogen
Favored by cool,
wet soil conditions
Lettuce – Common Diseases & Registered Fungicides
Lettuce – Common Diseases & Registered Fungicides
Rhizoctonia Extract of Reynoutria sachalinensis – Regalia Maxx – Marrone BioInnovations (OMRI approved) Actinovate (Streptomyces lydicus) – Natural Industries (OMRI approved)
Mustard Greens – Alternaria
Leaf Spot
CABI image
Gene McAvoy, UF
Minor problem in WI
Debris-borne causal agents
Alternaria brassicae Alternaria brassicicola
Mustards – Rhizoctonia solani Wire stem
Bottom rot symptoms
Pathogen attacks plants in the seedbed,
field and storage
Pathogen is soil borne - indefinite survival
Not a significant problem, but fairly
common in WI when soil temperatures are
less than ~55°F and soil moisture is high
Wirestem and Head Rot
Disease Characteristics
Mustard Greens/Cole Crops– Common Diseases &
Registered Fungicides
Mustard Greens/Cole Crops– Common Diseases &
Registered Fungicides
Mustard Greens/Cole Crops– Common Diseases &
Registered Fungicides
Rhizoctonia Extract of Reynoutria sachalinensis – Regalia Maxx – Marrone BioInnovations (OMRI approved) Actinovate (Streptomyces lydicus) – Natural Industries (OMRI approved)
Basil Downy Mildew Peronospora belbahrii
Seed, plant, & wind transmitted
Affects ornamental and herb basils
Spores on leaf undersides
Basil varieties susceptible to downy mildew
Aroma 2 Italian Large Leaf
Genovese Magical Micheal
Genoveser Martina Mariden
Nufar Opal Purple Variegated
Queenette Poppy Joe’s
Superbo
Basil varieties tolerant to downy mildew
Amethyst Imp Mrs. Burns Lemon
Red Rubin Red Leaf
Sweet Adin Lemon
Lemon standard Lemon Mrs. Burns
Lemona Lime
Basil varieties resistant to downy mildew
Spice Blue Spice
Blue Spice Fil
Control Measures for Limiting
Basil Downy Mildew
Keep foliage dry – water from below and water judiciously
Maintain airflow between plants in rows and between rows
Scout regularly and carefully for symptoms
Harvest early if disease is present and/or risk is high
Plant pathogen-free seed? – no seed treatments have been effective
Rogue and/or destroy sporulating plants to protect remaining crop
Few fungicides labeled for basil – no organic fungicides are effective
Photo courtesy: Bob Wick, UMASS
Photo courtesy: Meg McGrath, Cornell
University of Wisconsin Vegetable Disease
Website (& newsletter access)
http://www.plantpath.wisc.edu
UW – Vegetable Team Website
http://vegetables.wisc.edu/vegetable-team
Presentations from this session will be posted to
Team website after the meeting.
Further Information
Thank you - Amanda Gevens
[email protected] Phone: 608-890-3072