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

gevens@wisc.edu Phone: 608-890-3072