Types of Plant Pathogens · 2017-01-23 · 1/23/2017 6 18 Aug 2005 First symptoms of downy mildew...

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Organic Disease Management:

Concepts & Facts

Beginning Farmers

Need to Know

Meg McGrathDept. of Plant Pathology & Plant-Microbe Biology

LIHREC, Cornell University, Riverhead, NY

[email protected] University is an equal opportunity, affirmative action educator and employer.

Requirements for disease development:

- Pathogen

- Host

- Favorable environment

- Time

Organic Disease Management: Concepts & Facts

Knowledge of pathogen biology is founda-

tion of cultural management practices.

Pathogens vary substantially in survival

mechanism, dispersal, host range, etc.

Organic Disease Management: Concepts & Facts Types of Plant Pathogens1. Fungi (composed of thread-like hyphae; reproduce by

spores. Diseases include powdery mildew)

2. Oomycetes (similar to fungi. Diseases include late

blight)

3. Bacteria (one-celled organisms. Diseases include

bacterial wilt)

4. Viruses (replicating molecules composed of protein

and RNA or DNA)

5. Nematodes (non-segmented round worms)

6. Parasitic higher plants (ex. mistletoe, dodder)

7. Other biotic organisms (Viroids, phytoplasmas, etc.)

8. Abiotic causes (air pollution, etc.)

Most fungal and oomycete pathogens

reproduce sexually and asexually.

They can be obligates (need living plant

tissue), non-obligates (can survive in

infested debris), or soil-inhabitants.

Organic Disease Management: Concepts & Facts Sources of Pathogens1. Plants in another location (ex wind-dispersed

spores)

2. Alternate hosts (weeds, other crops)

3. Insect vectors

4. Infested seed

5. Infested debris (also tobacco)

6. Survival structures (ex. fungal sclerotia,

nematode cysts)

7. Live in soil in absence of host

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White Mold

Cabbage cf. Helene Dillard

sclerotia

White Mold

Snap Bean cf. Helene Dillard

TomatoWhite Mold

Dispersal Mechanisms

1. Wind

2. Rain and irrigation

3. Soil

4. Seed

5. Insects and other vectors

6. Humans (handling, equipment)

Management Practices1. Control the Source of Pathogens.

ex. Pathogen-free seed, remove diseased plant tissue.

2. Minimize the Opportunity for Dispersal.

ex. Cover soil with mulch, water base of plant.

3. Reduce Plant Susceptibility.

ex. Select disease resistant varieties.

4. Make Environment Less Favorable for Disease

Development.

ex. Reduce leaf wetness.

5. Examine Plants Weekly. Identify Cause of Problems.

6. Apply Fungicides.

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Pathogens change!

- new strains

late blight, cucurbit downy mildew

- new hosts

Phytophthora blight (beans)

- new pathogens in USA

basil downy mildew

Organic Disease Management: Concepts & FactsBasil

Downy

Mildew

cf. Rob Wick

Sporangiospores (aka conidia)

produced asexually.

Disease occurrence changes

associated with environment changes

- Powdery mildew of lettuce occurred on

Long Island during dry fall 2013.


Adriana

Butterhead

(Boston)

Ideal Cos

Romaine

Pathogen host range: narrow to broad

- Cucurbit downy mildew pathogen exists as

pathotypes infecting different cucurbit types.

- Cucurbit powdery mildew pathogen infects verbena.

- Phytophthora blight occurs on cucurbits, pepper,

eggplant, tomato, snap + lima beans, and some weeds.

- White mold – 100s of crops and weeds.


Challenges to successful rotation:

- host range of pathogen

- pathogen ability to survive in soil

- dispersal mechanisms of pathogen

- pathogen population able to

‘explode’


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Late blight is a unique disease.

Highly contagious and destructive.

A ‘community’ disease that has to

be managed by all.

Occurrence needs to be reported.

Organic Disease Management: Concepts & FactsLate blight pathogen (Phytophthora infestans) life cycle

Complete cycle: 4-10 days

100,000 – 300,000 sporangia

cf. Bill Fry

Managing Late BlightDestroy cull potato tubers and volunteers.Destroy tomato volunteers and solanaceous

weeds.Grow resistant varieties. Use certified seed potatoes. Monitor occurrence reports (USABlight). Apply fungicides, best preventively.Scout ALL year. REPORT! Submit sample.Destroy planting hot spots.Destroy plants with unmanaged late blight

promptly.

Resistant varieties vary in ability to

suppress disease. Some disease occurs.

Some late blight resistant tomatoes can provide

high levels (Ph2 and Ph3 genes).

Cucumber downy mildew – poor* or good.

Cucurbit powdery mildew – poor* to good.

* Excellent control in integrated program with fungicides.


Defiant PHR Mt Fresh Plus 9-14-12

Ph2 + Ph3

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9-14-12Legend Mt Fresh Plus

Ph2

9-14-12Plum Regal Mt Fresh Plus

Ph3

9-14-12New Yorker Mt Fresh Plus

Ph1

9-14-12Juliet Mt Fresh Plus

Reported resistant

Plant diseases cannot be cured.

Fungicides, especially organic ones, act

on pathogens prior to infection.

Critical to success to begin applications

very early in disease development.


There is a lag time between

infection and symptom appearance

(latent period).

Critical to success to begin applying

fungicides very early in disease development.


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18 Aug 2005

First symptoms of

downy mildew on

cucumber.

About 6 days after

spore dispersal to

area.

25 Aug 05

18 Aug 05

18 Aug 05 25 Aug 05 29 Aug 05

Ensuring good fungicide timing:

- decide what diseases to treat

- decide what products to use; source

- get sprayer ready, calibrated, old

nozzles replaced, etc.

- scout routinely

- use disease forecast programs

- monitor occurrence


Late Blightof Tomatoand Potato

http://www.usablight.org/

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Downy Mildew on Acorn Squash

Cucurbit Downy MildewIdeal Disease to Forecast Occurrence:

No survival over winter (no sexual reproduction).

No other crop hosts. Not seed-borne.

Only sources of pathogen north of Florida:

- Long-distance, wind-dispersed spores (asexual).

- Infected transplants (rare source).

CDM Forecast System is Unique:Predicting pathogen movement. AND

Conditions favorable for infection.

http://cdm.ipmpipe.org

Customized alerts via text or e-mail.

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Spore Exclusion Tunnel (Lou Lego)

Efficacy is not considered by EPA

when making registration decisions

for fungicides.


Biopesticides: Microbial Fungicides Actinovate AG. 0.0371% Streptomyces lydicus.

Companion. 0.03% Bacillus subtilis GB03.

Contans WG. 5.3% Coniothyrium minitans CON/M/91-08.

MeloCon WG. Paecilomyces lilacinus strain PL251.

RootShield (formerly PlantShield HC). 1.15% Trichoderma

harzianum Rifai strain KRL-AG2.

SoilGard 12G. 12% Gliocladium virens strain GL-21.

Taegro. Bacillus subtilis var. amyloliquefaciens strain FZB24

24.5%. Labeled for fungal root diseases.

Biopesticides: Microbial Fungicides Serenade. 14.6% Bacillus subtilis strain QST 713.

Serenade Soil. 1.34% Bacillus subtilis strain QST 713.

Cease. 1.34% Bacillus subtilis strain QST 713. Greenhouse.

Sonata. 1.38% Bacillus pumilus strain QST 2808.

Subtilis Biological Fungicide. 2.75% Bacillus subtilis strain MBI600.

Tenet WP. 2% Trichoderma asperellum and 2% T. gamsii.

(naturally occurring substances)

Kaligreen, MilStop. Potassium bicarbonate.

OxiDate, TerraClean. 27% hydrogen dioxide.

KeyPlex 350 OR. defensive proteins (alpha-keto

acids) and secondary and micronutrients.

SafeStrike. Blend of natural oils and surfactants,

containing vitamens, minerals, enzymes,

antioxidants, and plant hormones

Biopesticides: Biochemical Fungicides Biopesticides: Biochemical Fungicides Mildew Cure (formerly GC-3 Organic fungicide). 30%

cottonseed oil, 30% corn oil, 23% garlic extract.

Organocide. 5% sesame oil.

Promax and Proud-3. 3.5% and 5.6% thyme oil.

Regalia. 5% extract of Reynoutria sachalinensis.

Sporatec AG. 18% rosemary oil, 10% clove oil, and

10% thyme oil.

Trilogy. 70% clarified extract of neem oil.

Timorex Gold. 24% tea tree oil. Not registered in USA .

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Other Organic Fungicides

Nu-Cop HB. 77% copper hydroxide.

Microthiol Disperss. 80% sulfur.

JMS Stylet-Oil. 97.1% paraffinic (mineral) oil.

Saf-T-Side. 80% petroleum oil. Tritek is new name.

Many biopesticides CAN be used

with copper fungicides.

- organism is tolerant of copper

- active ingredient is chemical

produced by biocontrol agent

Check label


A fungicide approved for organic

production is not devoid of potential

harm to the applicator, workers, or

the environment.

Copper can cause irreversible eye damage.

Read the label! It is a legal document


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Diagnosis challenges – atypical symptoms


typical late blight leaf spot is large with wilted border

and pathogen growth on underside.

Late Blight

TomatoDrought Stress

Late Blight - Tomato

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Keep records about disease occurrence:

- when first seen

- how severe disease becomes; pictures

- perception of impact

- perception of control

Organic Disease Management

On the Web:

eOrganic

Plant Disease Management Reports

IR-4 Biopesticides & Organic Support

Organic Disease Management: Resources

ProductEvaluations

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Disease Folder on Flash Drive5.1_Plant Disease Basics_Penn State Extension_Start Farming Factsheet.pdf

5.2_Diagnosing Plant Problems_Penn State Extension_Start Farming Factsheet.pdf

5.3_Ecological Disease Management_Penn State Extension_Start Farming Factsheet.pdf

BFTeachingActivities (folder)Exercise 1 Reading Labels_Copper.docx

Exercise 2 Calculating small quantities_Copper.docx

Exercise 3 Calibration_Copper.docx

Plant Disease Pathogen Bio and Mgt Exercise_McGrath-DuPont-classroom setting.docx

Plant Disease Scouting ID and Management Exercise_DuPont_McGrath (modified for

classroom).docx

Science and stories storyteller version.pdf

Teaching Science using Stories.pdf

The Disease Triangle_Koenig_UF.docx

Value of Storytelling as a Teaching Tool_Stewart.docx

eOrganic Description MTM 2013.docx

Biopesticides_Veg Diseases_2013.doc

NEVF Conf 2013-Organic copper.docPhotographs (folder)

Veg Disease Master Gardener Talk March 2013.pptx

Types of Plant Pathogens · 2017-01-23 · 1/23/2017 6 18 Aug 2005 First symptoms of downy mildew...

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Transcript of Types of Plant Pathogens · 2017-01-23 · 1/23/2017 6 18 Aug 2005 First symptoms of downy mildew...