master gardener training: plant pathology...management handbook • use the handbook to answer...
TRANSCRIPT
Master Gardener Training:Plant Pathology
Brooke Edmunds, Ph.D.OSU Extension, Community Horticulture
• Extension Community Horticulturist
• Trained as plant pathologist
– M.S. in landscape plant diseases
– Ph.D. in vegetable diseases
• Work in plant diagnostic clinics
– Iowa, N. Carolina, Colorado, Oregon
– Homeowner & commercial samples
Resource Materials
• Sustainable Gardening: Chapter 15 & 16
• PNW Disease Management Handbook https://pnwhandbooks.org/plantdisease/
• Handout: How to use the PNW Disease Management Handbook
What is a plant disease?
• Any disorder that is detrimental to the health and value of the plant or any of its parts
http://www.permaculture.org.au/images/plant_sick.gif
Diseases Categories
• Biotic
– Caused by another living organism
– Can spread to a healthy plant
• Abiotic
– Caused by a nonliving factor
– Cannot spread to a healthy plant
Graphic from: https://www.flickr.com/photos/edrethink/8731759135
Biotic & Abiotic Problems
• Fungi• Bacteria• Virus• Nematodes• Parasitic plants
What else???
• Mechanical factors– Construction– Transplanting– Lawn mower blight
• Environmental factors– Temperature– Light– Moisture– Wind– Soil– Pollinator issues
• Chemical factors– Pesticides– Nutritional issues
Three conditions required for biotic diseases to occur
Ven diagram: http://commons.wikimedia.org/wiki/File:Plant_Disease_Triangle.svg; Stool drawing: Openclipart
Disease
Host
Environment Pathogen
Disease
Ho
st
Three conditions required for biotic diseases to occur
Stool drawing: Openclipart
Disease
Environment
Host plant
Pathogen
Symptoms
The visible effect of disease on the plant
Signs
Physical evidence of the pathogen
VS.
Plant Pathogen Groups
• Fungi
• Bacteria
• Phytoplasmas
• Viruses
• Nematodes
• Parasitic plants
From Plant Pathology – G. Agrios
https://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroFungi.aspx
Common features: Mycelium & hyphae
http://4.bp.blogspot.com/-okt31DN4hp0/UDUxD8jjJAI/AAAAAAAAGzU/4UM7Rc48z5o/s1600/myceliumDSC_0015.jpg
http://cdn.phys.org/newman/gfx/news/hires/2012/butten+mushrooms+on+substrate.jpg
Photo: https://flic.kr/p/ZLJYid
Common Features: Fruiting Bodies
Common features: Fruiting Bodies
• Most fungi produce some form of a fruiting body
• Can help with ID
Photo: http://bulletin.ipm.illinois.edu/photos/phyllosticta.jpg
Common Features: Reproductive Spores
http://oi30.tinypic.com/e6aonp.jpg
http://ars.usda.gov/is/br/canadathistle/teliospore.jpg
Example: Rust spores
Fungal Leaf Spots
Japanese Maple (Acer palmatum): Verticillium wilt (Verticullium dahliae)
Photo: Neil Bell
Vascular Wilts
http://pnwhandbooks.org/plantdisease/sites/default/files/imagecache/image_on_page/images/vascular_streaking.jpg
Streaking in Vine Maple
Phytophthora sp. (Oomycetes)
https://pnwhandbooks.org/plantdisease/pathogen-articles/common/oomycetes/diagnosis-control-phytophthora-diseases
Cankers Root rot Foliar & twig dieback
Bacteria
Bacterial Blight
(lilac, fruit trees)
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Phytoplasmas
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcSJmGrQaucBvEHM9lzPzpAv4WVvu8Re0O6GT1-xVrKTTnsabEgV
• Similar but not quite like a bacteria
• Obligate parasite
– What does that mean??
– Survives only in a living host (plant & insect vector)
Viruses
Tomato Spotted Wilt Virus (TSWV)
http://msue.anr.msu.edu/uploads/images/10-16TSWV-peppersRON.jpg
Tomato Spotted Wilt Virus (TSWV)
http://msue.anr.msu.edu/uploads/images/10-16TSWV-tomato-fruitRON.jpg
Photo: Robin Rosetta http://pnwhandbooks.org/plantdisease/sites/default/files/imagecache/image_on_page/images/rhododendron_necrotic_ringspot_virus_closeup.jpg
Necrotic Ringspot Virus on Rhododendron
Nematodes
• Round worm (round in cross-section)
• Animal & plant pathogens
• Not all parasitic
http://www.jgi.doe.gov/sequencing/why/hglycines.jpg
http://www.fao.org/docrep/009/a0100e/a0100e1h.jpg
http://www.apsnet.org/edcenter/illglossary/Article%20Images/stylet.jpg
https://www.youtube.com/watch?v=1JgTDnYPzjQ (1:45)
Ditylenchus dipsaci on onion
http://www.omafra.gov.on.ca/IPM/english/onions/diseases/bulb_stem_nematode.html
Healthy Damaged by Ditylenchus
Broadleaf mistletoe (Phoradendron sp.) on Quercus
http://upload.wikimedia.org/wikipedia/commons/8/86/Valley_Oak_Mount_Diablo.jpg
Parasitic Plants
What is dodder?
• Cuscuta sp.
• Parasitic plant
• Grows from seed and then plant to plant
Photo:http://www.fcps.edu/islandcreekes/ecology/dodder.htm
Photo:http://www.fcps.edu/islandcreekes/ecology/dodder.htm
Dodder grows into host plant
Key Characteristics?
Fungi Bacteria Phytoplasma
Viruses Nematodes
Parasitic Plants
Understanding Disease Cycles
Disease cycle example: Apple Scab(caused by the fungus Venturia inaequalis)
http://pnwhandbooks.org/plantdisease/sites/default/files/imagecache/image_lightbox/images/apple_scab_box143-005.jpg
Apple scab symptoms on leaves
http://www.agf.gov.bc.ca/cropprot/tfipm/images/leafscab.jpg
http://archive.agric.wa.gov.au/objtwr/imported_images/life-cycle-of-apple-
scab-fungus-sm.jpg
Principles of Biotic Plant Disease Management
1. Exclusion
2. Avoidance
3. Eradication
4. Protection
5. Resistance
Graphic: https://pixabay.com/static/uploads/photo/2014/04/02/16/18/toolbox-306888_960_720.png
1. Exclusion• Keep new diseases out of U.S. and Oregon
– Quarantines
– Inspections
– Certifications
http://www.city-data.com/forum/members/lifeshadower-623051-albums-california-folder-pic60811-california-agricultural-checkpoint-along-i-5.jpg
2. Avoidance
• Example: “Damping off”
• Avoid by planting in drier and warmer soils
3. Eradication
• Crop rotation
• Sanitation
• Remove alternate hosts
• Chemical applications
• Heat treatment*
Sanitation
• Eradicate by removing infected plant debris
http://ucanr.edu/blogs/strawberries_caneberries//blogfiles/17490_original.jpg
Fusarium on strawberry
What to do with diseased debris?
Burn
Bury
HOT compost
Not effective for composting diseased plants!
http://www.southerncompost.com/wp-content/uploads/compost-07.jpg
4. Protection
• Treat plant with pesticide before it becomes diseased
• Acts like a shield
http://upload.wikimedia.org/wikipedia/commons/1/1c/Disposable_gloves_09.JPG
5. Resistance
• Some plant varieties are resistant to certain diseases
• Very specific interaction
• Note: Resistance is not always 100%
Stool drawing: Openclipart
Disease
Environment
Host plant
Pathogen
Cornell University resistant vegetable tables
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Activity Time!
Station #1: How to use the PNW Disease Management Handbook
• Use the handbook to answer questions
Station #2: Recognizing Symptoms & Signs
• Match the photo to the definition using the provided glossary
Work at your own pace & it’s okay to work together