Basic Plant Pathology for Franklin County Master Gardener Volunteers. Nancy J. Taylor Plant Pathology Department Ohio State University

Basic Plant Pathology for Franklin County Master Gardener Volunteers Nancy J. Taylor Plant Pathology Department Ohio State University

https://www.youtube.com/watch?v=h4 PuP_QbD14

Mildews

Mildews Rots

Mildews Rots Rusts

Mildews Rots Diebacks Rusts

Just what is a plant disease?

Just what is a plant disease? A Plant Disease: Causes injury to plants Increases in severity and is progressive over time May be caused by a living or non-living agent

Major Causes of Plant Diseases Abiotic Non-living, or caused by a nonliving agent. Noninfectious, caused by an environmental factor Biotic Living, or caused by a living agent. Also infectious, caused by an agent which can spread from one plant to another

Biotic causes of plant diseases: Fungi Bacteria Viruses Nematodes Phytoplasmas, virions, others

Fungal Plant Diseases Fungus or Fungi

Fungi Mostly microscopic Most are multicellular Made up of filaments Cannot produce their own food Many form complex reproductive structures Most reproduce by producing spores Nonmotile Can actively penetrate plants

Fungi?

Biotic causes of plant diseases: Fungi Bacteria Viruses Nematodes Phytoplasmas, virions, others

Bacterial Plant Diseases

Bacteria Single celled Each is smaller than a fungal spore Most do have cell walls Do not form complex structures Some are slightly motile using flagella (tails) Cannot actively penetrate plants

Bacterial Diseases?

Biotic causes of plant diseases: Fungi Bacteria Viruses Nematodes Phytoplasmas, virions, others

Viral Plant Diseases Virus or Viruses

Brunt, A.A., Crabtree, K., Dallwitz, M.J., Gibbs, A.J., Watson, L. and Zurcher, E.J. (eds.) ( 1996 onwards). `Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 20th August 1996.'

Viruses Too small to see with microscope Cannot reproduce outside of living cells Most consist of nucleic acid (DNA) and a protein coat Most require an opening to infect Cannot move by themselves

Viral Diseases?

Nematode Plant Diseases Nematodes

Plant Parasitic Nematodes Nonsegmented roundworms Very small, some barely visible to naked eye Can be found everywhere Most are harmless, even beneficial Reproduce by laying eggs

Nematode Diseases?

What causes infectious plant diseases? Fungi Bacteria Viruses Nematodes Others Parasitic plants Bacteria without cell walls phytoplasmas, spiroplasmas Filamentous bacteria actinomycetes Viroids Straminophiles (water molds)

Disease Cycle

Disease Cycle The stages of development of the pathogen and its effect on the host plant.

Disease Cycle

Disease Cycle Inoculation: The pathogen comes into contact with the host or host organ Penetration: The initial invasion of the host by the pathogen Initial Establishment: The pathogen begins to obtain nutrients from the host Growth and Reproduction: Spread of the pathogen within the host Dissemination: Pathogen moves or is moved to another host or host organ Overwintering/Oversummering: Survival during adverse conditions

Disease Cycle

Disease Cycle Cherry Leaf Spot

New York State Agricultural Experiment Station for use of this figure. Taken from Tree Fruit Crops IPM Disease Identification Sheet No. 8.

Plant Diseases - Symptoms and Signs

Symptoms of plant disease The response or responses of a plant to an irritant, in this case a plant disease. How the plant responds to a pathogen The appearance of the diseased plant.

Signs of plant disease The visible presence of the pathogen in or on the plant. The parts or products of the pathogen which are found in or on the plant.

Which diagnosis is more definitive? Symptoms? Signs?

Leaf spot A dead area on a leaf. May be circular, angular or irregular.

Apple scab

Black spot Rose

Early Blight- Tomato

Tar Spot- Maple

Angular Leaf Spot- Cucurbit

Bacterial Leaf Spot- English Ivy

Leaf scorch or leaf tipburn Leaf death from the edge of the leaf inward. Usually in a uniform pattern on the leaf and may be uniform throughout the plant.

Scorch

Powdery Mildew Whitish growth on the plant surface, usually on leaves but may be on stems.

Powdery Mildew- Cucurbit

Powdery Mildew- Crabapple

Powdery Mildew- Sycamore

Powdery Mildew

Powdery Mildew- Lilac

Leaf blister Portions of the leaf are raised (distorted).

Peach Leaf Curl

Scab Rough, crusty spot or area on the surface of the plant tissue.

Apple Scab

Pyracantha Scab

Defoliation Loss of leaves. Leaf drop.

Sycamore Anthracnose

Chlorosis/Chlorotic Yellowing of normally green tissue

Pin Oak Chlorosis

Pin Oak Chlorotic

Dogwood Normal

Wilt Drooping of plants or plant parts, usually due to lack of water in the plant

Verticillium Wilt Tomato

Bacterial Wilt Cucumber

Root Knot Nematode

Verticillium Wilt Maple

Blight Sudden death of leaves, flowers, or stems. Usually occurs throughout a group of similar plants.

Botrytis Blight Geranium

Early Blight- Tomato

Fire Blight Apple

Pustule A raised, blisterlike area resulting from the growth of a pathogen beneath the surface

Fungal Pustule

Fungal Pustule Sphaeropsis

Fungal Pustule Rust

Rust Pustule Geranium

Rust Pustules Geranium

Canker A dead area or lesion on a stem, may be raised or sunken.

Canker

Nectria Canker Apple

Nectria Canker Apple Pustules

Early Blight Tomato

Fire Blight Apple

Gall Swollen or overgrown tissue on a plant.

Crown Gall Rose

Black Knot Plum

Root Knot Nematode Tomato

Root rot Death of roots. Softening, discoloration and/or disintegration of roots resulting from an infectious agent

Root Rot Rhododendron

Plant Diseases Symptoms=Plant s appearance Signs=Pathogen s appearance

DISEASE TRIANGLE

= HOST = Susceptible Plant

Virus Bacterium Nematode Fungus Pathogen Parasitic plants Abiotic factors Mollicutes Flagellate Protozoa

Favorable Environment

Environment Host Pathogen

Environment Host No Disease Pathogen

Environment Host ENPHYTIC DISEASE Pathogen

Environment Host Pathogen EPIPHYTOTIC DISEASE

Environment Host Pathogen Manage the ENVIRONMENT to reduce plant disease.

Environment Host Pathogen Manage the PATHOGEN to reduce plant disease.

Environment Host Pathogen Manage the HOST to reduce plant disease.

Environment Host Pathogen

Basic Plant Pathology for Ohio s Master Gardeners Understand the difference between abiotic and biotic diseases Recognize the diversity of plant pathogens Understand the disease cycle its impact on disease development and control Understand the disease triangle its effect on disease control Recognize some common symptoms of plant disease

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