Transcript Plant Diseases

Plant Diseases
• A disease is defined as any type of
injurious abnormality
• A pathogen is any biological agent that
causes an injurious abnormality
Plant diseases
• There are 4 types of commonly recognized
pathogens
– Virus
– Bacteria
– Fungi
– nematodes
Signs and Symptoms
• Symptom is the plants response to
attack by a pathogen
• Sign is structures produced by the
organism ( spore producing structures,
mycelium)
Virus
Tobacco Mosaic Virus
TMV
TMV
Virus symptoms
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Unthrifty plants
– Slow to grow
– Mosaic light spots and stripes
Aster Yellows
Acts like a virus but is a mycoplasma
Virus indexing
• If you are buying cloned plants they will
often say Virus Indexed.
• That means they are tested and proven to
be virus free.
• very important when buying raspberry
plants or strawberry plants
Bacteria- fire blight
Fire Blight
Bacterial symptoms
• Rapid spread, can be spread by wind or
insects,humans
• Soft rots producing snotty oooz
• Can be really smelly
Fungi
Botrytis – Grey Mold
Fungus
Fungus
• Signs: mycelium, fruiting bodies
• Symptoms: necrotic areas, wilt when
fungus attacks the roots
• Phloem blockage, xylem blockage
Nematodes
• Root Knot Nematode
Nematodes
• Feed on roots and allow secondary
infections
• Cause small tumors on roots
• Damage to plants by fungi bacteria and
nematodes can be classified in 3 types
– Direct damage by feeding
– Toxins injected into the plant
– From secondary infections that enter via the
physical damage caused by the primary agent
Crop infesting diseases are
troublesome because they will
continue to reproduce and feed
UNTIL
• 1. The food is used up
• 2. the environment becomes unfavorable
• 3. they are destroyed by some predator/
disease
Disease transmission
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Water is necessary for fungus infection
Insects
Humans
Infected seed
Infected soil – brought in on shoes or
tractor tires
Curing or avoiding plant disease?
• Any of the previous factors can be interrupted
• Cultural control
– Roguing, sanitation, plowing plant refuse under,
stirring the soil to expose egg masses, keep plants
healthy, avoid smoking, regulate pH, hot water
treatment of seed,
• Chemical control
What are those letters?
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V Verticillium Wilt Virus
F Fusarium Wilt Virus
N Nematodes
T, TMV, ToMV Tomato Mosaic Virus
BSK Bacterial Speck
ST Stemphyllium (Grey Leaf Spot)
FCR Fusarium Crown Rot