1. Low Temperature Kinds of non-infectious diseases: 2 ......the plant in a shady area, or heavy...
Transcript of 1. Low Temperature Kinds of non-infectious diseases: 2 ......the plant in a shady area, or heavy...
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What is a plant disease?
Any problem with a plant that causes a reduction in yield or
appearance.
General kinds of plant diseases:
1. Non infectious:– Can not be transmitted (or moved) from a
disease plant to a healthy plant.p y p
– Not caused by something living
Kinds of non-infectious diseases:
1. Low Temperature
2. High Temperature 3. Unfavorable Oxygen Levels
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4. Unfavorable Water Levels5. Lightning
5. Hail
Sweet Corn
5. Wind
6. Mineral Excesses
Salt Injury
7. Mineral Deficiencies
Boron Deficiency
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7. Mineral Deficiencies
Nitrogen deficiencydeficiency caused by high pH
7. Mineral Deficiencies
Nitrogen gDeficiency
7. Mineral Deficiencies
Calcium DeficiencyDeficiency
“Bitter Pit”
8. Pesticides (Herbicides)
Stinger Sencor
9. Air Pollution Toxicity
OzoneSulfur Dioxide
10. Other…Soil Compaction
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10. Other….Naturally Occurring Toxic Chemicals
High salt l tiaccumulation
General kinds of plant diseases:
1. Non infectious:– Can not be transmitted (or moved) from a
disease plant to a healthy plant.p y p
– Not caused by something living
2. Infectious:– Caused by a living organism that is capable of
moving to and/or infecting another plant.
Plant Disease Triangle
Pathogen
EnvironmentSusceptible
Host
Plant Disease Triangle
Pathogen
DISEASE Susceptible
HostEnvironment
Kinds (what causes) of Infectious diseases:
1. Bacteria2. Parasitic Seed Plants3. Fungi4. Viruses5. Nematodes6. Phytoplasma
1. Bacteria
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Bacterial Diseases
Watermelon Fruit Blotch
Bacterial Canker--Cherry
Bacteria in PotatoBacterial Blight in Peas
Bacterial Streaming
2. Flowering Seed Plants
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Dodder on Potato Dodder on Potato
Dwarf Mistletoe on Conifer Dwarf Mistletoe on Conifer
True Mistletoe
3. Fungi
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Powdery Mildew Powder Mildew
The “thumb test
Powdery Mildew Stripe Rust
Stripe Rust --- Close-up Photo Rust on Poplar
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Rust on Hollyhock Snow Mold
Snow Mold Closeup Snow Mold—Fungus Spores
Silver Scurf & Black Dot
Silver ScurfBlack Dot
Fungus Killing Seedling
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4. Virus
Needs a vector
Virus
Rose Mosaic Rose Mosaic
ZYMV in SquashPepper Mild Mottle Virus in
Pepper
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Beet Curley Top Virus
Squash Tomatoes
Beet Curley Top Virus
Tomato
5. Nematode
Nematode
-Size: 0.25 to 3 mm long-Live inside and outside plants-Most attack roots but some canMost attack roots but some can attack above ground plant parts
Nematode
Stylet
Nematode Damage in Potato
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Nematode Damage in Onions Nematode Damage in Carrots
Nematode Damage in Carrots
Eggs
6. Phytoplasma (Mycoplasma)
• Specialized Bacteria
• Live in phloem
• Obligate parasitesg p
• Need two things:
1. Living Host
2. Vector
Phytoplasma in Potato
General Definitions:
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General Definitions:
• Pathogen or Causal Agent:A specific living organism that causes a
contagious diseaseg
Living organism: Bacteria, fungus, nemotode, virus, plant etc
General Definitions:
• Symptoms:Any visual reaction of a plant to a disease
General Definitions:
• Inoculum or spores:Portions of the pathogen capable of being moved
and causing a new infection.g
General Definitions:
• Life CycleThe series of changes undergone by the
organism….the pathogen in this case.g p g
Typical Fungus Life Cycle
General Definitions:
• Susceptible (susceptibility):A plant that can be infected by a pathogen
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General Definitions:
• Resistant:The ability of the plant to reduce or suppress
damage of the pathogen.g p g
General Definitions:
• Predisposition:Factors that increase the susceptibility of the plant
to infection.
Factors like: too much water, not enough water, too much fertilizer, too little fertilizer, growing the plant in a shady area, or heavy soil.
Symptom:
Any visible reaction of a plant to a disease
Sign:
Any visible part of the pathogen
1. Abnormal Coloration of the Plant Tissue
• A. Yellowing (Chlorosis)
• B. Vein Clearing
• C. Interveinal (between veins) yellowing
• D. Mosaic (green and yellow mixed)
A. Yellowing (Chlorosis) B. Vein Clearing
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C. Interveinal Yellow or NecrosisD. Mosaic (Green, Yellow,
Necrotic Mix)
2. Wilt
One of the Most Common Symptoms
Wilting
Caused by root rot or lack of water?
Wilting
3. Death of Plant Tissue
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A. Death (Necrosis) B. Rot
C. Canker
4. Leaf and/or Fruit Drop
Leaf Drop
5. Abnormal Growth (Increase, appearance) of the Hostpp )
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Crown Gall on Almond Western Gall Rust on Pine
Crown Gall on Dahlia ZYMV on Cantaloupe
ZYMV on Yellow Crook-Neck Squash
6. Stunting of Host
Common Symptom
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Stunting in Onions Stunting in Sweet Corn
Stunting in Peas Stunting in Potatoes
7. Replacement of Plant Tissue with the Pathogeng
Loose Smut in Wheat
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Ergot in Grass Common Corn Smut
Symptom:
Any visible reaction of a plant to a disease
Sign:
Any visible part of the pathogen
SiSign
Not Disease Problems
Herbicide Injury on Onion
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Insect Injury on Lilac Leaf Miner on Beet
Insect Injury
What Causes This Symptom?
Mite Injury on Grape
Psyllid Injury on Hackberry Aphids on Poplar
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Disease Control
1. Breeding For Resistance
2. Inoculum (spore) Reduction
A. Removal of Infected Plant Nearby
B. Removal of Alternate Hosts
Hollyhock Rust Mallow Rust
C. Pruning of Host to RemoveInfected Areas
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D. Cleaning of Tools (Sanitation) E. Crop Rotation
Thi Y ’
Watermelon 2 Years in a Row
This Year’s Watermelon Field
Last Year’s Watermelon Field
F. Changing Growing (Cultural) Practices
G. Disease Free Seed and Propagating Material
Silver Scurf Fusarium and Blue Mold
H. Steam Treatment of Soil I. Solarization
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3. Chemical Control
• The Use of Fungicides
– Two Kinds:
A ProtectantA. ProtectantGo where applied…
B. SystemicGo everywhere, even where they are not
applied
Fungicides Do One of Two Things:
A. Delay or stop fungus growth (fungistatic)
B. Kills the fungus (Fungicidal)
For Chemical Control to be Effective, the Following Areas
Need To Be Addressed
Considerations:
A. Identification of the Pathogen
B. Proper Timing of Fungicide Use
C Life Cycle of the Pathogen needs to beC. Life Cycle of the Pathogen needs to be
considered
D. Temperature
E. Moisture
F. Beneficials
Considerations Cont.
G. Residues of the Fungicide
H. Proper Chemical
4. Biological Control
• KindsA. Parasites
B C titB. Competitors
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Practicing Diagnosing
Diagnosing Diseases
• Ask questions………LOTS of questions.
• Remember the Disease Triangle
• Things to consider:• Things to consider:– When and where the disease appeared
– Damage patterns: Uniform vs. Non-uniform
– What signs and symptoms do you see
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1111111111111111111111111111111111111111111111111111111
Healthy
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Plant Pathology Test
1. What are the two remaining components to the plant disease
triangle?
1 Host1. Host
2. ___________
3. ___________
1. What are the two remaining components to the plant disease triangle?
1 Host1. Host
2. Pathogen
3. Environment
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2. If one of the three componentsis missing or unfavorable, willa plant disease problem occur?
• YesYes_______
• No ________
2. If one of the three components is mission or unfavorable, will a
plant disease problem occur?
• YesYes_______
• No XXXX
3. Which of the following is an example of a noninfectious
disease?________Low Temperature
Bacteria________
________Mineral Excess
________Pesticides
________Fungi
________Air Pollution
3. Which of the following is an example of a noninfectious
disease?XXX Low Temperature
Bacteria_____
XXX Mineral Excess
XXX Pesticides
_____Fungi
XXX Air Pollution
4. Which of the following is not a symptom caused by a plant
disease?
Wilting_________
Stunting________
Virus __________
Chlorosis________
Yellowing_______
Mortality________
4. Which of the following is not a symptom caused by a plant
disease?
Wilting_________
Stunting________
Virus XXX
Chlorosis________
Yellowing_______
Mortality________
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5. Name two additional general groups of plant pathogens?
• Nematodes__________
__________
5. Name two additional general groups of plant pathogens?
• Nematodes
• BacteriaBacteria
• Fungi
• Virus
• Nematode
• Phytoplasma
6. Name three general ways to control a plant disease?
• Pesticide
• Rouging• Rouging
• Change Environment
7. What is the first thing one should know prior to beginning any kind of plant disease control measure?
Know the disease!
8. Name three sanitation methodsfor the control of a plant disease?
1. Rouging
2 Pruning2. Pruning
3. Solarization
4. Steam treatment of soil
5. Cleaning equipment
6. Removal of alternate hosts
9. What is the difference betweena systemic and protectant fungicide?
• The protectant only “protects” where it is p y papplied
• The systemic moves in the plant and will possibly protect new plant growth.
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10. Name a common plant disease?
• Powdery mildew on rose
11. Identify an environmentalcondition that favors the diseasethat you named in question 10?
O h d t i• Overhead watering
• Planting in the shade
12. Why does the environmentalcondition mentioned in question 11 favor the disease?
All th t i t d i f t• Allows the spores to germinate and infect.
13. Name a symptom that is caused by this disease from question 11? Carefull!!
• Leaf spots and or discoloration
• Not the white mycelium….that is a sign!
14. What commonly causes plantleaves to be distorted?
• Herbicides
• Insects
• Viruses
15. What is the first question to ask when someone has a problem with a plant?
• What kind of plant is it!!!!!
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16. Why is it sometimes important toremove plant residue from the previous crop before replanting?
• Spores from the previous crop may be found in the residue.
17. When applying fungicide, why would one use a systemic insteadof a protectant material if both were available for controlling thesame disease problem?same disease problem?
• Because the application doesn’t have to be 100 % coverage and new foliage is protected.
18. Why could it be important to disinfect equipment or toolswhen pruning disease wood caused by some plant diseases?y p
• Spores of the pathogen could be on the pruning tools and could be spread.
19. What is a plant disease?
• Any problem with a plant that causes (results) in a reduction in yield and or(results) in a reduction in yield and or appearance
20. Why is crop rotation important for controlling somekinds of plant disease problems?
• Reduce soil borne pathogens in the soil that do not feed (and therefore can not reproduce) on the rotational crops.
21. Name a general group of plantpathogens that can never be seenwithout the aid of a microscope?
• Viruses
• Bacteria
• Phytoplasma
• Nematodes?
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22. Name the two most commonfactors that contribute to plant problems that are not caused by ainfectious disease?
• Too much water
• Not enough water
• Too much fertilizer
• Too little fertilizer