General kinds of plant diseases: What is a plant disease? 1. Low Temperature. Kinds of non-infectious diseases:

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1 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. Not caused by something living 1. Low Temperature Kinds of non-infectious diseases: 2. High Temperature 3. Unfavorable Oxygen Levels 1

2 4. Unfavorable Water Levels 5. Lightning 5. Hail 5. Wind Sweet Corn 6. Mineral Excesses 7. Mineral Deficiencies Boron Deficiency Salt Injury 2

3 7. Mineral Deficiencies 7. Mineral Deficiencies Nitrogen deficiency caused by high ph Nitrogen Deficiency 7. Mineral Deficiencies 8. Pesticides (Herbicides) Calcium Deficiency Bitter Pit Stinger Sencor 9. Air Pollution Toxicity 10. Other Soil Compaction Sulfur Dioxide Ozone 3

4 10. Other.Naturally Occurring Toxic Chemicals High salt accumulation lti General kinds of plant diseases: 1. Non infectious: Can not be transmitted (or moved) from a disease plant to a healthy plant. 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 Plant Disease Triangle Pathogen Pathogen Environment Susceptible Host Environment D I S E A S E Susceptible Host Kinds (what causes) of Infectious diseases: 1. Bacteria 2. Parasitic Seed Plants 3. Fungi 4. Viruses 5. Nematodes 6. Phytoplasma 1. Bacteria 4

5 Bacterial Diseases Bacterial Canker--Cherry Watermelon Fruit Blotch Bacteria in Potato Bacterial Blight in Peas Bacterial Streaming 2. Flowering Seed Plants 5

6 Dodder on Potato Dodder on Potato Dwarf Mistletoe on Conifer Dwarf Mistletoe on Conifer True Mistletoe 3. Fungi 6

7 Powdery Mildew Powder Mildew The thumb test Powdery Mildew Stripe Rust Stripe Rust --- Close-up Photo Rust on Poplar 7

8 Rust on Hollyhock Snow Mold Snow Mold Closeup Snow Mold Fungus Spores Silver Scurf & Black Dot Fungus Killing Seedling Silver Scurf Black Dot 8

9 4. Virus Virus Needs a vector Rose Mosaic Rose Mosaic ZYMV in Squash Pepper Mild Mottle Virus in Pepper 9

10 Beet Curley Top Virus Beet Curley Top Virus Tomato Squash Tomatoes Nematode 5. Nematode -Size: 0.25 to 3 mm long -Live inside and outside plants -Most attack roots but some can attack above ground plant parts Nematode Nematode Damage in Potato Stylet 10

11 Nematode Damage in Onions Nematode Damage in Carrots Nematode Damage in Carrots 6. Phytoplasma (Mycoplasma) Specialized Bacteria Live in phloem Obligate parasites Need two things: Eggs 1. Living Host 2. Vector Phytoplasma in Potato General Definitions: 11

12 General Definitions: Pathogen or Causal Agent: A specific living organism that causes a contagious disease General Definitions: Symptoms: Any visual reaction of a plant to a disease Living organism: Bacteria, fungus, nemotode, virus, plant etc General Definitions: Inoculum or spores: Portions of the pathogen capable of being moved and causing a new infection. General Definitions: Life Cycle The series of changes undergone by the organism.the pathogen in this case. Typical Fungus Life Cycle General Definitions: Susceptible (susceptibility): A plant that can be infected by a pathogen 12

13 General Definitions: Resistant: The ability of the plant to reduce or suppress damage of the pathogen. 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 13

14 C. Interveinal Yellow or Necrosis D. Mosaic (Green, Yellow, Necrotic Mix) Wilting 2. Wilt One of the Most Common Symptoms Caused by root rot or lack of water? Wilting 3. Death of Plant Tissue 14

15 A. Death (Necrosis) B. Rot C. Canker 4. Leaf and/or Fruit Drop Leaf Drop 5. Abnormal Growth (Increase, appearance) of the Host 15

16 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 16

17 Stunting in Onions Stunting in Sweet Corn Stunting in Peas Stunting in Potatoes Loose Smut in Wheat 7. Replacement of Plant Tissue with the Pathogen 17

18 Ergot in Grass Common Corn Smut Symptom: Any visible reaction of a plant to a disease Sign Sign: Any visible part of the pathogen Herbicide Injury on Onion Not Disease Problems 18

19 Insect Injury on Lilac Leaf Miner on Beet Insect Injury Mite Injury on Grape What Causes This Symptom? Psyllid Injury on Hackberry Aphids on Poplar 19

20 1. Breeding For Resistance Disease Control A. Removal of Infected Plant Nearby 2. Inoculum (spore) Reduction B. Removal of Alternate Hosts C. Pruning of Host to Remove Infected Areas Hollyhock Rust Mallow Rust 20

21 D. Cleaning of Tools (Sanitation) E. Crop Rotation This Year s Watermelon Field Last Year s Watermelon Field Watermelon 2 Years in a Row 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 21

22 3. Chemical Control The Use of Fungicides Two Kinds: A. Protectant Go where applied B. Systemic Go 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 be considered D. Temperature E. Moisture F. Beneficials Considerations Cont. G. Residues of the Fungicide H. Proper Chemical 4. Biological Control Kinds A. Parasites B. Competitors 22

23 Diagnosing Diseases Practicing Diagnosing Ask questions LOTS of questions. Remember the Disease Triangle Things to consider: When and where the disease appeared Damage patterns: Uniform vs. Non-uniform What signs and symptoms do you see 23

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25 Healthy 25

26 Plant Pathology Test 1. What are the two remaining components to the plant disease triangle? 1. Host What are the two remaining components to the plant disease triangle? 1 Host 1. Host 2. Pathogen 3. Environment 26

27 2. If one of the three components is missing or unfavorable, will a plant disease problem occur? Yes No 2. If one of the three components is mission or unfavorable, will a plant disease problem occur? Yes 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 27

28 5. Name two additional general groups of plant pathogens? 5. Name two additional general groups of plant pathogens? Nematodes Nematodes Bacteria Fungi Virus Nematode Phytoplasma 6. Name three general ways to control a plant disease? Pesticide 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 methods for the control of a plant disease? 1. Rouging 2. Pruning 3. Solarization 4. Steam treatment of soil 5. Cleaning equipment 6. Removal of alternate hosts 9. What is the difference between a systemic and protectant fungicide? The protectant only protects where it is applied The systemic moves in the plant and will possibly protect new plant growth. 28

29 10. Name a common plant disease? Powdery mildew on rose 11. Identify an environmental condition that favors the disease that you named in question 10? Overhead watering Planting in the shade 12. Why does the environmental condition mentioned in question 11 favor the disease? 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 plant leaves 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!!!!! 29

30 16. Why is it sometimes important to remove 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 instead of a protectant material if both were available for controlling the 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 tools when pruning disease wood caused by some plant diseases? 19. What is a plant disease? Any problem with a plant that causes (results) in a reduction in yield and or appearance Spores of the pathogen could be on the pruning tools and could be spread. 20. Why is crop rotation important for controlling some kinds 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 plant pathogens that can never be seen without the aid of a microscope? Viruses Bacteria Phytoplasma Nematodes? 30

31 22. Name the two most common factors that contribute to plant problems that are not caused by a infectious disease? Too much water Not enough water Too much fertilizer Too little fertilizer 31