Diseases of Fruits and Vegetables


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Kansas Community Garden Conference
July 8, 2014
Dr. Megan Kennelly

This presentation covers the nuts and bolts of plant pathogens and plant disease management strategies.

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  • Slide 71.
    When packaging a sample: Place sample on a paper towel. Do not wet the towel; Double bag and seal the sample in zippable bags; If shipping, use a crush proof box with seams sealed completely with tape; Be sure to include the sample submission form required by your state.
  • Diseases of Fruits and Vegetables

    1. 1. Diseases of fruits and vegetables Community Garden Conference July 2014 Megan Kennelly Plant Pathology Kansas State University
    2. 2. Outline  References No way to cover all the diseases!!  Plant Path 101 Abiotic vs biotic problems  Tomato diseases  Ask questions any time!
    3. 3. “What is wrong with my plant?” *Environmental stress *Nutritional deficiency *Chemical injury *Insect damage *Infectious Disease: fungi, viruses, bacteria, nematodes
    4. 4. Two Types of Plant Disease Abiotic • noninfectious • weather stress • nutrient deficiency • chemical injury • soil factors • can make plants more susceptible to infectious diseases Biotic – Caused by infectious agents such as fungi, bacteria, viruses, nematodes
    5. 5. Biotic/infectious diseases: Disease triangle Host Pathogen fungi bacteria nematodes viruses Environment
    6. 6. Kansas = Weather Stress Hot, cold, drought, flooding (**recent story)
    7. 7. Symptoms & Signs Symptom Change in growth by the plant Sign Visible presence of a pathogen
    8. 8. Symptoms – change in growth. Not diagnostic Leaf spots Wilt Septoria -MMK TSWV -MMK Eggplant drought -MMK
    9. 9. Signs On Watermelon -David B. Langston, University of Georgia, Bugwood.org
    10. 10. Signs Photos courtesy Oliver T. Neher, University of Idaho, Bugwood.org
    11. 11. Microscopic signs
    12. 12. Infectious agents: pathogens Viruses Bacteria Fungi Nematodes most microbes are not pathogens
    13. 13. Abiotic stresses/injuries Soil structure Fertility/pH Phytotoxicity from pesticides Water – too much, too little Cold, heat
    14. 14. Possible clues Plant species, variety Planting date or age Weather/watering patterns Soil factors: drainage, compaction Chemical useage Spatial Distribution Timing
    15. 15. Spatial Distribution Random Aggregated Linear Disaster Biotic Abiotic Courtesy Cary Rivard
    16. 16. Copper Sulfate David Gadoury Sensitive variety – see Midwest Guide
    17. 17. Sclerotinia Lettuce Drop - Lettuce Courtesy Cary Rivard
    18. 18. Are multiple hosts affected?
    19. 19. Above ground Bacterial spot, pepper
    20. 20. Roots  Root rots often found in wet soils/poor drainage
    21. 21. To look for root diseases, you need roots Cmm
    22. 22. Wilt Diseases  Pathogen systemically colonizes water conducting system  Infections usually result in death
    23. 23. Papaya ringspot. Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org Papaya ringspot. M TMV tomato. MMK TSWV pepper, MMK Viruses
    24. 24. Viruses can be confused with: Herbicide injury Nutrient deficiencies/toxicities Fungal/bacterial
    25. 25. Alton N. Sparks, Jr., The University of Georgia, www.ipmimages.org Vectors: whiteflies, aphids, thrips Also spread by seed, sap/tools
    26. 26. Bacteria Many symptoms: leaf spots wilts rots galls blights cankers sticky ooze Spread – Insects, seed, transplants, grafting/pruning, WATER
    27. 27. Fungi  Most fungi dispersed by spores  Thread-like growth  Many kinds of symptoms
    28. 28. Winter spore/survival structure Repeating cycle spores http://strawberry.ifas.ufl.edu/ BerryTimes/BVTDec04.htm
    29. 29. Survival
    30. 30. Nematodes  Microscopic worms  Parasitic nematodes have stylet.  Most live in soil/roots.  Root deformity, stunting, yellowing, general decline DAFF Archives, , www.ipmimages.org Root-knot nematode on canteloupe
    31. 31. General management strategies prevention is best
    32. 32. Resistance Resistance can be full immunity or partial/tolerance Using resistant cultivars is critical first step in management Pathogens can overcome resistance genes
    33. 33. Cultural: Rotation Rotate to a non-host Not possible with all diseases Reference books will tell you
    34. 34. Cultural: clean planting material Quality seed Disease-free transplants Disease-free cuttings Sterile pots Sterile potting media/soil-less mix *ex: Pythium in field soil
    35. 35. Cultural: site management Proper spacing Raised beds Water management drainage, drip irrigation Airflow (fans in greenhouse) Staking/trellising
    36. 36. Cultural: sanitation Remove diseased material Control weeds may harbor pathogens or insect vectors Tillage: bury infected debris
    37. 37. Chemicals The label is the law, even for organic products *plants, diseases, sites, rates
    38. 38. Tomato Diseases
    39. 39. Septoria Leaf Spot  Most common fungal leaf disease  Survives in crop debris  Symptoms  Multiple, small black spots develop on leaves and stems; development starts on lower leaves and progresses upward  No fruit spotting
    40. 40. Early blight (Alternaria)  Survives in crop debris  Symptoms  Relatively large, target shaped lesions on leaves; lesions surrounded by yellow border  Progressions from lower to upper leaves  Normally doesn’t affect fruit
    41. 41. Fungal Fruit Rots  Anthracnose (Colletotrichum)  Survives in crop debris  Symptoms  Occurs on ripe fruit  Small, slightly depressed sunken spots  Small, black specks form in the center of the spots  Greatly reduces shelf life
    42. 42. Management of Fungal Leaf/fruit Diseases  Rotate crops (minimum of 3 years)  Clean debris off tools, stakes,  Stake, string or cage plants  Use mulches (plastic, straw)  Use drip vs. overhead irrigation  Avoid working with wet plants  Clean up garden at end of year
    43. 43. Bacterial Leaf and Fruit Spots Bacterial speck • Transmission - Seedborne - Survival on plant debris - Rain splash • Favored by cooler temperatures (64-75 F) and extended periods of leaf wetness • Leaf lesions usually have a bright yellow halo • Fruit spots are black and very small
    44. 44. Bacterial Leaf and Fruit Spots Bacterial spot • Transmission - Seedborne - Survival on plant debris • Warm, wet weather
    45. 45. Bacterial Canker of Tomato Bacterial Canker  Transmission  Seed borne  Overwinters on plant debris  Symptoms  Cankers and branch dieback  Wilt
    46. 46. To look for stem diseases, you need stems
    47. 47. More Bacterial canker  Symptoms  Bird’s eye spot  Lesions with raised brown centers that are surrounded by an opaque white halo
    48. 48. Management of Bacterial Diseases  Start with clean seed or transplants  A few resistant varieties are available for speck  All the same stuff for fungi!
    49. 49. Fusarium and Verticillium Wilt Systemic Fungal Pathogens  wilt symptoms  persistent in soil  crop rotation generally ineffective  Fungicides? No Resistant Varieties • Heirloom varieties may not be resistant New York State Ag Exp. Station
    50. 50. Root Knot Nematode Symptoms - Yellowing, stunting of plants; large galls or knots on roots  Nematodes are persistent  Avoid introduction of nematode with field equipment  Use resistant varieties
    51. 51. Blossom End Rot of Tomato  Physiological disorder caused by calcium deficiency brought on by dry weather  Certain varieties are more prone to damage  Damage more severe early in growing season  Avoid rapid vine growth, excessive nitrogen fertilizer, and soil moisture fluctuations *Also on pepper
    52. 52. Plant Sample Collection  Representative samples: ‘More is better!’  Include roots!  ‘Healthy + Affected’ plants for comparison.  Immediately place in plastic bags.  No wet paper towels.  Keep cool!  Ship Monday – Wednesday.  Include Site history: -