1 Rmnhort Ii Pottorff Path Talk Intro

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1 Rmnhort Ii Pottorff Path Talk Intro

  1. 1. Plant Pathology and Disease Diagnosis Laura Pottorff Colorado State University Cooperative Extension Adams County
  2. 2. Definition Abnormal growth or dysfunction of a ! plant Caused by: ! – biotic (living organisms) • pathogens – abiotic (non-living factors = environmentally induced disease)
  3. 3. Plant Diseases With Historical Impact Saint Anthony’s Fire or Holy Fire ! – Ergot • Claviceps purpurea Irish potato famine ! – Late blight of potato • Phytophthora infestans
  4. 4. Saint Anthony’s Fire Middle Ages ! – historical documents correlate malady with: • cool wet weather • occurs after the introduction or rye grains More common among ! – rural poor – children and feeble – animals also affected Not “contagious” ! – strike one family but not another
  5. 5. St. Anthony’s fire Symptoms ! – hallucinations – tingling skin (like insects crawling under skin) – miscarriages – gangrene due to constrictions of blood vessels. Hospitals dedicated to St. Anthony took ! care of the afflicted.
  6. 6. St. Anthony’s Fire What we know now ! – Fungus called ergot is responsible
  7. 7. Ergot Ergot bodies mixed Multifaceted role in ! ! in flour European history? – contain toxic – French Revolution alkaloids – Peter the Great • Lysergic acid – European population – LSD explosion 1750 - Used to ! 1850 (when ergot removed from grain) – treat migranes American history – treat blood pressure ! – treat mental illness – Salem Witch Trials – induce abortion
  8. 8. Irish Potato Famine – Irish peasants grew Background ! grains to pay British – potatoes replace rye landlords rent grain as sole food • grains grew poorly, source of “peasant” potatoes grew population exceptionally well – population explosion – sole dependence on potato for food in Europe 1750 - 1850 • Removal of ergot from diet? • High nutritional value of potato?
  9. 9. Potato Late Blight Potato native to ! South America Spanish explorers ! brought back potato to Europe, well established by 1800 – Brought back fungal disease with plants Stage set for ! disaster?
  10. 10. Impending disaster? The Plant Disease Triangle Host DISEASE Predisposing Environment factors Pathogen
  11. 11. Potato Late Blight Ireland, 1845 Potato plants and ! ! tubers rotted in field – Hot dry weather early summer Famine ! – Followed by 6 weeks of overcast cool, wet weather • temps 1.5 - 7 degrees lower than the average for previous 19 years
  12. 12. What causes abnormal plant growth or plant dysfunction? Pathogens (biotic) ! – we can manage Abiotic “disease” !
  13. 13. Abiotic Disease Causal agents (environmentally ! induced, non living) – Temperature extremes – Moisture extremes – Soil properties – Culture of plant (planting, care, etc) – Location of plant – Pesticide misuse (phytotoxicity)
  14. 14. Biotic disease Causal agents ! – virus – phytoplasma (mycoplasma-like organism) – bacteria – fungus – nematodes – parasitic plants
  15. 15. Viruses Are obligate ! parasites Circulate within the ! plant (systemic)
  16. 16. Viruses Cannot be seen ! without electron microscope
  17. 17. Viruses Many are ! transmitted by vectors
  18. 18. Viruses Also move within ! plant parts
  19. 19. Virus symptoms mosaic ! necrosis (leaf spots ! and cankers)
  20. 20. Virus symptoms distortion ring spots ! !
  21. 21. Phytoplasmas Can only be viewed by electron ! microscopy Are obligate parasites !
  22. 22. Phytoplasmas Circulate within the plant (systemic) ! Vectored by leaf hoppers ! Also move within plant parts !
  23. 23. Symptoms of Phytoplasma Disease Distortion ! Witches brooming ! Yellowing !
  24. 24. Bacteria Single celled Can be viewed with ! ! a high powered microscope
  25. 25. Bacteria Enter plant through ! – wounds – natural openings • flowers or stomates
  26. 26. Symptoms of Bacterial Disease Blights ! Wilts !
  27. 27. Symptoms of Bacterial Disease Galls ! Stem and root Rots ! Crown Gall Crown Gall
  28. 28. Symptoms of Bacterial Disease Cankers ! Fruit rots ! Bacterial blight on tomato (canker and fruit rot)
  29. 29. Signs of Bacterial Disease Ooze (not common in dry climates) !
  30. 30. Fungi Filamentous or thread-like body called ! hyphae (plural). A mass of hyphae is called mycellium.
  31. 31. Fungi Reproduce by spores. !
  32. 32. Fungi Most can live without host at certain ! times. Survive on plant debris, soil etc. Move in plant parts, water, soil, air ! currents, on tools, and help of insects.
  33. 33. Symptoms of Fungal Disease Leaf spots ! Generally round developing zones of different color or texture. May develop patterns of bull’s eye or concentric rings. Spots not limited by leaf veins.
  34. 34. Symptoms of Fungal Disease Cankers (fruiting ! structures often present)
  35. 35. Symptoms of Fungal Disease Wilting Blighting ! !
  36. 36. Symptoms of Fungal Disease Galls ! Cedar/apple rust gall
  37. 37. Symptoms of Fungal Disease Stem and root rots ! Fruit rots ! Rotted roots Healthy roots
  38. 38. Signs of Fungal Disease Spore masses ! Powdery mildew Rust
  39. 39. Signs of Fungal Disease Fruiting structures !
  40. 40. Signs of Fungal Disease Mushrooms/Conks !
  41. 41. Plant Parasitic Nematodes Microscopic roundworms ! Spear-like stylet ! Require free water ! Reproduce by eggs !
  42. 42. Nematodes Symptoms on plants ! – Stunting – Wilting – Root galls Healthy Root knot roots nematode galls
  43. 43. Parasitic Plant Characteristics Plant Photo UCIPM ! ! – Have modified roots, stems leaves, flowers. – Little to no chlorophyll • no photosynthesis • obtain food from other living plant – Examples: • dodder • mistletoe
  44. 44. The Diagnostic Process Identify the plant ! – not all plants are susceptible to the same pathogens or environmental stresses Examine the area the plant is growing in ! or influenced by (abiotic) Examine the plant ! – Symptoms – Signs
  45. 45. Identify the Plant: Identify the Plant: Growth Normal or Not? Growth Normal or Not?
  46. 46. Examine the area ! the plant is growing in or influenced by
  47. 47. Examine the plantplant Examine the
  48. 48. Symptom Vs. Sign Symptom = result Sign = cause ! ! – Wilting – Fruiting structures within stem – Sclerotinia
  49. 49. Diseases Caused by Fungi If the cause affects leaves/flowers only ! – Fungi • Powdery mildew • Rust • Anthracnose • Marsonnina
  50. 50. Common characteristics of fungi that affect leaves/flowers Live above ground ! Spread via wind, water, insects ! Often require a water film on leaf ! surface to germinate and penetrate plant tissue. Often overwinter on plant debris. !
  51. 51. Powdery mildew on poinsettia Powdery mildew on poinsettia
  52. 52. Powdery mildews Produces talcum powder-like growth on ! leaf surface. (Sign) Many, many plants are susceptible ! (even weeds).
  53. 53. Powdery mildew Example: ! – Western sand cherry
  54. 54. Powdery mildew Fungus overwinters ! on leaf debris Favored by ! – shade, poor air circulation
  55. 55. Powdery mildew management Clean up leaf debris. ! Improve air circulation with selective ! pruning. Fungicides ! – Potassium bicarbonates, Oils, Sulfur, Neem – Daconil 2787, Cleary’s 3336
  56. 56. Rust diseases Two types ! – single host • sunflower rust • snapdragon rust • rose rust – two hosts • Juniper - Hawthorn rust
  57. 57. Juniper - Hawthorn Rust Rocky Mt. Juniper ! – Galls
  58. 58. Juniper - Hawthorn Rust Hawthorn ! – Leaf spots
  59. 59. Cedar/apple rust leaf Cedar/apple rust “spores” on leaf spots on crabapple underside of crabapple June-August August - April April - June Cedar/apple rust gall on juniper Cedar/apple rust “spore horns” on juniper
  60. 60. Juniper Hawthorn Rust Management Separate hosts ! Prune out galls on juniper ! Clean up leaves in autumn on hawthorn ! Fungicides ! – Juniper • Daconil 2787, Bordeaux mixture – Hawthorn • Daconil 2787, Bayleton, Cleary’s 3336
  61. 61. Anthracnose Anthracnose
  62. 62. Anthracnose Anthracnose is a Hosts: oak, ! ! term for a type of sycamore, ash, and leaf spot disease. many other ornamentals Blotchy, necrotic ! lesions. Normally not ! serious. Outbreaks ! dependent on spring weather conditions.
  63. 63. Anthracnose Life cycle: ! – fungus overwinters on leaves that fall to the ground in autumn. – Spores become active in spring and blow up to newly emerging leaves. – Favored by spring moisture.
  64. 64. Anthracnose Management: ! – clean up leaf debris – allow for better air movement – fungicides are normally not needed
  65. 65. Marsonnina leaf spot on aspen
  66. 66. Marsonnina leaf spot Host: Aspen ! Damage: Yearly infestations may ! weaken tree. Causes premature leaf drop. Normally not a concern in native areas ! (except for ruining fall color) In landscaped areas may detract from ! look of tree.
  67. 67. Marsonnina leaf spot Symptoms ! – dark black spots on leaves
  68. 68. Marsonnina leaf spot Life cycle: ! – Fungus overwinters on leaf debris – Will spread to newly emerging leaves in the spring. – Symptoms visible in late summer - fall.
  69. 69. Marsonnina leaf spot management When symptoms are visible (late ! summer): – Clean up leaf debris – IT IS TOO LATE TO SPRAY If a fungicide application is warranted ! – Apply in the spring during bud break • Daconil 2787 • Cleary’s 3336 • 26GT
  70. 70. Integrated Pest Management of Fungal Leaf Spots Clean up leaf debris (sanitation) ! Avoid moisture on leaf surface ! Decrease relative humidity ! Improve air circulation ! Is the plant located in the “right place” ! Optional ! – Fungicides
  71. 71. Examples of Alternative Fungicides Labeled for Most** Leaf Spots **READ THE LABEL!!! ! – Copper sulfate (anthracnose, powdery mildew, juniper tip blights) – Neem oil (Triact, Rose Defense) for powdery mildew – Potassium bicarbonate (Kaligreen, First Step) for powdery mildew – Sulfur (powdery mildew, black spot)
  72. 72. Canker diseases What is a canker? ! – A Symptom • sunken, discolored area on bark or stem. • If caused by fungus – fruiting structures will form with in the cankered area.
  73. 73. Cytospora canker Hosts: Almost any ! woody plant in our landscapes. Commonly on Aspen, Cottonwood, Willow. Not an aggressive ! pathogen “Mother Natures’ ! Pruner”
  74. 74. Cytospora canker Fruiting structures ! contain spores. Spores blow to other trees.
  75. 75. Cytospora canker In spring, or when ! there is moisture the spores will “ooze” out of fruiting structure.
  76. 76. Cytospora canker management Pruning or removal ! – Prune infected branches. – If canker on main trunk, remove tree. – Fungicides not effective.
  77. 77. Crown Rot Yellowing of lower Canker at stem ! ! foliage base
  78. 78. Root and crown problems Possible causes ! – Too much water (poor soil drainage) • oxygen deprivation – Fungus + poor soil drainage • Fungus is secondary. – Mechanical injury to roots Primary problem: Plant is being cared ! for improperly
  79. 79. Symptoms of root rot Soft brown mushy roots ! – Sloughing of cortex
  80. 80. Root rot Where do we commonly see it? ! – Under too much irrigation • Turf • Trees and shrubs • Flowers
  81. 81. Root Rot Roots affected (plant parts above this ! may show symptoms) Healthy roots Root rot
  82. 82. Integrated Pest Management for Fungal Root Rots Avoid over watering/improve soil ! drainage Destroy severely affected plants ! Optional ! • Fungicides
  83. 83. Necrotic Ring Spot Host: Kentucky ! Bluegrass # 1 home lawn ! disease in Colorado related to soil ! condition and lack of soil preparation “Frog-eye” !
  84. 84. NRS Diagnostic features ! – Rings or arcs of dead grass. – Healthy grass in center of dead circle.
  85. 85. NRS Diagnostic features: Runner hyphae ! ! – Roots rotting – Runner hyphae present on roots and tillers.
  86. 86. NRS Symptoms develop Favored by: ! ! in summer – excessive inputs • water Fungus active in ! • fertilizer spring and fall – heavy thatch Favored by: ! – slopes – shade – poor soil
  87. 87. IPM for Necrotic Ring Spot Reduce thatch with Overseed with ! ! core aeration resistant cultivars (perennial ryegrass) Mow at 2.5 - 3 ! other KB (Midnight, inches Eclipse) Water deeply and ! Fungicides: ! infrequently – Banner Syringe (water ! • also Fertilome Liquid lightly to cool turf off) systemic in addition to normal – Rubigan, Patchwork watering. – Heritage Avoid excess N ! – Sentinel
  88. 88. Vascular wilts Affects internal plant tissues ! – Fungi • Fusarium wilt (soilborne) • Dutch Elm Disease (Vectored)
  89. 89. Vascular Wilt Disease Fusarium wilt Red to brown ! ! vascular streaking – Soilborne fungus – Hosts • Tomato • others
  90. 90. IPM for Fusarium Wilt Plant resistant Soil solarization ! ! varieties
  91. 91. Vascular wilt disease Dutch elm disease ! – Host • American Elm – Vectored by the elm bark beetle – Can also move between trees through root graphs
  92. 92. Integrated Pest Management for Dutch Elm Disease Prevention Fungicide injection ! ! – Resistant varieties – Fungicide injection • Arbotect (benzimadazole) • Alamo (propioconazole) Control ! Photo by Lise Mahnke – Remove tree – Trench potential root graphs – Control vector
  93. 93. Diseases caused by Bacteria If the cause affects leaves/flowers (and ! stems) only – Bacteria • Fire blight
  94. 94. Spring - Summer Fire blight cycle Shepherd’s crook Canker
  95. 95. Fire blight cycle Summer - Winter
  96. 96. Integrated Pest Management of Fire blight Prevention Control ! ! – Resistant varieties – Removal of symptomatic • Crabapples branches (disinfect – Centurion tools between each – David – Indian Summer cut) – Molten Lava – Pesticides – Profusion • Streptomycin sulfate – Robinson (for agricultural use – Biological control only) • Blight Ban • Copper (Pseudomonas flourescens)
  97. 97. Diseases caused by Viruses and Phytoplasmas Virus ! – Ring spot – Mosaic Phytoplasma ! – Aster yellows
  98. 98. Examples of virus diseases Peony ring spot !
  99. 99. Examples of virus diseases ! Mosaic virus on columbine Mosaic virus on columbine
  100. 100. Rose Mosaic Virus No insect vector ! graph transmission !
  101. 101. Examples of virus diseases Tomato spotted wilt ! – tospovirus Tomato Vectored by Thrips ! Gloxinia
  102. 102. Examples of virus diseases Impatiens necrotic spot ! – tospovirus New Guinea Vectored by thrips ! Impatiens New Guinea Impatiens thrips Lobelia Tomato
  103. 103. IPM/PHC Management of Virus Disease Leave it alone ! Remove entire plant and destroy ! Manage/control vector ! Preventive: Purchase symptom-free ! plants
  104. 104. Diseases caused by Phytoplasma Distortion ! Witches brooming ! Yellowing !
  105. 105. Examples of Phytoplasma Diseases Aster yellows ! Delphinium flower affected Healthy Delphinium with aster yellows
  106. 106. Aster Yellows Host ! – purple cone flower
  107. 107. Aster Yellows? What else could it Host ! ! be? – Petunia
  108. 108. IPM/PHC Management of Phytoplasma Diseases Leave it alone ! Remove entire plant and destroy ! Manage/control leaf hoppers ! Preventive: Purchase symptom-free ! plants
  109. 109. Abiotic Diseases environmentally induced disease ! the precursors or primary plant ! problems – lead to plant stress/weakness – lead to invasion of insects and disease
  110. 110. Dieback caused by? !
  111. 111. Abiotic factors Possible sources: air or soil ! External “pressures” typically “blow” in.
  112. 112. Abiotic problems affecting roots Root girdling ! Oxygen starvation ! Mechanical injury ! Raising grade !
  113. 113. Girdling root
  114. 114. Leaves affected – Freeze
  115. 115. Leaves affected Unexpected snowfall !
  116. 116. Affecting leaves 2,4-D herbicide injury to Ginnala maple !
  117. 117. Affecting Roots Soil condition and drainage are the ! primary problems
  118. 118. Affecting roots (and leaves) Abiotic- 80% of all ! landscape plant problems fall this category
  119. 119. Affecting Roots (and leaves) oxygen starved roots !
  120. 120. Affecting Roots (leaves symptomatic) Nutrient deficiency ! – brought on by • soil condition • excess moisture – oxygen starvation
  121. 121. Affecting roots (leaves symptomatic) Leaf scorch ! – an imbalance between water uptake and loss.
  122. 122. Drought Summer ! Winter (no spring ! green up)
  123. 123. Plant siting Natives and adapted ! non natives can be Ginnala maple planted together. – Watch that moisture regimes are similar Yucca
  124. 124. Colorado Blue spruce located on south facing slope in urban landscape.
  125. 125. “Great fleas have little fleas upon their backs to bite ‘em, And little fleas have lesser fleas and so ad infinitum.” Augustus deMorgan, 1871
  126. 126. Most Plant Disease is Secondary Epidemics (like irish potato famine) are ! the exception in nature Damage can often be tolerated in a ! landscape Before you spray ! – ask these questions
  127. 127. Is a Chemical Necessary? – Is the disease properly identified? • Is the primary cause biotic????? – Have cultural control practices been used? – Is the host plant valuable? – Is the disease life- or health-threatening? – Does this plant have a history of disease? – Are effective, legal treatments available? – Will one or two applications suffice?
  128. 128. Where to go for diagnostic help County Extension Office ! – Master Gardeners Jefferson County Plant Diagnostic Clinic ! – 15200 W. 6th Ave, Golden – 303-271-6620 CSU Plant Diagnostic Clinic ! – Colorado State University, Ft. Collins – 970-491-6950

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