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1 Rmnhort Ii Pottorff Path Talk Intro
 

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    1 Rmnhort Ii Pottorff Path Talk Intro 1 Rmnhort Ii Pottorff Path Talk Intro Presentation Transcript

    • Plant Pathology and Disease Diagnosis Laura Pottorff Colorado State University Cooperative Extension Adams County
    • Definition Abnormal growth or dysfunction of a ! plant Caused by: ! – biotic (living organisms) • pathogens – abiotic (non-living factors = environmentally induced disease)
    • Plant Diseases With Historical Impact Saint Anthony’s Fire or Holy Fire ! – Ergot • Claviceps purpurea Irish potato famine ! – Late blight of potato • Phytophthora infestans
    • 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 – historical documents correlate malady with: • cool wet weather • occurs after the introduction or rye grains More common among !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
    • 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.
    • St. Anthony’s Fire What we know now ! – Fungus called ergot is responsible
    • 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
    • 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?
    • 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?
    • Impending disaster? The Plant Disease Triangle Host DISEASE Predisposing Environment factors Pathogen
    • 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
    • What causes abnormal plant growth or plant dysfunction? Pathogens (biotic) ! – we can manage Abiotic “disease” !
    • 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)
    • Biotic disease Causal agents ! – virus – phytoplasma (mycoplasma-like organism) – bacteria – fungus – nematodes – parasitic plants
    • Viruses Are obligate ! parasites Circulate within the ! plant (systemic)
    • Viruses Cannot be seen ! without electron microscope
    • Viruses Many are ! transmitted by vectors
    • Viruses Also move within ! plant parts
    • Virus symptoms mosaic ! necrosis (leaf spots ! and cankers)
    • Virus symptoms distortion ring spots ! !
    • Phytoplasmas Can only be viewed by electron ! microscopy Are obligate parasites !
    • Phytoplasmas Circulate within the plant (systemic) ! Vectored by leaf hoppers ! Also move within plant parts !
    • Symptoms of Phytoplasma Disease Distortion ! Witches brooming ! Yellowing !
    • Bacteria Single celled Can be viewed with ! ! a high powered microscope
    • Bacteria Enter plant through ! – wounds – natural openings • flowers or stomates
    • Symptoms of Bacterial Disease Blights ! Wilts !
    • Symptoms of Bacterial Disease Galls ! Stem and root Rots ! Crown Gall Crown Gall
    • Symptoms of Bacterial Disease Cankers ! Fruit rots ! Bacterial blight on tomato (canker and fruit rot)
    • Signs of Bacterial Disease Ooze (not common in dry climates) !
    • Fungi Filamentous or thread-like body called ! hyphae (plural). A mass of hyphae is called mycellium.
    • Fungi Reproduce by spores. !
    • 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.
    • 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.
    • Symptoms of Fungal Disease Cankers (fruiting ! structures often present)
    • Symptoms of Fungal Disease Wilting Blighting ! !
    • Symptoms of Fungal Disease Galls ! Cedar/apple rust gall
    • Symptoms of Fungal Disease Stem and root rots ! Fruit rots ! Rotted roots Healthy roots
    • Signs of Fungal Disease Spore masses ! Powdery mildew Rust
    • Signs of Fungal Disease Fruiting structures !
    • Signs of Fungal Disease Mushrooms/Conks !
    • Plant Parasitic Nematodes Microscopic roundworms ! Spear-like stylet ! Require free water ! Reproduce by eggs !
    • Nematodes Symptoms on plants ! – Stunting – Wilting – Root galls Healthy Root knot roots nematode galls
    • 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
    • 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
    • Identify the Plant: Identify the Plant: Growth Normal or Not? Growth Normal or Not?
    • Examine the area ! the plant is growing in or influenced by
    • Examine the plantplant Examine the
    • Symptom Vs. Sign Symptom = result Sign = cause ! ! – Wilting – Fruiting structures within stem – Sclerotinia
    • Diseases Caused by Fungi If the cause affects leaves/flowers only ! – Fungi • Powdery mildew • Rust • Anthracnose • Marsonnina
    • 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. !
    • Powdery mildew on poinsettia Powdery mildew on poinsettia
    • Powdery mildews Produces talcum powder-like growth on ! leaf surface. (Sign) Many, many plants are susceptible ! (even weeds).
    • Powdery mildew Example: ! – Western sand cherry
    • Powdery mildew Fungus overwinters ! on leaf debris Favored by ! – shade, poor air circulation
    • Powdery mildew management Clean up leaf debris. ! Improve air circulation with selective ! pruning. Fungicides ! – Potassium bicarbonates, Oils, Sulfur, Neem – Daconil 2787, Cleary’s 3336
    • Rust diseases Two types ! – single host • sunflower rust • snapdragon rust • rose rust – two hosts • Juniper - Hawthorn rust
    • Juniper - Hawthorn Rust Rocky Mt. Juniper ! – Galls
    • Juniper - Hawthorn Rust Hawthorn ! – Leaf spots
    • 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
    • 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
    • Anthracnose Anthracnose
    • 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.
    • 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.
    • Anthracnose Management: ! – clean up leaf debris – allow for better air movement – fungicides are normally not needed
    • Marsonnina leaf spot on aspen
    • 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.
    • Marsonnina leaf spot Symptoms ! – dark black spots on leaves
    • 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.
    • 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
    • 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
    • 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)
    • 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.
    • Cytospora canker Hosts: Almost any ! woody plant in our landscapes. Commonly on Aspen, Cottonwood, Willow. Not an aggressive ! pathogen “Mother Natures’ ! Pruner”
    • Cytospora canker Fruiting structures ! contain spores. Spores blow to other trees.
    • Cytospora canker In spring, or when ! there is moisture the spores will “ooze” out of fruiting structure.
    • Cytospora canker management Pruning or removal ! – Prune infected branches. – If canker on main trunk, remove tree. – Fungicides not effective.
    • Crown Rot Yellowing of lower Canker at stem ! ! foliage base
    • 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
    • Symptoms of root rot Soft brown mushy roots ! – Sloughing of cortex
    • Root rot Where do we commonly see it? ! – Under too much irrigation • Turf • Trees and shrubs • Flowers
    • Root Rot Roots affected (plant parts above this ! may show symptoms) Healthy roots Root rot
    • Integrated Pest Management for Fungal Root Rots Avoid over watering/improve soil ! drainage Destroy severely affected plants ! Optional ! • Fungicides
    • Necrotic Ring Spot Host: Kentucky ! Bluegrass # 1 home lawn ! disease in Colorado related to soil ! condition and lack of soil preparation “Frog-eye” !
    • NRS Diagnostic features ! – Rings or arcs of dead grass. – Healthy grass in center of dead circle.
    • NRS Diagnostic features: Runner hyphae ! ! – Roots rotting – Runner hyphae present on roots and tillers.
    • 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
    • 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
    • Vascular wilts Affects internal plant tissues ! – Fungi • Fusarium wilt (soilborne) • Dutch Elm Disease (Vectored)
    • Vascular Wilt Disease Fusarium wilt Red to brown ! ! vascular streaking – Soilborne fungus – Hosts • Tomato • others
    • IPM for Fusarium Wilt Plant resistant Soil solarization ! ! varieties
    • Vascular wilt disease Dutch elm disease ! – Host • American Elm – Vectored by the elm bark beetle – Can also move between trees through root graphs
    • 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
    • Diseases caused by Bacteria If the cause affects leaves/flowers (and ! stems) only – Bacteria • Fire blight
    • Spring - Summer Fire blight cycle Shepherd’s crook Canker
    • Fire blight cycle Summer - Winter
    • 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)
    • Diseases caused by Viruses and Phytoplasmas Virus ! – Ring spot – Mosaic Phytoplasma ! – Aster yellows
    • Examples of virus diseases Peony ring spot !
    • Examples of virus diseases ! Mosaic virus on columbine Mosaic virus on columbine
    • Rose Mosaic Virus No insect vector ! graph transmission !
    • Examples of virus diseases Tomato spotted wilt ! – tospovirus Tomato Vectored by Thrips ! Gloxinia
    • Examples of virus diseases Impatiens necrotic spot ! – tospovirus New Guinea Vectored by thrips ! Impatiens New Guinea Impatiens thrips Lobelia Tomato
    • IPM/PHC Management of Virus Disease Leave it alone ! Remove entire plant and destroy ! Manage/control vector ! Preventive: Purchase symptom-free ! plants
    • Diseases caused by Phytoplasma Distortion ! Witches brooming ! Yellowing !
    • Examples of Phytoplasma Diseases Aster yellows ! Delphinium flower affected Healthy Delphinium with aster yellows
    • Aster Yellows Host ! – purple cone flower
    • Aster Yellows? What else could it Host ! ! be? – Petunia
    • IPM/PHC Management of Phytoplasma Diseases Leave it alone ! Remove entire plant and destroy ! Manage/control leaf hoppers ! Preventive: Purchase symptom-free ! plants
    • Abiotic Diseases environmentally induced disease ! the precursors or primary plant ! problems – lead to plant stress/weakness – lead to invasion of insects and disease
    • Dieback caused by? !
    • Abiotic factors Possible sources: air or soil ! External “pressures” typically “blow” in.
    • Abiotic problems affecting roots Root girdling ! Oxygen starvation ! Mechanical injury ! Raising grade !
    • Girdling root
    • Leaves affected – Freeze
    • Leaves affected Unexpected snowfall !
    • Affecting leaves 2,4-D herbicide injury to Ginnala maple !
    • Affecting Roots Soil condition and drainage are the ! primary problems
    • Affecting roots (and leaves) Abiotic- 80% of all ! landscape plant problems fall this category
    • Affecting Roots (and leaves) oxygen starved roots !
    • Affecting Roots (leaves symptomatic) Nutrient deficiency ! – brought on by • soil condition • excess moisture – oxygen starvation
    • Affecting roots (leaves symptomatic) Leaf scorch ! – an imbalance between water uptake and loss.
    • Drought Summer ! Winter (no spring ! green up)
    • Plant siting Natives and adapted ! non natives can be Ginnala maple planted together. – Watch that moisture regimes are similar Yucca
    • Colorado Blue spruce located on south facing slope in urban landscape.
    • “Great fleas have little fleas upon their backs to bite ‘em, And little fleas have lesser fleas and so ad infinitum.” Augustus deMorgan, 1871
    • 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
    • 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?
    • 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