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Microscopic Identification of Turfgrass Diseases. Horticulture In-service Training, September 30, 2005 The Inn at Virginia Tech, Blacksburg, VA. Purpose of session. Learn procedure for disease identification Locate and identify fungal structures

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microscopic identification of turfgrass diseases

Microscopic Identification of Turfgrass Diseases

Horticulture In-service Training, September 30, 2005

The Inn at Virginia Tech, Blacksburg, VA

purpose of session
Purpose of session
  • Learn procedure for disease identification
    • Locate and identify fungal structures
    • Help confirm/eliminate a field diagnosis based on symptoms
    • Possibly eliminate fungicide applications
diagnosing turfgrass samples
Diagnosing turfgrass samples
  • Disadvantage:
    • plants are small
    • many microorganisms in soil
  • Advantage:
    • plants are small
    • verification of initial field diagnosis
    • quicker treatment if necessary
useful equipment
Useful equipment
  • Dissecting microscope (4 – 40X)
  • Compound microscope (40 – 1000X)
  • Digital camera (Sony, Nikon)
    • Universal adapter
  • Lab supplies
    • Scapula, forceps, probing needle, distilled water or stains, slides & covers, etc.
dissecting microscope
Dissecting microscope
  • Useful for observing mites, insects, and some fungal structures
  • Helps pinpoint problematic areas
  • Not powerful enough for fungal ID
compound microscope
Compound microscope
  • Difficult to pinpoint if starting blind
  • Useful for distinguishing fungal hyphae, spores, fruiting bodies, and other structures
digital camera
Digital camera
  • Can be mounted on microscope
  • Provides documentation for archives
  • Rapid sharing of information
  • Tell a story
factors affecting disease diagnosis
Factors affecting disease diagnosis
  • Turf species and cultivar
  • Weather patterns, time of year
  • Cultural and chemical inputs
  • Symptoms and signs
diagnostic procedure
Diagnostic procedure
  • Collect information
  • Examine plant under dissecting scope
  • Identify problematic regions
  • Make wet mount from diseased tissue
  • Examine under compound scope
diagnostic procedure compound microscope
Diagnostic procedureCompound microscope
  • 4x- focus and find fungal structures
  • 10x- to pinpoint spores, hyphae, etc.
  • 40x- identify fungus based on spore and hyphae characteristics
what to look for
What to look for
  • Spores
  • Hyphae
  • Fruiting bodies
  • Plant parasitic nematodes
hyphal characteristics
Hyphal characteristics
  • Septation
  • Branching
  • Pigmentation
  • Consistency
spore morphology
Spore morphology
  • Shape
  • Number of cells
  • Spore origin
moist chamber
Moist Chamber
  • Promotes disease development, mycelial growth, sporulation
  • Sample placed in plastic container with moist paper towel & checked daily
rhizoctonia species on turf
Rhizoctonia species on turf
  • Rhizoctonia solani
    • Rhizoctonia blight
    • “warm weather” brown patch
  • Rhizoctonia cerealis
    • Yellow patch
    • “cool season” brown patch
  • Rhizoctonia zeae
    • Rhizoctonia leaf and sheath spot
    • “hot weather” brown patch
rhizoctonia characteristics
Rhizoctonia characteristics
  • Right angle branching
  • Septate (cross walls)
  • Uniform hyphae
  • Septae near branching
  • Constricted hyphae at branching point
pythium species
Pythium species
  • Pythium blight
  • Pythium root rot
pythium characteristics
Pythium characteristics
  • Coenocytic (no cross walls)
  • Small, thin filamentous hyphae
  • Oospores
  • Sporangia
  • Non-pigmented

250x

540x

dollar spot sclerotinia homoeocarpa
Dollar spotSclerotinia homoeocarpa
  • Clear hyphae
  • Variation in size
  • Often branches in V
  • Granular cytoplasm
gray leaf spot pyricularia grisea oryzae
Gray Leaf SpotPyricularia grisea (oryzae)
  • Spores (conidia) are hyaline
  • Pyriform shaped
    • Bowling pins, pear, ice cream cone
  • 2- to 3-celled conidia borne on slender stalks (conidiophores)
anthracnose colletotrichum graminicola
AnthracnoseColletotrichum graminicola
  • Acervulii w/ setae on leaf and crown tissue

U. Of Guelph

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