Diagnosis and Management of Turfgrass Diseases

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Diagnosis and Management of Turfgrass Diseases

• Lane Tredway
• Advanced Turfgrass Pest Management
• Lecture 2, Spring 2003

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Disease Triangle
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Diagnosis Triangle
MICROCLIMATE, RECENT WEATHER, RECENT CULTURAL
PRACTICES
PLANT AND STAND SYMTPOMS
DIAGNOSIS
SIGNS OF PATHOGEN
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Stand SymptomsSymptoms evident from a distance

• Spots less than 4 diameter
• Patches irregularly shaped areas greater than
  4 diameter
• Circles perfectly circular areas greater than
  4 diameter
• Rings surrounded by healthy turf to the inside
  and outside
• Irregular no pattern

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DOLLAR SPOT
SPOT
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COPPER SPOT
SPOT
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LARGE PATCH
PATCH
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CIRCLE
GRAY SNOW MOLD
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SUMMER PATCH
RING
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SUMMER PATCH
RING
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RUST
NO PATTERN
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Plant SymptomsSymptoms evident on individual
plants

• Leaf Spot round or oval areas on leaves with a
  distinct border
• Foliar Lesions large, irregular areas on leaves
  with a distinct border
• Stem Lesions large, irregular areas on leaf
  sheaths with a distinct border
• Foliar blight or dieback necrosis of leaves or
  entire tillers
• Crown Rot necrosis of the crown, rhizomes, or
  stolons
• Root Rot necrosis of the roots

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GRAY LEAF SPOT
LEAF SPOT
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BROWN PATCH
LESION
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LARGE PATCH
STEM LESIONS
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BROWN BLIGHT
FOLIAR BLIGHT
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NECROTIC RING SPOT
CROWN ROT
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SUMMER PATCH
ROOT ROT
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Pathogen SignsEvidence of Pathogen Growth

• Mycelium weblike masses of fungal growth
• Spore Masses fuzzy or gelatinous growth
• Fruiting Bodies spore producing structures
• Sclerotia small, round or thread-like survival
  structures
• Mushrooms reproductive structures produced by
  fairy ring fungi

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PYTHIUM BLIGHT
MYCELIUM
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BROWN PATCH
SMOKE RING
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COPPER SPOT
SPORE MASSES
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ANTHRACNOSE
FRUITING BODIES
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SLIME MOLD
FRUTING BODIES
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RED THREAD
SCLEROTIA
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SOUTHERN BLIGHT
SCLEROTIA
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FAIRY RING
MUSHROOMS
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Microclimate and Recent WeatherDiseases are
strongly influenced by environmental conditions

• Microclimate
• Shade
• Air movement
• Drainage surface and subsurface
• Soil Type
• Traffic, Wear, Compaction

• Weather
• High and low temperature
• Humidity
• Dewpoint
• Soil Temperature
• Rainfall

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Disease Triangle
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Management Triangle
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Key Components of Integrated Disease Management

• Species and variety selection
• Mowing practices
• Irrigation timing, amount, and frequency
• Nitrogen fertility
• Micronutrient availability / soil pH management
• Soil and thatch management
• Maximize fungicide use efficiency
• Fungicide resistance management

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Maximizing Fungicide Use Efficiency

• Know your fungicides, select the best fungicide
  for each situation
• Time applications based on weather conditions,
  not the calendar
• Apply fungicides properly

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Fungicide Nomenclature

• Chemical Name
• complete chemical formula for the active
  ingredient
• Common Name
• simplified chemical name for the active
  ingredient
• Trade Name(s)
• commercial name for the formulated product

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Fungicide Nomenclature Example

• Chemical Name
• tetrachloroisophthalonitrile
• Common Name
• chlorothalonil
• Trade Name(s)
• Daconil, Chlorostar, Concorde, Manicure, Echo

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Fungicide classification

• Chemical Class group of fungicides with similar
  chemical properties
• Topical mode of action how the fungicide moves
  on and in the plant
• Biochemical mode of action how growth of the
  fungus is inhibited
• Genetic mode of action number of genes in the
  fungus control that control the inhibited process

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Fungicides 15 Chemical Classes

• Anilides
• Aromatic hydrocarbons
• Benzamides
• Benzimidazoles
• Carbamates
• Dicarboximides
• Dithiocarbamates
• DMIs

• EBDC
• Nitriles
• Phenylamides
• Phenylpyrolles
• Phosphonates
• Polyoxins
• QoIs

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Topical Mode of Action - absorption and movement
in the plant

• contact stays on leaf surface
• localized penetrant absorbed but not
  translocated
• translaminar absorbed, moves to opposite side
  of leaf, but not translocated
• mesostemic absorbed, translaminar activity, and
  localized movement on leaf surface
• systemics
• acropetal penetrant absorbed and translocated
  in the xylem only
• true systemic absorbed and translocated in
  xylem and phloem

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What is a mesostemic fungicide?
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Why is topical mode of action important?

• Determines length of residual control
• Contacts generally ineffective for control of
  root and crown diseases
• Preventative vs. curative application contacts
  poor for curative control, acropetal penetrants
  best
• Tank mixing mixture components should have
  different topical modes of action

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Biochemical Mode of ActionHow pathogen growth is
inhibited

• Multi-site inhibitor interferes with more than
  one biochemical reaction in the fungal cell
• Single-site inhibitor interferes with one
  biochemical reaction

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Biochemical Mode of Action - Examples

• Chlorothalonil (multi-site inhibitor)
• Inhibits thiol-dependent enzymatic reactions
• Thiophanate-methyl (single-site inhibitor)
• Inhibits chromosome separation in cell division
  by binding to b-tubulin protein

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Genetic Mode of Action

• Monogenic
• anilides
• benzamides
• benzimidazoles
• phenylamides
• polyoxins
• QoIs
• Oligogenic
• Dicarboxamides
• DMIs

• Polygenic
• aromatic hydrocarbons
• carbamates
• dithiocarbamates
• EBDCs
• nitriles
• phenylpyrolles
• phosphonates

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Why is biochemical and genetic mode of action
important?

• These determine the risk for fungicide resistance
• Rotate or tank-mix products with different
  biochemical modes of action to prevent/delay
  resistance
• Fungicides within a chemical class have the same
  biochemical and genetic modes of action

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Heritage, Insignia, CompassBanner, Bayleton,
Eagle, RubiganWhats the Difference?

• Differences within a fungicide class
• Topical mode of action
• Spectrum of control
• Duration of residual control
• Side effects
• Cost

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QoI Fungicides

• 1996 - Heritage (azoxystrobin)
• 1999 Compass (trifloxystrobin)
• 2003 Insignia (pyraclostrobin)

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Preventative Brown Patch Control 2002
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Preventative Dollar Spot Control
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Daconil, Chlorostar, Manicure, Echo....Whats
the Difference?

• Differences within a common name
• Active ingredient often made by same company
• Formulations are different
• Formulation impacts disease control, especially
  longevity of residual control
• Formulation also affects mixing/handling

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Dollar Spot Control with Formulations of
Chlorothalonil
All products applied at 2.7 oz a.i. per 1000
ft2 data collected 14 days after one application
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Side Effects of Fungicides on Turfgrasses

• Prevention/control of other diseases
• Increase of other diseases
• Enhanced turf quality
• Growth regulation / thinning
• Increased thatch accumulation

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Fungicides that Enhance Non-Target Diseases

• chlorothalonil summer patch and stripe smut
• benzimidazoles and DMIs leaf spot / melting out
• benzimidazoles, dicarboxamides, and DMIs
  Pythium blight
• thiophanate-methyl powdery mildew
• azoxystrobin and flutolanil dollar spot
• DMI fungicides algae
• azoxystrobin yellow spot

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Heritage (0.4 oz, 28 day)
Triton (2 oz, 14 day)
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Choosing a Fungicide

• 1. efficacy on primary disease
• 2. residual control
• 3. control spectrum
• 4. side effects
• 5. Topical and biochemical mode of action
• 6.

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Cost of Gray Leaf Spot Control
8 weeks of preventative treatment for 30 acres
of fairways
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Developing a Fungicide Program
AUGUST
APRIL
JUNE
SEPT
JULY
MAY
OCT
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Applying Fungicides Properly

• Application rate
• Nozzle type
• Nozzle pressure
• Dilution rate
• Post-application irrigation
• Proper application timing

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Fungicide Application Rate

• Preventative applications before disease
  symptoms are evident
• Use low rate at short intervals or high rate at
  long intervals
• Contacts or acropetal penetrants are effective
• Curative applications after disease symptoms
  are evident
• Use high rate at short intervals
• Acropetal penetrants are best, tank-mixing with a
  contact fungicide is often beneficial

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Preventative Brown Patch Control 2002
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Nozzle Type Influences Fungicide Effectiveness
Flat Fan Nozzles
Rain Drop Nozzles
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Effect of Nozzle Type on Coverage Uniformity
Raindrop nozzles
Flat fan nozzles
Hamilton et al. 1997
Diquat applied at 1 oz. per 1000 sq ft
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Nozzle Type Impacts Dollar Spot Control with
Iprodione in Creeping Bentgrass
Chipco 26019 applied at 4 oz per 1000 sq ft with
FloodJet TK-30 or TeeJet T-8002 nozzles
H.B. Couch, 1995
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Nozzle Pressure and Droplet Size Impacts Dollar
Spot Control
Dyrene applied to creeping bentgrass at 4 oz per
1000 sq ft with TeeJet T-8002 nozzles
H.B. Couch, 1995
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Dilution Rate and Disease Control

• Dilution rate the amount of water per unit area
  in which a pesticide is applied (aka delivery
  rate)
• Industry Standard 2 gallons per 1000 sq ft
• Equivalent to 1.5 teaspoons per square foot
• Provides adequate coverage for control of foliar
  diseases

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Dilution Rate Impacts Dollar Spot Control with
Chlorothalonil
All products applied to deliver 2.7 oz a.i. per
1000 sq ft on 14 day intervals Data collected 15
Aug 2002 Wong et al., Rutgers University
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Control of Root Diseases in Turf

• PLACE FUNGICIDE WHERE THE PATHOGEN IS!!!!
• OPTIONS
• apply in 4 to 5 gallons of water per 1000 ft2
• water in immediately after application (1/4)
• fungicide injection

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Fungicide Application Timing

• Apply fungicides for root diseases based on
  temperature in top 1-2 of soil profile
• Summer Patch - gt65ºF
• Take-all Patch 40ºF to 60ºF
• Spring Dead Spot - ???

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Fungicide Application Timing

• Foliar diseases - Low temperature is the most
  important factor
• Dollar Spot - gt50ºF
• Brown Patch gt60ºF
• Pythium blight - gt65ºF

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Key Components of Integrated Disease Management

• Species and variety selection
• Mowing practices
• Irrigation timing, amount, and frequency
• Nitrogen fertility
• Micronutrient availability / soil pH management
• Soil and thatch management
• Maximize fungicide use efficiency
• Fungicide resistance management

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Resistance to metalaxyl in Pythium aphanidermatum
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Cases of Fungicide Resistance in Turfgrass

• Anthracnose benzimidazoles, QoIs
• Dollar Spot benzimidazoles, dicarboxamides,
  DMIs
• Gray Leaf Spot QoIs
• Powdery Mildew DMIs
• Pythium Blight phenylamides

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Fungicide Resistance

• Naturally occurring strains of some turf
  pathogens have the genetic ability to grow in the
  presence of a fungicide

Sclerotinia homoeocarpa
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How does fungicide resistance develop?
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• A small proportion of the pathogen population has
  genetic, heritable resistance to the fungicide

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How does fungicide resistance develop?
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• When the fungicide is applied, the resistant
  strain can grow rapidly without competition from
  other strains

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How does fungicide resistance develop?
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• When the resistant strain becomes dominant in the
  population, control failure occurs and resistance
  has developed

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Fungicide Resistance in Dollar Spot, caused by S.
homoeocarpa

• Benzimidazoles (Cleary 3336)
• Occurs rapidly and completely
• Resistant strains persist indefinitely
• No cross resistance with other fungicide classes
• Sterol Inhibitors (Banner, Bayleton, Eagle)
• Occurs slowly and gradually
• Resistant strains may not be as competitive
• Most resistant strains are also benzimidazole
  resistant

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Practical Tips for Preventing Fungicide Resistance

• Avoid repetitive use of fungicides from the same
  chemical class
• Alternate or tank-mix products from different
  chemical classes
• Use preventative control for resistance-prone
  diseases
• Minimize fungicide use
• Use disease-resistant cultivars and proper
  cultural practices

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Preventing Fungicide Resistance

• Tank Mix or Alternate?
• Alternating among fungicide classes is better
  than nothing, but resistance will still occur
  eventually
• Theoretically, tank mixing is a better long-term
  approach for prevention of fungicide resistance

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Tank Mixing Fungicides

• Do's
• test for compatibility
• read labels thoroughly
• use tank mixes that are additive or synergistic

• Donts
• tank mix chemicals with similar biochemical or
  topical modes of action
• apply components at less than labeled rate UNLESS
  they have been shown to be BALANCED