Grass Diseases

7/31/2019 Grass Diseases

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Disease Management inWarm-Season Turfgrasses

Lane Tredway

Extension Specialist in TurfgrassPathology

North Carolina State University


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Turfgrass Disease Diagnosis

A process of elimination

1. Start with a list of possibilities based onturf species and time of year

2. Look for clues3. Rule out diseases, narrow the list of

possibilities4. Repeat steps 2 and 3

5. Send sample to adiagnostic lab


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Cent ipedegrass

Seedhead

Alternate leaf arrangement

Flat vernation


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St . August inegrass

Leaves arrangedopposite of each otherat the nodes

St. Augustinegrass

seedhead


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Cent ipedegrass Diseases

Large patch

Dollar spot

Fairy Ring


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Zoysiagrass Diseases

Large patch

Dollar spot Curvularia

blight

Rust


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St . August inegrassDiseases

Large patch

Gray leaf spot Dollar spot

Pythiumroot

rot


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LARGE PATCH

Causal Agent: Rhizoctonia solani

Time of year: Fall and Spring

Hosts: Warm-season turfgrasses,

especially centipedegrass


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Large PatchCentipedegrass


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Large PatchCentipedegrass


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Large PatchZoysiagrass


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Large PatchZoysiagrass


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Large PatchSt. Augustinegrass

L P h S L i


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Large Patch Stem LesionsSt. Augustinegrass


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LARGE PATCH

Conditions Favoring Disease

Cool, wet weather Warm-season turf going into or coming

out of dormancy Nitrogen applications too early in spring

or too late in fall Excessive thatch, poor soil drainage, low

air movement, over-watering Low mowing heights


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What is wrong withthis picture?


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LARGE PATCH

Cultural Control

Do not apply N to centipedegrass before May 15

or after September 1

Apply max of 1 lb N/1000 ft2/yr to centipedegrass

Improve drainage and air circulation

Dethatch and aerify annually

Mow at optimal height

Irrigate in fall and spring only as needed toprevent severe drought stress


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LARGE PATCH

Chemical Control

Preventative applications in fall aremost effective, must be timed properly

Make first application when soil

temperature drops to 70F for several

consecutive days


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Fungic ides for Large Pat c h Cont ro l

DMIs

myclobutanil (Eagle,

Immunox) propiconazole (Banner Maxx,

Propiconazole Pro)

triadimefon (Bayleton)

Benzimidazoles

thiophanate-methyl (3336,Systec, T-storm)

Benzamides

flutolanil (Prostar)

Dicarboxamides

iprodione (Chipco 26GT,

Iprodione Pro)***

QoIs

azoxystrobin (Heritage)

pyraclostrobin (Insignia)

trifloxystrobin (Compass)

***Not labeled for use on residential lawns

Large Pat c h Cont ro l in Ra leigh St


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Large Pat c h Cont ro l in Ra leigh St .

Augustinegrass with Single Applications

0

1

2

3

4

5

6

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DiseaseIncidenc

Insignia

(0.9 oz)

Heritage

TL (2 fl oz)

Prostar

(3 oz)

Bayleton

(1 oz)

Bayleton

(2 oz)

Banner

Maxx

Untreated

(4 fl oz)All treatments applied on Aug 25, 2004Data collected Dec 10, 2004

Large Patch Control in Raleigh St


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Large Patch Control in Raleigh St.Augustinegrass with Two Applications

0

1

2

3

4

5

6

7

DiseaseIncidenc

Insignia (0.9

oz)

Heritage TL

(2 fl oz)

Prostar (3

oz)

Bayleton (1

oz)

Banner Maxx Untreated

All treatments applied on Aug 25, 2004Data collected Dec 10, 2004

(4 fl oz)

Large Pat c h Cont ro l , Wi lm ingt on, NC,


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g , g , ,12/10/04

Bayleton 50DF (2 oz)applied 8/25/05

Bayleton 50DF (1 oz)applied 8/25/05 and 10/7/04

Heritage TL (2 fl oz)


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Insignia (0.9 oz)applied 8/25/05 and 10/7/04

Untreated Control

Bayleton (2 oz)applied 8/25/05

Heritage TL (2 fl oz)applied 8/25/05


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Large Pat c h Cont ro l in Meyer


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a g a C y

Zoysiagrass (Lawrence, KS)

0

5

10

15

20

25

30

35

Disease

Incidenc

Heritage (0.4

oz)

Bayleton (1 oz) 3336 (4 oz) Compass (0.25

oz)

Untreated

Treatments applied on Sep 24, 1998Data collected Apr 23, 1999


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Cost Analys is Large Pat c h Cont ro l

ProductRate (oz/1000

ft2)Cost per

lbCost per1000 ft2

Bayleton 50DF 2 $81 $10.12

Heritage 50WG 0.4 $365 $9.12

Banner MAXX1.24MC

4 $289(gal)

$9.04

Prostar 70WP 2.2 $50 $6.88

3336 50WP 4 $22 $5.46

Eagle 40WP 1.2 $73 $5.50


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DOLLAR SPOT

Causal Agent: Sclerotinia homoeocarpa

Hosts: All turfgrasses

DOLLAR SPOT


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DOLLAR SPOTSymptoms & Signs

Bleached-white spots or patches up to 6

in diameter

White mycelium present when turf is wet

Leaf lesions are white with a reddish-

brown margin; often hourglass-shaped

On close-cut turf, appears as a tip blight

instead of distinct leaf lesions


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Dollar SpotDollar Spot

CentipedegrassCentipedegrass


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Dollar SpotEmerald Zoysiagrass


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Emerald Zoysiagrass


C i dC i d


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BermudagrassBermudagrass


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BermudagrassBermudagrass


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Managing Dol lar Spot Reduce leaf wetness with proper irrigation timing

Prune or remove trees to increase air movement

and sunlight penetration

Control thatch Do not mow below recommended height

Maintain adequate, but not excessive, nitrogen

Irrigate as needed to prevent drought stress


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GRAY LEAF SPOT

Causal Agent: Pyriculariagrisea

Hosts: Tall fescue Perennial ryegrass

St. Augustinegrass

GRAY LEAF SPOT


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GRAY LEAF SPOTSymptoms & Signs

Small, brown spots on leaves initially

Spots expand to round or oval lesions, gray

with reddish-brown borders

When wet, lesions are gray and water-

soaked

In severe cases, some foliar blighting may

occur

St. Augustinegrass


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GRAY LEAF SPOT


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Conditions Favoring Disease

75F to 95F

Extended periods of leaf wetness Most severe in newly established plantings

High mowing heights and/or infrequentmowing

Slowly growing turf

Turf stressed by nutrient deficiency,

drought, or traffic

GRAY LEAF SPOT


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Chemical Control

Fungicide applications rarely needed inSt. Augustinegrass except in newly

sprigged planting and in sod production

Fungicides: azoxystrobin, chlorothalonil,propiconazole, thiophanate-methyl,

trifloxystrobin


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Curvularia blight


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Curvularia blightZoysiagrass


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Curvular ia Leaf B l ightCul t ura l Cont ro l

Maintain thatch layer at or below 1

Moderate nitrogen applications

Irrigate in early morning hours Remove dew in morning

Increase air circulation

Improve drainage


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Curvular ia Leaf B l ightChem ic a l Cont ro l

DMI Fungicides most effectivepreventative or curative

fenarimol (Rubigan)

myclobutanil (Eagle)

propiconazole (Banner)

triadimefon (Bayleton)

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Grass Diseases