Turf Disease Management: Can it be done without fungicides?

Lane TredwayAssociate Professor and Extension SpecialistDepartment of Plant PathologyNorth Carolina State University

What is sustainable?

capable of being continued with minimal long-term effect on the environment (American Heritage Dictionary)

capable of being maintained at a steady level without exhausting natural resources or causing ecological damage (Collins)

of, relating to, or being a method of harvesting or using a resource so that the resource is not depleted or permanently damaged (Merriam-Webster)

Which practice is least sustainable?

1. removing trees to increase sunlight and air movement

2. planting a variety containing resistance genes from grasses collected in Poland

3. planting a variety containing frog dermaseptin genes

4. applying the biofungicide Rhapsody (Bacillus subtilis)

5. applying fungicide Heritage (azoxystrobin)

6. applying a mixture of soda, beer, soap, ammonia, and mouthwash

Which practice is most sustainable?

1. removing trees to increase sunlight and air movement

2. planting a variety containing resistance genes from grasses collected in Poland

3. planting a variety containing frog dermaseptin genes

4. applying the biofungicide Rhapsody (Bacillus subtilis)

5. applying fungicide Heritage (azoxystrobin)

6. applying a mixture of soda, beer, soap, ammonia, and mouthwash

How do plant diseases develop?

Amount of Disease

Disease-Conducive EnvironmentSu

scep

tible

Host

Pathogen

The environment triggers disease development.

Fungal growth is driven by temperature and moisture.

How are turfgrass diseases managed?

Amount of Disease

Disease-Conducive EnvironmentSu

scep

tible

Host

Pathogen

How are turfgrass diseases managed?

Disease-Conducive Environment

Pathogen

Plant a disease-resistant

species or variety

25% Disease

How are turfgrass diseases managed?

Remove trees to increase sunlight and air movement

Pathogen

10% Disease

Plant a disease-resistant species

or variety

How are turfgrass diseases managed?

Apply a fungicide to suppress pathogen

growth

2% Disease

Remove trees to increase

sunlight and air movement

Plant a disease-resistant species

or variety

Establish a threshold. How much damage is acceptable?

0% 5% 10%

Host

Pathogen

Environment

Host

Disease management begins at planting.

Host

Turf Species Vary in their Disease Susceptibility

Kentucky bluegrass - summer patch, dollar spot, leaf spot, rust

perennial ryegrass - dollar spot, red thread, Pythium blight, gray leaf spot, brown patch, rust

tall fescue - brown patch

fine fescues - dollar spot, summer patch, red thread

Varieties vary widely in their susceptibility to certain diseases.

Most land/grant universities evaluate turf varieties.

Host

ntep.org

Healthy, well-managed turf is very resistant to disease.

Host

Nitrogen has the greatest impact on turf growth.

EVERY turf disease is influenced by nitrogen.

AnthracnoseDollar SpotFairy Ring Pythium Root DysfunctionRed ThreadRust

Brown PatchPythium BlightGray Leaf Spot

Spring Dead SpotLarge PatchSnow Molds

Low Nitrogen High Nitrogen

Host

under-fertilizedwell-fertilized

Host

Over-fertilization produces leaves that are soft, lush, and easy to infect by the fungi that cause brown patch, Pythium, and other diseases.

Mowing has a tremendous effect on turf health.

Mowing practices influence gray leaf spot development.

Host

Mowing Height

0

10

20

30

40

50

1.5” 2.5” 3.5”Mowing Height

Gra

y Le

af S

pot I

ncid

ence

(%)

0

10

20

30

40

50

Collected Returned

Gra

y Le

af S

pot I

ncid

ence

(%)

Mowing practices influence gray leaf spot development.

Host

Clipping Collection

The environment drives disease development.

Does irrigation cause as many problems as it solves?

0

10

20

30

40

Light, Frequent Deep, Infrequent

1.5”3.0”

Summer Patch is Impacted by Mowing and Irrigation

Sum

mer

pat

ch in

cide

nce

(%)

Davis and Dernoeden, 1991

0

20

40

60

80

100

120

140

6/3

6/10

6/17

6/24 7/

17/8

7/15

7/22

7/29 8/

58/12

DewCure 2 oz Check

Reducing leaf wetness suppresses dollar spot.

Clarke, Rutgers University

Dol

lar S

pot I

ncid

ence

Pathogen

Suppressing pathogen growth and survival.

Are fungicides sustainable?

Environmental Impact Quotient (EIQ)What’s the real environmental impact?

http://www.nysipm.cornell.edu/publications/eiq/

Product Rate/1000 ft2 Interval EIQ/month

Heritage 50WG 0.2 oz 28 days 7.3

Rhapsody 5 oz 7 days 7.6

Bayer Fungus Control 2 lbs 14 days 28

Scotts Lawn Fungus Control 1.35 lbs 14 days 64

Daconil Ultrex 3.2 oz 14 days 538

Pathogen

flickr:kanickmoses

Toomany

fungicidesto choose from!

Get an accurate diagnosis!

Disease Management Utility

turffiles.ncsu.edu/diseasemgmt

Disease Management Utility on TurfFiles

turffiles.ncsu.edu/diseasemgmt

Soil pH impacts micronutrient availability.

Pathogen

Patch diseases are enhanced by high soil pH.

Spring dead spot Summer patch

Necrotic ring spotTake-all patch

NH4+

H+

Soil Root

soil pH decreases

NO3-

OH-soil pH increases

Nitrogen source influences soil pH

Biologicals

• a living organism is applied to the turf, which may inhibit disease through a variety of mechanisms

Biofungicides

• an inhibitory compound, derived from a specific microbe, is concentrated and applied to the turf

Composts

• stimulate activity of soil microbes

• some of which may be beneficial

• some may be harmful or pathogenic

What about biological control?

0

50

100

150

200

4 May 18 May 1 Jun 15 Jun 1 Jul 15 Jul

Rhapsody (2%) Rhapsody (3%) Untreated

Dolla

r Spo

t Inc

iden

ce

Rhapsody applied every 14 days

**

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