1. Turf Disease Management:
Can it be done without fungicides?
Lane Tredway
Associate Professor and Extension Specialist
Department of Plant Pathology
North Carolina State University

4. What is sustainable?
capable of being continued with minimal long-
term effect on the environment (American
Heritage Dictionary)
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)
capable of being maintained at a steady level
without exhausting natural resources or causing
ecological damage (Collins)

5. 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

6. 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

11. How do plant diseases develop?
Di
se
as
e-
st
Co
Ho
n
du
e
ibl
c
t
ive
ep
Amount of
sc
En
Disease
Su
vir
on
me
nt
Pathogen

12. The environment triggers disease development.

13. Fungal growth is driven by
temperature and moisture.

14. How are turfgrass diseases managed?
Di
se
as
e-
st
Co
Ho
n
du
e
ibl
c
t
ive
ep
Amount of
sc
En
Disease
Su
vir
on
me
nt
Pathogen

15. How are turfgrass diseases managed?
Plant a disease-
resistant Dise
ase-
species or Con
duc
variety ive En
viron
25% Disease men
t
Pathogen

16. How are turfgrass diseases managed?
Plant a disease- Remove trees to
resistant species increase sunlight
or variety and air movement
10% Disease
Pathogen

17. How are turfgrass diseases managed?
Remove trees
Plant a disease-
to increase
resistant species
sunlight and
or variety
air movement
2% Disease
Apply a fungicide to
suppress pathogen
growth

18. 0% 5% 10%
Establish a threshold. How much damage is acceptable?
En
vir
st
on
Ho
me
nt
Pathogen

19. Disease management begins at planting.
st
Ho

20. 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
st
Ho

21. Varieties vary widely in their susceptibility
to certain diseases.

22. Most land/grant universities evaluate turf varieties.

23. ntep.org
st
Ho

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

25. Ho
st

26. Nitrogen has the greatest impact on turf growth.

27. EVERY turf disease is influenced by nitrogen.
Anthracnose Brown Patch
Dollar Spot Pythium Blight
Fairy Ring Gray Leaf Spot
Pythium Root Dysfunction Spring Dead Spot
Red Thread Large Patch
Rust Snow Molds
Low Nitrogen High Nitrogen

29. well-fertilized under-fertilized
st
Ho

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

31. Mowing has a tremendous effect on turf health.

32. Mowing practices influence gray leaf spot development.
Mowing Height
50
Gray Leaf Spot Incidence (%)
40
30
20
10
0
1.5” 2.5” 3.5”
Mowing Height
st
Ho

33. Mowing practices influence gray leaf spot development.
Clipping Collection
50
Gray Leaf Spot Incidence (%)
40
30
20
10
0
Collected Returned
st
Ho

35. The environment drives disease
development.

37. Does irrigation cause as many
problems as it solves?

38. Summer Patch is Impacted by Mowing and Irrigation
40
1.5”
Summer patch incidence (%)
3.0”
30
20
10
0
Light, Frequent Deep, Infrequent
Davis and Dernoeden, 1991

43. Reducing leaf wetness suppresses dollar spot.
140
DewCure 2 oz
120
Dollar Spot Incidence
Check
100
80
60
40
20
0
3
1
8
5
10
17
24
15
22
29
12
6/
7/
7/
8/
6/
6/
6/
7/
7/
7/
8/
Clarke, Rutgers University

44. Suppressing pathogen growth and survival.
Pathogen

45. Are fungicides sustainable?

46. Environmental Impact Quotient (EIQ)
What’s the real environmental impact?
http://www.nysipm.cornell.edu/publications/eiq/

47. 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
2 lbs 14 days 28
Control
Scotts Lawn
1.35 lbs 14 days 64
Fungus Control
Daconil Ultrex 3.2 oz 14 days 538
Pathogen

48. Too
many
fungicides
to choose from!
flickr:kanickmoses

49. Get an accurate diagnosis!

50. Disease Management Utility
turffiles.ncsu.edu/diseasemgmt

51. Disease Management Utility on TurfFiles
turffiles.ncsu.edu/diseasemgmt

52. Soil pH impacts micronutrient availability.

53. Spring dead spot Summer patch
Take-all patch Necrotic ring spot
Patch diseases are enhanced by high soil pH.
Pathogen

55. Nitrogen source influences soil pH
Soil Root
NH4+
soil pH decreases H+
NO3-
soil pH increases OH-

56. What about biological control?
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

57. Rhapsody (2%) Rhapsody (3%) Untreated
200
Dollar Spot Incidence
150
*
*
100
50
0
4 May 18 May 1 Jun 15 Jun 1 Jul 15 Jul
Rhapsody applied every 14 days

59. How to follow along...
turfpathology.org
facebook.com/turfpathology
twitter.com/ncturfpathology
feeds.feedburner.com/turfpathology