Lane Tredway Southeastern Turf Conference Tifton, GA May 3, 2011

1. Impact of Fertilization Programs and Preventive
Fungicide Applications On Spring Dead Spot in
Hybrid Bermudagrass
L.P. Tredway, M.D. Soika, and E.L. Butler
Department of Plant Pathology
North Carolina State University
NC STATE TURFGRASS PATHOLOGY

2. Spring Dead Spot
• most severe disease of
hybrid bermudagrasses in
transition zone climates
• preventive fungicides erratic
in their performance, and
often not economical
• influence of soil properties
and fertilization programs
not well understood

3. Spring Dead Spot
• caused by root, rhizome,
and stolon infections by
Ophiosphaerella species
• fungal infections reduce
bermudagrass tolerance to
freezing temperatures
• ‘patch diseases’ typically
enhanced by high soil pH
• fall potassium applications
often recommended to
improve cold tolerance

4. Damage is often most severe on north-facing slopes...

5. Why is the damage more severe surrounding this green?

6. Regular aerification reduces spring dead spot development

7. Varieties with Improved Resistance to SDS
• Guymon
• Midiron
• Midlawn
• Midfield
• Mirage
• Patriot
• Sundevil
• Tifsport

8. Recovery from spring dead spot is very slow....

9. Speeding Spring Dead Spot Recovery
• avoid use of DNA herbicides in spring
- prodiamine (Barricade)
- dithiopyr (Dimension)
• aerify or spike affected areas every two weeks
• apply light and frequent irrigation
• apply 1 lb N per 1000 per month from May to Sept

10. How does soil pH influence take-all patch development?
• the take-all patch pathogen,
Gaeumannomyes graminis var. avenae,
facilitates infection by sequestering Mn on
the root surface
• lower pH increases the solubility of Mn in
the soil, allowing the root to better resist
infection
• lower pH also increases population of
fluorescent Pseudomonads, which
produce antifungal compounds on the
root surface

11. How does nitrogen source influence soil pH?
• calcium nitrate increases pH, whereas Soil Root
ammonium sulfate reduces it
• when the root absorbs a nitrate ion NO3-
(NO3-), a hydroxyl ion (OH-) is released,
therefore increasing rhizosphere pH OH-
• when the root absorbs an ammonium
ion (NH4+), a hydrogen ion (H+) is
released, therefore reducing
rhizosphere pH NH4+
H+
• sulfate (SO4-) and calclium (Ca+) have
little to no effect on soil pH

12. Previous Research: Fertilization and Spring Dead Spot
• Dernoeden, Crahay and Davis (1991) studied impact of nitrogen
source and potassium on spring dead spot development
• in greenhouse, ammonium sulfate or potassium chloride
increased bermudagrass survival after inoculation with O. korrae
• in field studies, ammonium sulfate, ammonium chloride, and
ammonium chloride + potassium chloride provided up to 46%
suppression
• significant correlation between SDS and soil pH detected

13. Previous Research: Fertilization and Spring Dead Spot
• McCarty, Lucas and DiPaola (1992) investigated the effect of fall
nitrogen and potassium applications
• late fall applications of sulfur coated urea (98 kg N/ha) or
potassium sulfate (269 kg K/ha) significantly increased SDS
severity
• Vincelli, Doney and Powell (1994) evaluated sulfur, lime, and KCl
• significant suppression of O. herpotricha from applications of
elemental sulfur at rates of from 6.9 to 10.4 lbs/M
• concomitant with reduction in soil pH

14. Spring dead spot can be controlled with fungicides

15. Fungicides for Spring Dead Spot Control
Benzimidazoles
thiophanate-methyl (3336, Systec, T-Storm)
DMIs
fenarimol (Rubigan)
myclobutanil (Eagle, Immunox)
propiconazole (Banner Maxx, Propiconazole Pro, Savvi, Spectator)
tebuconazole (Torque)
triticonazole (Trinity, Triton)
QoIs
azoxystrobin (Heritage)
fluoxastrobin (Disarm)
pyraclostrobin (Insignia)
Premixes
azoxystrobin + propiconazole (Headway)
fluoxastrobin + myclobutanil (Disarm M)

16. Rubigan (6 + 6 fl oz) Untreated Control

17. O. herpotricha O. korrae
Spring dead spot is caused by three Do these species respond to
management practices
species of Ophiosphaerella similarly?

18. Research Objectives: Spring Dead Spot
Management

19. Research Objectives: Spring Dead Spot
Management
1. Determine the effects of nitrogen source and fall fertilization
practices on spring dead spot development in bermudagrass
fairways/athletic fields

20. Research Objectives: Spring Dead Spot
Management
1. Determine the effects of nitrogen source and fall fertilization
practices on spring dead spot development in bermudagrass
fairways/athletic fields
2. Evaluate fungicides for preventive control of spring dead spot in
inoculated plots

21. Research Objectives: Spring Dead Spot
Management
1. Determine the effects of nitrogen source and fall fertilization
practices on spring dead spot development in bermudagrass
fairways/athletic fields
2. Evaluate fungicides for preventive control of spring dead spot in
inoculated plots
3. Compare and contrast the response of O. korrae and O. herpotricha
to the above management practices

22. Bermudagrass Establishment and Inoculation
• 10,000 ft2 plot established
with ‘Tifway’ sprigs on
Appling fine sandy loam
• 5’ x 10’ plots inoculated with
O. korrae and O. herpotricha
in October 2004
• at each inoculation point, 10
cc of infested ryegrain was
placed underneath a 2”-
deep cup-cutter plug

23. Bermudagrass Establishment and Inoculation
• 10,000 ft2 plot established 1.52 m
with ‘Tifway’ sprigs on
Appling fine sandy loam
Ok Oh
• 5’ x 10’ plots inoculated with
O. korrae and O. herpotricha
in October 2004 Ok Oh
3.05 m
• at each inoculation point, 10
cc of infested ryegrain was
placed underneath a 2”- Ok Oh
deep cup-cutter plug

24. Bermudagrass Establishment and Inoculation
• 10,000 ft2 plot established
with ‘Tifway’ sprigs on
Appling fine sandy loam
• 5’ x 10’ plots inoculated with
O. korrae and O. herpotricha
in October 2004
• at each inoculation point, 10
cc of infested ryegrain was
placed underneath a 2”-
deep cup-cutter plug

25. Bermudagrass Establishment and Inoculation
• 10,000 ft2 plot established
with ‘Tifway’ sprigs on
Appling fine sandy loam
• 5’ x 10’ plots inoculated with
O. korrae and O. herpotricha
in October 2004
• at each inoculation point, 10
cc of infested ryegrain was
placed underneath a 2”-
deep cup-cutter plug

26. Bermudagrass Establishment and Inoculation
• 10,000 ft2 plot established
with ‘Tifway’ sprigs on
Appling fine sandy loam
• 5’ x 10’ plots inoculated with
O. korrae and O. herpotricha
in October 2004
• at each inoculation point, 10
cc of infested ryegrain was
placed underneath a 2”-
deep cup-cutter plug

27. Experiment 1: Nitrogen Source and Fall Fertilization
Nitrogen Sources (Main Plots) Fall Fertilizers (Subplots)
• 1 lb N applied 4X per year • applied in Sept and/or Oct each
1. ammonium sulfate year
2. calcium nitrate 1. dolomitic lime (10 lb, 1 app)
3. sulfur coated urea 2. elemental sulfur (2 lb, 1 app)
4. urea 3. gypsum (10 lb, 1 app)
4. potassium chloride (1 lb, 1
- Split-plot, randomized complete block app)
with 4 replications 5. potassium chloride (0.5 lb, 2
- Treatments initiated in May 2006 apps)
- Applied to same plots in 2006, 2007, 6. potassium chloride (1 lb, 2
and 2008
apps)
- entire study fertilized with 0.33 lb P and
0.66 lb K at time of each N application

28. Experiment 2: Preventive Fungicide Applications
Fungicide Treatments Application Details
1. Banner Maxx (4 fl oz, 2 apps) • randomized complete block with 4
2. Eagle (2.4 fl oz, 2 apps) replications
3. Headway (3 fl oz, 2 apps) • fungicide treatments were applied
in September and/or October in
4. Heritage (0.4 oz, 2 apps)
2006, 2007, and 2008
5. Lynx (2 fl oz, 2 apps)
• applications made in water
6. Rubigan (6 fl oz, 1 app) equivalent to 5 gallons per 1000 ft2
7. Rubigan (4 fl oz, 2 apps)
• CO2 powered sprayer at 40 psi
8. Rubigan (6 fl oz, 2 apps) using TeeJet 8004 nozzles

29. Assessment of Spring Dead Spot Severity
• average diameter of each patch
recorded at 100% greenup
• digital image of each plot
captured from overhead for
digital analysis of disease
incidence
• SEVERITY INDEX (Average
Patch Diameter x Disease
Incidence) calculated separately
for O. korrae and O. herpotricha

30. Assessment of Spring Dead Spot Severity
• average diameter of each patch
recorded at 100% greenup
• digital image of each plot
captured from overhead for
digital analysis of disease
incidence
• SEVERITY INDEX (Average
Patch Diameter x Disease
Incidence) calculated separately
for O. korrae and O. herpotricha

31. Assessment of Spring Dead Spot Severity
• average diameter of each patch
recorded at 100% greenup
• digital image of each plot
captured from overhead for
digital analysis of disease
incidence
• SEVERITY INDEX (Average
Patch Diameter x Disease
Incidence) calculated separately
for O. korrae and O. herpotricha

32. Assessment of Spring Dead Spot Severity
• average diameter of each patch
recorded at 100% greenup
• digital image of each plot
captured from overhead for
digital analysis of disease
incidence
• SEVERITY INDEX (Average
Patch Diameter x Disease
Incidence) calculated separately
for O. korrae and O. herpotricha

33. Additional Data Collection (Fertility Study Only)
• leaf tissue samples collected from
each plot with a reel mower in mid-
September 2006, 2007 and 2008 for
nutrient analysis
• soil samples collected from each
plot in December 2006, 2007 and
2008 for measurement of soil pH
using 1:1 soil:water ratio

34. ANOVA: Nitrogen Source and Fall Fertilization
p-values
Source df 2007 2008 2009
N Source 3 0.0506 0.0032 <0.0001
Fall Nutrients 6 0.545 0.3794 0.4150
Pathogen Species 1 <0.0001 <0.0001 <0.0001
Block 3 <0.0001 0.0002 0.0115
N*Fall 18 0.9646 0.8604 0.3879
N*Species 3 0.02 0.0062 <0.0001
Fall*Species 6 0.4647 0.3706 0.2639
N*Fall*Species 18 0.9936 0.952 0.3840

35. Impact of Nitrogen Source on O. herpotricha
90
Sulfur Coated Urea a a
Calcium Nitrate a
75 Urea
a
Spring Dead Spot Index
Ammonium Sulfate
(diameter*incidence)
60
a
a
45 a a
a
b
a a b
a
30 ab
b ab
b
15 b
b b
b
0
c
c
2007 2008 2009
Waller-Duncan k-ratio t-
test

36. Impact of Nitrogen Source on O. korrae
30
Sulfur Coated Urea
Calcium Nitrate a
25 Urea
a
Spring Dead Spot Index
Ammonium Sulfate
(diameter*incidence)
a
20 a a
a
15
a a a a b
a
10
ab
b
ab
5
a ab
a b
a b b
0 c
2007 2008 2009
Waller-Duncan k-ratio t-
test

37. Calcium Nitrate Ammonium Sulfate
Urea
May 2009

38. Pearson Correlation Coefficients
log (spring dead spot index)
Factor O. herpotricha O. korrae
r=0.31 r=-0.45
soil pH
p=<0.0001 p<0.0001
r=-0.10 r=-0.07
N
p=0.88 p=0.3080
r=0.21 r=0.02
P
p=0.0016 p=0.7748
r=0.08 r=0.04
K
p=0.2448 p=0.5779
r=0.21 r=-0.36
Ca
p=0.0014 p=<0.0001
r=0.23 r=0.07
Mg
p=0.0006 p=0.3309
r=0.11 r=0.04
S
p=0.0996 p=0.5471
r=-0.08 r=-0.06
Fe
p=0.2428 p=0.4051
r=-0.29 r=0.28
Mn
p=<0.0001 p=<0.0001
r=-0.005 r=0.24
Zn
p=0.9443 p=0.0003
r=0.06 r=0.17
Cu
p=0.3665 p=0.0123

39. Pearson Correlation Coefficients
log (spring dead spot index)
Factor O. herpotricha O. korrae
r=0.31 r=-0.45
soil pH
p=<0.0001 p<0.0001
r=-0.10 r=-0.07
N
p=0.88 p=0.3080
r=0.21 r=0.02
P
p=0.0016 p=0.7748
r=0.08 r=0.04
K
p=0.2448 p=0.5779
r=0.21 r=-0.36
Ca
p=0.0014 p=<0.0001
r=0.23 r=0.07
Mg
p=0.0006 p=0.3309
r=0.11 r=0.04
S
p=0.0996 p=0.5471
r=-0.08 r=-0.06
Fe
p=0.2428 p=0.4051
r=-0.29 r=0.28
Mn
p=<0.0001 p=<0.0001
r=-0.005 r=0.24
Zn
p=0.9443 p=0.0003
r=0.06 r=0.17
Cu
p=0.3665 p=0.0123

40. Pearson Correlation Coefficients
log (spring dead spot index)
Factor O. herpotricha O. korrae
r=0.31 r=-0.45
soil pH
p=<0.0001 p<0.0001
r=-0.10 r=-0.07
N
p=0.88 p=0.3080
r=0.21 r=0.02
P
p=0.0016 p=0.7748
r=0.08 r=0.04
K
p=0.2448 p=0.5779
r=0.21 r=-0.36
Ca
p=0.0014 p=<0.0001
r=0.23 r=0.07
Mg
p=0.0006 p=0.3309
r=0.11 r=0.04
S
p=0.0996 p=0.5471
r=-0.08 r=-0.06
Fe
p=0.2428 p=0.4051
r=-0.29 r=0.28
Mn
p=<0.0001 p=<0.0001
r=-0.005 r=0.24
Zn
p=0.9443 p=0.0003
r=0.06 r=0.17
Cu
p=0.3665 p=0.0123

41. Pearson Correlation Coefficients
log (spring dead spot index)
Factor O. herpotricha O. korrae
r=0.31 r=-0.45
soil pH
p=<0.0001 p<0.0001
r=-0.10 r=-0.07
N
p=0.88 p=0.3080
r=0.21 r=0.02
P
p=0.0016 p=0.7748
r=0.08 r=0.04
K
p=0.2448 p=0.5779
r=0.21 r=-0.36
Ca
p=0.0014 p=<0.0001
r=0.23 r=0.07
Mg
p=0.0006 p=0.3309
r=0.11 r=0.04
S
p=0.0996 p=0.5471
r=-0.08 r=-0.06
Fe
p=0.2428 p=0.4051
r=-0.29 r=0.28
Mn
p=<0.0001 p=<0.0001
r=-0.005 r=0.24
Zn
p=0.9443 p=0.0003
r=0.06 r=0.17
Cu
p=0.3665 p=0.0123

42. Prevention of Spring Dead Spot with Fungicides
• significant fungicide effects were Rubigan (6 fl oz, 1X) Untreated
detected in 2007 (p=0.0017) and
2008 (p=0.0098), but not in 2009
(p=0.1264)
• a significant fungicide x species
interaction was detected in 2007
(p=0.0042) due to low index
values induced by O. korrae
• no significant fungicide x species
interaction was detected in 2008
(p=0.1111) or 2009 (p=0.0727)

43. Prevention of Spring Dead Spot with Fungicides
Spring Dead Spot Index (diameter*incidence)
Dunnett’s
Test

44. Prevention of Spring Dead Spot with Fungicides
Banner Maxx (4 fl oz, 2X)
Eagle (2.4 fl oz, 2X)
Headway (3 fl oz, 2X)
Heritage (0.4 oz, 2X)
Lynx (2 fl oz, 2X)
Rubigan (6 fl oz, 1X)
Rubigan (4 fl oz, 2X)
Rubigan (6 fl oz, 2X)
Untreated
0 5 10 15 20 25
Spring Dead Spot Index (diameter*incidence)
Dunnett’s
Test

45. Prevention of Spring Dead Spot with Fungicides
Banner Maxx (4 fl oz, 2X) *
Eagle (2.4 fl oz, 2X) *
Headway (3 fl oz, 2X) *
Heritage (0.4 oz, 2X)
Lynx (2 fl oz, 2X) *
Rubigan (6 fl oz, 1X) *
Rubigan (4 fl oz, 2X) *
Rubigan (6 fl oz, 2X) *
Untreated
0 5 10 15 20 25
Spring Dead Spot Index (diameter*incidence)
Dunnett’s
Test

46. Prevention of Spring Dead Spot with Fungicides
Banner Maxx (4 fl oz, 2X) *
Eagle (2.4 fl oz, 2X) *
*
Headway (3 fl oz, 2X) *
*
Heritage (0.4 oz, 2X)
Lynx (2 fl oz, 2X) *
*
Rubigan (6 fl oz, 1X) *
*
Rubigan (4 fl oz, 2X) *
*
Rubigan (6 fl oz, 2X) *
*
Untreated
0 5 10 15 20 25
Spring Dead Spot Index (diameter*incidence)
Dunnett’s
Test

47. Conclusions: Fertilization Programs and Preventive
Fungicides for SDS Management

48. Conclusions: Fertilization Programs and Preventive
Fungicides for SDS Management
• Spring dead spot pathogens exhibited a differential response to nitrogen
sources

49. Conclusions: Fertilization Programs and Preventive
Fungicides for SDS Management
• Spring dead spot pathogens exhibited a differential response to nitrogen
sources
• O. korrae was effectively suppressed by calcium nitrate

50. Conclusions: Fertilization Programs and Preventive
Fungicides for SDS Management
• Spring dead spot pathogens exhibited a differential response to nitrogen
sources
• O. korrae was effectively suppressed by calcium nitrate
• O. herpotricha was suppressed most effectively by ammonium sulfate

51. Conclusions: Fertilization Programs and Preventive
Fungicides for SDS Management
• Spring dead spot pathogens exhibited a differential response to nitrogen
sources
• O. korrae was effectively suppressed by calcium nitrate
• O. herpotricha was suppressed most effectively by ammonium sulfate
• O. korrae was negatively correlated with soil pH and foliar Ca content,
whereas O. herpotricha was positively correlated with these factors

52. Conclusions: Fertilization Programs and Preventive
Fungicides for SDS Management
• Spring dead spot pathogens exhibited a differential response to nitrogen
sources
• O. korrae was effectively suppressed by calcium nitrate
• O. herpotricha was suppressed most effectively by ammonium sulfate
• O. korrae was negatively correlated with soil pH and foliar Ca content,
whereas O. herpotricha was positively correlated with these factors
• Fall applications of potassium, dolomitic lime, gypsum, and elemental
sulfur had no effect on either spring dead spot pathogen

53. Conclusions: Fertilization Programs and Preventive
Fungicides for SDS Management
• Spring dead spot pathogens exhibited a differential response to nitrogen
sources
• O. korrae was effectively suppressed by calcium nitrate
• O. herpotricha was suppressed most effectively by ammonium sulfate
• O. korrae was negatively correlated with soil pH and foliar Ca content,
whereas O. herpotricha was positively correlated with these factors
• Fall applications of potassium, dolomitic lime, gypsum, and elemental
sulfur had no effect on either spring dead spot pathogen
• Spring dead spot pathogens responded similarly to preventive fungicide
applications

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