NCSTMA Meeting at Carter Finley Stadium 04/21/2010

1. NCSTMA
Diseases of Bermudagrass
Lee Butler
Dept. of Plant Pathology
North Carolina State University

2. An apple a day will keep the doctor away....
What does a turf plant need
to be healthy?
1. light
2. air (oxygen)
3. food
4. water
2

3. More with Less?
Fungicide performance is
determined by several factors
that YOU can control.

4. What factors influence fungicide performance?

5. Techniques for Improving
Fungicide Performance
1. Maintain healthy turf
2. Get an accurate diagnosis
3. Select the best fungicide
4. Time applications properly
5. Put the fungicide where the
pathogen is
6. Provide uniform coverage of
the target site
7. Prevent fungicide resistance

6. apply in 1 to 2
gallons per
apply in 2 to 3
gallons per
apply in 5 gallons per 1000 ft2
OR
water-in with 1/8” of irrigation
Proper placement is crucial Where is the pathogen attacking?

7. Fungicide Selection Tool

14. Turfgrasses are Susceptible to Disease when STRESSED

16. Spring Dead Spot (SDS)
“The most destructive disease on
bermudagrass in the United States.”

17. Distribution of spring dead spot in the United States

18. Spring Dead Spot Attacks All Below-Ground Tissues
Injury to roots, stolons, and rhizomes renders the bermudagrass
more prone to winter injury.

19. Spring dead spot symptoms appear in spring as the
bermudagrass resumes growth.

20. Spring dead spot causes long-term damage to bermudagrass
playing surfaces.

21. Spring dead spot of ‘El Toro’ zoysiagrass

22. Conditions Favoring Spring Dead Spot Development
• high soil pH
• any factor that restricts root growth
• soil compaction
• excessive thatch
• wet soils
• any factor that reduces winter hardiness
• excessive nitrogen in fall
• potassium deficiency
• wet soils

23. Damage is most severe on north-facing slopes...

24. Regular aerification reduces spring dead spot development

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

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

27. Speeding Spring Dead Spot Recovery
• avoid use of certain herbicides in spring
- dithiopyr (Dimension)
- pendimethalin (Pendulum)
- prodiamine (Barricade)
- oryzalin (Surflan)
- trifluralin + benefin (Team Pro)
• 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

28. Keys to Successful Control of SDS
• commit to implementing program for at least 3 years
• map affected areas in spring for treatment
• select an effective product
• apply preventatively in fall when soil temperatures
are between 60˚F and 80˚F
• water-in immediately with 1/8” to 1/4” of irrigation

29. Comparison of fungicides for spring dead spot control
in bermudagrass athletic fields, 2004
6 Heritage WG
Rubigan
5 Eagle
Banner Maxx
Untreated
Disease Incidence (%)
4
3
2
1
0
Field #4 Field #5

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

31. Certain fungicides increase the density of dormant bermudagrass

32. Density differences are due to control of fungi that attack dormant
bermudagrass leaves.

33. 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

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

35. 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

36. 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

37. 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
app)
- Split-plot, randomized complete block with
4 replications 5. potassium chloride (0.5 lb, 2
- Treatments initiated in May 2006 apps)
- Applied to same plots in 2006, 2007, and 6. potassium chloride (1 lb, 2
2008
apps)
- entire study fertilized with 0.33 lb P and
0.66 lb K at time of each N application

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

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

40. Calcium Nitrate Ammonium Sulfate
Urea
May 2009

41. 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)

42. 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
• 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

43. Large patch rarely causes long-term damage to
bermudagrass.

44. ‘Helminthosporium’ leaf spot caused by Bipolaris cynodontis

45. The most common leaf spot fungus in bermudagrass

47. Chemical Control of Leaf Spots
• Prevention is key
• Monitor frequently during conducive weather
• Applications most effective during early stages of
disease development
• Contact fungicides
- mancozeb (Fore & others)
- chlorothalonil (Daconil & others)

48. NC State Turf Diagnostics Lab

50. Questions?