NC State University Turfgrass Short Course 02/17/2011

1. Short Course - Diseases of Turf
Lane Tredway & Lee Butler
Dept. of Plant Pathology
North Carolina State University

2. What is a disease?
An abnormality in structure or function
caused by a long-term association with an infectious agent
that injures the plant or reduces its economic value

4. Turfgrasses are Susceptible to Disease when STRESSED

6. Some diseases caused widespread damage in a
short period of time...

7. ...others might reduce the uniformity of a playing surface...

8. ...others may reduce the aesthetic appearance of the turf.

9. Injury is caused by humans or non-living factors.

10. Three factors are required for disease to develop
t
en
nm
Ho
o
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Disease
En
Pathogen

11. Five types of microorganisms cause disease
Fungi (1X) Nematodes (400X)
Bacteria (2,500X)
Mollicutes (25,000X) Viruses (36,000X)

12. Number of Known Diseases by Pathogen Type
Mycoplasmas
Viruses
Bacteria
Nematodes
Fungi

13. Percent of Turf Problems by Pathogen Type
Nematodes
Fungi

14. Nematode Classification
Nematodes are grouped by type of symptom induced, or unique
characteristic of nematode
• Sting
• Lesion
• Lance
• Ring
• Stubby root
• Spiral
• Cyst
• Root knot

15. The sting nematode is most damaging to turfgrasses.

16. Nematode damage is more severe in sandy soils.

17. Reduction of root depth is the most obvious symptom of nematode injury.

18. Diseases attack the turf in different locations
Foliar Diseases:
Copper spot
Bipolaris & Drechslera leaf spots
Brown patch
Dollar spot
Gray leaf spot
Gray snow mold
Stripe smut
Pink patch
Stem and Crown Pink snow mold
Diseases: Powdery mildew
Anthracnose basal rot Pythium blight
Algae Red thread
Bentgrass dead spot Rusts
Large patch Southern blight
Melting out Yellow tuft
White patch
Root diseases:
Bermudagrass decline
Necrotic ring spot
Pythium root dysfunction
Pythium root rot
Spring dead spot
Summer patch
Take-all patch

19. Mycology 101: Key Characteristics of Fungi
• need water or high humidity to grow
• grow and cause disease in a narrow temperature range
• ubiquitous - they are everywhere!
• primary role in nature is decomposition
• some able to use a living plant as a food source

20. Most pathogens are facultative saprophytes, surviving in the thatch
and soil when not causing disease

21. Hyphae are the basic vegetative structure of most fungi.

22. Masses of hyphae, visible to the naked eye, are called mycelium.

23. Many fungi also produce spores.

24. Some fungi produce spores directly on the leaf surface, while
others produce them inside of special structures.

25. The Environment Triggers Disease Development
• Weather – temperature, rain, humidity, dew, sunlight,
day length
• Microclimate – shade, air movement, soil type,
drainage, traffic
• Management – mowing, fertilization, irrigation,
cultivation

26. The Environment Triggers Disease Development
• Temperature and water are the most important factors
influencing disease development
• Foliar Diseases – low night temperature, leaf wetness
duration
• Root and Crown Diseases – soil temperature, soil
moisture

27. The Environment Triggers Disease Development
Foliar diseases are triggered by low night temperature
• Dollar Spot - >50ºF
• Brown Patch – >60ºF
• Pythium blight - >65ºF

28. The Environment Triggers Disease Development
Root diseases are triggered by soil temperature
• Summer Patch - > 65ºF
• Take-all Patch - 40ºF to 60ºF
• Spring Dead Spot - 60ºF to 80ºF
• Large Patch - <70ºF

29. Diagnosis of Turfgrass Diseases

30. “Textbook Symptoms”

31. Turfgrass diseases can appear
very similar.
Which is gray leaf spot and
which is Pythium blight?

32. Many turfgrass problems
appear very similar from a
distance.

33. Herbicide injury can appear
very similar to a disease.
Which is large patch and
which is herbicide injury?

34. How to Tell the Difference???

39. Why is Accurate Diagnosis Important?
• Essential for prompt and effective problem
management
• Incorrect diagnoses cost TIME and MONEY, and
may result in further turf damage
• New generation of fungicides and insecticides
control a smaller number of diseases or pests

40. Turfgrass Disease Diagnosis: A process of elimination
1. Start with a list of possibilities based on turf species and time
of year
2. Look for clues
3. Rule out diseases, narrow the list of possibilities
4. Repeat steps 2 and 3
5. Send sample to a diagnostic lab

41. RE MI
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Diagnosis Triangle
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DIAGNOSIS
AN
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42. Stand Symptoms
Symptoms evident from a distance
Spots – less than 4” diameter
Patches – irregularly shaped areas greater than 4” diameter
Circles – perfectly circular areas greater than 4” diameter
Rings – surrounded by healthy turf to the inside and outside
Irregular – no pattern

43. SPOT DOLLAR SPOT

44. SPOT

45. SPOT

46. PATCH BROWN PATCH

47. PATCH

48. PATCH

49. RING SUMMER PATCH

50. RING

51. RING

52. IRREGULAR RUST

53. IRREGULAR

54. Plant Symptoms
Symptoms evident on individual plants
Leaf Spot – round or oval areas on leaves with a distinct border
Foliar Lesions – large, irregular areas on leaves with a distinct border
Stem Lesions – large, irregular areas on leaf sheaths with a distinct
border
Foliar blight or dieback – necrosis of leaves or entire tillers
Crown Rot – necrosis of the crown, rhizomes, or stolons
Root Rot – necrosis of the roots

55. LEAF SPOT GRAY LEAF SPOT

56. LEAF SPOT

57. LESION BROWN PATCH

58. LESION

59. STEM LESIONS LARGE PATCH

60. FOLIAR
BLIGHT

61. CROWN ROT NECROTIC RING SPOT

62. CROWN
ROT

63. ROOT ROT SUMMER PATCH

64. Pathogen Signs
Evidence of Pathogen Growth
Mycelium – weblike masses of fungal growth
Spore Masses – fuzzy or gelatinous growth
Fruiting Bodies – spore producing structures
Sclerotia – small, round or thread-like survival structures
Mushrooms – reproductive structures produced by fairy ring fungi

65. MYCELIUM PYTHIUM BLIGHT

66. MYCELIUM

67. MYCELIUM

68. SMOKE RING

69. SPORE MASSES

70. FRUITING BODIES ANTHRACNOSE

71. FRUITING
BODIES

72. SCLEROTIA RED THREAD

73. SCLEROTIA SOUTHERN BLIGHT

74. MUSHROOMS

75. NC State Turf Diagnostics Lab

84. Digital Images of Turf Problems

85. Summer Diseases of Tall Fescue
Pythium blight Brown patch
Gray leaf spot
Immature turf is more susceptible to these destructive diseases!

86. Brown Patch (Rhizoctonia solani)

87. BROWN PATCH

88. BROWN PATCH

89. Conditions Favoring Disease
• Extended periods of hot/humid weather
• Most severe when daily low/high is above 70/90 respectively
• 10-12 hours continuous leaf wetness
• Poor water management
• Excessive nitrogen
• Perfect recipe ... repeating afternoon thunderstorms after dry spell
• Front porch rule

90. Brown Patch Resistance in Tall Fescue Cultivars
1996 NTEP Trial, Lexington KY
KENTUCKY-31
JAGUAR 3
REBEL 2000
WOLFPACK
PLANTATION
CHAPEL HILL
ARID
RENEGADE
APACHE II
MUSTANG II
FALCON III (MB 212)
TAR HEEL
FALCON II
COCHISE II
SOUTHERN CHOICE
SHORTSTOP II
COYOTE
BONSAI
TOMAHAWK-E
CORONADO
0 5 10 15 20
% Brown Patch

91. Brown Patch Control
• All of the labeled fungicides control brown
patch effectively
• Products differ in “residual control”, or the
number of days of control
• For tall fescue, application intervals can be
extended by 7 to 14 days

92. Residual Control of Brown Patch
QoIs – 21 to 28 days
Dicarboxamides – 14 to 21 days
Carboxamides – 14 to 21 days
Benzimidazoles – 10 to 14 days
DMIs – 7 to 10 days
Contacts – 7 to 10 days
Polyoxin D – 7 to 10 days

93. Cost Analysis – Brown Patch Control
Product Rate (oz/1000 ft2) Cost per lb Cost per 1000 ft2
Insignia 20WG 0.5 $111 $3.49
Heritage TL 1 $576 (gal) $4.50
Banner Maxx 2 $289 (gal) $4.52
Heritage 50WG 0.2 $356 $4.56
Compass 50WG 0.25 $300 $4.69
Prostar 70WP 1.5 $52 $4.88
Insignia 20WG 0.7 $111 $4.88
Bayleton 50DF 1 $81 $5.06
SysStar 80WDG 2.25 $44 $6.19
Insignia 20WG 0.9 $111 $6.28
Prostar 70WP 2.25 $52 $7.17
Heritage TL 2 $576 (gal) $9.00
Heritage 50WG 0.4 $356 $9.12

94. Gray Leaf Spot (Pyricularia grisea)

95. GRAY LEAF SPOT

97. GRAY LEAF SPOT

98. Conditions Favoring Disease
• Most devastating first year of establishment
• Temperatures between 70 and 95 F
• 14 hours of continuous leaf wetness
• Excessive nitrogen
• Heavy rains will promote rapid spread of spores
due to splashing effect ... as will mowing

99. Pythium blight (Pythium aphanidermatum)

100. Pythium blight
Tall fescue

101. PYTHIUM BLIGHT OF TALL FESCUE

102. PYTHIUM BLIGHT OF TALL FESCUE

103. Conditions Favoring Disease
• Low temperatures above 65°F
• 12-14 or more hours of leaf wetness or high
relative humidity
• High nitrogen levels
• Poor surface or subsurface drainage
• High soil pH (above 7.0)

105. Conditions Favoring Dollar Spot
• Low temperatures >50°F
• High temperatures <95°F
• 10 consecutive hours of leaf wetness
• Low nitrogen and other nutrients
• Low mowing height
• Excessive thatch accumulations

106. Dollar spot is most severe in under-fertilized turf.

108. Seed Size
Tall Fescue vs. Kentucky Bluegrass
Tall Fescue Kentucky Bluegrass
500 seeds/gram 4,800 seeds/gram

109. Mixing Ratios and Seed Numbers
Tall Fescue vs. Kentucky Bluegrass
Mix Ratio Tall Fescue Kentucky Bluegrass
(TF:KBG) Seeds (#) Seeds (#)
90:10 204,000 218,000
95:5 216,000 109,000
97.5:2.5 221,000 54,000

110. Kentucky bluegrass can become
dominant in a short period of time…
%TF in 1999
90:10 %TF in 2002
TF:KBG seed by weight
95:5
97.5:2.5
100:00
10.0 32.5 55.0 77.5 100.0
% Tall Fescue

111. Tall Fescue
Kentucky bluegrass

112. Questions?