Diseases ›

Red Thread

Symptoms

Red thread develops in circular or irregular patches from 4 inches to 2 feet in diameter. Affected leaves within these patches are tan or bleached-white in color. From a distance, the patches usually have a reddish appearance, due to the presence of thick, red strands of fungal growth emanating from the affected leaves. It is through production of these “red threads 9sclerotia)” that the fungus spreads to healthy plants and survives unfavorable conditions. Small tufts of pink, fuzzy mycelium may also be present in or around the patches when the leaves are wet or humidity is high. After prolonged periods of disease development, the patches may merge to produce large irregularly shaped areas of damaged turf.

Development Factors

The red thread fungus is able to cause disease at temperatures ranging from 40 to 80°F, but develops most rapidly at approximately 70°F. Red thread affects grass that is growing slowly for any reason: inadequate fertilization, drought stress, cool weather, low light intensity, excessive traffic, or many other pest or environmental stresses.

Red thread is most severe in the spring and fall, when extended periods of cool, wet, and overcast weather slow growth of the turf and favor growth of the pathogen. Because of its wide temperature range, red thread can develop at any time of year when a slow-growing host and sufficient leaf wetness are available.

Cultural Control

Fertilize to meet the nutritional needs of the turf and maintain vigorous growth. Submit a soil sample for nutrient analysis regularly, and apply recommended amounts of phosphorus, potassium, and lime. Apply nitrogen based on university recommendations to prevent weak, thin turf; however, avoid overstimulation and the development of lush, succulent turf.

Irrigation should be performed between midnight and 6 AM to prevent prolonged periods of leaf wetness. Never irrigate in the late afternoon or early evening. Apply a sufficient amount of water to wet the entire root zone, then reapply when the turf first starts to show signs of drought stress. Use the Turf Irrigation Management System available on TurfFiles to schedule irrigation based on weather conditions and turf needs. Prune or remove trees, shrubs, or other barriers to increase air movement and sunlight penetration. Remove clippings from affected areas when the disease is active to reduce spread of the disease, and wash infected clippings from equipment before entering uninfected areas.

Chemical Control

Fungicides are available for control of red thread, but are usually not necessary if proper cultural practices are implemented.

Fungicide and Formulation1
Amount of Formulation2
Application Interval3
Efficacy Rating
Resistance Risk
Fungicide and Formulation1

azoxystrobin
(Heritage, Strobe)
(HeritageTL)
(Heritage G)
(Strobe L)

Amount of Formulation2


0.2 to 0.4
1 to 2
2 to 4 lbs
0.38 to 0.77

Application Interval3


14 to 28
14 to 28
14 to 28
14 to 28

Efficacy Rating

++++



Resistance Risk

Low



Fungicide and Formulation1

azoxystrobin + acibenzolar-S-methyl (Heritage Action)*

Amount of Formulation2

0.2 to 0.4

Application Interval3

14 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

azoxystrobin + chlorothalonil (Renown)*

Amount of Formulation2

2.5 to 4.5

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

azoxystrobin + difenoconazole (Briskway)*

Amount of Formulation2

0.5 to 0.725

Application Interval3

14 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

azoxystrobin + propiconazole (Headway)
ME
G

Amount of Formulation2


1.5 to 3
2 to 4 lbs

Application Interval3


14 to 28
14 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

azoxystrobin + tebuconazole (Strobe T)*

Amount of Formulation2

0.75 to 1.5

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil
(Daconil Ultrex)*

(Daconil Weather Stik, Legend)*

(Daconil Zn)*

(Chlorothalonil 500ZN)*

(Chlorothalonil 720SFT)*

(Chlorothalonil)*

Amount of Formulation2


1.8 to 3.25
3.25 to 5
2 to 5.5
5.5
3 to 5
5.3 to 8
3 to 5
7.9
2.12 to 3.5
5.5
1.8 to 3.2

Application Interval3


7 to 10
14
7 to 14
14
7 to 10
14
7 to 10
14
7 to 10
14
7 to 10

Efficacy Rating

+++










Resistance Risk

Low










Fungicide and Formulation1

chlorothalonil + acibenzolar-S-methyl (Daconil Action)*

Amount of Formulation2

2 to 3.5
3.6 to 5.4

Application Interval3

7 to 10
14

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil + fluoxastrobin (Fame C)*

Amount of Formulation2

3 to 5.9

Application Interval3

14 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil + iprodione + thiophanate-methyl + tebuconazole (Enclave)*

Amount of Formulation2

3 to 4
7 to 8

Application Interval3

14 to 21
28

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil + propiconazole (Concert)*

Amount of Formulation2

3 to 5.5
5.5 to 8.5

Application Interval3

7 to 14
14 to 21

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil + propiconazole + fludioxonil (Instrata)*

Amount of Formulation2

2.75 to 6

Application Interval3

14 to 21

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil + thiophanate-methyl
(Spectro)*
(TM/C)*

Amount of Formulation2


3.72 to 5.76
3 to 8

Application Interval3


14
14 to 21

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

fluoxastrobin (Fame)

Amount of Formulation2

0.18 to 0.36

Application Interval3

14 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

fluoxastrobin + tebuconazole (Fame T)*

Amount of Formulation2

0.45 to 0.9

Application Interval3

21 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

flutolanil (Prostar)

Amount of Formulation2

1.5

Application Interval3

21 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

iprodione (iprodione (26GT, Iprodione Pro, IPro)*

Amount of Formulation2

4

Application Interval3

14

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

iprodione + thiophanate-methyl (26/36)*

Amount of Formulation2

2 to 4

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

iprodione + trifloxystrobin (Interface)*

Amount of Formulation2

3 to 4

Application Interval3

14

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

myclobutanil (Eagle, Myclobutanil)
penthiopyrad (Velista)
polyoxin D
(Affirm)
(Endorse)

Amount of Formulation2

1.2
0.3 to 0.5

0.88
4

Application Interval3

14 to 21
14

7 to 14
7 to 14

Efficacy Rating

++
?
?

Resistance Risk

Low
?
Low

Fungicide and Formulation1

Propiconazole (Banner MAXX, Propiconazole)

Amount of Formulation2

2

Application Interval3

14 to 21

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

pyraclostrobin (Insignia)
WG
SC

Amount of Formulation2


0.5 to 0.9
0.4 to 0.7

Application Interval3


14 to 28
14 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

pyraclostrobin + boscalid (Honor)*

Amount of Formulation2

0.55 to 1.1

Application Interval3

14 to 28

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

pyraclostrobin + fluxapyroxad (Lexicon Intrinsic)

Amount of Formulation2

0.34 to 0.47

Application Interval3

14

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

thiophanate-methyl
(3336)
(3336 Plus)
(TM WDG)
(3336 G)
(TM L)

Amount of Formulation2


2 to 4
2 to 4
0.67 to 1.3
1.5 to 6 lbs
1 to 2

Application Interval3


14
14 to 28
14
14
14

Efficacy Rating

+




Resistance Risk

Low




Fungicide and Formulation1

triadimefon (Bayleton)

Amount of Formulation2

0.5 to 1

Application Interval3

15 to 30

Efficacy Rating

++

Resistance Risk

Low

Fungicide and Formulation1

trifloxystrobin (Compass)

Amount of Formulation2

0.1 to 0.15
0.2 to 0.25

Application Interval3

14
21

Efficacy Rating

++

Resistance Risk

Low

Fungicide and Formulation1

trifloxystrobin + triadimefon
(Armada)
(Tartan)*

Amount of Formulation2


0.6 to 1.2
1 to 2

Application Interval3


14 to 28
14 to 28

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

triticonazole
(Trinity)
(Triton)

Amount of Formulation2


0.5 to 1
0.15 to 0.3

Application Interval3


14 to 28
14 to 28

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

triticonazole + chlorothalonil (Reserve)*

Amount of Formulation2

3.2 to 4.5

Application Interval3

refer to label

Efficacy Rating

+++

Resistance Risk

Low

1 Other trade names with the same active ingredients are labeled for use on turfgrasses and can be used according to label directions.
2 Apply fungicides in 2 to 5 gallons of water per 1,000 square feet according to label directions. Use lower rates for preventive and higher rates for curative applications.
3 Use shorter intervals when conditions are very favorable for disease.
* Products marked with an asterisk are not labeled for home lawn use.

Efficacy Rating
++++ = excellent control when conditions are highly favorable for disease development
+++ = good control when disease pressure is high, excellent control when disease pressure is moderate
++ = good control when disease pressure is moderate, excellent control when disease pressure is low
+ = good control when disease pressure is low
? = not rated due to insufficient data

Resistance Risk
Low = Rotate to different chemical class after 3-4 applications; tank mixing not necessary
Medium = Rotate to different chemical class after 1-2 applications; tank-mixing with low or medium risk product recommended
High = Rotate to different chemical class after EVERY application; tank-mix with low or medium risk product for EVERY application
? = not rated due to insufficient data

Presentations

Publications

Species Data

Host species

Kentucky bluegrass, tall fescue, fine fescue, perennial ryegrass

red thread2 ltc
red thread2 ltc
red thread2 ltc
Months with symptoms

March to June, September to December

Stand symptoms

spots, circles, patches (4 to 12 inches)

redthread standsymptoms patch ltc
redthread standsymptoms patch ltc
redthread standsymptoms patch ltc
redthread standsymptom patch ltc
redthread standsymptom patch ltc
redthread standsymptom patch ltc
redthread symptomsandsigns patch myceliumandsclerotia3 ltc
redthread symptomsandsigns patch myceliumandsclerotia3 ltc
redthread symptomsandsigns patch myceliumandsclerotia3 ltc
redthread symptomsandsigns patch mycelium ltc
redthread symptomsandsigns patch mycelium ltc
redthread symptomsandsigns patch mycelium ltc
red thread2 ltc
red thread2 ltc
red thread2 ltc
red thread3 ltc
red thread3 ltc
red thread3 ltc
red thread5 ltc
red thread5 ltc
red thread5 ltc
red thread7 ltc
red thread7 ltc
red thread7 ltc
Foliar symptoms location/shape

dieback from leaf tip, blighting of entire leaves

redthread plantsymptoms blighting2 ltc
redthread plantsymptoms blighting2 ltc
redthread plantsymptoms blighting2 ltc
Foliar symptoms color

red, pink, tan

redthread plantsymptoms blighting2 ltc
redthread plantsymptoms blighting2 ltc
redthread plantsymptoms blighting2 ltc
red thread2 ltc
red thread2 ltc
red thread2 ltc
red thread3 ltc
red thread3 ltc
red thread3 ltc
Root/Crown symptoms

none

Fungal Signs

thread-like sclerotia

redthread signs myceliumandsclerotia2 ltc
redthread signs myceliumandsclerotia2 ltc
redthread signs myceliumandsclerotia2 ltc
redthread signs myceliumandsclerotia3 ltc
redthread signs myceliumandsclerotia3 ltc
redthread signs myceliumandsclerotia3 ltc
redthread signs myceliumandsclerotia ltc
redthread signs myceliumandsclerotia ltc
redthread signs myceliumandsclerotia ltc
redthread signs sclerotia ltc
redthread signs sclerotia ltc
redthread signs sclerotia ltc
redthread symptomsandsigns patch myceliumandsclerotia3 ltc
redthread symptomsandsigns patch myceliumandsclerotia3 ltc
redthread symptomsandsigns patch myceliumandsclerotia3 ltc
redthread symptomsandsigns patch mycelium ltc
redthread symptomsandsigns patch mycelium ltc
redthread symptomsandsigns patch mycelium ltc