Red Thread
[Laetisaria
fuciformis]
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” 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.
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red thread sclerotia
|
Characteristic
|
Description
|
|
Host
Grass Species
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Kentucky
bluegrass, tall fescue, fine fescue, perennial ryegrass
|
|
Month(s)
with symptoms
|
March
to June, September to December
|
|
Stand
Symptoms
|
spots,
circles, patches (4 to 12 inches)
|
|
Foliar
Symptoms - Location/Shape
|
dieback
from leaf tip, blighting of entire leaves
|
|
Foliar
Symptoms - Color
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red,
pink, tan
|
|
Root/Crown
Symptoms
|
none
|
|
Fungal
Signs
|
thread-like
sclerotia
|
Note: Still not
sure if this is the right disease? The Turfgrass Disease
Identification program may be helpful. Or consult the experts at the Turf
Diagnostics Lab. Check the TurfFiles glossary for definitions
of unfamiliar terms.
FACTORS
AFFECTING DISEASE DEVELOPMENT
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 entire root zone is no
longer moist. 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
|
Efficacy (1)
|
Resistance Risk (2)
|
Class (3)
|
Products (4)
|
|
flutolanil
|
++++
|
2
|
carboxamide
|
ProStar
|
|
iprodione**
|
++++
|
2
|
dicarboxamide
|
26GT, Iprodione Pro
|
|
azoxystrobin
|
++++
|
3
|
QoI
|
Heritage
|
|
fluoxastrobin
|
++++
|
3
|
QoI
|
Disarm
|
|
pyraclostrobin
|
++++
|
3
|
QoI
|
Insignia
|
|
propiconazole
|
+++
|
2
|
DMI
|
Banner MAXX, Propiconazole G-Pro, Propiconazole Pro,
Quali-Pro Propiconazole, Savvi, Spectator
|
|
chlorothalonil**
|
+++
|
1
|
nitrile
|
Daconil, Chlorostar, Echo, Manicure
|
|
vinclozolin**
|
++
|
2
|
dicarboxamide
|
Curalan, Touche
|
|
mancozeb**
|
++
|
1
|
dithiocarbamate
|
Fore, Dithane, Protect
|
|
maneb**
|
++
|
1
|
dithiocarbamate
|
Pentathlon
|
|
fenarimol**
|
++
|
2
|
DMI
|
Rubigan
|
|
myclobutanil
|
++
|
2
|
DMI
|
Eagle
|
|
triadimefon
|
++
|
2
|
DMI
|
Bayleton
|
|
trifloxystrobin
|
++
|
3
|
QoI
|
Compass
|
|
thiophanate-methyl
|
+
|
3
|
benzimidazole
|
3336, Fungo, Systec, T-Storm
|
|
thiram**
|
+
|
1
|
dithiocarbamate
|
Spotrete
|
|
triticonazole
|
?
|
2
|
DMI
|
Trinity
|
|
polyoxin D
|
?
|
2
|
polyoxins
|
Endorse
|
|
** Not for application to
residential lawns.
|
|
Footnotes:
|
|
(1)
|
Efficacy Codes:
|
|
|
++++
|
excellent control when
conditions are highly favorable for disease development
|
|
|
+++
|
good control when disease
pressure is high, or 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
|
|
|
0
|
does
not provide adequate control under any conditions
|
|
|
?
|
cannot be rated due to
insufficient data
|
|
(2)
|
Resistance Risk:
|
|
|
1
|
Rotating and tank-mixing not necessary,
but recommended to avoid potential side effects from continuous use of same
chemical class.
|
|
|
2
|
Rotate to different chemical
class after 3-4 applications; tank-mixing not necessary.
|
|
|
3
|
Rotate to different chemical class
after 2-3 applications; tank-mixing not necessary.
|
|
|
4
|
Rotate to different chemical
class after 1-2 applications; tank-mixing not necessary.
|
|
|
6
|
Rotate to different chemical
class after 1-2 applications; tank-mixing with low or moderate risk product
recommended.
|
|
|
9
|
Rotate to different chemical
class after EVERY application; tank-mix with low or moderate risk product for
EVERY application.
|
|
(3)
|
Continual use of fungicides with
similar control mechanisms (modes of action) can result in fungi that are
resistant to some chemicals. Poor or ineffective disease control can be
expected when this occurs. Managers can reduce the chances of this happening
by mixing or alternating fungicides belonging to different chemical classes.
|
|
(4)
|
Recommendations of specific
chemicals are based upon information on the manufacturer's label and
performance in a limited number of trials. Because environmental conditions
and methods of application may vary widely, performance of the chemical will
not always conform to the safety and pest control standards indicated by
experimental data. When more than one brand name exists for an agricultural
chemical, the name of brand that first came onto the market is listed first.
Otherwise, brand names are listed in alphabetical order. The order in which
brand names are given is not an indication of a recommendation or criticism.
|
|
|
Recommendations for the use of agricultural
chemicals are included in this publication as a convenience to the reader.
The use of brand names and any mention or listing of commercial products or
services does not imply endorsement by North Carolina State University or
discrimination against similar products or services not mentioned. Other
brand names may be labeled for use on turfgrasses. Individuals who use
agricultural chemicals are responsible for ensuring that the intended use
complies with current regulations and conforms to the product label. Be sure
to obtain current information about usage regulations and examine a current
product label before applying any chemical. For assistance, contact your
county's Cooperative Extension agent.
|
© North Carolina State University. This information sheet was prepared
by Lane P. Tredway, Gail G. Wilkerson, Bridget R. Lassiter, Jenifer J.
Reynolds, and Gregory S. Buol. Departments of Plant Pathology and Crop Science,
College of Agriculture & Life Sciences, North Carolina State University.
Prepared