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BROWN BLIGHT
 Brown Blight
[Drechslera
siccans]
SYMPTOMS
Brown
blight is a disease that occurs on perennial ryegrass during cool, wet, and cloudy
periods in the spring or fall. Brown blight is a ‘Helminthosporium’ disease,
which is a complex of diseases caused by fungi that produce large, cigar-shaped
spores. Symptoms of brown blight initially appear as small, brown, round or
oval spots on the perennial ryegrass leaves. As the disease progresses, the
lesions expand and become more numerous, causing a brown or yellowish brown
dieback of entire leaves or plants. This foliar blight stage appears in
irregular patterns, although certain ‘hot spots’ may be more severely damaged
than others.
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brown blight of perennial ryegrass
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Characteristic
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Description
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Host
Grass Species
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perennial
ryegrass
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Month(s)
with symptoms
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March
to May, Sept to Nov
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Stand
Symptoms
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spots,
irregular distribution across turf stand
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Foliar
Symptoms - Location/Shape
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round
or oval leaf spots, blighting of entire leaves
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Foliar
Symptoms - Color
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brown,
yellow, tan
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Root/Crown
Symptoms
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none
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Fungal
Signs
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none
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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
Brown blight
is one of several Helminthosporium diseases which survive in thatch during
periods that are unfavorable for disease development. These fungi are most
active during periods of cool (60 to 65°F) and wet weather. Brown blight is
most severe on turf that is growing slowly due to adverse weather conditions or
improper management practices. Shaded areas with little or no air movement
result in weak turf and extended periods of leaf wetness that favor infection
and disease development. Deficient or excessive nitrogen, excessive thatch,
extended periods of leaf wetness, drought stress, and mowing heights that are
too low or too high encourage the development of Helminthosporium diseases.
Certain cultivars of turfgrasses are very susceptible to injury from
Helminthosporium diseases while many of the newly released cultivars exhibit good
resistance.
CULTURAL
CONTROL
Use
turfgrass cultivars with resistance to this disease when available. Use of
resistant cultivars is one of the best means of prevention. Select cultivars
based on regional trials and University recommendations. Use blends and
mixtures of cool-season grasses whenever possible. Fertilize to meet the
nutritional needs of the turf but avoid over-stimulation and the development of
lush, succulent growth. Do not apply more than one pound of nitrogen per 1,000
square feet in a single application. Mowing should be done within the
recommended range for each turfgrass species. Keep the mower blades sharp to
prevent open wounds through which the fungus can enter. Reduce extended periods
of leaf wetness by watering deeply but infrequently to wet the entire root zone.
Do not irrigate before sunset or after sunrise, and ensure good surface and
soil drainage. Remove unwanted vegetation that impedes air movement and prune
trees to allow for light penetration. Power rake or hollow-tine aerify to
remove excessive thatch and reduce pathogen survival.
CHEMICAL
CONTROL
Brown blight can be controlled on
a preventative or curative basis. For best results, fungicides should be
applied in the early stages of disease development.
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Fungicide
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Efficacy (1)
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Resistance Risk (2)
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Class (3)
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Products (4)
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iprodione**
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++++
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4
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dicarboxamide
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26GT, Iprodione Pro
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vinclozolin**
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++++
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4
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dicarboxamide
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Curalan, Touche
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mancozeb**
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++++
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2
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dithiocarbamate
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Fore, Dithane, Protect
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azoxystrobin
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++++
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6
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QoI
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Heritage
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chlorothalonil**
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+++
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2
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nitrile
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Daconil, Chlorostar, Echo, Manicure
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pyraclostrobin
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+++
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6
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QoI
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Insignia
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propiconazole
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++
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4
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DMI
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Banner MAXX, Propiconazole G-Pro, Propiconazole Pro,
Quali-Pro Propiconazole, Savvi, Spectator
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myclobutanil
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+
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4
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DMI
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Eagle
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thiophanate-methyl
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?
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6
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benzimidazole
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3336, Fungo, T-Storm, Systec
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maneb**
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?
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2
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dithiocarbamate
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Pentathlon
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thiram**
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?
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2
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dithiocarbamate
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Spotrete
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triticonazole
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?
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2
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DMI
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Trinity
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fludioxonil
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?
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2
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phenylpyrolle
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Medallion
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fluoxastrobin
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?
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6
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QoI
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Disarm
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trifloxystrobin
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?
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6
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QoI
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Compass
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** Not for application to
residential lawns.
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Footnotes:
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(1)
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Efficacy Codes:
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++++
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excellent control when
conditions are highly favorable for disease development
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+++
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good control when disease
pressure is high, or excellent control when disease pressure is moderate
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++
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good control when disease
pressure is moderate, excellent control when disease pressure is low
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+
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good control when disease
pressure is low
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0
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does
not provide adequate control under any conditions
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?
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cannot be rated due to
insufficient data
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(2)
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Resistance Risk:
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1
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Rotating and tank-mixing not necessary,
but recommended to avoid potential side effects from continuous use of same
chemical class.
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2
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Rotate to different chemical
class after 3-4 applications; tank-mixing not necessary.
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3
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Rotate to different chemical class
after 2-3 applications; tank-mixing not necessary.
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4
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Rotate to different chemical
class after 1-2 applications; tank-mixing not necessary.
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6
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Rotate to different chemical
class after 1-2 applications; tank-mixing with low or moderate risk product
recommended.
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9
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Rotate to different chemical
class after EVERY application; tank-mix with low or moderate risk product for
EVERY application.
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(3)
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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.
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(4)
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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.
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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.
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© 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 April 29, 2008. Available on-line at
www.turffiles.ncsu.edu. This publication was made possible through a grant
provided by the Center for Turfgrass Environmental Research & Education
(CENTERE) whose purpose is to support worthwhile projects that will benefit
both the private sector and the public, and protect the environment.
KEYWORDS FOUND IN THIS ARTICLE:
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