Turffiles:Diseases:Brown Blight

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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.

brown blight of perennial ryegrass

Characteristic

Description

Host Grass Species

perennial ryegrass

Month(s) with symptoms

March to May, Sept to Nov

Stand Symptoms

spots, irregular distribution across turf stand

Foliar Symptoms - Location/Shape

round or oval leaf spots, blighting of entire leaves

Foliar Symptoms - Color

brown, yellow, tan

Root/Crown Symptoms

none

Fungal Signs

none

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.

Fungicide	Efficacy ⁽¹⁾	Resistance Risk ⁽²⁾	Class ⁽³⁾	Products ⁽⁴⁾
iprodione**	++++	4	dicarboxamide	26GT, Iprodione Pro
vinclozolin**	++++	4	dicarboxamide	Curalan, Touche
iprodione + thiophanate-methyl**	++++	6	dicarboxamide + benzimidazole	26/36, Fluid Fungicide, Pro Turf
mancozeb**	++++	2	dithiocarbamate	Fore, Dithane, Pentathlon, Protect
mancozeb + copper hydroxide**	++++	2	dithiocarbamate	Junction
azoxystrobin	++++	6	QoI	Heritage
azoxystrobin + propiconazole	++++	6	QoI + DMI	Headway
chlorothalonil**	+++	2	nitrile	Daconil, Chlorostar, Echo, Manicure
chlorothalonil + thiophanate-methyl**	+++	4	nitrile + benzimidazole	Spectro, ConSyst
chlorothalonil + propiconazole**	+++	3	nitrile + DMI	Concert
chlorothalonil + propiconazole + fludioxonil**	+++	2	nitrile + DMI + phenylpyrolle	Instrata
pyraclostrobin	+++	6	QoI	Insignia
propiconazole	++	4	DMI	Banner MAXX, Propiconazole G-Pro, Propiconazole Pro, Quali-Pro Propiconazole, Savvi, Spectator
myclobutanil	+	4	DMI	Eagle
thiophanate-methyl	?	6	benzimidazole	3336, Fungo, T-Storm
flutolanil + thiophanate-methyl	?	6	carboxamide + benzimidazole	SysStar
triticonazole	?	2	DMI	Trinity, Triton
triadimefon + trifloxystrobin	?	6	DMI + QoI	Tartan, Armada
fludioxonil	?	2	phenylpyrolle	Medallion
fluoxastrobin	?	6	QoI	Disarm
trifloxystrobin	?	6	QoI	Compass

** 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 March 23, 2009. 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.

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