Turffiles:Diseases:Brown Patch

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Brown Patch

[Rhizoctonia solani]

SYMPTOMS

The symptoms of brown patch vary according to mowing height. In landscape situations, where mowing height is greater than 1”, brown patch appears as roughly circular patches that are brown, tan, or yellow in color and range from 6” to several feet in diameter. The affected leaves typically remain upright, and lesions are evident on the leaves that are tan in color and irregular in shape with a dark brown border. When the leaves are wet or humidity is high, small amounts of gray cottony growth, called mycelium, may be seen growing amongst affected leaves. In close-cut turfgrasses (1” or less), brown patch develops in roughly circular patches, ranging from a few inches to several feet in diameter, that are brown or orange in color. Distinct foliar lesions are not visible and mycelium is typically not present, but a black or dark gray ring, called a smoke ring, may surround the brown patches. The smoke ring is evidence of active disease development and is only present when the turfgrass leaves are wet or humidity is near 100%.

brown patch leaf lesions

Characteristic

Description

Host Grass Species

bentgrass, bluegrasses, fescues, ryegrasses

Month(s) with symptoms

May to September

Stand Symptoms

patches (4 inches to greater than 3 feet)

Foliar Symptoms - Location/Shape

leaf lesions

Foliar Symptoms - Color

tan, brown, or yellow

Root/Crown Symptoms

none

Fungal Signs

mycelium or 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 patch is most severe during extended periods of hot, humid weather. The disease can begin to develop when night temperatures exceed 60°F, but is most severe when low and high temperatures are above 70°F and 90°F, respectively. The turfgrass leaves must be continuously wet for at least 10 to 12 hours for the brown patch fungus to infect. Poor soil drainage, lack of air movement, shade, cloudy weather, dew, over-watering, and watering in late afternoon favor prolonged leaf wetness and increased disease severity. Brown patch is particularly severe in turf that has been fertilized with excessive nitrogen. Inadequate levels of phosphorus and potassium also contribute to injury from this disease.

CULTURAL CONTROL

Varieties of tall fescue vary widely in their susceptibility to brown patch. Selection of a tall fescue variety with a high level of brown patch resistance is a critical first step in any management program. There are few differences in brown patch resistance among varieties of bluegrass, ryegrass, or bentgrass.

Do not apply excess nitrogen when conditions favor disease development. In general, cool-season grasses should not receive more than 1 pound of nitrogen per 1,000 square feet at any one time. Avoid applying nitrogen to cool-season grasses in late spring or summer, or use very low rates (0.25 lb N/1000 ft² or less) if necessary. Ensure adequate amounts of potassium and phosphorus by applying these nutrients based on soil test results.

Avoiding prolonged periods of leaf wetness will drastically reduce the severity of brown patch. Leaf wetness can originate from irrigation, dew, or guttation (which is the water that is sometimes exuded from turfgrass leaves during the night). To minimize leaf wetness, do not irrigate daily. Instead, irrigation should be applied based on weather conditions and the water requirements of the turf. The Turf Irrigation Management System is available on TurfFiles as a guide to irrigation scheduling. The time of day that irrigation is applied is also critical; it is best to irrigate early in the morning, just before sunrise. This removes large droplets of dew and water from the leaves and speeds drying of the foliage after sunrise. Avoid watering after sunrise or in the late afternoon or evening, as this will increase the duration of leaf wetness. In golf course turf, daily removal of morning dew can help to shorten leaf wetness periods and reduce brown patch development. This can be accomplished by mowing, dragging a hose, or by whipping the greens with a bamboo or fiberglass pole.

Proper landscape design and site preparation can help to minimize brown patch problems. Turf surrounded by trees, shrubs, buildings, or other barriers will remain wet for extended periods of time due to reduced air movement and sunlight. Removal or pruning of trees and other barriers will help minimize leaf wetness and discourage brown patch development. In shady areas, plant turfgrass species that are tolerant of low light levels, such as hard fescue, chewings fescue, or strong creeping red fescue..

Good surface and soil drainage will also help reduce the incidence of brown patch. Avoid establishing turf in low areas that collect water or in soil that is heavily compacted. Aerate high-traffic areas each fall to reduce compaction and maintain soil drainage. Golf course putting greens should be cultivated regularly to maintain soil drainage and aeration.

CHEMICAL CONTROL

Fungicides are effective for brown patch control, and can be applied on a preventative or curative basis. Curative applications may not be effective during periods of hot weather because the cool-season grasses are growing slowly and are unable to recover from the damage under these conditions. Consider a preventive fungicide program for tall fescue and creeping bentgrass when conditions favor disease development. For best results, preventative applications should be initiated in the late spring or early summer when night temperatures consistently exceed 60°F.

Fungicide	Efficacy ⁽¹⁾	Resistance Risk ⁽²⁾	Class ⁽³⁾	Products ⁽⁴⁾
flutolanil + thiophanate-methyl	++++	6	benzimidazole + carboxamide	SysStar
flutolanil	++++	4	carboxamide	ProStar
pyraclostrobin + boscalid**	++++	3	carboxamide + QoI	Honor
azoxystrobin + propiconazole	++++	6	DMI + QoI	Headway
fluoxastrobin + myclobutanil	++++	3	DMI + QoI	Disarm M
chlorothalonil + fluoxastrobin**	++++	3	nitrile + QoI	Disarm C
azoxystrobin	++++	6	QoI	Heritage
fluoxastrobin	++++	6	QoI	Disarm, Disarm G
pyraclostrobin	++++	6	QoI	Insignia
chloroneb + thiophanate-methyl	+++	3	aromatic hydrocarbon + benzimidazole	Fungicide IX
thiophanate-methyl	+++	6	benzimidazole	3336, Fungo, Systec, T-Bird, T-Storm, Tee-Off, TM
iprodione + thiophanate-methyl**	+++	6	benzimidazole + dicarboxamide	26/36, Dovetail, Fluid Fungicide
chlorothalonil + thiophanate-methyl**	+++	4	benzimidazole + nitrile	Spectro, ConSyst, Peregrine, Tee-1-Up, TM/C
iprodione**	+++	4	dicarboxamide	26/36, IPro, Iprodione Pro, Raven
mancozeb**	+++	2	dithiocarbamate	Fore, 4 Flowable Mancozeb, Dithane, Mancozeb DG, Pentathlon, Protect, Wingman
mancozeb + myclobutanil**	+++	3	dithiocarbamate + DMI	Manhandle
mancozeb + copper hydroxide**	+++	2	dithiocarbamate + inorganic	Junction
chlorothalonil + propiconazole**	+++	3	DMI + nitrile	Concert
chlorothalonil + propiconazole + fludioxonil**	+++	2	DMI + nitrile + phenylpyrolle	Instrata
triadimefon + trifloxystrobin	+++	6	DMI + QoI	Armada, Tartan
chlorothalonil**	+++	2	nitrile	Daconil, Chlorostar, Chlorothalonil, Echo, Legend, Manicure, Pegasus
chlorothalonil + phosphorous acid**	+++	2	nitrile + phosphonate	Vitalonil
fludioxonil	+++	2	phenylpyrolle	Medallion
polyoxin D	+++	4	polyoxins	Endorse, Affirm
trifloxystrobin	+++	6	QoI	Compass
thiram**	++	2	dithiocarbamate	Spotrete
metconazole	++	4	DMI	Tourney
tebuconazole**	++	4	DMI	Torque
triticonazole	++	4	DMI	Trinity, Triton
mineral oil**	++	1	hydrocarbon	Civitas
chloroneb	+	2	aromatic hydrocarbon	Teremec, Terraneb
vinclozolin**	+	4	dicarboxamide	Curalan, Touche
fenarimol**	+	4	DMI	Rubigan
myclobutanil	+	4	DMI	Eagle, Myclobutanil
propiconazole	+	4	DMI	Banner MAXX, Kestrel, Kestrel MEX, ProPensity, Propiconazole, Propiconazole G-Pro, Propiconazole Pro, Savvi, Spectator, Strider
triadimefon	+	4	DMI	Bayleton, Granular Turf Fungicide, Systemic Fungicide

** 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 7, 2011. 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:

aeration	fescue	large patch	potassium
bentgrass	fine fescue	management	ryegrass
bluegrass	fungicide	mowing	tall fescue
brown patch	fungus	nitrogen	variety
circular patch	irrigation	phosphorus	watering
creeping bentgrass	Kentucky bluegrass

BROWN PATCH