Turffiles:Diseases:Yellow Patch

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Yellow Patch

[Rhizoctonia cerealis]

SYMPTOMS

Yellow patch is a common disease of cool-season turfgrasses (bentgrasses, bluegrasses, fescues) during the fall, winter, and spring. Symptoms appear as irregular patches or rings up to 3 feet in diameter that are yellow in color. Multiple rings or patches may coalesce to form large, irregularly-shaped areas. Individual plants exhibit a yellow dieback of leaves or blighting of entire plants. No distinct lesions are evident on the affected plants, and the pathogen does not produce mycelium or other signs. Recovery from yellow patch can be very slow because it occurs at a time of the year when the turf is growing slowly.

yellow patch in bentgrass

Characteristic

Description

Host Grass Species

creeping bentgrass, annual bluegrass, Kentucky bluegrass, tall fescue

Month(s) with symptoms

October to March

Stand Symptoms

patches (4 to 12 inches), rings

Foliar Symptoms - Location/Shape

dieback from leaf tip, blighting of entire leaves, leaf lesions

Foliar Symptoms - Color

yellow

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

Yellow patch develops during extended periods of cool, cloudy, wet weather. The pathogen is most active when temperatures are between 50°F and 65°F, but may cause infections under a broader temperature range (45°F to 75°F). Excessive nitrogen applications, heavy thatch accumulations, and poor soil drainage also encourage development of this disease.

CULTURAL CONTROL

Avoid high rates of nitrogen (>0.25 lb N/1000 ft²) during the late fall and early spring when yellow patch is most active, and use slow release fertilizers during this time so as to prevent flushes of foliar growth. Ensure adequate surface and subsurface drainage, and aerify and topdress to reduce thatch accumulations. Pruning or removal of trees will increase sunlight penetration and speed recovery from yellow patch if symptoms appear.

CHEMICAL CONTROL

Yellow patch is best controlled on a preventative basis where it is a persistent problem. Curative applications will prevent further spread, but recovery will be slow if weather conditions are not conducive to turfgrass growth. In North Carolina and other areas of the southern United States, yellow patch can be controlled curatively as fluctuating temperatures in fall, winter, and spring lead to intermittent periods of disease development and turfgrass growth.

Fungicide	Efficacy ⁽¹⁾	Resistance Risk ⁽²⁾	Class ⁽³⁾	Products ⁽⁴⁾
azoxystrobin + propiconazole	++++	3	DMI + QoI	Headway
fluoxastrobin + myclobutanil	++++	3	DMI + QoI	Disarm M
chlorothalonil + fluoxastrobin**	++++	3	nitrile + QoI	Disarm C
azoxystrobin	++++	3	QoI	Heritage
fluoxastrobin	++++	3	QoI	Disarm, Disarm G
flutolanil + thiophanate-methyl	+++	3	benzimidazole + carboxamide	SysStar
flutolanil	+++	2	carboxamide	ProStar
chlorothalonil + propiconazole + fludioxonil**	+++	1	DMI + nitrile + phenylpyrolle	Instrata
iprodione + thiophanate-methyl**	++	3	benzimidazole + dicarboxamide	26/36, Dovetail, Fluid Fungicide
chlorothalonil + thiophanate-methyl**	++	2	benzimidazole + nitrile	Spectro, ConSyst, Peregrine, Tee-1-Up, TM/C
propiconazole	++	2	DMI	Banner MAXX, Kestrel, Kestrel MEX, ProPensity, Propiconazole, Propiconazole G-Pro, Propiconazole Pro, Savvi, Spectator, Strider
chlorothalonil + propiconazole**	++	2	DMI + nitrile	Concert
chlorothalonil**	++	1	nitrile	Daconil, Chlorostar, Chlorothalonil, Echo, Legend, Manicure, Pegasus
fludioxonil	++	1	phenylpyrolle	Medallion
metconazole	?	2	DMI	Tourney
tebuconazole**	?	2	DMI	Torque
triticonazole	?	2	DMI	Trinity, Triton

** 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.

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